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.

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.

The identification of a B-cell epitope in bovine viral diarrhea virus (BVDV) core protein based on a mimotope obtained from a phage-displayed peptide library

Bovine pestivirus A and B, previously known as bovine viral diarrhea virus (BVDV)-1 and 2, respectively, are important pathogens of cattle worldwide, which causes significant economic losses. B-cell epitopes in BVDV glycoprotein E2 and nonstructural protein NS2/3 have been extensively identified. In this study, we screened a 12-mer phage display peptide library using commercial goat anti-BVDV serum, and identified a mimotope "LTPHKHHKHLHA" referred to as P3. With sequence alignment, a putative B-cell epitope "77ESRKKLEKALLA88" termed as P3-BVDV1/2 residing in BVDV core protein was identified. The synthesized peptides of both P3 and P3-BVDV1/2 show strong reactivity with BVDV serum in immune blot assay. Immunization of mice with these individual peptides leads to the production of antibody that cannot neutralize virus infectivity. Thus for the first time we identified a B-cell epitope, "77ESRKKLEKALLA88", in BVDV core protein. Interestingly, the epitope was highly conserved in Pestivirus A, B, C, D, as well as emerging Pestivirus E and I, but highly variable in Pestiviruses H, G, F, and J, as well as unclassified Pestivirus originated from non-ruminant animals. Whether this putative B-cell epitope is implicated in pestivirus pathogenesis or evolution needs further investigations once large numbers of isolates are available in the future.

No effects of noncytopathic bovine viral diarrhea virus type 2 on the reproductive tract of experimentally inoculated boars

Bovine viral diarrhea virus (BVDV) infections in pigs may result in transient leukopenia, chronic gastroenteritis, septicemia, and hemorrhagic lesions. Both classical swine fever virus (CSF) and the atypical porcine pestivirus (APPV) are shed in the semen of infected boars. Because these viruses share conserved regions and present antigenic similarity, they may not be the only species belonging to the genus Pestivirus that can be shed in the semen of infected pigs. The objective of this study was to evaluate the testicular and epididymal changes, seminal parameters, and viral shedding in the reproductive tract of boars experimentally inoculated with noncytopathic BVDV-2. Six males were selected, and samples of blood, semen, and preputial swabs were collected every four days until the 52nd day after inoculation. The samples were tested for the presence of viral RNA by RT-PCR. An aliquot of whole blood was used to perform hematological analyses, which showed a significant reduction in monocyte counts and a significant increase in lymphocyte counts when comparing the pre- and postinoculation periods. The neutralizing antibody titers were determined by the virus neutralization test. None of the animals presented clinical signs or worsening of the seminal parameters that were evaluated. Moreover, BVDV-2 shedding by the reproductive route was not observed.

Genetic identification of pestiviruses from beef cattle in Southern Brazil

Bovine pestiviruses, e.g., bovine viral diarrhea virus types 1 (BVDV-1 or Pestivirus A), BVDV-2 (Pestivirus B), and HoBi-like pestiviruses (HoBiPeV or Pestivirus H), have been shown to circulate in Brazilian cattle in varied proportions. In this study, we identified genetically pestiviruses circulating in beef cattle in Rio Grande do Sul, the southern most Brazilian state. Screening of serum of 15.584 beef calves destined to be export by an antigen capture ELISA and, subsequently, by reverse-transcription polymerase chain reaction (RT-PCR), revealed 135 containing pestivirus RNA. Genetic typing of these viruses based on nucleotide sequencing and phylogenetic analysis of the 5' untranslated region (5' UTR) of the viral genome allowed for the identification of 90 different viruses, being 38 BVDV-1 (42.2%), 31 BVDV-2 (34.4%), and 21 HoBiPeV (23.4%). Among BVDV-1, only subtypes BVDV-1a (n = 28, 31.1%) and BVDV-1b (n = 10, 11.1%) were identified. All 31 BVDV-2 isolates belonged to BVDV-2b subtype and the 21 HoBiPeV viruses clustered to subgroup 3a. Thus, this study provides an approximate genetic profile of pestiviruses circulating in beef cattle in a traditional Brazilian beef cattle-raising state.

Identification of BVDV2b and 2c subgenotypes in the United States: Genetic and antigenic characterization

Bovine viral diarrhea virus (BVDV), a ubiquitous pathogen of cattle, causes subclinical to severe acute disease. Two species of BVDV are recognized, BVDV1 and BVDV2 with BVDV1 divided into at least 21 subgenotypes and BVDV2 into 3-4 subgenotypes, most commonly using sequences from the 5' untranslated region (5' UTR). We report genomic sequencing of 8 BVDV2 isolates that did not segregate into the 2a subgenotype; but represented two additional BVDV2 subgenotypes. One BVDV2 subgenotype was previously recognized only in Asia. The other seven viruses fell into a second subgenotype that was first reported in Brazil and the U.S. in 2002. Neutralization assays using antiserum raised against vaccine strain BVDV2a 296c revealed varying degrees of neutralization of genetically diverse BVDV2 isolates. Neutralization titers decreased from 1.8 to more than a four log(2) decrease. This study illustrated the considerable genetic and antigenic diversity in BVDV2 circulating in the U.S.

Priming Cross-Protective Bovine Viral Diarrhea Virus-Specific Immunity Using Live-Vectored Mosaic Antigens

Bovine viral diarrhea virus (BVDV) plays a key role in bovine respiratory disease complex, which can lead to pneumonia, diarrhea and death of calves. Current vaccines are not very effective due, in part, to immunosuppressive traits and failure to induce broad protection. There are diverse BVDV strains and thus, current vaccines contain representative genotype 1 and 2 viruses (BVDV-1 & 2) to broaden coverage. BVDV modified live virus (MLV) vaccines are superior to killed virus vaccines, but they are susceptible to neutralization and complement-mediated destruction triggered by passively acquired antibodies, thus limiting their efficacy. We generated three novel mosaic polypeptide chimeras, designated N^proE2¹²³; NS²³¹; and NS²³², which incorporate protective determinants that are highly conserved among BVDV-1a, 1b, and BVDV-2 genotypes. In addition, strain-specific protective antigens from disparate BVDV strains were included to broaden coverage. We confirmed that adenovirus constructs expressing these antigens were strongly recognized by monoclonal antibodies, polyclonal sera, and IFN-γ-secreting T cells generated against diverse BVDV strains. In a proof-of-concept efficacy study, the multi-antigen proto-type vaccine induced higher, but not significantly different, IFN-γ spot forming cells and T-cell proliferation compared to a commercial MLV vaccine. In regards to the humoral response, the prototype vaccine induced higher BVDV-1 specific neutralizing antibody titers, whereas the MLV vaccine induced higher BVDV-2 specific neutralizing antibody titers. Following BVDV type 2a (1373) challenge, calves immunized with the proto-type or the MLV vaccine had lower clinical scores compared to naïve controls. These results support the hypothesis that a broadly protective subunit vaccine can be generated using mosaic polypeptides that incorporate rationally selected and validated protective determinants from diverse BVDV strains. Furthermore, regarding biosafety of using a live vector in cattle, we showed that recombinant human adenovirus-5 was cleared within one week following intradermal inoculation.

