Rotaviruses (RVs) cause acute gastroenteritis in infants and young children. Since 2006, live-attenuated vaccines have reduced the number of RV-associated deaths; however, RV is still responsible for an estimated 228,047 annual deaths worldwide. RV, a member of the family Reoviridae, has an 11-segmented double-stranded RNA genome contained within a non-enveloped, triple layered virus particle. In 2017, a long-awaited helper virus-free reverse genetics system for RV was established. Since then, numerous studies have reported the generation of recombinant RVs; these studies verify the robustness of reverse genetics systems. This review provides technical insight into current reverse genetics systems for RVs, as well as discussing basic and applied studies that have used these systems.

Oligoadenylate synthetases-like (OASL) protein exerts various effects on DNA and RNA viruses by inhibiting cGAS-mediated IFN production and by enhancing RIG-I-mediated IFN induction, respectively. In this study, we aimed to examine the role of OASL in pseudorabies virus (PRV) proliferation and investigate the function of the PRV UL24 protein in cellular innate immunity. We found that OASL regulates PRV proliferation by enhancing RIG-I signaling. PRV infection decreased the expression of OASL at both the mRNA and protein levels in PK15 and HeLa cells. OASL expression suppressed the proliferation of PRV in a RIG-I-dependent manner and boosted RIG-I-mediated IFN expression as well as IFN-stimulated gene (ISG) induction. In contrast, knockdown of OASL enhanced PRV proliferation and reduced RIG-I signaling. However, the PRV UL24 protein was found to impair RIG-I signaling, thus inhibiting transcription of IFN and ISGs. In addition, the UL24 protein reduced RIG-I-induced expression of endogenous OASL in an IRF3-dependent manner, thereby antagonizing the OASL antiviral effect. Taken together, our findings characterize the role of OASL in PRV proliferation and provide new insights into the role of UL24 in PRV pathogenesis.

PML nuclear bodies are matrix-bound nuclear structures with a variety of functions in human cells. These nuclear domains are interferon regulated and play an essential role during virus infections involving accumulation of SUMO-dependent host and viral factors. PML-NBs are targeted and subsequently manipulated by adenoviral regulatory proteins, illustrating their crucial role during productive infection and virus-mediated oncogenic transformation. PML-NBs have a longstanding antiviral reputation; however, the genomes of Human Adenoviruses and initial sites of viral transcription/replication are found juxtaposed to these domains, resulting in a double-edged capacity of these nuclear multiprotein/multifunctional complexes. This enigma provides evidence that Human Adenoviruses selectively counteract antiviral responses, and simultaneously benefit from or even depend on proviral PML-NB associated components by active recruitment to PML track-like structures, that are induced during infection. Thereby, a positive microenvironment for adenoviral transcription and replication is created at these nuclear subdomains. Based on the available data, this review aims to provide a detailed overview of the current knowledge of Human Adenovirus crosstalk with nuclear PML body compartments as sites of SUMOylation processes in the host cells, evaluating the currently known principles and molecular mechanisms.

HIV-1 protease expression in the laboratory is demanding because of its high cytotoxicity, making it difficult to express in bacterial expression systems such as Escherichia coli. To overcome these challenges, HIV-1 protease fusion with solubility enhancing tags helps to mitigate its cytotoxic effect and drive its expression as a soluble protein. Therefore, this review focuses on the expression of bioactive HIV-1 protease using solubility-enhancing fusion tags in Escherichia coli and summarises the characteristic features of the different common fusion tags that have been used in the expression of HIV-1 protease. This review will assist researchers with their choice of protein fusion tag for HIV-1 protease expression.

In India, begomovirus infection causing tomato leaf curl disease (ToLCD) is a major constraint for tomato productivity. Here, we have identified two distinct monopartite begomovirus and betasatellite complexes causing ToLCD in the western part of India. A new monopartite begomovirus (Tomato leaf curl Mumbai virus, ToLCMumV) and betasatellite (Tomato leaf curl Mumbai betasatellite, ToLCMumB) were isolated from the Mumbai sample. A distinct Tomato leaf curl Gandhinagar virus (ToLCGanV) and Tomato leaf curl Gandhinagar betasatellite (ToLCGanB) were identified from the Gandhinagar sample. Both of the cloned begomoviruses were recombinants. The demonstration of systemic infection caused by begomovirus (ToLCGanV or ToLCMumV) alone in N. benthamiana and tomato (a virus resistant variety) emphasizes that they were monopartite begomoviruses. Co-inoculation of cognate begomovirus and betasatellite reduces the incubation period and increases symptom severity. Thus, Koch's postulates were satisfied for these virus complexes. Further, an enhanced accumulation of ToLCGanV was detected in the presence of cognate ToLCGanB, however ToLCMumB did not influence the level of ToLCMumV in the agro-inoculated tomato plants. Our results indicate that the cloned viruses form potential virus resistance breaking disease complexes in India. This necessitates to investigate the spread of these disease complexes to major tomato growing regions in the country.

To better understand the pathogenicity of duck plague virus (DPV). The DPV Chinese standard challenge strain (DPV CSC) was continuously passaged 20 times in duck embryo fibroblasts (DEFs). DPV F1 was lethal for 2-week-ducks, but DPV F10 and F20 were not lethal for 2-week ducks, the 528 bp in UL2 region of DPV F1-F20 was deleted, which suggested that the deletion in UL2 region was not related with the virulence of DPV. Compared with DPV F20 infected ducks, IL-8 in DPV F1 infected ducks was significantly upregulated, but IL-1, IL-2,IFNγ and MHC-II were significantly downregulated. ISKNV copies in DPV F10 and F20 infected ducks were lower than the DPV F1 infected ducks. These results showed that massive viruses replication, upregulation of IL-8 expresssion, repression of IL-1, IL-2, IFNγ and MHC-II expression resulted in serious lesions and high mortality. This study provided a in-depth understanding of the immune-related genes expression in the different virulence of DPV.

