TNF-Mediated Inhibition of Classical Swine Fever Virus Replication Is IRF1-, NF-κB- and JAK/STAT Signaling-Dependent.

The sera from pigs infected with virulent classical swine fever virus (CSFV) contain substantial amounts of tumor necrosis factor (TNF), a prototype proinflammatory cytokine with pleiotropic activities. TNF limits the replication of CSFV in cell culture. In order to investigate the signaling involved in the antiviral activity of TNF, we employed small-molecule inhibitors to interfere specifically with JAK/STAT and NF-κB signaling pathways in near-to-primary endothelial PEDSV.15 cells. In addition, we knocked out selected factors of the interferon (IFN) induction and signaling pathways using CRISPR/Cas9. We found that the anti-CSFV effect of TNF was sensitive to JAK/STAT inhibitors, suggesting that TNF induces IFN signaling. Accordingly, we observed that the antiviral effect of TNF was dependent on intact type I IFN signaling as PEDSV.15 cells with the disrupted type I IFN receptor lost their capacity to limit the replication of CSFV after TNF treatment. Consequently, we examined whether TNF activates the type I IFN induction pathway. With genetically modified PEDSV.15 cells deficient in functional interferon regulatory factor 1 or 3 (IRF1 or IRF3), we observed that the anti-CSFV activity exhibited by TNF was dependent on IRF1, whereas IRF3 was dispensable. This was distinct from the lipopolysaccharide (LPS)-driven antiviral effect that relied on both IRF1 and IRF3. In agreement with the requirement of IRF1 to induce TNF- and LPS-mediated antiviral effects, intact IRF1 was also essential for TNF- and LPS-mediated induction of IFN-ß mRNA, while the activation of NF-κB was not dependent on IRF1. Nevertheless, NF-κB activation was essential for the TNF-mediated antiviral effect. Finally, we observed that CSFV failed to counteract the TNF-mediated induction of the IFN-ß mRNA in PEDSV.15 cells, suggesting that CSFV does not interfere with IRF1-dependent signaling. In summary, we report that the proinflammatory cytokine TNF limits the replication of CSFV in PEDSV.15 cells by specific induction of an IRF1-dependent antiviral type I IFN response.

Improved Antiviral Activity of Classical Swine Fever Virus-Targeted siRNA by Tetrahedral Framework Nucleic Acid-Enhanced Delivery.

DNA self-assembled nanostructures have been considered as effective vehicles for biomolecule delivery because of their excellent biocompatibility, cellular permeability, noncytotoxicity, and small size. Here, we report an efficient antiviral strategy with self-assembled tetrahedral framework nucleic acids (tFNAs) delivering small interfering RNA (t-siRNA) to silence classical swine fever virus (CSFV) gene in porcine host cells. In this study, two previously reported siRNAs, C3 and C6, specifically targeting the CSFV genome were selected and modified on tFNAs, respectively, and termed t-C3 and t-C6. Results indicate that t-C3 and t-C6 can inhibit the viral proliferation of CSFV in kidney derived porcine cells, PK-15, effectively and that inhibition was markedly stronger than free siRNA-C3 or siRNA-C6 only. In addition, the DNA nanostructure also has high cargo-carrying capacity, allowing to deliver multiple functional groups. To improve the antiviral ability of tFNAs, a dual-targeting DNA nanostructure t-C3-C6 was constructed and used to silence the CSFV gene in porcine host cells. This study found that t-C3-C6 can inhibit the viral release and replication, exhibiting outstanding anti-CSFV capabilities. Therefore, these dual-targeting tFNAs have great potential in virus therapy. This strategy not only provides a novel method to inhibit CSFV replication in porcine cells but also verifies that tFNAs are effective tools for delivery of antiviral elements, which have great application potential.

Curcumin inhibits classical swine fever virus replication by interfering with lipid metabolism.