Genetic and Clinical Analyses of Bovine Viral Diarrhea Virus Isolates from Dairy Operations in the United States of America

To assess the prevalence of bovine viral diarrhea virus (BVDV) on the basis of the genotype and clinical signs, isolates from 16 dairy herds (bulk milk samples) and 37 BVDV-infected cattle were examined. Isolates for this study were selected from submissions that contained an adequate clinical history. A part of the E2 gene of BVDV from these isolates was amplified by reverse transcription-polymerase chain reaction. From the nucleotide sequence of the amplified products, phylogenetic analyses were performed and genotypes or subgenotypes were identified. Forty percent of the selected field isolates were BVDV-2, and 60% were BVDV-1. Eighty-one percent of BVDV-1 isolates were determined to be the BVDV-1b subgenotype. BVDV-1b and BVDV-2 formed more closely related clusters in each group than did the BVDV-1a isolates. There was no obvious association of any genotype or subgenotype with geographical localization or clinical manifestations. A higher prevalence of BVDV-2 infection was found in the United States than in other countries. BVDV-1a has been thought of as a prototype of BVDV; however, there were fewer isolations of BVDV-1a than of other subgenotypes of BVDV Phylogenetic analyses of BVDV isolates using the E2 region of the genome generated results similar to those of studies done in the United States using the 5' untranslated region.

Molecular detection and characterization of bovine viral diarrhea virus in Mongolian cattle and yaks

Bovine viral diarrhea virus (BVDV) is classified into two species, namely, Bovine viral diarrhea virus 1 and Bovine viral diarrhea virus 2, and affects cattle worldwide, resulting in significant economic loss. The prevalence of BVDV-1 and BVDV-2 infections and its genotypes in Mongolian animals has not been studied. In this study, we surveyed BVDV infection in dairy cattle and yaks from Bornuur and Bulgan counties by RT-PCR, and the average infection rate in the sampling sites was 15.8 % and 20.0 %, respectively. In addition, molecular features of the 5'-UTR region of the BVDV genome in Mongolian cattle and yaks were identified as belonging to the subtypes BVDV-1a and BVDV-2a, respectively. Determining the prevalence, geographical distribution, and molecular diversity of BVDV-1 and BVDV-2 in various host species in Mongolia is important for further studies and process control programs.

Cross-priming amplification for detection of bovine viral diarrhoea virus species 1 and 2

AIMS

The aim of the study was the development of cross-priming amplification for ubiquitous detection of bovine viral diarrhoea virus (BVDV) species 1 and 2.

METHODS AND RESULTS

Three and five specific primers, respectively, for the detection of BVDV-1 and BVDV-2, were designed on the basis of the sequences of the 5'UTR region. Incubation temperature and reaction time were determined. The optimal incubation conditions using water bath were 63°C for 75 min. Reverse transcription step (RT) was not required. The results were visualized under UV-light as a bright yellow fluorescence in positive samples. Additional method for results interpretation was agarose gel electrophoresis. Positive samples showed the presence of ladder-like banding patterns, formed by harpin-like cross-priming amplification (CPA) products. Sensitivity of CPA was compared with conventional RT-PCR and real-time RT-PCR. The CPA detection limit was 3500 copies for BVDV-1 and 80000 copies for BVDV-2 per reaction. For RT-PCR it was 350 and 80 copies for BVDV-1 and BVDV-2, respectively, and for real-time RT-PCR it was 35 copies for BVDV-1 and 80 copies for BVDV-2. The sensitivity of the developed method is sufficient to detect persistently infected (PI) animals. Positive results were found in 24 of 25 BVDV isolates belonging to species 1 and 2. Additionally, one false-negative result for BVDV-2 was detected. There were no false-positive results in negative samples and in the negative control. Both sets of primers used for the detection of BVDV-1 and BVDV-2 were not able to detect atypical pestiviruses. CPA positive results were confirmed by RT-PCR and real-time RT-PCR.

CONCLUSIONS

CPA is a rapid method for the detection of BVDV-1 and BVDV-2 in field samples from PI animals.

SIGNIFICANCE AND IMPACT OF STUDY

This is the first report on the application of the CPA method for the detection of BVDV.

Bovine viral diarrhea virus type 2 in vivo infection modulates TLR4 responsiveness in differentiated myeloid cells which is associated with decreased MyD88 expression

Symptoms of bovine viral diarrhea virus (BVDV) infection range from subclinical to severe, depending on strain virulence. Several in vitro studies showed BVDV infection impaired leukocyte function. Fewer studies have examined the effects of in vivo BVDV infection on monocyte/macrophage function, especially with strains of differing virulence. We characterized cytokine production by bovine myeloid cells isolated early or late in high (HV) or low virulence (LV) BVDV2 infection. Given BVDV infection may enhance susceptibility to secondary bacterial infection, LPS responses were examined as well. Monocytes from HV and LV infected calves produced higher levels of cytokines compared to cells from controls. In contrast, monocyte-derived macrophage cytokine levels were generally reduced. Modulated cytokine expression in HV BVDV2 macrophages was associated with decreased MyD88 expression, likely due to its interaction with viral NS5A. These data and those of others, suggest that certain Flaviviridae may have evolved strategies for subverting receptor signaling pathways involving MyD88.

High frequency of bovine viral diarrhea virus type 2 in Southern Brazil

Ruminant pestiviruses can infect cattle populations worldwide and cause significant economic losses due to their impact on productivity and health. Knowledge of pestivirus diversity is important for control programs and vaccine development and for determining probable sources of infection. In this paper, we describe a search for ruminant pestiviruses with RT-PCR in sera of 9078 calves from 6 to 12 months of age. The calves were first analyzed in pools and then analyzed individually. Thirty-three RT-PCR positive animals were detected (0.36%) from 6.9% (24) of the 346 herds. The sequencing analysis of the 5' non-coding region and N terminal autoprotease showed the presence of BVDV-1a (15 isolates), -1b (3), -1d (1) and -2b (14), with a higher frequency (42.4%) of BVDV-2 in comparison with other countries. The presence of sheep was significantly associated with BVDV infection. Our results also suggested that a BVDV control program based only on the investigation of cattle would not be successful, especially in regions with farms harboring multiple animal species. This study may also serve as a reference for future control programs in Southern Brazil because it reports the prevalence of cattle with active infections and the genetic background of the circulating strains.