Although Pseudoalteromonas is an abundant, ubiquitous, marine algae-associated bacterial genus, there is still little information on their phages. In the present study, a marine phage AL, infecting Pseudoalteromonas marina, was isolated from the coastal waters off Qingdao. The AL phage is a siphovirus with an icosahedral head of 53 ± 1 nm and a non-contractile tail, length of 99 ± 1 nm. A one-step growth curve showed that the latent period was approximately 70 min, the rise period was 50 min, and the burst size was 227 pfu/cell. The genome sequence of this phage is a 33,582 bp double-stranded DNA molecule with a GC content of 40.1 %, encoding 52 open reading frames (ORFs). The order of the functional genes, especially those related to the structure module, is highly conserved and basically follows the common pattern used by siphovirus. The stable order has been formed during the long-term evolution of phages in the siphovirus group, which has helped the phages to maintain their normal morphology and function. Phylogenetic trees based on the major capsid protein (mcp) and genome-wide sequence have shown that the AL phage is closely related to four Pseudoalteromonas phages, including PHS21, PHS3, SL25 and Pq0. Further analysis using all-to-all BLASTP also confirmed that this phage shared high sequence homology with the same four Pseudoalteromonas phages, with amino acid sequence identities ranging from 44 % to 71 %. In particular, their similarity in virion structure module may imply that these phages share common assembly mechanism characteristics and infection pathways. Pseudoalteromonas phage AL not only provides basic information for the further study of the evolution of Pseudoalteromonas phages and interactions between marine phage and host but also helps to explain the unknown viral sequences in the metagenomic databases.

Mature HIV-1 protease (PR) functions as a dimer. Changes in HIV-1 PR activation can block virus assembly via premature or enhanced Gag cleavage. HIV-1 PR precursor contains N terminal-linked p6*, a possible modulating factor in PR activation. We found that p6* replacement with a leucine zipper (LZ) dimerization motif (creating a DWzPR construct) or an LZ insertion at the PR C-terminus significantly reduced virus yields due to enhanced Gag cleavage, suggesting that an LZ insertion promotes PR activation by facilitating PR dimer formation. However, introducing T26S (a PR activity-attenuated mutation) into DWzPR strongly impaired Gag cleavage, except when the native C-terminal p6* tetrapeptide remained at the LZ/PR junction. LZ insertion at the PR C-terminus still strongly enhanced PR T26S Gag cleavage. Our data suggest that in addition to p6* mutations, a single amino acid substitution within PR can impair PR activation, likely due to conformational changes triggered by the PR precursor.

Porcine endogenous retroviruses (PERVs) -A and -B are integrated in the genome of all pigs, whereas PERV-C is found in many, but not all pigs. Some immortalized pig cell lines, among them lymphoma cells, but also mitogen activated primary lymphocytes have been shown to release virus particles, which were able to infect human cells and some of them were recombinant PERV-A/C. Since retroviruses can induce lymphomas, two newly established pig lymphoma cell lines and an older one (L23) were analysed for PERV expression. All three lines harboured PERV-A, PERV-B and PERV-C proviruses, but PERV-A/C recombinants were found only in the genome of L23 cells. The expression at the RNA level was very low and no protein expression and particle release was observed, suggesting that PERVs were not involved in the pathogenesis of these lymphomas. However, all three cell lines were infected with the porcine lymphotropic herpesvirus-3 (PLHV-3), which may have been involved in lymphoma development.

In this study, we showed that a codon optimized version of the spike (S) protein of SARS-CoV-2 can migrate to the cell membrane. However, efficient production of Moloney murine leukemia (MLV) infectious viral particles was only achieved with stable expression of a shorter S version in C-terminal (ΔS) in MLV Gag-pol expressing cells. As compared to transient transfections, this platform generated viruses with a 1000-fold higher titer. ΔS was 15-times more efficiently incorporated into VLPs as compared to S, and that was not due to steric interference between the cytoplasmic tail and the MLV capsid, as similar differences were also observed with extracellular vesicles. The amount of ΔS incorporated into VLPs released from producer cells was high and estimated at 1.25 μg/mL S2 equivalent (S is comprised of S1 and S2). The resulting VLPs could potentially be used alone or as a boost of other immunization strategies for COVID-19.

An East African isolate of the maize-associated polerovirus, maize yellow mosaic virus (MaYMV) was previously shown to cause leaf reddening on singly infected maize plants (Zea mays). Here we describe the construction of a full-length infectious clone of an East African isolate and, for the first time, show infectivity of clone-derived transcripts in the primary host, maize, through vascular puncture inoculation (VPI), as well as in the dicotyledonous research model plant species, Nicotiana benthamiana, through agrobacterium inoculation. Characteristic leaf reddening symptoms were observed in a subset of maize plants inoculated with clone-derived transcripts, and infection was confirmed by RT-PCR and Northern blot analyses. In N. benthamiana plants, infections were entirely asymptomatic even at high virus titers, as was also reported for the cloned Chinese isolate. In this study, however, we demonstrated that N. benthamiana can serve as a clone launching platform for maize infection, as VPI of sap of infected N. benthamiana plants into maize kernels resulted in infection and the typical red leaf symptoms. We further demonstrated that the cloned East African isolate virus was aphid transmissible to maize, with experimental transmission rates up to 97 %, comparable to that shown previously for the native virus. Interestingly, our data additionally showed a definitive correlation of leaf reddening symptoms with increased expression of chalcone synthase, thus suggesting upregulation of the flavonoid biosynthesis pathway as the molecular basis for symptom induction in maize. As the first report of experimental infection of maize with transcripts from a cloned polerovirus, this work constitutes a breakthrough for studies on molecular maize-polerovirus-aphid interactions.

Dengue virus NS3 is a prototypical DEx(H/D) helicase that binds and hydrolyzes NTP to translocate along and unwind double-stranded nucleic acids. NS3 and NS4B are essential components of the flavivirus replication complex. Evidences showed that NS4B interacted with NS3 and modulated the helicase activity of NS3. Despite important insights into structural, mechanistic, and cellular aspects of the NS3 function, there is still a gap in understanding how it coordinates the helicase activities within the replicase complex for efficient replication. Here, using the DENV2 as a model, we redefined the critical region of NS4B required for NS3 function by pull-down and MST assays. The FRET-based unwinding assay showed that NS3 would accelerate unwinding duplex nucleic acids in the presence of NS4B (51-83). The simulated NS3-NS4B complex models based on the rigid-body docking delineated the potential interaction sites located in the conserved motif within the core domain of NS3. Mutations in motif I (I190A) and motif III (P319L) of NS3 interfered with the unwinding activity stimulated by NS4B. Upon binding to the NS3 helicase, NS4B assisted NS3 to dissociate from single-stranded nucleic acid and enabled NS3 helicase to keep high activity at high ATP concentrations. These results suggest that NS4B probably serves as an essential cofactor for NS3 to coordinate the ATP cycles and nucleic acid binding during viral genome replication.

