The host protein CALCOCO2 interacts with bovine viral diarrhoea virus Npro, inhibiting type I interferon production and thereby promoting viral replication

Bovine viral diarrhoea-mucosal disease caused by bovine viral diarrhoea virus (BVDV) is a major infectious disease that affects the cattle industry. The nonstructural protein Npro of BVDV antagonizes the type I interferon (IFN-I) pathway, thereby escaping the host immune response. The exact mechanism by which Npro uses host proteins to inhibit IFN-I production is unclear. The host protein CALCOCO2 was identified as a binding partner of Npro using a yeast two-hybrid screen. The interaction between Npro and CALCOCO2 was confirmed by yeast co-transformation, co-immunoprecipitation assays, and GST pull-down assays. The stable overexpression of CALCOCO2 markedly promoted BVDV propagation, while the knockdown of CALCOCO2 significantly inhibited BVDV replication in MDBK cells. Interestingly, CALCOCO2 inhibited IFN-I and IFN-stimulated gene production in BVDV-infected cells. Ectopic expression of CALCOCO2 effectively reduced IRF3 protein levels via the proteasome pathway. CALCOCO2 was found to promote Npro-mediated ubiquitination degradation of IRF3 by interacting with IRF3. Our results demonstrate the molecular mechanism by which Npro recruits the CALCOCO2 protein to regulate IRF3 degradation to inhibit IFN-I production.

Bovine viral diarrhoea viruses from New Zealand belong predominantly to the BVDV-1a genotype

AIM

To determine which genotypes of bovine viral diarrhoea virus (BVDV) circulate among cattle in New Zealand.

METHODS

Samples comprised BVDV-1-positive sera sourced from submissions to veterinary diagnostic laboratories in 2019 (n = 25), 2020 (n = 59) and 2022 (n = 74) from both beef and dairy herds, as well as archival BVDV-1 isolates (n = 5). Fragments of the 5' untranslated region (5' UTR) and glycoprotein E2 coding sequence of the BVDV genome were amplified and sequenced. The sequences were aligned to each other and to international BVDV-1 sequences to determine their similarities and phylogenetic relationships. The 5' UTR sequences were also used to create genetic haplotype networks to determine if they were correlated with selected traits (location, type of farm, and year of collection).

RESULTS

The 5' UTR sequences from New Zealand BVDV were closely related to each other, with pairwise identities between 89% and 100%. All clustered together and were designated as BVDV-1a (n = 144) or BVDV-1c (n = 5). There was no evidence of a correlation between the 5' UTR sequence and the geographical origin within the country, year of collection or the type of farm. Partial E2 sequences from New Zealand BVDV (n = 76) showed 74-100% identity to each other and clustered in two main groups. The subtype assignment based on the E2 sequence was the same as based on the 5' UTR analysis. This is the first comprehensive analysis of genomic variability of contemporary New Zealand BVDV based on the analysis of the non-coding (5' UTR) and coding (E2) sequences.

CONCLUSIONS AND CLINICAL RELEVANCE

Knowledge of the diversity of the viruses circulating in the country is a prerequisite for the development of effective control strategies, including a selection of suitable vaccines. The data presented suggest that New Zealand BVDV are relatively homogeneous, which should facilitate eradication efforts including selection or development of the most suitable vaccines.

Specificity and sensitivity of an indirect fluorescent antibody test to detect antibodies against bovine viral diarrhea virus

Since being reported in 1979 and 2006, indirect fluorescent antibody (IFA) tests have not been reported to detect bovine viral diarrhea virus (BVDV) antibodies to our knowledge. Thus, we re-evaluated the efficacy and usefulness of IFA tests for BVDV serology. We tested 4 combinations of 2 antibody conjugates (fluorescein isothiocyanate [FITC]-conjugated rabbit IgG anti-bovine IgG; rabbit IgG F(ab')2 fragment anti-bovine IgG [F(ab')2 FITC-IgG]) and 2 washing solutions (PBS; carbonate-bicarbonate-buffered saline [CBBS]) to evaluate the specificity of an IFA test for BVDV. We compared the sensitivity of the optimal combination with virus neutralization (VN) tests and an ELISA, and compared IFA with VN titers against different genotype (subgenotype) strains. For the F(ab')2 FITC-IgG/CBBS combination, only 1 of the 156 (0.6%) 4-fold diluted cattle sera resulted in a nonspecific reaction; other combinations led to a much higher incidence (22.9-37.2%). For the F(ab')2 FITC-IgG/CBBS combination, IFA detection rates were identical (36 of 59) for BVDV1 and BVDV2 genotypes, and IFA titers against them were strongly correlated (r = 0.99). The antibody-detection rates of the IFA tests were almost identical to those of VN tests and the ELISA (κ: 0.96 and 0.89, respectively). The IFA titers against 4 strains (BVDV1a, BVDV1j, BVDV2a, and an unidentified strain) were similar, 1,024 to ≥4,096, although the VN titers were different. Thus, our IFA tests were specific and sensitive, and more useful than VN tests given that the IFA tests could evaluate the immune status of cattle using a representative strain, regardless of genotype (subgenotype).

Unveiling tetrahydroquinolines as promising BVDV entry inhibitors: Targeting the envelope protein

Bovine viral diarrhea virus (BVDV) is known to cause financial losses and decreased productivity in the cattle industry worldwide. Currently, there are no available antiviral treatments for effectively controlling BVDV infections in laboratories or farms. The BVDV envelope protein (E2) mediates receptor recognition on the cell surface and is required for fusion of virus and cell membranes after the endocytic uptake of the virus during the entry process. Therefore, E2 is an attractive target for the development of antiviral strategies. To identify BVDV antivirals targeting E2 function, we defined a binding site in silico located in domain IIIc at the interface between monomers in the disulfide linked dimer of E2. Employing a de novo design methodology to identify compounds with the potential to inhibit the E2 function, compound 9 emerged as a promising candidate with remarkable antiviral activity and minimal toxicity. In line with targeting of E2 function, compound 9 was found to block the virus entry into host cells. Furthermore, we demonstrated that compound 9 selectively binds to recombinant E2 in vitro. Molecular dynamics simulations (MD) allowed describing a possible interaction pattern between compound 9 and E2 and indicated that the S enantiomer of compound 9 may be responsible for the antiviral activity. Future research endeavors will focus on synthesizing enantiomerically pure compounds to further support these findings. These results highlight the usefulness of de novo design strategies to identify a novel class of BVDV inhibitors that block E2 function inhibiting virus entry into the host cell.

Uncommon bovine viral diarrhea virus subtype 1e associated with abortions in cattle in southern Brazil

We characterized bovine viral diarrhea virus (BVDV)-related abortions in cattle and identified the species and subgenotypes in the state of Santa Catarina, southern Brazil. Our RT-PCR assay was positive for BVDV in 5 fetuses from different farms; however, 3 of the 5 fetuses were also PCR-positive for Neospora caninum. In the 5 BVDV-positive fetuses, gross lesions included fetal mummification (1), hepatomegaly (1), subcutaneous edema (1), and perirenal edema (1). Predominant histologic lesions included epicarditis and mild-to-moderate lymphoplasmacytic myocarditis (5), mild multifocal lymphoplasmacytic interlobular pneumonia (4), nephrosis associated with moderate multifocal interstitial nephritis (1), moderate multifocal lymphoplasmacytic necrotic hepatitis (1), and mild multifocal lymphoplasmacytic meningitis (1). The amplification products from the Pestivirus 5'UTR region of 4 of the 5 fetuses had 96.3-100% similarity between fetal strains and reference strains. The samples were distributed into 2 branches of the phylogenetic tree; strains UDESC:01, UDESC:02, and UDESC:05 clustered in the BVDV-1e branch, uncommon in the Americas, and strain UDESC:04 clustered in the BVDV-2b branch. The three 1e strains had 96.9-97.4% similarity.