Genetic characterization of a noncytopathic bovine viral diarrhea virus 2b isolated from cattle in China

In January 2013, several clinical signs of cattle with diarrhea, cough, nasal discharge, and fever were reported in Jilin province, China. One virus named SD1301 was isolated and identified. Complete genome of the virus is 12258nt in length and contains a 5'UTR, one open reading frame encoding a polyprotein of 3,897 amino acids and a 3'UTR. Phylogenetic analysis of 5'UTR, N(pro), E1 and E2 gene demonstrated the virus belonged to BVDV 2b, and genetically related to the BVDV strain Hokudai-Lab/09 from Japan in 2010. This bovine viral diarrhea virus displays a unique genetic signature with 27-nucleotide deletion in the 5'UTR, which is similar to the bovine viral diarrhea virus C413 (AF002227). This was the first confirmed isolation of ncp BVDV2b circulating in bovine herd of China.

Antigenic variability in bovine viral diarrhea virus (BVDV) isolates from alpaca (Vicugna pacos), llama (Lama glama) and bovines in Chile

Llamas and alpacas are domesticated South American camelids (SACs) important to ancestral population in the Altiplano region, and to different communities where they have been introduced worldwide. These ungulates have shown to be susceptible to several livestock viral pathogens such as members of the Pestivirus genus and mainly to bovine viral diarrhea virus (BVDV). Seventeen Chilean BVDV isolates were analyzed by serum cross neutralization with samples obtained from five llama, six alpacas, three bovines, plus three reference strains belonging to different subgroups and genotypes. The objective was to describe antigenic differences and similarities among them. Antigenic comparison showed significant differences between different subgroups. Consequently, antigenic similarities were observed among isolates belonging to the same subgroup and also between isolates from different animal species belonging the same subgroup. Among the analyzed samples, one pair of 1b subgroup isolates showed significant antigenic differences. On the other hand, one pair of isolates from different subgroups (1b and 1j) shared antigenic similarities indicating antigenic relatedness. This study shows for the first time the presence of antigenic differences within BVDV 1b subgroup and antigenic similarities within 1j subgroup isolates, demonstrating that genetic differences within BVDV subgroups do not necessary corresponds to differences on antigenicity.

Microarray chip based identification of a mixed infection of bovine herpesvirus 1 and bovine viral diarrhea 2 from Indian cattle

Bovine herpesvirus 1 (BHV1) and bovine viral diarrhea virus 2 (BVD2) are endemic in India although no mixed infection with these viruses has been reported from India. We report first mixed infection of these viruses in cattle during routine screening with a microarray chip. 62 of the 69 probes of BHV1 and 42 of the 57 BVD2 probes in the chip gave positive signals for the virus. The virus infections were subsequently confirmed by RT-PCR. We also discuss the implications of these findings.

Bovine viral diarrhea virus: global status

Despite the success of regional bovine viral diarrhea viruses (BVDV) eradication programs, infections remain a source of economic loss for producers. The wide variation among BVDV results in differences in genotype, biotype, virulence, and types of infections. BVDV infect a range of domestic and wild ruminants. Clinical presentation varies depending on strain of virus, species of host, immune status of host, reproductive status of host, age of host, and concurrent infections. Recent advances in BVDV research and diagnostics have led to the development of regional eradication/control programs, the most efficacious of which focus on biosecurity, surveillance, and control.

[Genome sequencing and analysis of the bovine viral diarrhea virus-2 strain JZ05-1 isolated in China]

Bovine viral diarrhea virus (BVDV) is a member of the genus Pestivirus, which is a widespread problem for beef and dairy herds, and has given rise to a significant loss in the livestock industry all over the world. The BVDV strain JZ05-1 isolated from cattle in Jilin, China generated cytopathic effect (CPE) in MDBK cells. Eight overlapped gene fragments were amplified by RT-PCR and sequenced, the complete genom sequence of BVDV strain JZ05-1 was assembled. According to the results, the JZ05-1 genome was composed of 12285 nucleotides in length (GenBank accession No. GQ888686), which could be divided into three regions: a 387 nt 5'-untranslated region (UTR), a 11694 nt single large open reading frame encoding a polyprotein, and a 204 nt 3'-UTR. The 5'-UTR and genome sequences were analyzed by sequence alignment and construction of phylogenetic trees. The strain JZ05-1 was classified as BVDV type 2a. The BVDV-2 strain JZ05-1 genome showed high similarity to the p11Q isolated in Canada and the XJ-04 isolated in China, with 90% and 91% identity in nucleotide sequence, respectively. Compared with the similarity within the BVDV-2 genotype (96%), the JZ05-1 had low sequence similarity to other BVDV-2 strains.

Bone marrow depletion with haemorrhagic diathesis in calves in Germany: characterization of the disease and preliminary investigations on its aetiology

Since 2007 a new fatal haemorrhagic diathesis in calves has been observed in all areas of Germany. Analysis of 56 cases submitted for necropsy allowed its characterization. Calves fell ill within the first month of life independent of breed and sex. Only single or a few animals per herd were affected. Petechial and ecchymotic haemorrhages in many organs and tissues, particularly in skin, subcutis and gastrointestinal tract, were major findings in all animals. Microscopically a severe depletion of bone marrow cells was always observed. Lymphocytic depletion (43%) and inflammatory lesions (46%) were less frequently observed. Blood analysis of five animals indicated an aplastic pancytopenia. The resulting thrombocytopenia is regarded as major pathomechanism of this Haemorrhagic Disease Syndrome (HDS). Pedigree analysis gave no indication of hereditary disease. Tests for specific toxins such as S-(1,2-Dichlorovinyl)-L-cysteine (DCVC), furazolidone, or mycotoxins resulting in bone marrow depletion were negative. Bacterial infections, Bovine Viral Diarrhoea Virus, and Bluetongue Virus were ruled out as cause of the disease. HDS shares similarities with a circoviral infection in chickens (chicken infectious anaemia). A broad-spectrum PCR allowed detection of circoviral DNA in 5 of 25 HDS cases and in 1 of 8 non-HDS cases submitted for necropsy. Sequencing of the whole viral genome revealed a high similarity (up to 99%) with Porcine Circovirus type 2b. Single bone marrow cells stained weakly positive for PCV2 antigen by immunohistochemistry in 1 of 8 tested HDS animals. This is the first report of circovirus detection in cattle in Germany. The exact cause of HDS still remains unknown. A multifactorial aetiology involving infection, poisoning, immunopathy, or a genetic predisposition is conceivable. Additional research is necessary to clarify the pathogenesis and the potential role of PCV2 in HDS.

Identification of a bovine viral diarrhea virus 2 isolated from cattle in China

The identification and characterization of bovine viral diarrhea virus 2 (BVDV-2) strain SD-06 isolated from cattle in China is reported. We performed sequence analysis of 5'-untranslated region (5'-UTR) and E2 sequences and the identity at the nucleotide and amino acid level indicated that the isolate was closely related to BVDV-2. The BVDV-2 strain New York'93 showed the highest sequence homology with the isolate SD-06. The phylogenetic analysis revealed that the isolate SD-06 belonged to BVDV-2a subtype. Furthermore, immunofluorescence assay with the monoclonal antibody specific for BVDV-2 glycoprotein E2 confirmed this identification. Thus, the strain SD-06 was the first isolate of BVDV-2 identified in China.