Psittacine beak and feather disease (PBFD), caused by beak and feather disease virus (BFDV) is a highly contagious disease in wild and captive psittacine populations and has an almost global presence. However, the BFDV infection in Saudi Arabia remains largely unknown. In the present study, we report the full genome sequence of BFDV strains from Saudi Arabia and its genetic diversity. The complete genome sequences were analyzed for 14 BFDV-infected birds representing 6 psittacine species. The complete genome sequence of BFDV strains was compared with 201 previously reported sequences to evaluate their diversity and possible recombination events, if any. Our analysis revealed that newly sequenced BFDV genomes from Saudi Arabia belonged to six different strains. Phylogenetic analysis suggested that the isolated BFDV genomes were highly recombinant with a high degree of diversity. It is evident from the study that psittacine species in Saudi Arabia are at risk from the spread of BFDV. As per the CITES trade database, about 190,000 parrots have been imported to Saudi Arabia since 1975 over a thousand instances. Presumably, during any of these trade events or unregulated trade of birds has predisposed the introduction of BFDV to Saudi Arabia. Understanding the epidemiology of BFDV is necessitated to address the threat posed by the virus to the psittacine population of Saudi Arabia.

Monitoring of the epidemic situation is imperative to control the risk of infection with avian influenza H5 and H7 subtype viruses. A microneutralization (MN) assay was employed to detect hemagglutinin (HA) subtype-specific antibodies. However, the conventional MN assay raises biosafety concerns and is labor-intensive and time-consuming. Therefore, a safer and more convenient assay that can be applied in a high-throughput format is warranted. In this study, PB2 knockout (PB2-KO) influenza viruses of H5 and H7 subtypes expressing different colored fluorescent proteins were generated using a reverse genetics system and applied to a novel MN assay for the detection of specific antibodies. The detection sensitivity of our PB2-KO virus-based MN assay was evaluated by observing fluorescent proteins under a fluorescence microscope and measuring fluorescence intensities using a plate reader. In addition, the PB2-KO virus-based MN assay was used for the simultaneous detection of H5 and H7 subtype-specific antibodies in a single assay. Expression of the reporter fluorescent protein from H5 and H7 PB2-KO viruses was restricted toin PB2 protein-expressing cells. The MN titer as determined using fluorescence microscopy and plate reader revealed that the detection sensitivity of our PB2-KO virus-based MN assay was comparable to that of the conventional MN assay. Moreover, H5 and H7 PB2-KO viruses could be usedapplied forto the simultaneous detection of H5 and H7 subtype-specific antibodies in a single assay. Our study demonstrates a safe and convenient assay for the detection of H5 and H7 subtype-specific antibodies.

The nearly 3 orders of magnitude variation in size observed among double-stranded DNA viruses (dsDNA) has important ecological consequences, but the factors responsible for this variation remain poorly understood. Here we first evaluate if a relationship exists between the genome size of diverse dsDNA viruses and their hosts in single-celled organisms (prokaryotes and eukaryotes). We find that dsDNA genome size increases systematically, though less than proportionally, with host genome size. We next evaluate possible relationships between virus size, host size and burst size in an analysis that includes both single-celled and multicellular hosts where genome size and cell volume are not as highly correlated. Here we find that virus volume increases sublinearly with host cell volume (but not genome size) across species, and that virus burst volume (burst size * virus volume) increases with host cell volume. These findings suggest that the size and number of dsDNA viruses produced by a particular host may be constrained by the volume of the infected host cell. This may be useful for better understanding virus-host population dynamics, and ultimately, a better understanding of which viruses may infect which hosts (i.e., host specificity) and the likelihood of cross-species transmission events (i.e., host jumping).

The negative strand RNA virus family contains many human pathogens. Finding new antiviral drug targets against this class of human pathogens is one of the significant healthcare needs. Nucleocapsid proteins of negative strand RNA viruses wrap the viral genomic RNA and play essential roles in gene transcription and genome replication. Chandipura virus, a member of the Rhabdoviridae family, has a negative strand RNA genome. In addition to wrapping the genomic RNA, its nucleocapsid protein interacts with the positive strand leader RNA and plays a vital role in the virus life-cycle. We have designed a peptide, based on prior knowledge and demonstrated that the peptide is capable of binding specifically to the positive strand leader RNA. When the peptide was transported inside the cell, it inhibited viral growth with IC50 values in the low micromolar range. Given the widespread occurrence of leader RNAs in negative strand RNA viruses and its interaction with the nucleocapsid protein, it is likely that this interaction could be a valid drug target for other negative strand RNA viruses.

Cholesterol 25-hydroxylase (CH25 H) is a key enzyme regulating cholesterol metabolism and also acts as a broad antiviral host restriction factor. Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that can cause vomiting, diarrhea, dehydration and even death in newborn piglets. In this study, we found that PDCoV infection significantly upregulated the expression of CH25H in IPI-FX cells, a cell line of porcine ileum epithelium. Overexpression of CH25H inhibited PDCoV replication, whereas CH25H silencing using RNA interference promoted PDCoV infection. Treatment with 25-hydroxycholesterol (25HC), the catalysate of cholesterol via CH25H, inhibited PDCoV proliferation by impairing viral invasion of IPI-FX cells. Furthermore, a mutant CH25H (CH25H-M) lacking hydroxylase activity also inhibited PDCoV infection to a lesser extent. Taken together, our data suggest that CH25H acts as a host restriction factor to inhibit the proliferation of PDCoV but this inhibitory effect is not completely dependent on its enzymatic activity.

Despite being an important health problem, there are only supportive care treatments for respiratory syncytial virus (RSV) infection. Thus, discovery of specific therapeutic drugs for RSV is still needed. Recently, an antiparasitic drug niclosamide has shown a broad-spectrum antiviral activity. Here, our in vitro model was used to study the antiviral effect of niclosamide on RSV and its related mechanism. Niclosamide inhibited RSV with time and dose-dependent manner. Pretreatment with submicromolar concentration of niclosamide for 6 h presented the highest anti-RSV activity of 94 % (50 % effective concentration; EC50 of 0.022 μM). Niclosamide efficiently blocked infection of laboratory strains and clinical isolates of both RSV-A and RSV-B in a bronchial epithelial cell line. Although a disruption of the mechanistic target of rapamycin complex 1 (mTORC1) pathway by niclosamide was previously hypothesized as a mechanism against pH-independent viruses like RSV, using a chemical mTORC1 inhibitor, temsirolimus, and a chemical mTORC1 agonist, MHY1485 (MHY), we show here that the mechanism of RSV inhibition by niclosamide was mTORC1 independent. Indeed, our data indicated that niclosamide hindered RSV infection via proapoptotic activity by a reduction of AKT prosurvival protein, activation of cleaved caspase-3 and PARP (poly ADP-ribose polymerase), and an early apoptosis induction.