The activation of liver X receptors in Madin-Darby bovine kidney cells and mice restricts infection by bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is prevalent worldwide and is an important pathogen that represents a serious threat to the development of the cattle industry by causing significant economic losses. Liver X receptors (LXRs) are members of the nuclear receptor superfamily and have become attractive therapeutic targets for cardiovascular disease. In the present study, we found that LXRs in both Madin-Darby bovine kidney (MDBK) cells and mice were associated with BVDV infection. GW3965, an agonist for LXRs, significantly inhibited BVDV RNA and protein levels in MDBK cells. In vivo studies in a mouse model also confirmed the inhibitory role of GW3965 in BVDV replication and the ameliorating effect of GW3965 on pathological injury to the duodenum. In vitro investigations of the potential mechanisms involved showed that GW3965 significantly inhibited BVDV-induced increases in cholesterol levels and viral internalization. Furthermore, the antiviral activity of GW3965 was significantly reduced following cholesterol replenishment, thus demonstrating that cholesterol was involved in the resistance of GW3965 to BVDV replication. Further studies indicated the role of ATP-binding cassette transporter A1 (ABCA1) and cholesterol-25-hydroxylase (CH25H) in the antiviral activity of GW3965. We also demonstrated the significant antiviral effect of 25hydroxycholesterol (25HC), a product of the catalysis of cholesterol by CH25H. In addition, the anti-BVDV effects of demethoxycurcumin (DMC), cyanidin-3-O-glucoside (C3G), and saikosaponin-A (SSA), three natural agonizts of LXRs, were also confirmed in both MDBK cells and mice. However, the antiviral activities of these agents were weakened by SR9243, a synthetic inhibitor of LXRs. For the first time, our research demonstrated that the activation of LXRs can exert significant anti-BVDV effects in MDBK cells and mice.

Up-regulated lncRNA CYLD as a ceRNA of miR-2383 facilitates bovine viral diarrhea virus replication by promoting CYLD expression to counteract RIG-I-mediated type-I IFN production

Bovine viral diarrhea virus (BVDV) is one of the most important pathogens of cattle, causing numerous economic losses to the cattle industry. To date, many potential mechanisms of BVDV evading or subverting innate immunity are still unknown. In this study, an lnc-CYLD/miR-2383/CYLD axis involved in BVDV-host interactions was screened from RNA-seq-based co-expression networks analysis of long noncoding RNAs, microRNAs and mRNAs in BVDV-infected bovine cells, and underlying mechanisms of lnc-CYLD/miR-2383/CYLD axis regulating BVDV replication were explored. Results showed that BVDV-induced up-regulation of the lnc-CYLD competed for binding to the miR-2383, and then promoted CYLD expression, thereby inhibiting RIG-I-mediated type-I interferon (IFN) production, which was subsequently confirmed by treatment with lnc-CYLD overexpression and miR-2383 inhibitor. However, miR-2383 transfection and small interfering RNA-mediated lnc-CYLD knockdown inhibited CYLD expression and enhanced RIG-I-mediated type-I IFN production, inhibiting BVDV replication. In addition, interaction relationship between lnc-CYLD and miR-2383, and colocalization relationship of lnc-CYLD, miR-2383 and CYLD were confirmed by dual-luciferase assay and in situ hybridization assay. Conclusively, up-regulation of the lnc-CYLD as a competing endogenous RNA binds to the miR-2383 to reduce inhibitory effect of the miR-2383 on the CYLD expression, playing an important role in counteracting type-I IFN-dependent antiviral immunity to facilitate BVDV replication.

[Persistent form of bovine viral diarrhea]

The review provides an analysis of literature data on the persistent form of Bovine Viral diarrhea/Mucosal disease (BVD) and is focused on virus and host factors, including those related to immune response, that contribute the persistence of the virus. BVD is a cattle disease widespread throughout the world that causes significant economic damage to dairy and beef cattle. The disease is characterized by a variety of clinical signs, including damage to the digestive and respiratory organs, abortions, stillbirths and other failures of reproductive functions.

[Bovine viral diarrhea virus Erns protein expressed in Chinese hamster ovary cells and its immunogenicity analysis]

The aim of this study was to produce Erns protein of bovine viral diarrhea virus (BVDV) by using suspensively cultured CHO cells expression system and to analyze the immunogenicity of the purified Erns protein. In this study, the recombinant eukaryotic expression plasmid pcDNA3.1-BVDV-Erns was constructed based on the gene sequence of BVDV-1 NADL strain. The Erns protein was secreted and expressed in cells supernatant after transfecting the recombinant expression plasmid pcDNA3.1-BVDV-Erns into CHO cells. The expression and purification of the Erns protein was analyzed by SDS-PAGE, the reactivity was determined with anti-His monoclonal antibodies and BVDV positive serum with Western blotting. Immunogenicity analysis of the Erns protein was determined after immunizing New Zealand white rabbits, and the serum antibodies were tested by indirect ELISA (iELISA) and indirect immunofluorescence (IFA). The serum neutralizing titer of the immunized rabbits was determined by virus neutralization test. The concentration of the purified Erns protein was up to 0.886 mg/mL by BCA protein quantification kit. The results showed that the Erns protein could be detected with anti-His monoclonal antibodies and anti-BVDV sera. Serum antibodies could be detected by iELISA on the 7th day post-prime immunization, and the antibody level was maintained at a high titer until the 28th day post-immunization. The antibody titer was 1:128 000. Furthermore, the expression of the Erns protein in BVDV-infected MDBK cells could be detected with immunized rabbits sera by IFA. Moreover, antigen-specific neutralizing antibodies of 2.71 log10 was induced in rabbits. In this study, purified BVDV Erns protein was successfully produced using CHO suspension culture system, and the recombinant protein was proved to have a good immunogenicity, which may facilitate the development of BVD diagnosis method and novel subunit vaccine.

Novel genomic targets for proper subtyping of bovine viral diarrhea virus 1 (BVDV-1) and BVDV-2

Whole-genome phylogenetic analysis, the most suitable strategy for subtyping bovine viral diarrhea virus 1 (BVDV-1) and BVDV-2, is not feasible for many laboratories. Consequently, BVDV isolates/strains have been frequently subtyped based on analysis of single genomic regions, mainly the 5' untranslated region (UTR). This approach, however, may lead to inaccurate and/or poorly statistically supported viral classification. Herein, we describe novel primer sets whose amplicons may be easily sequenced and used for BVDV subtyping. Initially, genomic regions previously described as the most suitable targets for BVDV subtyping were analyzed for design of high-coverage primers. The putative amplicons were analyzed in silico for their suitability to reproduce the phylogenetic classification of 118 BVDV-1 and 88 BVDV-2 complete/near-complete genomes (CNCGs) (GenBank). This analysis was also performed considering the region amplifiable by primers HCV90-368, 324-326 and BP189-389 (5'UTR), which have been used for BVDV diagnosis and/or classification. After confirming the agreement between the analyses of our primers' amplicon versus the CNCGs, we optimized the RT-PCRs and evaluated their performance for amplification of BVDV isolates/strains (n = 35 for BVDV-1; n = 33 for BVDV-2). Among the potential targets for BVDV subtyping, we designed high-coverage primers for NS3-NS4A (BVDV-1) (526 bp amplicon) and NS5B (BVDV-2) (728 bp). The classification based on these regions fully reproduced the subtyping of all CNCGs. On the other hand, subtyping based on the putative amplicons from primers HCV90-368, 324-326 and BP189-389 showed disagreements in relation the CNCG analysis. The NS3-NS4A and NS5B primers also allowed the amplification of all BVDV isolates/strains tested. Finally, we suggest the use of these primers in future phylogenetic and epidemiological studies of BVDVs.

Multivariate Analysis as a Method to Evaluate Antigenic Relationships between Bovine Viral Diarrhea Virus 1b Isolates and Vaccine Strains

The antigenicity of bovine viral diarrhea virus (BVDV) has been evaluated using virus-neutralizing titer data analyzed by principal component analysis (PCA) and has demonstrated numerous isolates to be antigenically divergent from US vaccine strains. The lack of BVDV-1b strains in currently licensed vaccines has raised concerns regarding the lack of protection against BVDV-1b field strains. The aim of this study was to evaluate the antigenic diversity of BVDV-1b strains and better understand the breadth of antigenic relatedness using BVDV-1b antisera and antisera from vaccine strains. Results from this analysis demonstrate the antigenic diversity observed among BVDV-1b isolates and genetic assignment into the BVDV-1b subgenotype is not representative of antigenic relatedness. This is demonstrated by BVDV-1b isolates (2280N, SNc, Illc, MSU, and 2337) observed to be as antigenically dissimilar as BVDV-2a isolates when using BVDV-1b antisera. Additionally, when BVDV-1a vaccine antisera was used for comparisons, a greater percentage of BVDV-1b isolates clustered with BVDV-1a vaccine strains as part of PC1, suggesting antigenic relatedness and potentially partial protection. Collectively, data from this study would suggest that while most BVDV-1b isolates are antigenically similar, there are antigenically dissimilar BVDV-1b isolates as determined by the lack of cross-reactivity, which may contribute to the lack of protection.