Virus recovery and full-length sequence analysis of atypical bovine pestivirus Th/04_KhonKaen

Phylogenetic analysis of recently identified "atypical" bovine pestiviruses, performed based on different gene regions, has revealed unclear relationships with other established species, therefore, their phylogenetic position could not be determined so far. In this study, the atypical pestivirus Th/04_KhonKaen was recovered from serum of a naturally infected calf and the complete genome sequence was determined and analysed, as means to define its position. The viral genome is 12,337 nucleotides (nt) long, and comprises a 5'-UTR of 383 nt, a 3'-UTR of 254 nt and an open reading frame of 11,700 nt, without duplication of viral sequences or insertions of cellular sequences. The phylogenetic analyses of the full-length sequence, performed by Neighbor-joining, Maximum likelihood, and the Bayesian approach, unanimously placed Th/04_KhonKaen in a single lineage, distinct from the established pestivirus species, and close to bovine viral diarrhea virus types 1 and 2. Furthermore, Th/04_KhonKaen and two previously reported atypical pestiviruses D32/00_'HoBi' and CH-KaHo/cont formed a well-supported monophyletic clade in trees based on the complete N(pro) and E2 gene regions. The finding provides conclusive classification of the Th/04_KhonKaen virus and confirms the standing of the "atypical" bovine pestiviruses as a novel pestivirus species.

Genomic sequencing and characterization of a Chinese isolate of Bovine viral diarrhea virus 2

The complete genomic sequencing and characterization of Bovine viral diarrhea virus (BVDV) isolate XJ-04 originated from cattle in China was described. The genomic RNA of the isolate was 12,284 nt long and contained short 5'- untranslated region (UTR), 3'-non-coding regions (NCR), and one open reading frame (ORF) encoding a large polyprotein of 3,895 amino acids with 20 potential N-glycosylation sites. The identity of the isolate XJ-04 with reference strains NADL (BVDV-1) and 890 (BVDV-2) in autoprotease (N(pro)) gene and structural genes (C, E(rns), E1, E2) was analyzed. The percentage of nt and aa identity in analyzed genes indicated that the isolate XJ-04 was closer to the reference strain 890 (BVDV-2) than to NADL (BVDV-1). Phylogenetic analysis revealed that the isolate belonged to BVDV-2a subtype. Furthermore, comparison analysis indicated that the isolate XJ-04 did not contain any genomic insertions that can be directly related to the cytopathic phenotype.

DNA prime protein boost strategies protect cattle from bovine viral diarrhea virus type 2 challenge

At present, infections with bovine viral diarrhea virus (BVDV) type 2 occur nearly as frequently as those with BVDV type 1, so development of vaccines that protect cattle from both type 1 and type 2 BVDV has become critical. In this study, we compared various DNA prime-protein boost vaccination strategies to protect cattle from challenge with BVDV-2 using the major protective antigen of BVDV, glycoprotein E2. Calves were immunized with a plasmid encoding either type 1 E2 (E2.1) or type 2 E2 (E2.2) or with both plasmids (E2.1+E2.2). This was followed by a heterologous boost with E2.1, E2.2 or E2.1 and E2.2 protein formulated with Emulsigen and a CpG oligodeoxynucleotide. Subsequently, the calves were challenged with BVDV-2 strain 1373. All vaccinated calves developed both humoral and cell-mediated immune responses, including virus-neutralizing antibodies and IFN-gamma-secreting cells in the peripheral blood. Depletion studies showed that CD4+ T cells were responsible for IFN-gamma production. Furthermore, the calves vaccinated with either the E2.2 or the E2.1+E2.2 vaccines were very well protected from challenge with BVDV-2, having little leukopenia and showing no weight loss or temperature response. In addition, the animals vaccinated with the E2.1 vaccine were partially protected, so there was a certain level of cross-protection. These data demonstrate that a vaccination strategy consisting of priming with E2.2 or E2.1+E2.2 DNA and boosting with E2.2 or E2.1+E2.2 protein fully protects cattle from BVDV-2 challenge.

Co-existence of genetically and antigenically diverse bovine viral diarrhoea viruses in an endemic situation

Bovine viral diarrhoea virus (BVDV) is an important cattle pathogen that causes acute or persistent infections. These are associated with immunotolerance to the viral strain persisting in animals that became infected early in their intrauterine development. To this date, the epidemiology of BVD in Switzerland runs virtually undisturbed by control measures such as restrictions on animal traffic or vaccination. Here, we analysed the viral genetics of 169 Swiss isolates and carried out crossed serum neutralisation tests to assess the antigenic spectrum of BVDV strains present in the cattle population. Besides confirming the presence of BVDV type 1 subgroups b, e, h and k, a single "orphan" BVDV-1 virus was detected that does not belong to any known BVDV-1 subgroup. No BVDV type 2 viruses were detected, suggesting that they are rare or not present in the cattle population. Antigenic comparison revealed significant differences between the different subgroups, with anti-1k immune serum having up to tenfold lower neutralising activity against 1b, 1e and 1h subgroup viruses, which however may still suffice to protect 1k-immune animals against superinfection by viruses of those other subgroups. Serum from routinely vaccinated animals revealed generally low titres but good cross-neutralisation. A geographic information system revealed that the viruses of the different subgroups are distributed in an apparently randomised fashion in the cattle population. This geographic distribution pattern may reflect peculiarities of the management practice in the Swiss cattle industry that, especially through annual transhumance of up to 25% of the entire population in the alpine region, tend to optimise the spread of BVDV.

Genetic analysis of a bovine viral diarrhea virus 2 isolate from Slovakia

The identification and genetic characterization of bovine viral diarrhea virus (BVDV) isolate 17237 detected in western Slovakia is described. The analysis of 5'-untranslated region (5'-UTR), autoprotease (Npro) gene, and structural genes (C, Erns, E1, E2) was carried out. The percentage of nucleotide and deduced amino acid identity in analyzed genes implied that the isolate was closely related to the bovine viral diarrhea virus 2 (BVDV-2). Furthermore, the phylogenetic analysis revealed that this isolate fall into BVDV-2b subtype that is sporadic in Europe. The cleavage sites between viral proteins were similar to the ones of a reference strain of BVDV-2.