Although previous reports have shown that Curcumin inhibits many viruses, including some important members of different genera of Flaviviridae family (Japanese encephalitis virus, dengue virus and hepatitis C virus), the antiviral activity of curcumin against Classical swine fever virus (CSFV), which belongs to Pestivirus genus, is still unclear. In this study, we found that curcumin inhibited CSFV replication in a dose-dependent manner, but had no effect on virus adsorption and entry. Furthermore, the results showed that curcumin inhibited the expression of FASN, one of the key enzymes of fatty acid synthesis pathway, thereby, causing the reduction of the production of LDs upon infection. To this end, we detected transcription factor 6 (ATF6), the key factor of regulating lipid metabolism along with other related molecules (CHOP and GPR78) and found that curcumin significantly impaired the gene synthesis of ATF6, while CSFV infection promoted ATF6 expression. Therefore, it is confirmed that curcumin inhibited CSFV replication by interfere lipid metabolism. In addition, our subsequent studies found that curcumin played an antiviral role by promoting the innate immune independent of NF-κB signaling pathway. Taken together, our finding highlights that curcumin is a potential candidate drug against CSFV for controlling CSF.

Broad neutralization of CSFV with novel monoclonal antibodies in vivo.

Classical swine fever is a highly contagious disease in China. Although vaccination against Classical swine fever virus (CSFV) has been widely carried out in China, CSFV cases still emerge in an endless stream. Therefore, it is necessary to take new antiviral measures to eliminate CSFV. Glycoprotein E2 of CSFV is the major vaccine candidate that confers protective immunity. Thus, in this study, a batch of neutralizing monoclonal antibodies (mAbs) against E2, as alternative antiviral strategies, were produced. Among them, mAbs 6D10, 8D8 and 3C12 presented neutralizing reactivity against CSFV in a dose-dependent manner. Based on truncated overlapping fragments of E2 and mutants, three linear neutralizing epitopes were identified highly conserved in various CSFV strains. Epitopes 8YRYAIS13 and 254HECLIG259 were reported for the first time. All the three epitopes are involved in virus internalization and attachment as shown in pre- or post-attachment neutralization. Recombinant polypeptides carrying epitopes successfully inhibit virus infection in PK-15 cells, indicating epitopes were located in receptor-binding domain (RBD). Further, both prophylactic and therapeutic functions of neutralizing antibody were evaluated in rabbits upon CSFV challenge, confirming the efficacy in vivo. These findings provide alternative antiviral strategies against CSFV and deepen the understanding in E2 function during virus entry.

MiR-140 inhibits classical swine fever virus replication by targeting Rab25 in swine umbilical vein endothelial cells.

Classical swine fever virus (CSFV) is one of the most important viral pathogens leading worldwide threats to pig industry. MicroRNAs (miRNAs) play important roles in regulating virus replication, but whether miRNAs affect CSFV infection is still poorly understood. In previous study, we identified four miRNAs that were down-regulated by CSFV in swine umbilical vein endothelial cells (SUVEC). In this study, miR-140, one of the most potently down-regulated genes was investigated. We found that the miRNA expression was significantly inhibited by CSFV infection. Subsequent studies revealed that miR-140 mimics significantly inhibited CSFV replication, while the inhibition of endogenous miR-140 enhanced CSFV replication. By using bioinformatics prediction, luciferase reporter system, real-time fluorescence quantitative PCR (RT-qPCR) and Western blot assays, we further demonstrated that miR-140 bind to the 3' UTR of Rab25 mRNA to regulate its expression. We also analyzed the expression pattern of Rab25 in SUVECs after CSFV infection. The results showed that CSFV infection induced Rab25 expression. Finally, Rab25 was found to promote CSFV replication. In conclusion, this study demonstrated that CSFV inhibits miR-140 expression and miR-140 inhibits replication by binding to host factor Rab25.

Salt inactivation of classical swine fever virus and African swine fever virus in porcine intestines confirms the existing in vitro casings model.