Packaging defects in pestiviral NS4A can be compensated by mutations in NS2 and NS3

The non-structural (NS) proteins of the Flaviviridae members play a dual role in genome replication and virion morphogenesis. For pestiviruses, like bovine viral diarrhea virus, the NS2-3 region and its processing by the NS2 autoprotease is of particular importance. While uncleaved NS2-3 in complex with NS4A is essential for virion assembly, it cannot replace free NS3/4A in the viral replicase. Furthermore, surface interactions between NS3 and the C-terminal cytosolic domain of NS4A were shown to serve as a molecular switch between RNA replication and virion morphogenesis. To further characterize the functionality of NS4A, we performed an alanine-scanning mutagenesis of two NS4A regions, a short highly conserved cytoplasmic linker downstream of the transmembrane domain and the C-terminal domain. NS4A residues critical for polyprotein processing, RNA replication, and/or virion morphogenesis were identified. Three double-alanine mutants, two in the linker region and one close to the C-terminus of NS4A, showed a selective effect on virion assembly. All three packaging defective mutants could be rescued by a selected set of two second-site mutations, located in NS2 and NS3, respectively. This phenotype was additionally confirmed by complementation studies providing the NS2-3/4A packaging molecules containing the rescue mutations in trans. This indicates that the linker region and the cytosolic C-terminal part of NS4A are critical for the formation of protein complexes required for virion morphogenesis. The ability of the identified sets of second-site mutations in NS2-3 to compensate for diverse NS4A defects highlights a surprising functional flexibility for pestiviral NS proteins. IMPORTANCE Positive-strand RNA viruses have a limited coding capacity due to their rather small genome size. To overcome this constraint, viral proteins often exhibit multiple functions that come into play at different stages during the viral replication cycle. The molecular basis for this multifunctionality is often unknown. For the bovine viral diarrhea virus, the non-structural protein (NS) 4A functions as an NS3 protease cofactor, a replicase building block, and a component in virion morphogenesis. Here, we identified the critical amino acids of its C-terminal cytosolic region involved in those processes and show that second-site mutations in NS2 and NS3 can compensate for diverse NS4A defects in virion morphogenesis. The ability to evolve alternative functional solutions by gain-of-function mutations highlights the astounding plasticity of the pestiviral system.

First report of bovine viral diarrhea virus subgenotypes 1d and 1e in southern Chile

Bovine viral diarrhea virus (BVDV) affects cattle worldwide causing severe productive and economic loss. In this study, we investigated the subgenotypes of BVDV circulating in cattle samples from the Aysén region, an active cattle breeding area located in southern Chile. Partial amplification of the 5' untranslated region (UTR) was performed by polymerase chain reaction (PCR), and twelve samples were analyzed by Sanger sequencing and phylogenetic analysis. Eight samples were identified as belonging to Pestivirus bovis subgenotype 1e, three to 1-b, and one to 1-d. The phylogenetic analyses performed revealed a marked distance between these now-identified strains and those previously reported in the country. These findings support the need to continually expand the analysis of the variability of the viral phylogeny for the currently circulating BVDV strains and to update the vaccines recommended for this livestock area and surrounding areas.

Molecular and serological survey of bovine viral diarrhea virus infection in cattle in Kazakhstan

The aim of this study was to estimate the occurrence of bovine viral diarrhea virus (BVDV) infection and to assess the population immunity in cattle vaccinated against BVDV in different regions of Kazakhstan. Cattle samples were collected in 12 oblasts (43 districts) of Kazakhstan. A total of 2477 cattle from 114 herds and 21 Bukhara deer (Cervus elaphus bactrianus) were examined by ELISA and conventional RT-PCR. Univariate and multivariate logistic regression analysis was performed to identify risk factors associated with BVDV infection in the country. In total, antibodies against BVDV were found in 79.3% (1965/2477) of all the animals and 92.1% (105/114) of all the herds examined. Seroprevalence in unvaccinated and vaccinated animals was 48.6% (447/920) and 98.7% (1391/1410), respectively. Seroprevalence in deer was 19.1% (4/21). The BVDV RNA was detected in six unvaccinated cattle (0.2%). Sequence analysis of the 5'-untranslated region demonstrated that four of the detected strains belonged to BVDV-1 and two strains to BVDV-2. Regression analysis revealed that age, production type, housing method, farm size, and geographic location were risk factors for BVDV infection in cattle in Kazakhstan. The present data confirm circulation of BVDV-1 and BVDV-2 in Kazakhstan and highlight the need to improve strategies for prevention and control of BVDV infection in the country.

Genomic evolution of bovine viral diarrhea virus based on complete genome and individual gene analyses

Bovine viral diarrhea virus (BVDV) genome consists of a single-stranded, positive-sense RNA with high genetic diversity. In the last years, significant progress has been achieved in BVDV knowledge evolution through phylodynamic analysis based on the partial 5'UTR sequences, whereas a few studies have used other genes or the complete coding sequence (CDS). However, no research has evaluated and compared BVDV evolutionary history based on the complete genome (CG), CDS, and individual genes. In this study, phylodynamic analyses were carried out with BVDV-1 (Pestivirus A) and BVDV-2 (Pestivirus B) CG sequences available on the GenBank database and each genomic region: CDS, UTRs, and individual genes. In comparison to the CG, the estimations for both BVDV species varied according to the dataset used, pointing out the importance of considering the analyzed genomic region when concluding. This study may provide new insight into BVDV evolution history while highlighting the need to increase the available BVDV CG sequences to perform more comprehensive phylodynamic studies in the future.

Different impact of bovine complement regulatory protein 46 (CD46bov) as a cellular receptor for members of the species Pestivirus H and Pestivirus G

The genus Pestivirus within the family Flaviviridae comprises highly relevant animal pathogens such as bovine viral diarrhoea virus 1 and 2 (BVDV-1 and -2) classified into the two species Pestivirus A and Pestivirus B, respectively. First described in 2004, HoBi-like pestiviruses (HoBiPeV) represent emerging bovine pathogens that belong to a separate species (Pestivirus H), but share many similarities with BVDV-1 and -2. Additionally, two giraffe pestivirus (GPeV) strains both originating from Kenya represent another distinct species (Pestivirus G), whose members replicate very efficiently in bovine cells. In this study, we investigated the role of bovine complement regulatory protein 46 (CD46bov), the receptor of BVDV-1 and -2, in the entry of HoBiPeV and GPeV. For this purpose, bovine CD46-knockout and CD46-rescue cell lines were generated by CRISPR/Cas9 technology and subsequent trans-complementation, respectively. Our results provide strong evidence that the impact of CD46bov differs between viruses belonging to Pestivirus H and viruses representing Pestivirus G: CD46bov revealed to be a major cellular entry factor for HoBiPeV strain HaVi-20. In contrast, GPeV strain PG-2 presented as largely independent of CD46bov, suggesting a different entry mechanism involving other molecular determinants which remain to be identified. In addition, we demonstrated that, similar to BVDV-1 and -2, virus isolates of both Pestivirus H and Pestivirus G are able to adapt to cell culture conditions by using heparan sulfate to enter the host cell. In conclusion, our findings show that different bovine pestiviruses use diverse mechanisms of host cell entry.

Quercetin Inhibits Hsp70 Blocking of Bovine Viral Diarrhea Virus Infection and Replication in the Early Stage of Virus Infection

Bovine viral diarrhea virus (BVDV), a positive-strand RNA virus of the genus Pestivirus in the Flaviviridae family, is the causative agent of viral diarrheal disease in bovine. BVDV has been used as a surrogate model for the hepatitis C virus (HCV) to evaluate the efficacy of antiviral drugs. The plant flavonol quercetin causes multiple health-promoting effects in humans and animals. It can be made into a variety of additives, and it exerts a variety of immunomodulatory effects with the potential to be used as an antiviral agent. However, quercetin's antiviral effect and mechanism of action on BVDV are still unclear. Therefore, this study was designed to evaluate quercetin's effect on BVDV virus replication in vitro and in vivo and elucidate its mechanism of action. A CCK-8 kit was used to analyze the toxicity of the quercetin to the MDBK cells. Western blot, qRT-PCR, TCID₅₀, and histological analysis were used to determine the mechanism of quercetin's anti-BVDV activity. An oxidative stress kit was used to evaluate the effects of quercetin on ROS, antioxidant enzymes, and MDA indexes. The effect of quercetin on IL-2 and IFN-γ in the serum of mice was determined by using an ELISA kit. The results showed that quercetin inhibits Hsp70, blocks BVDV infection in the early stage of virus infection and inhibits BVDV replication by inhibiting oxidative stress or ERK phosphorylation. In addition, quercetin alleviated the decrease in IFN-γ and IL-2 in the serum of BVDV-infected mice. Quercetin ameliorated BVDV-induced histopathological changes. In summary, this study demonstrated for the first time the role of Hsp70 in BVDV infection and the potential application of quercetin in treating BVDV infection.