Sweet potato (Ipomoea batatas) ranks among the most important crops in the world and provides nutritional and economic sustainability for subsistence farmers in sub-Saharan Africa. Its production is mainly constrained by sweet potato virus disease (SPVD) caused by the coinfection of two positive-sense single-stranded RNA viruses, sweet potato chlorotic stunt virus (SPCSV) and sweet potato feathery mottle virus (SPFMV). Current understanding of sweet potato responses to SPCSV and SPFMV at the molecular level remains very limited. In this study, we performed deep sequencing of both messenger RNA (mRNA) and small RNA (sRNA) populations in an SPVD-susceptible cultivar 'Beauregard' upon viral infection, to identify biological pathways that contribute to both general and specific host responses to these important viral pathogens. We found that pathways related to stress response and signaling were significantly affected by viral infection. sRNA components of these pathways were predominantly affected in late stages of the coinfection by SPCSV and SPFMV. We identified several novel microRNAs that were responsive to viral infection, some of which were predicted to target nucleotide-binding site leucine-rich repeat (NBS-LRR) disease resistance genes. The downregulation of the salicylic acid-mediated defense response pathway in particular seems to be a result of the viral infection process, and can in part explain the susceptible nature of the 'Beauregard' cultivar.

Human immunodeficiency virus (HIV) and human T-lymphotropic virus type I (HTLV-I) are two retroviruses that attack the immune cells and impair their functions. Both HIV and HTLV-I can be transmitted between individuals through direct contact with certain body fluids from infected individuals. Therefore, a person can be co-infected with both viruses. HIV causes acquired immunodeficiency syndrome, while HTLV-I is the causative agent for adult T-cell leukemia and HTLV-I-associated myelopathy/tropical spastic paraparesis. Several mathematical models have been developed in the literature to describe the within-host dynamics of HIV and HTLV-I mono-infections. However, modeling a within-host dynamics of HIV/HTLV-I co-infection has not been involved. In the present paper, we are concerned to formulate and analyze a new HIV/HTLV co-infection model under the effect of Cytotoxic T lymphocytes (CTLs) immune response. The model describes the interaction between susceptible CD4+T cells, silent HIV-infected cells, active HIV-infected cells, silent HTLV-infected cells, Tax-expressing HTLV-infected cells, free HIV particles, HIV-specific CTLs and HTLV-specific CTLs. The HIV can spread by two routes of transmission, virus-to-cell and cell-to-cell. On the other side, HTLV-I has two modes of transmission, (i) horizontal transmission via direct cell-to-cell contact, and (ii) vertical transmission through mitotic division of Tax-expressing HTLV-infected cells. The well-posedness of the model is established by showing that the solutions of the model are nonnegative and bounded. We define a set of threshold parameters which govern the existence and stability of all equilibria of the model. We explore the global asymptotic stability of all equilibria by utilizing Lyapunov function and LaSalle's invariance principle. We have presented numerical simulations to justify the applicability and effectiveness of the theoretical results. In addition, we evaluate the effect of HTLV-I infection on the HIV dynamics and vice versa.

In this study, we investigated the involvement of keratin 8 during human influenza A/NWS/33 virus (H1N1) infection in semi-permissive rhesus monkey-kidney (LLC-MK2) and permissive human type II alveolar epithelial (A549) cells. In A549 cells, keratin 8 showed major expression and phosphorylation levels. Influenza A/NWS/33 virus was able to subvert keratin 8 structural organization at late stages of infection in both cell models, promoting keratin 8 phosphorylation in A549 cells at early phases of infection. Accordingly, partial colocalizations of the viral nucleoprotein with keratin 8 and its phosphorylated form were assessed by confocal microscopy at early stages of infection in A549 cells. The employment of chemical activators of phosphorylation resulted in structural changes as well as increased phosphorylation of keratin 8 in both cell models, favoring the influenza A/NWS/33 virus's replicative efficiency in A549 but not in LLC-MK2 cells. In A549 and human larynx epidermoid carcinoma (HEp-2) cells inoculated with respiratory secretions from pediatric patients positive for, respectively, influenza A virus or respiratory syncytial virus, the keratin 8 phosphorylation level had increased only in the case of influenza A virus infection. The results obtained suggest that in A549 cells the influenza virus is able to induce keratin 8 phosphorylation thereby enhancing its replicative efficiency.

Bats carry diverse severe acute respiratory syndrome-related coronaviruses (SARSr-CoVs). The suspected interspecies transmission of SARSr-CoVs from bats to humans has caused two severe CoV pandemics, the SARS pandemic in 2003 and the recent COVID-19 pandemic. The receptor utilization of SARSr-CoV plays the key role in determining the host range and the interspecies transmission ability of the virus. Both SARS-CoV and SARS-CoV-2 use angiotensin-converting enzyme 2 (ACE2) as their receptor. Previous studies showed that WIV1 strain, the first living coronavirus isolated from bat using ACE2 as its receptor, is the prototype of SARS-CoV. The receptor-binding domain (RBD) in the spike protein (S) of SARS-CoV and WIV1 is responsible for ACE2 binding and medicates the viral entry. Comparing to SARS-CoV, WIV1 has three distinct amino acid residues (442, 472, and 487) in its RBD. This study aimed at exploring whether these three residues could alter the receptor utilization of SARSr-CoVs. We replaced the three residues in SARS-CoV (BJ01 strain) S with their counterparts in WIV1 S, and then evaluated the change of their utilization of bat, civet, and human ACE2s using a lentivirus-based pseudovirus infection system. To further validate the S-ACE2 interactions, the binding affinity between the RBDs of these S proteins and the three ACE2s were verified by flow cytometry. The results showed that the single amino acid substitution Y442S in the RBD of BJ01 S enhanced its utilization of bat ACE2 and its binding affinity to bat ACE2. On the contrary, the reverse substitution in WIV1 S (S442Y) significantly attenuated the pseudovirus utilization of bat, civet and human ACE2s for cell entry, and reduced its binding affinity with the three ACE2s. These results suggest that the S442 is critical for WIV1 adapting to bats as its natural hosts. These findings will enhance our understanding of host adaptations and cross-species infections of coronaviruses, contributing to the prediction and prevention of coronavirus epidemics.