Natural casings, to be used as sausage containers, are being traded worldwide and may be contaminated with contagious viruses. Standard processing of such natural casings is by salt treatment with a duration of 30 days before shipment. Since information is lacking about the efficacy of these virus inactivation procedures, an in vitro 3D collagen matrix model, mimicking natural casings, was developed previously to determine the efficacy of salt to inactivate specific viruses. To validate this model, a comparison in vivo experiment was performed using intestines of pigs experimentally infected with African swine fever virus (ASFV) and classical swine fever virus (CSFV). Decimal reduction (D) values, were determined at 4 °C, 12 °C, 20 °C and 25 °C. The standard salt processing procedure showed an efficient inactivation of ASFV and CSFV over time in a temperature dependent way. Dintestine values of both viruses, treated with the standard salt treatment, were in line with the Dcollagen values. It was concluded that these results underline the suitability of the 3D collagen matrix model to determine virus inactivation and to replace animal experiments. Furthermore, an increase in storage time for standard salt processed casings derived from CSFV endemic regions is highly recommended for an efficient inactivation of CSFV.

U18666A inhibits classical swine fever virus replication through interference with intracellular cholesterol trafficking.

The level of cholesterol in host cells has been demonstrated to affect viral infection. Our previous studies showed that cholesterol-rich membrane rafts mediated the entry of classical swine fever virus (CSFV) into PK-15 or 3D4/21 cells, but the role of cholesterol post entry was still not clear. In this study, we found that CSFV replication before fusion was affected when the cholesterol trafficking in infected cells was disrupted using a cholesterol transport inhibitor, U18666A. Our data showed that U18666A affected both the fusion and replication steps in the life cycle of the virus, but not its binding and entry steps. The subsequent experiments confirmed that niemann-pick C1 (NPC1), a lysosomal membrane protein that helps cholesterol to leave the lysosome, was affected by U18666A, which led to the accumulation of cholesterol in lysosomes and inhibition of CSFV replication. Imipramine, a cationic hydrophobic amine similar to U18666A, also inhibited CSFV replication via similar mechanism. Surprisingly, the antiviral effect of U18666A was restored by the histone deacetylase inhibitor (HDACi), Vorinostat, which suggested that HDACi reverted the dysfunction of NPC1, and intra-cellular cholesterol accumulation disappeared and CSFV replicability resumed. Together, these data indicated that CSFV transformed from early endosome and late endosome into lysosome after endocytosis for further replication and that U18666A was a potential drug candidate for anti-pestivirus treatment.

Novel Uridine Glycoconjugates, Derivatives of 4-Aminophenyl 1-Thioglycosides, as Potential Antiviral Compounds.

A novel series of uridine glycoconjugates, derivatives of 4-aminophenyl 1-thioglycosides, was designed and synthesized. All compounds were evaluated in vitro for their antiviral activity against hepatitis C virus (HCV) and classical swine fever virus (CSFV), two important human and animal viral pathogens for which new or improved therapeutic options are needed. The antiviral activity of all synthesized compounds was confirmed using pseudo-plaque reduction assays in which a significant arrest of CSFV and HCV growth was observed in the presence of these compounds. Two of the synthesized compounds, 9 and 12, displayed a significant inhibitory effect on HCV and CSFV propagation with IC50 values of 4.9 and 13.5 µM for HCV and 4.2 and 4 µM for CSFV, respectively, with low cytotoxicity. Using various infection and replication models, we have shown that both compounds were able to significantly reduce viral genome replication by up to 90% with IC50 values in the low micromolar range. A structure activity analysis of the synthesized compounds showed that the high antiviral activity was attributed to the hydrophobicity of glycoconjugates and the introduction of elements capable to coordinate metal ions into the spacer connecting the sugar and uridine moiety, which can be useful in the development of new antiviral compounds in the future.

Porcine Viperin protein inhibits the replication of classical swine fever virus (CSFV) in vitro.