Recombinant Bovine Herpesvirus Type I Expressing the Bovine Viral Diarrhea Virus E2 Protein Could Effectively Prevent Infection by Two Viruses

Bovine respiratory disease complex (BRDC) is a comprehensive disease in cattle caused by various viral and bacterial infections. Among them, bovine herpesvirus type I (BoHV−1) and bovine viral diarrhea virus (BVDV) play important roles and have caused huge financial losses for the cattle industry worldwide. At present, vaccines against BRDC include trivalent attenuated BoHV−1, BVDV−1, and BVDV−2 live vaccines, BoHV−1 live attenuated vaccines, and BoHV−1/BVDV bivalent live attenuated vaccines, which have limitations in terms of their safety and efficacy. To solve these problems, we optimized the codon of the BVDV−1 E2 gene, added the signal peptide sequence of the BoHV−1 gD gene, expressed double BVDV−1 E2 glycoproteins in tandem at the BoHV−1 gE gene site, and constructed a BoHV−1 genetics-engineered vectored vaccine with gE gene deletion, named BoHV−1 gE/E2−Linker−E2⁺ and BoHV−1 ΔgE. This study compared the protective effects in BoHV−1, BoHV−1 ΔgE, BoHV−1 gE/E2−Linker−E2⁺, and BVDV−1 inactivated antigen immunized guinea pigs and calves. The results showed that BoHV−1 gE/E2−Linker−E2⁺ could successfully induce guinea pigs and calves to produce specific neutralizing antibodies against BVDV−1. In addition, after BoHV−1 and BVDV−1 challenges, BoHV−1 gE/E2−Linker−E2⁺ can produce a specific neutralizing antibody response against BoHV−1 and BVDV−1 infections. Calves immunized with this type of virus can be distinguished as either vaccinated animals (gE^-) or naturally infected animals (gE⁺). In summary, our data suggest that BoHV−1 gE/E2−Linker−E2⁺ and BoHV−1 ΔgE have great potential to prevent BVDV−1 or BoHV−1 infection.

Mechanism of drug resistance of BVDV induced by F224S mutation in RdRp: A case study of VP32947

Bovine viral diarrhea virus (BVDV) is an enveloped virus with an RNA genome, causing serious economic losses to the areas dominated by livestock industry. Currently, although several compounds with biological activities of inhibiting virus replication have been reported, amino acid mutations (especially F224S mutation) frequently occurring in the RNA-dependent RNA polymerase (RdRp) have greatly reduce their value of further research. In this study, we introduced an effective and rapid in silico strategy to explore the differences in the binding modes of VP32947 between the wild/mutant-type RdRp at the molecular level, and further explained the main reasons for the variations in the inhibitory activities of VP32947 against the two types of enzymes. Firstly, the binding site of VP32947 in the finger domain was determined based on the previously reported experimental data, and the initial conformation of VP32947 in the wild RdRp was constructed using molecular docking. Then, the mutant research system was obtained directly by artificial mutation strategy. Afterwards, the built research systems were subjected to microsecond-timescale molecular dynamic simulation, and the conformational and energic profile analyses were performed according to the simulation trajectories. It was found that after 1 μs simulation, VP32947 in the mutant system was transferred to the left side of Loop α, and its interactions with the residues in the loop region were weakened. However, VP32947 in the wild system remained at the right side of Loop α, and could have a good fit with the sub-pocket formed by F224, I261, P262, N264, S532, which was conducive to maintaining its stable binding conformation in the wild RdRp. The illustration of the difference in the binding mechanisms of VP32947 in the wild/mutant RdRp would provide a theoretical basis for the rational design of innovative inhibitors based on the enzyme.

Limitations of bacterial culture, viral PCR, and tulathromycin susceptibility from upper respiratory tract samples in predicting clinical outcome of tulathromycin control or treatment of bovine respiratory disease in high-risk feeder heifers

A cross-sectional prospective cohort study including 1026 heifers administered tulathromycin due to high risk of clinical signs of bovine respiratory disease (BRD), measured poor association between BRD clinical outcomes and results of bacterial culture and tulathromycin susceptibility from BRD isolates of deep nasopharyngeal swabs (DNS) and adequate association with viral polymerase chain reaction (PCR) results from nasal swabs. Isolation rates from DNS collected on day-0 and at 1st BRD-treatment respectively were: Mannheimia haemolytica (10.9% & 34.1%); Pasteurella multocida (10.4% & 7.4%); Mycoplasma bovis (1.0% & 36.6%); and Histophilus somni (0.7% & 6.3%). Prevalence of BRD viral nucleic acid on nasal swabs collected exclusively at 1st BRD-treatment were: bovine parainfluenza virus type-3 (bPIV-3) 34.1%; bovine viral diarrhea virus (BVDV) 26.3%; bovine herpes virus type-1 (BHV-1) 10.8%; and bovine respiratory syncytial virus (BRSV) 54.1%. Increased relative risk, at 95% confidence intervals, of 1st BRD-treatment failure was associated with positive viral PCR results: BVDV 1.39 (1.17-1.66), bPIV-3 1.26 (1.06-1.51), BHV-1 1.52 (1.25-1.83), and BRSV 1.35 (1.11-1.63) from nasal swabs collected at 1st BRD-treatment and culture of M. haemolytica 1.23 (1.00-1.51) from DNS collected at day-0. However, in this population of high-risk feeder heifers, the predictive values of susceptible and resistant isolates had inadequate association with BRD clinical outcome. These results indicate, that using tulathromycin susceptibility testing of isolates of M. haemolytica or P. multocida from DNS collected on arrival or at 1st BRD-treatment to evaluate tulathromycin clinical efficacy, is unreliable.

Viruses in Bovine Respiratory Disease in North America: Knowledge Advances Using Genomic Testing

Advances in viral detection in bovine respiratory disease (BRD) have resulted from advances in viral sequencing of respiratory tract samples. New viruses detected include influenza D virus, bovine coronavirus, bovine rhinitis A, bovine rhinitis B virus, and others. Serosurveys demonstrate widespread presence of some of these viruses in North American cattle. These viruses sometimes cause disease after animal challenge, and some have been found in BRD cases more frequently than in healthy cattle. Continued work is needed to develop reagents for identification of new viruses, to confirm their pathogenicity, and to determine whether vaccines have a place in their control.

Bovine viral diarrhoea virus loses quasispecies diversity rapidly in culture

Bovine viral diarrhoea (BVD) is an important disease of cattle, with significant impacts on animal health and welfare. The wide host range of the causative pestiviruses may lead to formation of virus reservoirs in other ruminant or wildlife species, presenting a concern for the long-term success of BVD eradication campaigns. It is likely that the quasispecies nature of these RNA viruses contributes to their interspecies transmission by providing genetic plasticity. Understanding the spectrum of sequence variants present in persistently infected (PI) animals is, therefore, essential for studies of virus transmission. To analyse quasispecies diversity without amplification bias, we extracted viral RNA from the serum of a PI cow, and from cell culture fluid after three passages of the same virus in culture, to produce cDNA without amplification. Sequencing of this material using Illumina 250 bp paired-read technology produced full-length virus consensus sequences from both sources and demonstrated the quasispecies diversity of this pestivirus A genotype 1a field strain within serum and after culture. We report the distribution and diversity of over 800 SNPs and provide evidence for a loss of diversity after only three passages in cell culture, implying that cultured viruses cannot be used to understand quasispecies diversity and may not provide reliable molecular markers for source tracing or transmission studies. Additionally, both serum and cultured viruses could be sequenced as a set of 25 overlapping PCR amplicons that demonstrated the same consensus sequences and the presence of many of the same quasispecies variants. The observation that aspects of the quasispecies structure revealed by massively parallel sequencing are also detected after PCR and Sanger sequencing suggests that this approach may be useful for small or difficult to analyse samples.

Quinolinecarboxamides Inhibit the Replication of the Bovine Viral Diarrhea Virus by Targeting a Hot Spot for the Inhibition of Pestivirus Replication in the RNA-Dependent RNA Polymerase

The bovine viral diarrhea virus (BVDV), a pestivirus from the family of Flaviviridae is ubiquitous and causes a range of clinical manifestations in livestock, mainly cattle. Two quinolinecarboxamide analogues were identified in a CPE-based screening effort, as selective inhibitors of the in vitro bovine viral diarrhea virus (BVDV) replication, i.e., TO505-6180/CSFCI (average EC₅₀ = 0.07 µM, SD = 0.02 µM, CC₅₀ > 100 µM) and TO502-2403/CSFCII (average EC₅₀ = 0.2 µM, SD = 0.06 µM, CC₅₀ > 100 µM). The initial antiviral activity observed for both hits against BVDV was corroborated by measuring the inhibitory effect on viral RNA synthesis and the production of infectious virus. Modification of the substituents on the quinolinecarboxamide scaffold resulted in analogues that proved about 7-fold more potent (average EC₅₀ = 0.03 with a SD = 0.01 µM) and that were devoid of cellular toxicity, for the concentration range tested (SI = 3333). CSFCII resistant BVDV variants were selected and were found to carry the F224P mutation in the viral RNA-dependent RNA polymerase (RdRp), whereas CSFCI resistant BVDV carried two mutations in the same region of the RdRp, i.e., N264D and F224Y. Likewise, molecular modeling revealed that F224P/Y and N264D are located in a small cavity near the fingertip domain of the pestivirus polymerase. CSFC-resistant BVDV proved to be cross-resistant to earlier reported pestivirus inhibitors (BPIP, AG110, LZ37, and BBP) that are known to target the same region of the RdRp. CSFC analogues did not inhibit the in vitro activity of recombinant BVDV RdRp but inhibited the activity of BVDV replication complexes (RCs). CSFC analogues likely interact with the fingertip of the pestivirus RdRp at the same position as BPIP, AG110, LZ37, and BBP. This indicates that this region is a “hot spot” for the inhibition of pestivirus replication.