The natural course of type I and III interferon (IFN) response in the respiratory tract of COVID-19 patients needs to be better defined. We showed that type I/III IFNs, IFN-regulatory factor 7 (IRF7), and IFN stimulated genes (ISGs), are highly expressed in the oropharyngeal cells of SARS-CoV-2 positive patients compared to healthy controls. Notably, the subgroup of critically-ill patients that required invasive mechanical ventilation had a general decrease in expression of IFN/ISG genes. Heterogeneous patterns of IFN-I/III response in the respiratory tract of COVID-19 patients may be associated to COVID-19 severity.

The life-threatening re-emerged chikungunya virus (CHIKV) can cause an epidemic outbreak and still has no vaccine available so far. Alphavirus unique domain (AUD) of CHIKV nsP3 is a multifunctional domain that remains conserved among alphaviruses and is critical for CHIKV replication. The understanding of AUD-host protein-protein interactions and their association with the cellular processes concerning CHIKV infection are not well studied. In the current study, the protein-protein interactions of AUD and its human host were elucidated by screening of universal human cDNA library using yeast two-hybrid system. The chosen interactions were further validated by GST pull-down assay, and their network mapping was analyzed. The study revealed that the identified interactors are linked with the vesicle trafficking and transcription corepressor activities. Further, the interfacial residues of interactions between viral and host proteins were predicted, which will further provide the new platform to develop novel antivirals.

The frequency of infection of duck circovirus (DuCV) in Anhui province, China is not well-characterized. Therefore, in this study, we collected 69 samples from sick ducks and tested them for the presence of DuCV by conventional polymerase chain reaction (PCR) analysis. The complete viral genomes of five DuCV strains from five different cities were randomly selected, amplified via PCR, sequenced, and subjected to recombination analysis. The five DuCV genomes were named as AHAU9, AHAU25, AHAU28, AHAU37, and AHAUHQ. We found that 36.2 % of the ducks were infected with DuCV. The five DuCV strains had genome lengths ranging from 1987 to 1995 nucleotides, with a sequence similarity of 81.8-98.2 %. Among them, AHAU28, AHAU37, and AHAUHQ were closely related to the reference strain YF180403, GX1105 strain, and wd2015028 of DuCV, respectively. AHAU9 and AHAU25 were found to belong to a new DuCV subtype, DuCV-1d. Moreover, recombination analysis showed that the DuCV-1d subtype strains had the same recombination pattern. These results improve the understanding of the frequency of DuCV infection in Anhui province. Our findings may be useful for preventing and controlling the spread of DuCV.

Flaviviruses are the fastest spreading arthropod-borne viruses that cause severe symptoms such as hepatitis, hemorrhagic fever, encephalitis, and congenital deformities. Nearly 40 % of the entire human population is at risk of flavivirus epidemics. Yet, effective vaccination is restricted only to a few flaviviruses such as yellow fever and Japanese encephalitis viruses, and most recently for select cases of dengue virus infections. Despite the global spread of dengue virus, and emergence of new threats such as Zika virus and a new genotype of Japanese encephalitis virus, insights into flavivirus targets for potentially broad-spectrum vaccination are limited. In this review article, we highlight biochemical and structural differences in flavivirus proteins critical for virus assembly and host interactions. A comparative sequence analysis of pH-responsive properties of viral structural proteins identifies trends in conservation of complementary acidic-basic character between interacting viral structural proteins. This is highly relevant to the understanding of pH-sensitive differences in virus assembly in organelles such as neutral ER and acidic Golgi. Surface residues in viral interfaces identified by structural approaches are shown to demonstrate partial conservation, further reinforcing virus-specificity in assembly and interactions with host proteins. A comparative analysis of epitope conservation in emerging flaviviruses identifies therapeutic antibody candidates that have potential as broad spectrum anti-virals, thus providing a path towards development of vaccines.

Zika is a major teratogenic virus that can be transmitted from pregnant women to the fetus via the transplacental route. At present, no specific vaccines or treatments are available. Large-scale functional genomics approaches for the analysis of host cell function in infection greatly improve the understanding of molecular infection processes and advance the discovery of antiviral targets. We conducted a pooled CRISPR/Cas9 screen to explore trophoblast function upon Zika infection. The identified Zika virus host factors enrich in the ER membrane complex and the signal peptide processing pathway. Finally, we demonstrate that signal peptidase complex subunit 1 (SPCS1) is crucial for virus replication in trophoblasts.

The intestinal mucosa plays an important role as an immune barrier due to its continual exposure to invading pathogens, including viruses. It is thus highly important to evaluate virus infection profiles in the intestinal mucosa for prevention of virus infection and development of antivirus medicines; however, only a few enterocyte lines are available as in vitro intestinal models for the evaluation of virus infection. In this study, we evaluated profiles of infection and innate immune responses following infection with a mammalian orthoreovirus (hereafter reovirus), which has often been used as a tractable model for studies of viral pathogenesis, in human iPS cell-derived small intestinal epithelial-like cell (hiPS-SIEC) monolayers and cells of a human colon adenocarcinoma cell line, Caco-2. The levels of reovirus infection were similar between hiPS-SIEC and Caco-2 cell monolayers, which are often used as an intestinal model, after apical and basolateral infection. In hiPS-SIEC monolayers, more efficient replication of the virus genome was observed following basolateral infection than apical infection, while apical infection resulted in higher levels of virus protein expression and progeny virus production than basolateral infection. Reovirus significantly induced innate immune responses, including expression of type I and III interferons (IFNs), in hiPS-SIEC monolayers more efficiently than Caco-2 cells. Higher levels of type I and III interferon (IFN) expression were found in hiPS-SIEC monolayers following apical infection than basolateral infection. These results suggested that hiPS-SIECs are a promising in vitro model for the evaluation of virus infection.

Hepatitis C virus (HCV) can cause chronic lifelong infections in humans, resulting in sustained hepatic inflammation, liver cirrhosis, and hepatocellular carcinoma. The clearance of HCV infections is dependent upon effective and coordinated innate and adaptive antiviral immune responses. However, HCV has evolved a range of strategies that enable it to evade or overcome the host immune response, enabling the virus to persist in susceptible hosts through mechanisms that remain to be fully clarified. Herein, we describe a novel mechanism whereby HCV can evade immune surveillance by activating microRNA (miR)-125a. Hepatocytes upregulate miR-125a following HCV infection, and serum from HCV-infected patients similarly exhibits the upregulation of this miRNA. We found that miR-125a is able to target and suppress the expression of two key genes associated with the interferon (IFN) signaling pathway - mitochondrial antiviral signaling (MAVS) and TNF receptor-associated factor 6 (TRAF6). Disrupting the expression of these genes can in turn compromise type I IFN responses to HCV. Together, our data reveal that HCV infection results in the upregulation of miR-125a, which negatively regulates IFN signaling via inhibiting the expression of MAVS and TRAF6, thereby enabling the virus to evade innate antiviral immunity. Targeting this pathway may thus represent an efficient approach to treating HCV and bolstering antiviral immune responses in infected patients.