BACKGROUND: Classical swine fever virus (CSFV) is the causative pathogen of Classical swine fever (CSF), a highly contagious disease of swine. Viperin is one of the hundreds of interferon-stimulated genes (ISGs), and possesses a wide range of antiviral activities. The aim of this study was to explore whether porcine Viperin has the anti-CSFV activity. METHOD: The influences of CSFV infection on Viperin expression and Newcastle disease virus (NDV)/Pseudorabies virus (PRV)-induced Viperin expression were examined in 3D4/21 cells and porcine peripheral blood mononuclear cells (PBMCs). Porcine Viperin gene was amplified to generate cell line PK-Vi over-expressing Viperin. CSFV was inoculated in the cell lines and viral load was detected by qRT-PCR, virus titration and Western blot. The influence of Viperin expression on CSFV binding, entry and release in the cells was also examined. The co-localization of Viperin with CSFV and its proteins (E2, NS5B) was determined by confocal laser scanning microscopy test. Co-IP assay was performed to check the interaction of Viperin with CSFV proteins. RESULTS: CSFV infection could not induce Viperin expression in vitro while significantly inhibiting NDV/PRV-induced Viperin expression at 12, 24 and 48 h post infection (hpi; P < 0.05). The proliferation of CSFV in PK-Vi was significantly inhibited at 24, 48 and 72 hpi (P < 0.05), comparing with control cells (PK-C1 expressing EGFP). Virus in both cell culture supernatants and cell pellets were reduced equally. CSFV binding and entry in the cells were not interfered by Viperin expression. These results indicated its anti-CSFV function occurred during the genome and/or protein synthesis step. Confocal laser scanning microscopy test showed the Viperin-EGFP protein co-localized with CSFV E2 protein in CSFV infected PK-Vi cells. Further experiments indicated that Viperin protein co-localized with E2 and NS5B proteins of CSFV in the transfected 293 T cells. Furthermore, Co-IP assay confirmed the interaction of Viperin with E2 protein, but not NS5B. CONCLUSION: Porcine Viperin effectively inhibited CSFV replication in vitro, potentially via the interaction of Viperin with CSFV E2 protein in cytoplasm. The results provided foundation for further studies of the interaction of Viperin with CSFV and other viruses.

Novel thioglycosyl analogs of glycosyltransferase substrates as antiviral compounds against classical swine fever virus and hepatitis C virus.

Hepatitis C virus (HCV) and classical swine fever virus (CSFV) are important pathogens for which new therapeutic approaches are in high demand. Herein, we report the synthesis of newly designed thioglycosyl analogs of glycosyltransferase substrates which were evaluated using cell-based assays for cytotoxicity and antiviral activity against both viruses. The antiviral activity of synthesized compounds against CSFV and HCV was confirmed using pseudo-plaque reduction assays where a significant arrest of viral growth was observed in the presence of selected compounds. We showed that compounds 13 and 14 exerted the most significant inhibitory effect on in vitro CSFV and HCV infections in the series. Glycoconjugates 13 and 14 not only inhibited both viral propagation with IC50 values in low micromolar range, but efficiently suppressed the production of viral proteins in a dose-dependent manner. In addition, studies using in vitro HCV infection and replication models have shown that both compounds are able to significantly reduce viral genomic replication. We demonstrated that compounds 13 and 14 showed a strong inhibition, up to 90% of replication which inscribe them in the promising alternative approach for the development of new anti-CSFV and anti-HCV drugs.

CSFV proliferation is associated with GBF1 and Rab2.