Real Time Analysis of Bovine Viral Diarrhea Virus (BVDV) Infection and Its Dependence on Bovine CD46

Virus attachment and entry is a complex interplay of viral and cellular interaction partners. Employing bovine viral diarrhea virus (BVDV) encoding an mCherry-E2 fusion protein (BVDVE2-mCherry), being the first genetically labelled member of the family Flaviviridae applicable for the analysis of virus particles, the early events of infection-attachment, particle surface transport, and endocytosis-were monitored to better understand the mechanisms underlying virus entry and their dependence on the virus receptor, bovine CD46. The analysis of 801 tracks on the surface of SK6 cells inducibly expressing fluorophore labelled bovine CD46 (CD46fluo) demonstrated the presence of directed, diffusive, and confined motion. 26 entry events could be identified, with the majority being associated with a CD46fluo positive structure during endocytosis and occurring more than 20 min after virus addition. Deletion of the CD46fluo E2 binding domain (CD46fluo∆E2bind) did not affect the types of motions observed on the cell surface but resulted in a decreased number of observable entry events (2 out of 1081 tracks). Mean squared displacement analysis revealed a significantly increased velocity of particle transport for directed motions on CD46fluo∆E2bind expressing cells in comparison to CD46fluo. These results indicate that the presence of bovine CD46 is only affecting the speed of directed transport, but otherwise not influencing BVDV cell surface motility. Instead, bovine CD46 seems to be an important factor during uptake, suggesting the presence of additional cellular proteins interacting with the virus which are able to support its transport on the virus surface.

Bioprocess optimization for purification of chimeric VLP displaying BVDV E2 antigens produced in yeast Hansenula polymorpha

Chimeric virus-like particles (VLP) are known as promising tools in the development of safe and effective subunit vaccines. Recently, a technology platform to produce VLP based on the small surface protein (dS) of the duck hepatitis B virus was established. In this study, chimeric VLP were investigated displaying the 195 N-terminal amino acids derived from the glycoprotein E2 of the bovine viral diarrhea virus (BVDV) on their surface. Isolation of the VLP from methylotrophic yeast Hansenula polymorpha was allowed upon co-expression of wild-type dS and a fusion protein composed of the BVDV-derived antigen N-terminally fused to the dS. It was shown the VLP could be purified by a process adapted from the production of a recombinant hepatitis B VLP vaccine. However, the process essentially depended on costly ultracentrifugation which is critical for low cost production. In novel process variants, this step was avoided after modification of the initial batch capture step, the introduction of a precipitation step and adjusting the ion exchange chromatography. The product yield could be improved by almost factor 8 to 93 ± 12 mg VLP protein per 100 g dry cell weight while keeping similar product purity and antigenicity. This allows scalable and cost efficient VLP production.

Genotyping of Pestivirus A (Bovine Viral Diarrhea Virus 1) detected in faeces and in other specimens of domestic and wild ruminants at the wildlife-livestock interface

Pestiviruses are widespread in the world among ungulates and infect both domestic and wild animals causing severe economic losses in livestock. Bovine Viral Diarrhea Virus type 1 (BVDV-1), now re-designated as Pestivirus A, causes diseases mainly in cattle, while few data are available about infection in wild ruminants and about the role of these animals in viral maintenance and spread. In order to investigate BVDV-1 infection in domestic and wild ruminants, especially at the wildlife/livestock interface, bulk tank milk from dairy cattle and sheep and spleen from red deer, roe deer and fallow deer were analysed. Furthermore, faecal samples from Apennine chamois and from wild deer were evaluated as a suitable sample for detecting and genotyping pestiviruses. BVDV-1 RNA was found in all animal species tested but not sheep. Genotyping based on partial 5'UTR and N^pro sequences detected BVDV-1a in samples from Apennine chamois, red deer, roe deer and pasture-raised cattle, while BVDV-1c was found in a faecal sample from Apennine chamois and in a spleen sample from roe deer. For the first time BVDV-1 RNA was found and genotyped from faecal samples of wild ruminants and of cattle. BVDV-1a detection in Apennine chamois, red deer, roe deer and pasture-raised cattle suggests that the eventuality of viral transmission at the wildlife/livestock interface should be carefully evaluated. BVDV subgenotype 1c was found for the first time in roe deer and Apennine chamois in Central Italy, therefore the epidemiological role of these animals and the viral ecology should be further investigated.

Bovine viral diarrhea in captive Rocky Mountain bighorn sheep associated with administration of a contaminated modified-live bluetongue virus vaccine

In late summer 2017, we observed acute, fatal cases of bovine viral diarrhea in captive Rocky Mountain bighorn sheep ( Ovis canadensis canadensis) in Colorado following use of a contaminated modified-live bluetongue virus vaccine. Following vaccination, at least 14 of 28 (50%) vaccinated bighorn sheep developed hemorrhagic diarrhea, and 6 of 28 (21%) vaccinated bighorn sheep died. Autopsy findings were predominantly necroulcerative-to-necrohemorrhagic gastrointestinal lesions. Less frequent lesions included suffusive hemorrhages of serosal surfaces of abdominal viscera, and lymphoid necrosis in gut-associated lymphoid tissues. All of the 6 bighorn sheep that died were positive on real-time PCR (rtPCR) for bovine viral diarrhea virus (BVDV) in multiple tissues. Seroconversion to BVDV-1 and immunohistochemistry for BVDV in affected tissues confirmed rtPCR results. Next-generation sequencing confirmed a match between the infecting strain of BVDV-1b and the contaminated vaccine.

Traces of history conserved over 600 years in the geographic distribution of genetic variants of an RNA virus: Bovine viral diarrhea virus in Switzerland

The first records of smallpox and rabies date back thousands of years and foot-and-mouth disease in cattle was described in the 16th century. These diseases stood out by their distinct signs, dramatic way of transmission from rabid dogs to humans, and sudden appearance in cattle herds. By contrast, infectious diseases that show variable signs and affect few individuals were identified only much later. Bovine viral diarrhea (BVD), endemic in cattle worldwide, was first described in 1946, together with the eponymous RNA virus as its cause. There is general agreement that BVD was not newly emerging at that time, but its history remains unknown. A search for associations between the nucleotide sequences of over 7,000 BVD viral strains obtained during a national campaign to eradicate BVD and features common to the hosts of these strains enabled us to trace back in time the presence of BVD in the Swiss cattle population. We found that animals of the two major traditional cattle breeds, Fleckvieh and Swiss Brown, were infected with strains of only four different subgenotypes of BVDV-1. The history of these cattle breeds and the events that determined the current distribution of the two populations are well documented. Specifically, Fleckvieh originates from the Bernese and Swiss Brown from the central Alps. The spread to their current geographic distribution was determined by historic events during a major expansion of the Swiss Confederation during the 15th and 16th centuries. The association of the two cattle populations with different BVD viral subgenotypes may have been preserved by a lack of cattle imports, trade barriers within the country, and unique virus-host interactions. The congruent traces of history in the distribution of the two cattle breeds and distinct viral subgenotypes suggests that BVD may have been endemic in Switzerland for at least 600 years.