Genetic and antigenic characterization of bovine viral diarrhea virus type 2 isolated from Indian goats (Capra hircus)

Recent studies have shown that bovine viral diarrhea virus (BVDV) type 1 is widely prevalent in Indian cattle. In a surveillance of randomly collected 562 blood samples from seven states during 2004-2006, BVDV type 2 was detected in two native Indian goats by nested reverse transcription polymerase chain reaction (nRT-PCR). The virus isolated from them was classified antigenically as BVDV 2 on the basis of virus neutralization test and reactivity with monoclonal antibodies. Phylogenetic analysis of three different genomic regions, 5' un-translated region (5' UTR), E(rns) structural coding region and NS5B nonstructural coding region typed Indian goat isolate as BVDV 2a having close similarity with strains from North America and Europe suggesting its probable introduction through trade. It was placed in a separate clade within the 2a branch having unique mutations in E(rns) and NS5B region. This is the first report of BVDV 2 in India and only second time recorded in goat species. The isolation of BVDV 2 from goat warrants intensive surveillance in cattle and sheep.

Numerical taxonomy of the genus Pestivirus based on palindromic nucleotide substitutions in the 5' untranslated region

The palindromic nucleotide substitutions (PNS) at the three variable loci (V1, V2 and V3) in the 5' untranslated region (UTR) of Pestivirus RNA have been considered for taxonomical segregation of species, through the evaluation of 430 genomic sequences. On the basis of qualitative and quantitative secondary structure characteristics, six species have been identified: Bovine viral diarrhea virus 1 (BVDV-1), Bovine viral diarrhea virus 2 (BVDV-2), Classical swine fever virus (CSFV), Border disease virus (BDV), the tentative species Giraffe and a new proposed taxon named Pronghorn. The first step was qualitative and consisted in the characterization of the different positions of the three stems and loops in the 5' UTR sequences of all the strains under consideration belonging to the genus. Secondary structure sequences showing divergent base-pair combinations have been aligned for comparison. Palindromic positions have been characterized according to changes in nucleotide base-pairs identifying low-variable positions (LVP) including base-pairs present in less than 80% of the genus. The second step was quantitative, allowing the identification of genomic groups by clustering the base-pair combinations according to LVP. Relatedness among types was evaluated to identify homogeneous groups. Cross comparisons between types within the genus have been evaluated by computing the divergence percentage thus clarifying borderline and multirelated sequences.

Genomic analyses of bovine viral diarrhea viruses isolated from cattle imported into Japan between 1991 and 2005

Thirty-one isolates of bovine viral diarrhea virus (BVDV) isolated within the past 15 years from imported cattle by the Japanese Animal Quarantine Service (AQS) were used in this study in which a 5'-untranslated region of each isolate was genetically analyzed. Twenty-six of the 31 isolates were classified as BVDV1 and the remainder as BVDV2. Phylogenetic analysis of the RT-PCR fragments amplified from the isolates showed the presence of viruses belonging to the BVDV1a, BVDV1b, BVDV1c, unclassified BVDV1 genotypes, and BVDV2. From the cattle of Australian origin, 16 of 17 isolates were classified as BVDV1c. This result was in agreement with a report showing that BVDV1c was a predominant subgenotype in Australia. From the cattle of North American origin, BVDV1 and BVDV2 species were both found. BVDV2 from the North American cattle was identified as the same cluster as the BVDV 890 strain, which is the prototype of BVDV2. These results suggest that the BVDVs isolated from exported cattle at the AQS reflect the predominant genotypes of BVDVs found in the exporting countries. The unclassified BVDV1 genotype of Chinese origin was in the same cluster as the ZM-95 strain, which was isolated from pigs in China. In this study, the genomic properties of 31 isolates of BVDV collected in the AQS were investigated. We concluded that isolates are genetically heterogeneous but geographically restricted. The information obtained from this report will be useful when carrying out epidemiological surveys of BVDV isolated in Japan.

Compatibility of plasmids encoding bovine viral diarrhea virus type 1 and type 2 E2 in a single DNA vaccine formulation

Type 2 bovine viral diarrhea virus (BVDV) has become increasingly prevalent worldwide, and currently the ratio of type 2 to type 1 strains in the USA approaches 50%. Although there is cross-reactivity between BVDV type 1 and type 2 strains, BVDV1 vaccine strains poorly protect from type 2 infection, so vaccines against BVDV should contain antigens from both BVDV types. Previously we demonstrated efficacy of a BVDV1 E2 DNA vaccine, and in this study we optimized a BVDV2 E2 DNA vaccine. Furthermore, as an approach to vaccinate with a DNA vaccine against both BVDV types, we compared two strategies, mixing of plasmids encoding type 1 and type 2 E2, and co-expression of type 1 and type 2 E2 from one plasmid with an internal ribosomal entry site (IRES). An evaluation of the IRES-containing plasmids demonstrated that the C-terminally expressed protein is produced at lower levels and induces weaker immune responses than the N-terminally expressed protein, regardless of the position of the type 1 and type 2 E2 genes. In contrast, when both plasmids encoding type 1 and type 2 E2 were administered to mice, the immune responses were similar to those induced by the individual plasmids. Thus, a mixture of plasmids encoding type 1 and type 2 E2 could be a potential DNA vaccine candidate against both BVDV1 and BVDV2.

Evidence for positive selection on the E2 gene of bovine viral diarrhoea virus type 1

Despite the growing interest in the molecular epidemiology of pestivirus, there have been few attempts to determine which regions of the pestivirus genome are subject to positive selection, although this may be a key indicator of the nature of the interaction between host and virus. By using likelihood-based methods for phylogenetic inference, the positive selection pressure of BVDV-1 E2 gene were assessed and a site-by-site analysis of the dN/dS ratio was performed, to identify specific codons undergoing diversifying positive selection. The overall omega was 0.20, indicating that most sites were subject to strong purifying selection and five positively selected sites (886, 888, 905, 944, and 946) were identified. It is surprising to find that all the potential positively selected sites fall within the C-terminal of E2, and out of the N-terminal of E2 which is thought to be surface-exposed and therefore prime targets for host antibody response. In conclusion, these results suggest that selection favoring avoidance of antibody recognition has not been a major factor in the history of BVDV-1. Further analysis is necessary to see if amino acid substitutions in the BVDV-1 positively selected sites can lead to change of host tropism or\and escape from epitope-specific CD8 T-cell response.

Genetic variability of bovine viral diarrhoea virus subtypes at 3'-nontranslated region

Ten isolates belonging to different BVDV-1 subtypes and three BVDV-2 isolates were studied in 3'-nontranslated region (3'-NTR) by sequencing of PCR products and comparative computer-assisted nucleotide sequence analysis. The alignment of nucleotide sequences revealed that all BVDV-1 isolates except BVDV-1a isolates represented by NADL strain were characterised with a deletion of 38 nucleotides in the variable region located after the stop codon. For all BVDV-1 subtypes, a constant region at the end of viral genome was highly conserved. The variable and constant regions with no significant insertions or deletions were also identified in BVDV-2 isolates. The poly AT reach region was situated at different locations in both pestiviruses.