The Golgi apparatus and its resident proteins are utilized and regulated by viruses to facilitate their proliferation. In this study, we investigated Classical swine fever virus (CSFV) proliferation when the function of the Golgi was disturbed. Golgi function was disturbed using chemical inhibitors, namely, brefeldin A (BFA) and golgicide A (GCA), and RNA interfering targets, such as the Golgi-specific BFA-resistance guanine nucleotide exchange factor 1 (GBF1) and Rab2 GTPases. CSFV proliferation was significantly inhibited during RNA replication and viral particle generation after BFA and GCA treatment. CSFV multiplication dynamics were retarded in cells transfected with GBF1 and Rab2 shRNA. Furthermore, CSFV proliferation was promoted by GBF1 and Rab2 overexpression using a lentiviral system. Hence, Golgi function is important for CSFV multiplication, and GBF1 and Rab2 participate in CSFV proliferation. Further studies must investigate Golgi-resident proteins to elucidate the mechanism underlying CSFV replication.

Identification of cleavage of NS5A of C-strain classical swine fever virus.

NS5A is a multifunctional non-structural protein of classical swine fever virus (CSFV) that plays an important role in viral replication, but how it exerts its functions is unknown. Here, we report the cleavage of NS5A of the vaccine C-strain, resulting in two truncated forms (b and c). Further experiments using calpain- and caspase-family-specific inhibitors, followed by a caspase-6-specific shRNAs and inhibitor, showed that the cleavage of C-strain NS5A to produce truncated form c is mediated by caspase-6, mapping to 272DTTD275, while the cleavage producing truncated form b is probably mediated by another unknown protease. shRNA-mediated downregulation of caspase-6 and blocking of enzyme activity in ST cells significantly impaired genome replication and virus production, indicating that NS5A cleavage is required for CSFV replication.

Treatment with interferon-alpha delays disease in swine infected with a highly virulent CSFV strain.

Interferon-alpha (IFNα) can effectively inhibit or abort a viral infection within the host. It has been reported that IFN induction and production is hindered during classical swine fever virus (CSFV) infection. Most of those studies have been performed in vitro, making it difficult to elucidate the actual role of IFNs during CSFV infection in swine. Here, we report the effect of IFNα treatment (delivered by a replication defective recombinant human adenovirus type 5, Ad5) in swine experimentally infected with highly virulent CSFV strain Brescia. Treatment with two different subtypes of IFNα delayed the appearance of CSF-related clinical signs and virus replication although it did not prevent lethal disease. This is the first report describing the effect of IFNα treatment during CSFV infection in swine.

Specific ligands for classical swine fever virus screened from landscape phage display library.

Classical swine fever (CSF) is a devastating infectious disease caused by classical swine fever virus (CSFV). The screening of CSFV-specific ligands is of great significance for diagnosis and treatment of CSF. Affinity selection from random peptide libraries is an efficient approach to discover ligands with high stability and specificity. Here, we screened phage ligands for the CSFV E2 protein from f8/8 landscape phage display library by biopanning and obtained four phage clones specific for the E2 protein of CSFV. Viral blocking assays indicated that the phage clone displaying the octapeptide sequence DRATSSNA remarkably inhibited the CSFV replication in PK-15 cells at a titer of 10(10) transduction units, as evidenced by significantly decreased viral RNA copies and viral titers. The phage-displayed E2-binding peptides have the potential to be developed as antivirals for CSF.

Generation of a recombinant classical swine fever virus stably expressing the firefly luciferase gene for quantitative antiviral assay.

Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a highly contagious swine disease leading to significant economic losses worldwide. Vaccines are widely used to control the disease, and no CSFV-specific antivirals are currently available. To facilitate anti-CSFV molecule discovery, we developed a reporter virus CSFV-N(pro)Fluc stably expressing the firefly luciferase (Fluc) gene in the N(pro) gene. The reporter virus enabled more sensitive and convenient detection of the N(pro) protein expression and the viral replication by luciferase reporter assay than by traditional methods. The CSFV N(pro) protein was detectable as early as 4.5h post-infection. As a proof-of-concept for its utility in rapid antiviral screening, this reporter virus was used to quantify anti-CSFV neutralizing antibodies of 50 swine sera and to assess 12 small interfering RNAs targeting different regions of the CSFV genome. The results were comparable to those obtained by traditional methods. Taken together, the reporter virus CSFV-N(pro)Fluc represents a useful tool for rapid and quantitative screening and evaluation of antivirals against CSFV.