Quantitative and rapid interference of bovine viral diarrhea virus BVDV/END- and BVDV/END+ strains

Homologous interference in vitro is defined as the ability of primary viral infection to prevent secondary homologous superinfection. Non-cytopathic bovine viral diarrhea virus (ncp BVDV) has been classified according to the exaltation of Newcastle disease phenomenon (END) as END positive (E+) and END negative (E-) strains. Simultaneous inoculation of MDBK-SY cell monolayers with BVDV/E- virus and a three log higher amount of BVDV RK13/E+ virus, leads to acquisition of the BVDV/E- feature of blocking Newcastle disease virus (NDV) infection in cells. BVDV/E- strains, particularly at a high titre and MOI ≥1.25, can exert and impose their effects in BVDV/E+ infected cells; however, if BVDV/E- MOI is reduced to MOI below 0.625, the BVDV/E+ effect can be restored leading to cytopathic effects (CPE) induction by NDV reciprocal to the titre of the BVDV RK13/E+ strain. Moreover, blocking and prevention of induced CPE by NDV or vesicular stomatitis virus (VSV) occurs even when BVDV/E- superinfects primary BVDV/E+ infected cells, indicating a defective homologous interference between BVDV/E+ and BVDV/E- strains. Taken together, BVDV/E- strains have a strong competitive potency and mediate a fast acting (i.e. within 60 min) influence against BVDV/E+ activity. This may be relevant in vivo where BVDV/E- and BVDV/E+ combinations are frequently isolated from infected individuals.

Bovine viral diarrhea virus genomic variation within persistently infected cattle

Bovine viral diarrhea virus (BVDV) is a single stranded RNA virus in the family Flaviviridae that causes a form of persistent infection. If a fetus is infected in utero during the first 120days of gestation the resulting calf will be immunotolerant to the infecting strain and maintain the virus for life. These animals are epidemiologically important in maintaining BVDV on farms, but also present a unique opportunity to study quasispecies in vivo in the absence of significant selection by the host adaptive immune response. We used deep sequencing and novel analytical methods to characterize the viral populations within the mesenteric lymph nodes of 10 persistently infected animals. Our results indicate that the pattern of variability across the viral genome from animal to animal is very consistent within BVDV subgenotypes. However, the individual mutations that constitute this variation are not necessarily the same in each animal. Even in the absence of significant immune selection the structural genes of BVDV vary more extensively than the non-structural genes. These findings could be useful for future vaccine design against BVDV as well as for measuring and understanding patterns of variation in other ssRNA viruses, especially those that belong to the family Flaviviridae.

Variability and Global Distribution of Subgenotypes of Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is a globally-distributed agent responsible for numerous clinical syndromes that lead to major economic losses. Two species, BVDV-1 and BVDV-2, discriminated on the basis of genetic and antigenic differences, are classified in the genus Pestivirus within the Flaviviridae family and distributed on all of the continents. BVDV-1 can be segregated into at least twenty-one subgenotypes (1a–1u), while four subgenotypes have been described for BVDV-2 (2a–2d). With respect to published sequences, the number of virus isolates described for BVDV-1 (88.2%) is considerably higher than for BVDV-2 (11.8%). The most frequently-reported BVDV-1 subgenotype are 1b, followed by 1a and 1c. The highest number of various BVDV subgenotypes has been documented in European countries, indicating greater genetic diversity of the virus on this continent. Current segregation of BVDV field isolates and the designation of subgenotypes are not harmonized. While the species BVDV-1 and BVDV-2 can be clearly differentiated independently from the portion of the genome being compared, analysis of different genomic regions can result in inconsistent assignment of some BVDV isolates to defined subgenotypes. To avoid non-conformities the authors recommend the development of a harmonized system for subdivision of BVDV isolates into defined subgenotypes.

Molecular Characterization of a Novel Bovine Viral Diarrhea Virus Isolate SD-15

As one of the major pathogens, bovine viral diarrhea virus caused a significant economic loss to the livestock industry worldwide. Although BVDV infections have increasingly been reported in China in recent years, the molecular aspects of those BVDV strains were barely characterized. In this study, we reported the identification and characterization of a novel BVDV isolate designated as SD-15 from cattle, which is associated with an outbreak characterized by severe hemorrhagic and mucous diarrhea with high morbidity and mortality in Shandong, China. SD-15 was revealed to be a noncytopathic BVDV, and has a complete genomic sequence of 12,285 nucleotides that contains a large open reading frame encoding 3900 amino acids. Alignment analysis showed that SD-15 has 93.8% nucleotide sequence identity with BVDV ZM-95 isolate, a previous BVDV strain isolated from pigs manifesting clinical signs and lesions resembling to classical swine fever. Phylogenetic analysis clustered SD-15 to a BVDV-1m subgenotype. Analysis of the deduced amino acid sequence of glycoproteins revealed that E2 has several highly conserved and variable regions within BVDV-1 genotypes. An additional N-glycosylation site (240NTT) was revealed exclusively in SD-15-encoded E2 in addition to four potential glycosylation sites (Asn-X-Ser/Thr) shared by all BVDV-1 genotypes. Furthermore, unique amino acid and linear epitope mutations were revealed in SD-15-encoded E^rns glycoprotein compared with known BVDV-1 genotype. In conclusion, we have isolated a noncytopathic BVDV-1m strain that is associated with a disease characterized by high morbidity and mortality, revealed the complete genome sequence of the first BVDV-1m virus originated from cattle, and found a unique glycosylation site in E2 and a linear epitope mutation in E^rns encoded by SD-15 strain. Those results will broaden the current understanding of BVDV infection and lay a basis for future investigation on SD-15-related pathogenesis.

Genomic characterization of three bovine viral diarrhea virus isolates from cattle

Three strains of the bovine viral diarrhea virus (BVDV) were isolated from cattle in Beijing, China. To investigate their genomic features, we sequenced and characterized the complete genome of each of the isolates. Each of the three virus genomes is about 12,220 bp in length, containing a 5' untranslated region (UTR), one open reading frame (ORF) encoding a 3897-amino-acid polypeptide, and a 3' UTR. The nucleotide sequence of the three isolates were 99.0 % identical to each and other shared nucleotide sequence identities of 73.4 % to 98.3 % with other BVDV-1 strains, about 70.0 % with BVDV-2 strains, about 67.0 % with BVDV-3, and less than 67.0 % with other pestiviruses. Phylogenetic analysis of the full-length genome, 3' UTR, and the N^pro gene demonstrated that the three viruses were BVDV-1 isolates. This is the first report of complete genome sequences of BVDV 1d isolates from China and might have implications for vaccine development.

Distribution and Cellular Heterogeneity of Bovine Viral Diarrhea Viral Antigen Expression in the Brain of Persistently Infected Calves: A New Perspective

Persistent infection following in utero exposure to bovine viral diarrhea virus (BVDV) early in gestation is a serious cause of morbidity and mortality in cattle industries worldwide. The brain is a primary target of persistent infection. In the current study, the types of cells infected and topography of viral antigen expression were examined in brain sections from 9 BVDV persistently infected crossbred calves, all less than 1 year of age, by immunohistochemical staining using the 15C5 primary monoclonal antibody. BVDV antigen was detected in the brains of all persistently infected calves. A variety of cell types was infected, including neurons, astrocytes, oligodendroglia, blood vessel-associated cells (pericytes, perivascular macrophages, smooth muscle cells), and cells in the leptomeninges (blood vessel-associated cells). Conclusive demonstration of viral antigen in vascular endothelial cells was elusive. The intensity and distribution of viral antigen staining in neurons were highly variable. Viral antigen staining was most consistent and intense in thalamic nuclei, most notably in dorsal and medial nuclear groups, followed by the hippocampus, entorhinal cortex, basal nuclei, and piriform cortex. Staining in other brain areas was often less intense and inconsistent. The variability in the intensity and topography of viral antigen in the brain may explain the heterogeneity in the clinical manifestations of BVDV-induced disease. Additionally, infection of the brain in persistently infected calves may underlie or at least contribute to endocrine disturbances and immunologic deficits that are protean manifestations of BVDV-induced disease.

Failure to Detect Bovine Viral Diarrhea Virus in Necropsied Farm-Raised White-Tailed Deer (Odocoileus Virginianus) in Pennsylvania

Between January 1 and December 31, 2005 gross and histologic examinations were performed on carcasses of 61 farm-raised white-tailed deer originating from Pennsylvania. Single-tube real-time reverse transcription polymerase chain reaction (real-time RT-PCR) for the detection of bovine viral diarrhea virus type 1 (BVDV-1) and type 2 (BVDV-2) was performed on each animal. Virus isolation was performed on tissue samples from 25 of 61 animals. Immunohistochemical (IHC) staining of ear-notch skin to identify BVDV antigen was performed on each animal. All tissues samples tested negative for both BVDV-1 and BVDV-2 by real-time RT-PCR, virus isolation, and IHC. Gross or histopathologic lesions suggestive of BVDV infection were not detected. Results of this study suggest that BVD is not a common cause of mortality in farm-raised white-tailed deer in Pennsylvania.