Molecular characterization of pestiviruses isolated from bovines in Chile

Thirty-three pestiviruses isolated from bovines on different farms in Chile were characterized at the molecular level. The 5'-untranslated region (5'UTR) of the isolates was amplified by reverse transcription-polymerase chain reaction (RT-PCR) and subsequently digested with restriction enzymes (RE) Bgl I, Xho I and Pst I. Furthermore, the isolates were amplified by differential RT-PCR, which selectively amplified bovine viral diarrhea virus type 2 (BVDV-2) but not bovine viral diarrhea virus type 1 (BVDV-1). Of the 33 isolates, 16 were classified as BVDV-1 and 17 as BVDV-2. Phylogenetic analysis of the PCR-amplified fragments from 14 isolates showed the presence of viruses belonging to the BVDV-1a, BVDV-1b, BVDV-1c, and BVDV-2 types. Antigenicity of some viruses belonging to both genotypes was studied by cross-seroneutralization, revealing great antigenic differences among them. It is concluded that BVDV viruses circulating in Chile are genetically and antigenically heterogeneous, comprising isolates of genogroups 1 and 2.

Bovine viral diarrhoea virus (BVDV) subgenotypes in diagnostic laboratory accessions: distribution of BVDV1a, 1b, and 2a subgenotypes

The prevalence of bovine viral diarrhoea virus (BVDV) biotypes and subgenotypes was determined from 131 BVDV positive samples from a diagnostic laboratory. The majority of the isolates were from Oklahoma; however, other states including Kansas, Texas, and Arkansas were represented. These BVDV samples were from submissions of 76 live animals and 55 necropsy samples. There were 131 BVDV samples represented by 117 noncytopathic (NCP), 11 cytopathic (CP) and 3 cases with mixed NCP and CP biotypes. The NCP isolates were more common (P < 0.05) than the CP and NCP/CP combination. The BVDV samples were segregated into three subgenotypes by differential PCR and sequencing of a viral genomic region, 5'-untranslated region (5'-UTR). There were more BVDV1b subgenotypes 60/131 (45.8%) than BVDV1a, 37/131 (28.2%) or BVDV2a, 34/131 (26.0%) (P < 0.05). The organ system involvement included the major categories such as respiratory, digestive, mixed/multiple organs, abortions, and persistent infections (PI). All three BVDV subgenotypes were found in persistently infected (PI) cattle and respiratory diseases, both major requests for BVDV diagnosis. Only one of the 131 viruses was genetically similar to the strains present in U.S. vaccines.

Oesophagoscopy and detection of viral nucleic acids in oesophageal biopsies--A contribution to BVDV diagnosis

The endoscopic appearance of the oesophagus of animals infected with bovine virus diarrhoea virus (BVDV) but without signs of acute mucosal disease (MD) was investigated for any common or 'early warning' lesions. Thirty-seven BVDV-infected animals [36 persistently infected (PI) and one transiently infected] were examined clinically and endoscopically for typical erosions of the oronasal and oesophageal mucosa, respectively. During oesophagoscopy, mucosal biopsies were taken and tested for pestivirus-specific nucleic acids by reverse transcription polymerase chain reaction (RT-PCR). The results were compared with those of RT-PCR with various sample materials (blood, nasal and conjunctival swabs and faecal samples) usually used for routine diagnosis of BVDV infection. The average age of the 36 PI animals was 13.5 months, eight animals were 24 months or older. None of the PI animals had clinically visible erosions of the oronasal mucous membranes. During oesophagoscopy, all animals showed a reddening but unexpectedly no erosions or ulcerations of the oesophageal mucosa. Although in 21 of 36 PI animals all samples tested positive, the oesophageal biopsies were with no exception constantly RT-PCR positive in contrast to all other materials investigated. Remarkably, in the transiently infected animal all samples tested negative except for the oesophageal biopsy. Hence, this infection would have been missed by conventional diagnostic sampling.

Multiple outbreaks of severe acute BVDV in North America occurring between 1993 and 1995 linked to the same BVDV2 strain

The first reported outbreak of bovine viral diarrhea (BVD) in 1946 described a transmissible acute disease characterized by severe leukopenia, high fever, gastrointestinal erosions and hemorrhages. However, in the ensuing years, the most commonly observed acute form of BVD was clinically mild. There was limited viral shed and spread following these acute infections. This led to the assumptions that acute infections with BVD viruses (BVDV) were clinically unimportant, spread of the virus within a group was always due to the presence of a persistently infected animal and transmission between healthy immunocompetent cattle was insignificant. These assumptions were challenged when outbreaks of severe acute BVDV were observed in North America starting in the late 1980s. This study demonstrates that widespread outbreaks of severe acute BVD observed in 1993 in North America can be traced to a single strain of BVDV that apparently spread explosively following acute infection. These findings are notable in that they draw into question management of acute BVD infection, design of studies examining virulence and nomenclature used to identify strains for GenBank submission.

Retrospective genome analysis of a live vaccine strain of bovine viral diarrhea virus

A live bovine viral diarrhea (BVDV) vaccine, marketed as a derivate of the Oregon C24V strain, was used between the end of the 1960s and the beginning of the 1990s in Central Europe. Since laboratory investigations of mucosal disease cases in vaccinated animals suggested recombinations between the vaccine and wild type variants of BVDV, and recombinational nucleotide sequences seemed distinct from BVDV Oregon C24V, the aim of the present retrospective study was to analyze the genomes of pre-registration (termed here BVDV-Xpre) and of marketed (BVDV-X) batches of the vaccine. The results of the complete genome analysis of BVDV-Xpre confirmed that the original virus strain used at the start of the vaccine production was Oregon C24V. Surprisingly, the analysis of the complete nucleotide sequence of the BVDV-X marketed vaccine revealed that this strain belongs to the BVDV 1b subgroup, with a 93.7% nucleotide sequence homology to BVDV reference strain Osloss. The homology to BVDV Oregon C24V was significantly lower (77.4%), and a thorough sequence scanning showed that the genome of BVDV-X had not derived from Oregon C24V. These data indicate the very likely scenario that a strain different to Oregon C24V was picked up during the in vitro or in vivo passages for vaccine development. Despite of the virus-switch, the BVDV-X vaccine continuously maintained its innocuity and efficacy, as proven by the regular quality testing data, and the presence of the foreign virus remained unnoticed over many years. The results of this work emphasize that the contamination of commercially available live vaccines with exogenous BVDV strains is a real risk factor, and a unequivocal analysis, including molecular methods, is needed to verify their authenticity.