Synthesis and antiviral activity of a novel glycosyl sulfoxide against classical swine fever virus.

A novel compound-2″,3″,4″,6″-tetra-O-acetyl-ß-d-galactopyranosyl-(1→4)-2',3',6'-tri-O-acetyl-1-thio-ß-d-glucopyranosyl-(5-nitro-2-pyridyl) sulfoxide-designated GP6 was synthesized and assayed for cytotoxicity and in vitro antiviral properties against classical swine fever virus (CSFV) in this study. We showed that the examined compound effectively arrested CSFV growth in swine kidney cells (SK6) at a 50% inhibitory concentration (IC50) of 5 ± 0.12 µg/ml without significant toxicity for mammalian cells. Moreover, GP6 reduced the viral E2 and E(rns) glycoproteins expression in a dose-dependent manner. We have excluded the possibility that the inhibitor acts at the replication step of virus life cycle as assessed by monitoring of RNA level in cells and culture medium of SK6 cells after single round of infection as a function of GP6 treatment. Using recombinant E(rns) and E2 proteins of classical swine fever virus produced in baculovirus expression system we have demonstrated that GP6 did not influence glycoprotein production and maturation in insect cells. In contrast to mammalian glycosylation pathway, insect cells support only the ER-dependent early steps of this process. Therefore, we concluded that the late steps of glycosylation process are probably the main targets of GP6. Due to the observed antiviral effect accompanied by low cytotoxicity, this inhibitor represents potential candidate for the development of antiviral agents for anti-flavivirus therapy. Further experiments are needed for investigating whether this compound can be used as a safe antiviral agent against other viruses from unrelated groups.

Substituted 2,6-bis(benzimidazol-2-yl)pyridines: a novel chemical class of pestivirus inhibitors that targets a hot spot for inhibition of pestivirus replication in the RNA-dependent RNA polymerase.

2,6-Bis(benzimidazol-2-yl)pyridine (BBP/CSFA-0) was identified in a CPE-based screening as a selective inhibitor of the in vitro bovine viral diarrhea virus (BVDV) replication. The EC50-values for the inhibition of BVDV-induced cytopathic (CPE) effect, viral RNA synthesis and the production of infectious virus were 0.3±0.1µM, 0.05±0.01µM and 0.3±0.04µM, respectively. Furthermore, BBP/CSFA-0 inhibits the in vitro replication of the classical swine fever virus (CSFV) with an EC50 of 0.33±0.25µM. BBP/CSFA-0 proved in vitro inactive against the hepatitis C virus, that belongs like BVDV and CSFV to the family of Flaviviridae. Modification of the substituents on the two 1H-benzimidazole groups of BBP resulted in analogues equipotent in anti-BVDV activity (EC50=0.7±0.1µM), devoid of cytotoxicity (S.I.=142). BBP resistant BVDV was selected for and was found to carry the I261M mutation in the viral RNA-dependent RNA polymerase (RdRp). Likewise, BBP-resistant CSFV was selected for; this variant carries either an I261N or a P262A mutation in NS5B. Molecular modeling revealed that I261 and P262 are located in a small cavity near the fingertip domain of the pestivirus polymerase. BBP-resistant BVDV and CSFV proved to be cross-resistant to earlier reported pestivirus inhibitors (BPIP, AG110 and LZ37) that are known to target the same region of the RdRp. BBP did not inhibit the in vitro activity of recombinant BVDV RdRp but inhibited the activity of BVDV replication complexes (RCs). BBP interacts likely with the fingertip of the pestivirus RdRp at the same position as BPIP, AG110 and LZ37. This indicates that this region is a "hot spot" for inhibition of pestivirus replication.

In vitro inhibition of the replication of classical swine fever virus by porcine Mx1 protein.