Comparison of Five Diagnostic Methods for Detecting Bovine Viral Diarrhea Virus Infection in Calves

Five diagnostic techniques performed on skin biopsies (shoulder region) and/or serum were compared for detection of bovine viral diarrhea virus infection in 224 calves 0–3 months of age, 23 calves older than 3 months but younger than 7 months, and 11 cattle older than 7 months. The diagnostic methods used were immunohistochemistry (IHC), 2 commercial antigen ELISAs, 1 commercial antibody ELISA, and realtime RT-PCR. Results of 249 out of 258 skin and serum samples were identical and correlated within the 3 antigen detection methods and the real-time RT-PCR used. Twenty-six of these 249 samples were BVDV-positive with all antigen detection methods and the real-time RT-PCR. Nine out of 258 samples yielding discordant results were additionally examined by RT-PCR, RT-PCR Reamplification (ReA), and antigen ELISA I on serum and by immunohistochemistry on formalin fixed and paraffin-embedded skin biopsies. Virus isolation and genotyping was performed as well on these discordant samples. In 3 cases, transiently infected animals were identified. Two samples positive by real-time RT-PCR were interpreted as false positive and were ascribed to cross-contamination. The antigen ELISA II failed to detect 2 BVDV-positive calves due to the presence of maternal antibodies; the cause of 2 false-positive cases in this ELISA remained undetermined. Only persistently infected animals were identified in skin samples by IHC or antigen ELISA I. The 3 antigen detection methods and the real-time RT-PCR used in parallel had a high correlation rate (96.5%) and similar sensitivity and specificity values.

A Comparison of Polymerase Chain Reaction with and without RNA Extraction and Virus Isolation for Detection of Bovine Viral Diarrhea Virus in Young Calves

Previously, the authors described a multiplex reverse transcriptase–polymerase chain reaction (PCR) assay for detection and typing of bovine viral diarrhea virus (BVDV) from blood of persistently infected (PI) cattle that could be used with or without RNA extraction. In the present study, the PCR assay was evaluated for its ability to detect BVDV in young calves as a screening tool for detection of persistent infections. Both methods, PCR after RNA extraction (rPCR) and the direct method without RNA extraction (dPCR) were applied and compared with virus isolation (VI) with diagnostic specimens. From 450 whole blood samples from Ontario calves, 47 and 39 samples were positive by rPCR and VI, respectively. From the 47 samples positive by rPCR, 45 (96%) also were positive by dPCR when samples were tested both undiluted and diluted 1:10. In comparison to VI, the relative sensitivities of both PCR assays were 100%. Examination of the results indicates that both PCR assays can be used for screening calves for persistent infection with BVDV.

Comparison of the breadth and complexity of bovine viral diarrhea (BVDV) populations circulating in 34 persistently infected cattle generated in one outbreak

Exposure to bovine viral diarrhea viruses (BVDV) results in acute and persistent infections. Persistent infections result from in utero exposure during the first trimester of gestation. Clinical presentation, in persistently infected cattle (PI), is highly variable. The reasons for this variation is largely unknown. The BVDV circulating in PI exist as quasispecies (swarms of individual viruses). An outbreak resulting in 34 PI cattle presented an opportunity to compare a large number of PI׳s. Methods were developed to compare the circulating viral populations within PI animals. It was found that PI animals generated in the same outbreak carry circulating viral populations that differ widely in size and diversity. Further, it was demonstrated that variation in PI viral populations could be used as a quantifiable phenotype. This observation makes it possible to test the correlation of this phenotype to other phenotypes such as growth rate, congenital defects, viral shed and cytokine expression.

XRN1 stalling in the 5' UTR of Hepatitis C virus and Bovine Viral Diarrhea virus is associated with dysregulated host mRNA stability

We demonstrate that both Hepatitis C virus (HCV) and Bovine Viral Diarrhea virus (BVDV) contain regions in their 5’ UTRs that stall and repress the enzymatic activity of the cellular 5’-3’ exoribonuclease XRN1, resulting in dramatic changes in the stability of cellular mRNAs. We used biochemical assays, virus infections, and transfection of the HCV and BVDV 5’ untranslated regions in the absence of other viral gene products to directly demonstrate the existence and mechanism of this novel host-virus interaction. In the context of HCV infection, we observed globally increased stability of mRNAs resulting in significant increases in abundance of normally short-lived mRNAs encoding a variety of relevant oncogenes and angiogenesis factors. These findings suggest that non-coding regions from multiple genera of the Flaviviridae interfere with XRN1 and impact post-transcriptional processes, causing global dysregulation of cellular gene expression which may promote cell growth and pathogenesis.

Understanding how a persistent virus like Hepatitis C Virus (HCV) interfaces with the cellular machinery during infection can provide significant insights into mechanisms of pathogenesis. We demonstrate that while trying to degrade HCV transcripts, a major cellular exonuclease called XRN1 stalls and gets repressed in the 5’ noncoding region of the viral mRNA. Interestingly, the region where XRN1 stalls in the 5’ UTR includes the viral IRES that is required for translation initiation, uncovering a novel, unexpected function for this well-studied region. Differential mRNA stability is a major regulator of gene expression in cells. Curiously, repression of the cellular XRN1 exonuclease is associated with a general repression of mRNA decay in general in HCV-infected cells. Thus numerous cellular mRNAs are stabilized and accumulate in a dysregulated fashion during HCV infection. Normally short-lived mRNAs are disproportionately affected—including mRNAs that encode immune regulators and oncogenes. Thus, this study suggests a novel role for the 5’ UTR of HCV in molecular pathogenesis—including hepatocellular carcinoma. Furthermore, the 5’ UTR of Bovine Viral Diarrhea virus also represses the XRN1 enzyme and stabilizes cellular mRNA. Therefore a strategy of 5’ UTR-mediated XRN1 repression appears to be conserved among the vector-independent members of the Flaviviridae.

Polymorphic genetic characterization of E2 gene of bovine viral diarrhea virus in China

Bovine viral diarrhea virus (BVDV) is one of the wide distributed pathogenic viruses of livestock and wild animals worldwide. E2 glycoprotein is a major structural component of the BVDV virion and plays a key role in viral attachment to host cells and inducing immune responses against viral infection. In order to gain detailed information of the E2 coding region of BVDV circulating in China, 46 positive samples were tested by RT-PCR for the E2 coding region. The 1122 nt nucleotide sequences of full-length E2 were harvested and analyzed. The results suggested that full-length E2 was an ideal target for BVDV genotyping and divided the domestic BVDV isolates into 9 subgenotypes, namely BVDV-1a, -1b1, -1c, -1d, -1o, -1m, -1p, -1q and BVDV-2a, showing great diversity. The difference of nonsynonymous and synonymous substitution rates (dN-dS) inferred both positive and purifying selection of the E2. However, combination of positive and purifying selection at different points indicated purifying selection within the complete E2. Protein properties analysis based on glycosylation sites and epitope prediction demonstrated that the biological character of E2 among individual BVDV subgenotype was similar, but may alter due to amino acid changes. For the first time, the comprehensive collection of E2 sequences of Chinese BVDV isolates was elucidated, which would provide information for future vaccine design and BVD control in China.

Genetic diversity of bovine viral diarrhea viruses in commercial bovine serum batches of Chinese origin

Bovine viral diarrhea virus (BVDV) is often detected in commercial bovine serum. BVDV genetic diversity was investigated in commercial bovine serum of Chinese origin. Twenty-two batches of bovine serum were obtained from 10 suppliers with different geographic origins in China, and 20 batches of bovine serum were positive by reverse-transcription polymerase chain reaction (RT-PCR) and sequencing. Phylogenetic reconstructions of partial 5'UTR sequences indicated that the samples examined in this work clustered within the BVDV type 1 and BVDV type 2 genotypes. Interestingly, 3 sample sequences clustered into CSFV. These results suggest a high genetic diversity in Chinese BVDV field isolates. This study will benefit epidemiological surveys of BVDV detected in China.

[Pathogenicity of noncytophatic isolates of bovine viral diarrhea virus in experimentally infected seronegative calves]

The results of experimental infection of seronegative calves with three non-cytopathogenic (NCP) isolates of BVDV isolated from cattle with different clinical manifestations of the disease belonging to genotype 1 (subgenotype 1a, 1b and 1d) are presented. All tested isolates showed the virulence for seronegative calves 4 to 6 months of age. Belonging to biotype did not correlate with the ability of the virus to infect the lymphoid tissues and to induce leukopenia. All isolates of the virus led to "transiting" leukopenia (up to 2880-3800 kl/mm3) for 8-10 days after infection. Isolate cluster 1d was more virulent and caused the development of a mild respiratory syndrome and short-term diarrhea. The virulence was "strain-dependent".