Cherry rusty mottle-associated virus (CRMaV), which belongs the genus Robigovirus of the family Betaflexiviridae, is strongly associated with cherry rusty mottle disease of sweet cherry, Prunus avium. Here, we report on the successful development of an Agrobacterium-based inoculation system for a cloned CRMaV cDNA construct. Agro-inoculation of virus-free cherry rootstock 'Krymsk6' [P. cerasus x (P. cerasus x P. maackii)] resulted in the development of chlorotic yellow mottle symptoms on systemic leaves beginning at 50 days post inoculation. The presence of CRMaV in 'Krymsk6' agro-inoculated plants was confirmed by RT-PCR and ELISA. Subsequently, CRMaV from agro-inoculated 'Krymsk6' was graft-transmissible onto virus-free sweet cherry rootstock P. avium 'Mazzard' as evidenced by the production of typical cherry rusty mottle symptoms beginning at 35 days post grafting, and further confirmed by western blotting and RT-PCR. These results showed conclusively that CRMaV is the causal agent of cherry rusty mottle disease in sweet cherry. The reverse genetic system presented in this study can be used as a tool to investigate the molecular biology of CRMaV and also a template for infectious clone development for other viruses in the genus Robigovirus.

DEAD-box RNA helicases, the largest family of superfamily 2 helicases, are a profoundly conserved family of RNA-binding proteins, containing a distinctive Asp-Glu-Ala-Asp (D-E-A-D) sequence motif, which is the origin of their name. Aside from the ATP-dependent unwinding of RNA duplexes, which set up these proteins as RNA helicases, DEAD-box proteins have been found to additionally stimulate RNA duplex fashioning and to uproot proteins from RNA, aiding the reformation of RNA and RNA-protein complexes. There is accumulating evidence that DEAD-box helicases play functions in the recognition of foreign nucleic acids and the modification of viral infection. As intracellular parasites, viruses must avoid identification by innate immune sensing mechanisms and disintegration by cellular machinery, whilst additionally exploiting host cell activities to assist replication. The capability of DEAD-box helicases to sense RNA in a sequence-independent way, as well as the broadness of cellular roles performed by members of this family, drive them to affect innate sensing and viral infections in numerous manners. Undoubtedly, DEAD-box helicases have been demonstrated to contribute to intracellular immune recognition, function as antiviral effectors, and even to be exploited by viruses to support their replication. Relying on the virus or the viral cycle phase, a DEAD-box helicase can function either in a proviral manner or as an antiviral factor. This review gives a comprehensive perspective on the various biochemical characteristics of DEAD-box helicases and their links to structural data. It additionally outlines the multiple functions that members of the DEAD-box helicase family play during viral infections.

Interferon-lambda (IFN-λ) is a type-III IFN and is considered a candidate of antiviral therapeutics. Although the antiviral effects of IFN-λ have been investigated in several studies, it has not been clinically approved as an antiviral agent. In this study, an adenoviral vector expression system employing a tetracycline-operator system was developed to control the expression of canine IFN-λ3. The antiviral effects of canine IFN-λ3 were determined in Madin-Darby canine kidney cells and canine tracheal epithelial cells. After transducing each cell line with recombinant adenovirus containing canine interferon lambda3 gene (Ad-caIFNλ3), the mRNA-expression of interferon-stimulated genes Mx1, ISG15, and OAS1 increased significantly (P < 0.05). The replication of canine influenza virus (CIV) was significantly suppressed in Ad-caIFNλ3-infected cells. These results indicate that the newly constructed adenoviral vector system could express canine IFN-λ3, which could subsequently inhibit CIV replication in two canine cell lines. These data imply that the recombinant Ad-caIFNλ3 can potentially be used to treat canine influenza and other viral diseases.

A new variant of pseudorabies virus (PRV) with high pathogenicity has been prevalent in many swineherds vaccinated with Bartha-K61 in China since 2011. Several gene-deleted vaccine candidates have been developed based on new emerging PRV variants. PRV-AH, a new emerging PRV strain from Anhui Province, was isolated in our laboratory in 2013. In the present study, rPRV-AH-gI-/gE- and rPRV-AH-gI-/gE-/gC+ were generated based on PRV-AH by homologous recombination. The growth kinetics of rPRV-AH-gI-/gE- and rPRV-AH-gI-/gE-/gC+ were similar to their parental strains. Compared with the commercial inactivated vaccine of Ea strain, the immune efficacy of the inactivated vaccine based on recombinant viruses was evaluated in mice and weaned pigs. The result showed that the level of neutralizing antibody in mice immunized with rPRV-AH-gI-/gE-/gC+ was higher compared with those immunized with rPRV-AH-gI-/gE- at a dose of 106 TCID50 at 8 weeks post initial immunization (p < 0.0001). Among the groups immunized at a dose of 105 TCID50, the rPRV-AH-gI-/gE- group showed a survival rate of 37.5 %, while the rPRV-AH-gI-/gE-/gC+ group showed a protection rate of 87.5 % against the PRV-AH challenge. Besides, the rPRV-AH-gI-/gE- and rPRV-AH-gI-/gE-/gC+ group immunized at a dose of 106 TCID50 showed a survival rate of 100 %. Interestingly, compared with the commercial vaccine group, the group of 105 TCID50 rPRV-AH-gI-/gE-/gC+ showed a lower level of neutralizing antibodies (p < 0.0001) but the same protection rate in mice. Moreover, in the pig experiment, the level of neutralizing antibodies in the group vaccinated with inactivated rPRV-AH-gI-/gE-/gC+ was higher than any other groups at 8 weeks post initial immunization (p < 0.05). More importantly, the milder symptoms and pathological lesions occurred in pigs vaccinated with rPRV-AH-gI-/gE-/gC+ after challenge with 106 TCID50 PRV-AH, revealing that additional insertion of gC gene could enhance the protective efficacy in PRV gI/gE-deleted vaccine in pigs. Collectively, these above-mentioned findings suggested that the inactivated vaccine of rPRV-AH-gI-/gE-/gC+ had a better immune efficacy, which could be regarded as a promising inactivated vaccine candidate for PRV control.