Classical swine fever virus (CSFV) is the causative pathogen of classical swine fever (CSF), a highly contagious disease of swine. Mx proteins are interferon-induced dynamin-like GTPases present in all vertebrates with a wide range of antiviral activities. Although Zhao et al. (2011) have reported that human MxA can inhibit CSFV replication, whether porcine Mx1 (poMx1) has anti-CSFV activity remains unknown. In this study, we generated a cell line designated PK-15/EGFP-poMx1 which expressed porcine Mx1 protein constitutively, and we observed that the proliferation of progeny virus in this cell line was significantly inhibited as measured by virus titration, indirect immune fluorescence assay, Q-PCR and Western blot. Furthermore, when PTD-poMx1 fusion protein expressed in Escherichia coli (Zhang et al., 2013) was used to treat CSFV-infected PK-15 cells, the results showed that PTD-poMx1 inhibited CSFV replication in a dose-dependent manner. Additionally, the proliferation of progeny virus was inhibited as measured by virus titration and Q-PCR. Overall, the results demonstrated that poMx1 effectively inhibited CSFV replication, suggesting that poMx1 may be a valuable therapeutic agent against CSFV infection.

Autophagy enhances the replication of classical swine fever virus in vitro.

Autophagy plays an important role in cellular responses to pathogens. However, the impact of the autophagy machinery on classical swine fever virus (CSFV) infection is not yet confirmed. In this study, we showed that CSFV infection significantly increases the number of autophagy-like vesicles in the cytoplasm of host cells at the ultrastructural level. We also found the formation of 2 ubiquitin-like conjugation systems upon virus infection, including LC3-I/LC3-II conversion and ATG12-ATG5 conjugation, which are considered important indicators of autophagy. Meanwhile, high expression of ATG5 and BECN1 was detected in CSFV-infected cells; conversely, degradation of SQSTM1 was observed by immunoblotting, suggesting that CSFV infection triggered a complete autophagic response, most likely by the NS5A protein. Furthermore, by confocal immunofluorescence analysis, we discovered that both envelope protein E2 and nonstructural protein NS5A colocalized with LC3 and CD63 during CSFV infection. Examination by immunoelectron microscopy further confirmed the colocalization of both E2 and NS5A proteins with autophagosome-like vesicles, indicating that CSFV utilizes the membranes of these vesicles for replication. Finally, we demonstrated that alteration of cellular autophagy by autophagy regulators and shRNAs affects progeny virus production. Collectively, these findings provide strong evidence that CSFV infection needs an autophagy pathway to enhance viral replication and maturity in host cells.

Approved and experimental countermeasures against pestiviral diseases: Bovine viral diarrhea, classical swine fever and border disease.

The pestiviruses, bovine viral diarrhea virus (BVDV), classical swine fever (CSFV) and border disease virus, are important livestock pathogens in many countries, but current vaccines do not completely prevent the spread of infection. Control of pestiviral diseases is especially difficult due to the constant viremia and viral shedding of persistently infected (PI) animals, which must be identified and eliminated to prevent disease transmission. Existing vaccines are limited by the delay between vaccination and the onset of protection, the difficulty of differentiating serologically between vaccinated and naturally infected animals and the need for broad vaccine cross-protection against diverse virus strains. Antiviral therapy could potentially supplement vaccination by providing immediate protection in the case of an outbreak. Numerous compounds with in vitro antiviral activity against BVDV have been identified through its role as a surrogate for hepatitis C virus. Fewer drugs active against CSFV have been identified, but many compounds that are effective against BVDV will likely inhibit CSFV, given their similar genomic sequences. While in vitro research has been promising, the paucity of efficacy studies in animals has hindered the commercial development of effective antiviral drugs against the pestiviruses. In this article, we summarize the clinical syndromes and routes of transmission of BVD, CSF and border disease, discuss currently approved vaccines, review efforts to develop antiviral therapies for use in outbreak control and suggest promising directions for future research.