Immunogenicity of a bovine viral diarrhea virus E2-C3d fusion protein containing a bovine homolog of C3d

Recently we demonstrated that attachment of three copies of murine C3d (muC3d) to the E2 envelope protein of bovine viral diarrhea virus results in a 10,000-fold increase in the immunogenicity of E2. Here we describe the cloning of the bovine homolog of C3d (boC3d), construction of an E2-boC3d expression cassette and expression and purification of the E2-boC3d fusion protein. We then show that E2, when coupled to boC3d, exhibits greatly enhanced immunogenicity. Thus, boC3d represents the second mammalian C3d homolog, thus far, shown to enhance the immunogenicity of a protein to which it has been coupled. Although the primary sequence of boC3d differs from muC3d by about 19%, we were able to demonstrate the enhanced immunogenicity of E2-boC3d using mice. The ability of boC3d to function in mice provides a less costly and more convenient animal model than cattle for the preliminary evaluation of E2-boC3d and other bovine antigen-boC3d fusion proteins.

Genetic diversity of international bovine viral diarrhoea virus (BVDV) isolates: identification of a new BVDV-1 genetic group

In the last decade, several studies were performed to characterise bovine viral diarrhoea virus (BVDV) isolates and define genetic groups by genotyping. Much data is now available from GenBank, predominantly sequences from the 5' untranslated region (5'-UTR). In order to find out whether genetic grouping of isolates from different countries could be harmonised, 22 new isolates from five countries were analysed in combination with published sequences. Eighteen of these isolates were typed as BVDV genotype 1 (BVDV-1), and one isolate from Argentina and three isolates from Brazil were typed as BVDV-2. BVDV-1 isolates were clustered into five previously defined genetic groups: BVDV-1a, b, d, e and f. Two isolates from Finland and one from Egypt formed a group which was tentatively labelled as BVDV-1j, since statistical support was low. By using a fragment of the Npro gene for typing, we found that these isolates fall into the same group as a deer strain, and are statistically significant. Some Swiss BVDV strains taken from GenBank were found in a new genetic group which was designated as BVDV-1k. The BVDV-2 isolates included in this study seemed to fall into two genetic groups.

Attenuation of a virulent type 2 bovine viral diarrhea virus

The purpose of this study was to produce an attenuated bovine viral diarrhea virus (BVDV) type 2 strain as a tool for identifying potential virulence markers in the BVDV2 genome. The attenuation of the virulent strain, BVDV2-24515, was accomplished by in vivo and in vitro passage. The strain was initially used to infect an elk (Cervus elaphus) [J. Wildl. Dis. 35 (1999) 671], re-isolated at 7 days post-inoculation from serum, and then subsequently passaged 56 times in cell culture. Two groups of calves were inoculated intranasally with either BVDV2-24515 or the putative attenuated virus, designated BVDV2-LATT. Calves inoculated with BVDV2-24515 had cumulative clinical scores which ranged from 6 to 53. Clinical signs in these calves consisted of anorexia, depression, dehydration, diarrhea (+/-bloody), and pneumonia. Several calves developed leukocytopenia, primarily a neutrocytopenia, and presented lesions of enteritis or pneumonia at necropsy. In contrast, cattle inoculated with BVDV2-LATT had cumulative clinical scores which ranged from 0 to 2. This was not significantly different from that of controls which received no virus (range: 0-1). Calves inoculated with BVDV2-LATT produced high neutralizing antibody titers against BVDV2. Thus, in addition to its potential use as a tool for identifying virulence markers, the attenuated virus is also worthy of further study as a candidate virus for inclusion in a modified-live vaccine.

Characterisation of a type 2 bovine viral diarrhoea virus isolated from cattle in the UK

Two genotypes of bovine viral diarrhoea virus (BVDV) are recognised. Type 2 was first recognised when virulent strains caused significant losses among cattle in North America. Subsequently, BVDV type 2 has been found in many other countries, but recent studies have shown that only type 1 BVDV is circulating in the UK herds (sheep and cattle) with type 1a predominating. During routine genotyping of UK BVDV isolates, a type 2 isolate was identified. Phylogenetic analysis of the 5'-untranslated region of the viral genome showed it to be a BVDV type 2a, most similar to a low virulent US strain of BVDV type 2. Antigenic typing with a panel of monoclonal antibodies verified this classification. This is the first confirmed isolation of BVDV type 2 found circulating in the UK.

Genetic variety of bovine viral diarrhea virus 2 strains isolated from sheep

Bovine viral diarrhea virus 2 (BVDV-2) strains, isolated from sheep showing clinical symptoms of border disease, have been evaluated by the palindromic nucleotide substitution (PNS) method at the three variable loci (V1, V2 and V3) in the 5'-untranslated region (UTR) of genomic RNA. The characteristic two base-pairings common to the BVDV-2 species, a C-G pairing which was common to the V1 locus, and a G*U pairing common to the V2 locus, were observed in all tested strains. Strains BD-78 and C413 were identified by a unique C-G pairing at position 4 from the bottom of the V2 stem region, which is characteristic to BVDV-2b. BVDV-2d characteristic U-A pairing at position 18 of the V1 stem region was observed in five strains, Lees, 167 237, 168 149, 173 157 and 175 375. No strains have been assigned to the genotypes BVDV-2a or BVDV-2c. Furthermore, the investigation at the level of the 5'-UTR excluded the application in sheep of the proposed BVDV-2 genetic virulence markers described in cattle. The two specific positions of uracil and cytosine nucleotides related to low or high virulence where indifferently present in the ovine BVDV-2 strains responsible of border disease.

Gene expression changes in MDBK cells infected with genotype 2 bovine viral diarrhoea virus

Bovine viral diarrhoea viruses (BVDVs) are ubiquitous viral pathogens of cattle. These viruses exist as one of two biotypes, cytopathic and noncytopathic, based on the ability to induce cytopathic effect in cell culture. The noncytopathic biotypes are able to establish inapparent, persistent infections in both cell culture and in bovine foetuses of less than 150 days gestation. Interactions with the host cell and the mechanism by which viral tolerance is established are unknown. To examine the changes in gene expression that occur following infection of host cells with BVDV, serial analysis of gene expression (SAGE), a global gene expression technology was used. SAGE allows quantitation of virtually every transcript in a cell type without prior sequence information. Transcript expression levels and identities are determined by sequencing libraries composed of concatamers of 14 base DNA fragments (tags) derived from the 3'-end of each cellular mRNA transcript. Comparison of data obtained from uninfected and BVDV genotype 2-infected cell libraries revealed changes in gene expression associated with distinct biochemical pathways or functions. Isotypes of both alpha- and beta-tubulins were down-regulated, indicating possible dysfunction in cell division and other functions where microtubules play a major role. Expression of genes encoding proteins involved in energy metabolism were expressed at essentially equivalent levels in both infected and uninfected cells. Genes encoding proteins involved in protein translation and post-translational modifications, functions necessary for viral replication, were generally up-regulated. These data indicate that following infection with BVDV, changes in gene expression occur that are beneficial for virus replication while having only minor changes in energy metabolism.