Emergence of novel SARS-CoV-2 lineages are under the spotlight of the media, scientific community and governments. Recent reports of novel variants in the United Kingdom, South Africa and Brazil (B.1.1.28-E484K) have raised intense interest because of a possible higher transmission rate or resistance to the novel vaccines. Nevertheless, the spread of B.1.1.28 (E484K) and other variants in Brazil is still unknown. In this work, we investigated the population structure and genomic complexity of SARS-CoV-2 in Rio Grande do Sul, the southernmost state in Brazil. Most samples sequenced belonged to the B.1.1.28 (E484K) lineage, demonstrating its widespread dispersion. We were the first to identify two independent events of co-infection caused by the occurrence of B.1.1.28 (E484K) with either B.1.1.248 or B.1.91 lineages. Also, clustering analysis revealed the occurrence of a novel cluster of samples circulating in the state (named VUI-NP13L) characterized by 12 lineage-defining mutations. In light of the evidence for E484K dispersion, co-infection and emergence of VUI-NP13 L in Rio Grande do Sul, we reaffirm the importance of establishing strict and effective social distancing measures to counter the spread of potentially more hazardous SARS-CoV-2 strains.

The complete gag gene from small ruminant lentiviruses (SRLV) encodes for a polyprotein of 55 kDa, known as p55gag. p55gag presents multiple antigenic epitopes, which can be recognized by antibodies, increasing the opportunity to detect SRLV-positive animals. Therefore, this polyprotein is considered an excellent candidate to use in diagnostic tests to detect antibodies against SRLV. Different studies have suggested that the selection of the recombinant antigen, which must be representative of the virus strains circulating in the test population, is crucial to avoid false negative results. Thus, the use of proteins from different viral strains isolated from goats or sheep of a given region or country may be a useful strategy to increase the ability to detect SRLV-infected animals. In the present study, the pMAL-p5X vector was used to express and purify p55gag (now called rp55gag for recombinant polyprotein 55 gag). The cloned gene was inserted downstream from the malE gene of Escherichia coli, which encodes a maltose-binding protein (MBP), resulting in the expression of an MBP fusion protein. The complete gag gene was amplified by RT-PCR. Finally, after digestion, the product was cloned into the pMAL-p5X vector and used to transform E. coli ER2325 cells. After the purification of MBP-rp55gag by affinity chromatography, the eluted fraction was observed by SDS-PAGE and Western Blot (WB). The WB was carried out with 85 serum samples from small ruminants previously analysed and compared by two commercial ELISAs. The results show that 76 of the serum samples were concordant with those by both ELISAs. Regarding the other nine serum samples, which showed discordant results between both ELISAs, were positive by WB. The results thus show that the rp55gag could be considered as an antigen in a confirmatory diagnostic assay to detect SRLV by WB. For this purpose, a future study with a high number of sera to determine the test specificity and sensitivity, using the p55gag of the circulating strain in Argentina will be necessary.

The open reading frame 8 (orf8) is an accessory protein of SARS-CoV-2. It has 121 amino acids with two genotypes, orf8L and orf8S. In this study, we overexpressed the orf8L and orf8S of SARS-CoV-2 as well as the orf8b of SARS-CoV to investigate their roles in the regulation of endoplasmic reticulum (ER) stress and the inhibition of interferon beta (IFNß) production. We found that the two genotypes of SARS-CoV-2 orf8 are capable of inducing ER stress without significant difference by triggering the activating transcription factor 6 (ATF6) and inositol-requiring enzymes 1 (IRE1) branches of the ER stress pathway. However, the third branch of ER stress pathway, i.e. the protein kinase-like ER kinase (PERK), was unaffected by the overexpression of SARS-CoV-2 orf8L or orf8S. Moreover, both orf8L and orf8S of SARS-CoV-2 are capable of down regulating the production of IFNß and interferon-stimulated genes (ISG), ISG15 and ISG56 induced by polyinosinic-polycytidylic acid (poly (I:C)). Moreover, we also found decreased nuclear translocation of Interferon regulatory factor 3 (IRF3), after overexpressing orf8L and orf8S induced by poly (I:C). Our data demonstrated that SARS-CoV-2 orf8 protein could induce ER stress by activating the ATF6 and IRE1 pathways, but not the PERK pathway, and functions as an interferon antagonist to inhibit the production of IFNß. However, these functions appeared not to be affected by the genotypes of SARS-CoV-2 orf8L and orf8S.

Chronic hepatitis C virus (cHCV) is a leading cause for liver cirrhosis (LC) and hepatocellular carcinoma (HCC) globally. So far, there is no optimal non-invasive biomarker for diagnosing HCV associated hepatic disorders. Circulatory miRNAs have drawn great attention as potential non-invasive biomarkers in various diseases. We quantified miR-221 and miR-542 levels in the plasma of 153 Egyptian patients (38 healthy controls (HC), 36 cHCV, 39 HCV-LC and 40 HCV mediated HCC groups) using qRT-PCR. All diseased groups exhibited significant upregulation in miR-221 expression (P < 0.001) with an increasing trend towards late stages (HCV-LC+HCV-HCC) as compared to early stages (cHCV). MiR-221 could significantly discriminate HCC patients from cHCV and HCV-LC with (AUC=0.698; P = 0.002) and (AUC=0.644; P = 0.032) respectively. Furthermore, miR-221 could significantly discriminate between HCC and non-HCC groups (AUC=0.670, P<0.001). HCV-LC & cHCV groups showed significant upregulation in miR-542 with remarkable downregulation in HCC group (P = 0.004). MiR-542 exhibited diagnostic power of (AUC=0.640; P = 0.044) and (AUC= 0.644; P = 0.040) for discriminating HCV-LC from HCC and cHCV groups respectively. Both miR-221 and miR-542 were significantly upregulated in cirrhotic group (HCV-LC) (P = 0.046 and P = 0.002 respectively) as compared to non-cirrhotic group (cHCV+HC). Combining both miRNAs in a panel significantly improved diagnostic performance as follows; HC and HCC (AUC=0.714, P < 0.001); HCC and LC (AUC=0.714, P = 0.001); HC and LC (AUC=0.710, P = 0.002) and also cHCV and HCC (AUC=0.672, P = 0.006). In conclusion, both miR-221 & miR-542 could stand as a standalone biomarker for staging various HCV associated disorders. Combining them would greatly enhance their diagnostic potential.