Stability of the resistance to the thiosemicarbazone derived from 5,6-dimethoxy-1-indanone, a non-nucleoside polymerase inhibitor of bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is the prototype Pestivirus. BVDV infection is distributed worldwide and causes serious problems for the livestock industry. The thiosemicarbazone of 5,6-dimethoxy-1-indanone (TSC) is a non-nucleoside polymerase inhibitor (NNI) of BVDV. All TSC-resistant BVDV variants (BVDV-TSC^r T_1–5) present an N264D mutation in the NS5B gene (RdRp) whereas the variant BVDV-TSC^r T₁ also presents an NS5B A392E mutation. In the present study, we carried out twenty passages of BVDV-TSC^r T_1–5 in MDBK cells in the absence of TSC to evaluate the stability of the resistance. The viral populations obtained (BVDV R_1–5) remained resistant to the antiviral compound and conserved the mutations in NS5B associated with this phenotype. Along the passages, BVDV R₂, R₃ and R₅ presented a delay in the production of cytopathic effect that correlated with a decrease in cell apoptosis and intracellular accumulation of viral RNA. The complete genome sequences that encode for NS2 to NS5B, Npro and Erns were analyzed. Additional mutations were detected in the NS5B of BVDV R₁, R₃ and R₄. In both BVDV R₂ and R_3, most of the mutations found were localized in NS5A, whereas in BVDV R₅, the only mutation fixed was NS5A V177A. These results suggest that mutations in NS5A could alter BVDV cytopathogenicity. In conclusion, the stability of the resistance to TSC may be due to the fixation of different compensatory mutations in each BVDV-TSC^r. During their replication in a TSC-free medium, some virus populations presented a kind of interaction with the host cell that resembled a persistent infection: decreased cytopathogenicity and viral genome synthesis. This is the first report on the stability of antiviral resistance and on the evolution of NNI-resistant BVDV variants. The results obtained for BVDV-TSC^r could also be applied for other NNIs.

Interaction of CSFV E2 protein with swine host factors as detected by yeast two-hybrid system

E2 is one of the envelope glycoproteins of pestiviruses, including classical swine fever virus (CSFV) and bovine viral diarrhea virus (BVDV). E2 is involved in several critical functions, including virus entry into target cells, induction of a protective immune response and virulence in swine. However, there is no information regarding any host binding partners for the E2 proteins. Here, we utilized the yeast two-hybrid system and identified fifty-seven host proteins as positive binding partners which bound E2 from both CSFV and BVDV with the exception of two proteins that were found to be positive for binding only to CSFV E2. Alanine scanning of CSFV E2 demonstrated that the binding sites for these cellular proteins on E2 are likely non-linear binding sites. The possible roles of the identified host proteins are discussed as the results presented here will be important for future studies to elucidate mechanisms of host protein-virus interactions during pestivirus infection. However, due to the limitations of the yeast two hybrid system, the proteins identified is not exhaustive and each interaction identified needs to be confirmed by independent experimental approaches in the context of virus-infected cells before any definitive conclusion can be drawn on relevance for the virus life cycle.

Analysis of BVDV isolates and factors contributing to virus transmission in the final stage of a BVDV eradication program in lower Austria

The BVDV eradication program in Lower Austria according to the Swedish model started in 1997 as a voluntary strategy and became obligatory for all herd owners in 2004. In this paper we analyse BVDV isolates found in PI animals of the last infected cattle farms at the genetic level and describe possible risk factors for virus transmission in the final stage of the BVDV eradication program in Lower Austria, where only five infected herds were identified in 2010. Viral isolates from 23 farms on which PI animals had been detected in 2009 (n = 10), 2010 (n = 5), 2008 (n = 5) and in 2006 (n = 3) were analysed at a genetic level at the 5'-UTR. All isolates analysed by phylogenetic analysis fall into five BVDV-1 subgenotypes, i.e., b, e, f, g, and h. No new subgenotypes were identified when compared to isolates analysed at the beginning of the BVDV eradication program. The phylogenetic analysis also revealed three groups of herds with genetically identical isolates; the first group comprised two herds, the second seven herds and the third four herds. Analysis of several factors such as distance between herds, purchase of cattle, work of farmers, veterinarians, assistants of milk recording associations and animal carriers indicated the latter as the most critical factor for transmitting the same viruses. Seven herds of two groups of identical BVDV isolates were served by the same cattle carrier, six herds shared the veterinarian and five herds had the same assistant of the milk recording association who could be the risk factor for the introduction of BVDV into the herd. The analysis helped to stop virus transmission. Therefore, from early 2012 up to now, no new infection has occurred in Lower Austria. The results indicated that biosecurity is a very important factor to prevent the spreading of viruses in the final stage of the BVDV eradication program.

Serological and molecular evidence for natural infection of Bactrian camels with multiple subgenotypes of bovine viral diarrhea virus in Western China

Bovine viral diarrhea virus (BVDV) infects both domestic and wild animals, causing substantial economic losses. In order to investigate possible infection in Bactrian camels in Western China, a total of 56 blood samples were collected from clinically healthy Bactrian camels and tested for BVDV antigens and antibodies using antigen capture enzyme-linked immunosorbent assay (ELISA) and virus neutralization test. The antigen-positive samples (n=17) were further tested for viral nucleic acids by species-specific real-time RT-PCR assays, which showed presence of BVDV-1, but not BVDV-2 nor atypical bovine pestivirus, in the camel samples. Twelve non-cytopathogenic viruses were isolated and genetically typed by sequencing of the 5'untranslated region (5'UTR) and N(pro) coding sequences. Phylogenetic analysis divided the isolates into six known subgenotypes: BVDV-1a, BVDV-1b, BVDV-1c, BVDV-1m, BVDV-1o, BVDV-1p and a putative subgenotype, BVDV-1q. This study provides, for the first time, serological and molecular evidence for natural infection of Bactrian camels in Western China with highly divergent BVDV-1 strains. Further investigations are needed to elucidate the possible roles of Bactrian camels in the epidemiology of BVD in Western China.

Identification and characterization of a novel subgenotype of bovine viral diarrhea virus isolated from dairy cattle in Northwestern China

Bovine viral diarrhea virus (BVDV) was detected by RT-PCR in 105 out of 391 samples which were collected from five dairy farms in Ningxia, China during 2010-2011. Non-cytopathogenic BVDV was isolated from 13 samples and a 230-bp fragment of the 5'-untranslated region was amplified and sequenced. While the predominant subgenotypes were BVDV-1b and BVDV-1d, a potentially novel subgenotype was identified by phylogenetic analysis, which may have implications for vaccine development.

Biological properties of bovine viral diarrhea virus quasispecies detected in the RK13 cell line

The rabbit kidney cell line RK13 has been reported to be contaminated with noncytopathogenic (ncp) bovine viral diarrhea virus (BVDV). Persistent infection was confirmed by demonstrating the stability of virus titers (10(4.6±0.5) TCID50/ml) and BVDV positive cells (71.9 ± 3.12 %), over six successive passages. Based on the "exaltation of Newcastle disease virus" (END) and reverse plaque formation methods, two types of ncp viruses were isolated, END-phenomenon-positive and negative. Isolates, RK13/E(+) and RK13/E(-), demonstrated (1) differing levels of reproducibility in cell cultures, (2) similar antigenicity against BVDV antisera, (3) identical 5'-UTR region nucleotide sequences, (4) four amino acid differences throughout the genomic open reading frame, and (5) better growth ability in primary rabbit cells than other laboratory strains when inoculated in parallel at an MOI of 0.01. Overall, the BVDV population in RK13 cells consists of at least two different END characteristic quasispecies that are adapted to cultures of rabbit origin, giving rise to naturally attenuated BVDV strains that can be used in vaccine development.

[Retrospective evaluation of data over five years of the BVDV prevention program using ear notch samples from the autonomous province of Bolzano (Italy)]

In 2005 the Autonomous Province of Bolzano implemented a BVD-Virus control programme by testing all newborn calves for Bovine Viral Diarrhoea Virus (BVDV) antigen by analysing ear notch samples. In eradication programs between November 2005 and October 2010 a total of 344,108 newborn calves were ear notch sampled and analysed for BVDV by an antigen ELISA detecting the E(rns) (HerdCheck BVDV Antigen/Serum Plus, Idexx Laboratories, Switzerland). The tissue samples were collected during calf ear tagging (within the first 20 days of life) using two sampling devices (TypiFix-System, Agrobiogen GmbH [Germany] and Allflex [France]). 0.4% (1400) of the collected samples showed a positive result, and of these, 583 calves were subjected to a follow-up examination, analysing the samples again by ELISA as well blood samples by Reverse transcriptase-PCR. Blood samples were also collected from the dam, if still present on the farm by the time of sampling. These results suggest that a BVDV control programme testing all newborn calves sampled for BVDV antigen by analysing an ear notch sample in principle is practicable. However, due to the low positive predictive value (75%) of the E(rns)-ELISA used, not all persistently infected calves can be detected.