Identification of new recombinant HCV strains and positive selection sites are crucially important for the formulation of virus intervention measures. However, little is known about the recombinant variant information and positive selection sites of circulating HCV strains in mainland China. In this study, we systematically identified recombinant variants and positive selection sites of HCV in mainland China during the 2010-2019. Phylogenetic analysis results indicated that HCV-6 was one of the dominant genotypes in mainland China during 2010-2019, whereas genotypes 7 and 8 were not detected. Recombinant analysis based on 102 full-length genome sequences of Chinese epidemic strains of HCV identified four intra-genotypic recombinants (strains WYHCV286, GB28, GZ2983, and HCV156) and one inter-genotypic recombinant (strain HH075). Specifically, two breakpoints in the 5' UTR of two recombinants, the strains HH075 and WYHCV286, are rather unusual and has not been described before. Further, selection pressure analyses revealed five positive selective sites, which were located in the core, E2, and NS5B protein. Notably, positive selective sites in NS5B and core protein may be partially responsible for the drug resistance and immune evasion. To the best of our knowledge, this study firstly reported five specific intertypic and intratypic recombinants of Chinese epidemic strains of HCV, which highlight their significance for anti-HCV treatment and vaccine development.

A new canine picornavirus (CanPV) variant, designated as dog/SH1901/CHN/2019, was detected in a pool of various canine fecal samples in the mainland of China using a viral metagenomic analysis, and its nearly complete genome sequence was determined and analyzed. Sequence analyses revealed that it had a standard picornavirus genome organization, a type I internal ribosome entry site (IRES) in the 5'UTR. However, dog/SH1901/CHN/2019 has generated a serial of unique aa mutations and 7aa insertion when compared with the closely related CanPVs. Phylogenetic analysis and pairwise sequence comparisons based on the P1, 2C, 3C, and 3D protein sequences showed that dog/SH1901/ CHN/2019 was closely related to CanPV strains 244 F, 325 F and 6D, which clustered into an independent evolutionary clade and distantly related to CanPV strain A128thr of the genus Mischivirus, which indicated the unclassified CanPV strains may belong to a novel species or genus in the family Picornaviridae. This study extends our knowledge on the evolution and genetic diversity of CanPVs.

Knowledge of viral load is essential to formulate strategies for antiviral treatment, vaccination, and epidemiological control of COVID-19. Moreover, identification of patients with high viral loads can also be useful to understand risk factors such as age, comorbidities, severity of symptoms and hypoxia, to decide on the need for hospitalization. Several ongoing studies are analyzing viral load in different types of samples and evaluating its relationship with clinical outcomes and viral transmission pathways. However, in a great number of emerging studies, cycle threshold (Ct) values alone are often used as viral load indicators, which may be a mistake. In this study, we compared tracheal aspirate with nasopharyngeal swab samples obtained from critically ill COVID-19 patients and here we report how the raw Ct can lead to misinterpretation of results. Furthermore, based on analysis of nasopharyngeal swab samples we propose a method to reduce evaluation errors that could occur from using raw Ct data. Based on these findings, we show the impact that normalization of Ct values has on interpretation of SARS-CoV-2 viral load from different biological samples.

Avian H7N9 influenza virus, which emerged in 2013 China, had caused the fifth wave of peaks in 2016-2017. Gansu Province locate in western China far away from the epicenter of the virus, also detected cases in this wave. During the monitoring, five human cases with H7N9 virus infection, three cases in Jiuquan and two cases in Zhangye, were reported and investigated. A total of 88 environmental samples collected from March to June, in poultry farms and live poultry markets were H7N9 positive by real time RT-PCR assay. The two human viruses were identified as LPAI viruses, and phylogenetic analysis showed that the viruses might be introduced into Gansu by two distinct trade routes. Avian influenza H7N9virus posed a pandemic potential to threaten human health, and monitoring among birds and the environment should be strengthened.

The family Rhabdoviridae is one of the most ecological diverse groups of RNA viruses, with remarkable genome complexity and wide host range. Rhabdoviruses are discovered in many insect species, and insects, such as midges, mosquitoes, aphids and leafhoppers, act as crucial vectors for rhabdovirus transmission. Here, a novel rhabdovirus was identified in green rice leafhopper, Nephotettix cincticeps (Hemiptera: Cicadellidae), a common virus vector on rice. This virus was named as Nephotettix cincticeps negative-stranded RNA virus-1 (NcNSRV-1). The genome of NcNSRV-1 is 12,361 nucleotides in length, flanked by untranslated 3' leader and 5' trailer. The anti-sense viral genome consists of five major structural protein genes (N, P, M, G and L), which shares a typical architecture with the family Rhabdoviridae. An additional gene, P6, is interposed between G and L genes. NcNSRV-1 is phylogenetically clustered with the unclassified rhabdoviruses isolated from insects and exhibits low sequence identities with other viruses. The transcription regulatory sequences in NcNSRV-1 gene junctions were determined, revealing a unique transcription initiation sequence. In view of the phylogeny, sequence identity and genome organization, NcNSRV-1 is likely to be an insect rhabdovirus. Field surveys showed NcNSRV-1 was prevalent in the rice field populations of N. cincticeps in China.

Cytokine-inducible Srchomology2 (SH2)-containing protein (CIS) belongs to the suppressors of cytokine signaling (SOCS) protein family function as a negative feedback loop inhibiting cytokine signal transduction. J subgroup avian leukosis virus (ALV-J), a commonly-seen avian virus with a feature of immunosuppression, poses an unmeasurable threat to the poultry industry across the world. However, commercial medicines or vaccines are still no available for this virus. This study aims to evaluate the potential effect of chicken CIS in antiviral response and its role on ALV-J replication. The results showed that ALV-J strain SCAU-HN06 infection induced CIS expression in DF-1 cells, which was derived from chicken embryo free of endogenous avian sarcoma-leukosis virus (ASLV) like sequences. By overexpressing CIS, the expression of chicken type I interferon (IFN-I) and interferon-stimulated genes (ISGs; PKR, ZAP, CH25H, CCL4, IFIT5, and ISG12) were both suppressed. Meanwhile, data showed that CIS overexpression also increased viral yield. Interestingly, knockdown of CIS enhanced induction of IFN-I and ISGs and inhibited viral replication. Collectively, we proved that modulation of CIS expression not only affected SCAU-HN06 replication in vitro but also altered the expression of IFN-I and ISGs that act as an essential part of antiviral innate immune system. Our data provide a potential target for developing antiviral agents for ALV-J.