Experimental infection of calves with bovine viral diarrhoea virus type-2 (BVDV-2) isolated from a contaminated vaccine

A non-cytopathic strain of BVDV-2 was isolated from a batch of live infectious bovine rhinotracheitis (IBR) vaccine, and inoculated intranasally into four 3-month-old calves. Severe signs of disease developed by days 4 and 6 in three of the calves, free of BVDV and antibodies to BVDV, that had been exposed to the virus. These calves survived the acute phase of the infection and progressively recovered. BVDV was consistently isolated, or the respective viral RNA was detected, in the buffy coats from blood samples collected starting from days 2 or 4 up to days 11 or 14 after the experimental infection. Viral RNA was also detected in sera from these infected calves until the presence in the serum of virus neutralizing antibodies was demonstrated. By contrast, the only calf having pre-existing neutralizing antibodies to BVDV at the start of the study was protected from the disease. No virus was detected at any time after experimental inoculation of this calf. Genomic characterization of the BVDV-2 isolated in cell cultures, or detected in sera from the experimentally infected animals, revealed 100%, homology in the nucleotide sequence with the BVDV-2 detected as a contaminant of the live IBR virus vaccine. These findings provided evidence of the infective nature of the contaminant BVDV-2 and of its potential to generate disease outbreaks when inoculated into susceptible animals.

A hepadnavirus regulatory element enhances expression of a type 2 bovine viral diarrhea virus E2 protein from a bovine herpesvirus 1 vector

Recently, the possibility of using virus vectors to immunize cattle against selected bovine viral diarrhea virus (BVDV) genes has gained widespread interest. However, when we attempted to express the E2 protein from type 2 (890 strain) BVDV in a bovine herpesvirus 1 (BHV1) vector, we observed that expression was poor. This often happens when genes from a cytoplasmic virus are expressed in the cell nucleus. To counter this effect, we attempted to enhance expression by a strategy employed by viruses. RNAs of retroviruses and hepadnaviruses contain cis-acting elements that facilitate expression of RNAs that otherwise are degraded or retained within the nucleus. In Mason-Pfizer monkey virus, the required RNA sequence element is known as a constitutive transport element (CTE). A related element from woodchuck hepatitis virus is known as the woodchuck posttranscriptional regulatory element (WPRE). We tested the ability of the CTE, the WPRE, and introns to enhance expression of E2. All three elements stimulated expression of E2 from plasmids. The combination of the WPRE and an intron yielded the highest level of E2 expression in plasmids. However, when E2 was expressed from a BHV1 vector, the presence of an intron was inhibitory. In contrast, the WPRE was very efficient at stimulating E2 expression from a BHV1 vector. This result represents the first expression of a type 2 BVDV E2 protein from a mammalian virus vector and raises the possibility that the WPRE may provide a general method of enhancing foreign gene expression from BHV1 and other herpesvirus vectors.

Gene expression changes in BVDV2-infected MDBK cells

Bovine viral diarrhoea virus (BVDV) is a ubiquitous viral pathogen of cattle. The virus exists as one of two biotypes, cytopathic and non-cytopathic, based on the ability to induce cytopathic effect in cell culture. The non-cytopathic biotypes are able to establish non-apparent, persistent infections in both cell culture and in bovine foetuses of fewer than 150 days gestation. The mechanism by which viral tolerance is established is unknown. To examine the changes in gene expression that occur following infection of host cells with BVDV, serial analysis of gene expression (SAGE), a global gene expression technology was used. SAGE, a sequence-based technology, allows quantification of virtually every transcript in a cell type without prior sequence information. Transcript expression levels and identities are determined by DNA sequencing of libraries composed of 14 base DNA fragments (tags) derived from the 3' end of each cellular mRNA transcript. Comparison of data obtained from non-infected and BVDV2-infected cell libraries revealed a number of changes in gene expression. Many of these transcriptional changes could be placed into distinct biochemical pathways or functions. Both alpha and beta tubulins were downregulated, indicating possible dysfunction in cell division and other functions where microtubules play a major role. Expression of several genes encoding proteins involved in energy metabolism were downregulated, indicating possible decreased ATP synthesis. Genes encoding proteins involved in protein translation and post-translational modifications were generally upregulated. These data indicate that following infection with BVDV, changes in gene expression occur that are beneficial for virus replication while placing the cell at a metabolic disadvantage.

Evaluation of the reverse transcription-polymerase chain reaction/probe test of serum samples and immunohistochemistry of skin sections for detection of acute bovine viral diarrhea infections

Bovine viral diarrhea viruses (BVDV) cause both acute and persistent infections. While diagnostic tests have been designed to detect animals persistently infected (PI) with BVDV, the reliability of these tests in detecting acute BVDV infections is not known. It is also possible that acute BVDV infections may be confused with persistent infections in surveys for PI animals. In this study, 2 tests presently in use in diagnostic laboratories to test for PI animals, polymerase chain reaction amplification followed by probe hybridization (RT-PCR/probe) of serum samples and immunohistochemical detection of viral antigen in skin biopsies (IHC), were evaluated for their ability to detect acute BVDV infections. Sixteen colostrum-deprived, BVDV-free, and BVDV-antibody-free calves were infected with 6 different BVDV strains. Clinical signs, seroconversion, and virus isolation indicated that inoculated animals did replicate virus. Virus could be detected in 19% (3/16) of acutely infected animals by the RT-PCR/probe technique. No acutely infected animals were positive by IHC.

Phylogenetic analysis of the 5'-untranslated region of german BVDV type II isolates

On the basis of genetic differences, bovine viral diarrhoea viruses (BVDV) are subclassified into two distinct genotypes, BVDV type I and BVDV type II. We selected German BVDV type II isolates using the BVDV type I-specific monoclonal antibody WB160 and flow cytometric analysis for further characterization. For molecular characterization, a 288-bp fragment of the 5'-untranslated region (5'-UTR) of the selected isolates was investigated by reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. Sequence comparisons of the partial 5'-UTR sequences and their phylogenetic analyses demonstrated that the 18 German BVDV type II isolates all belong to either subtype IIa (10 isolates) or subtype IIc (eight isolates). Nevertheless, the German BVDV type II isolates were genetically different (89.9-94.3% sequence identity) from the standard BVDV type II strain 890 from North America, which was recently classified as BVDV type IIa. Furthermore, a clear subdivision of the German BVDV type II isolates into two distinct subtypes (BVDV IIa Germany and BVDV IIc Germany) is shown. Viruses of both subgroups differed in the analysed 5'-UTR fragment from each other (91.6-95.2% sequence identity), but were highly conserved within the same German subtype (97.2-100% sequence identity). These findings are discussed in the context of BVDV type II origin, possible introduction into Germany, its epidemiology and impact for vaccine development.

Nylon membrane-immobilized PCR for detection of bovine viruses

Bridge Technology is an amplification technique in which pairs of primers are immobilized on a solid support, allowing amplification only at the location of the primer pair spot. The technique has diagnostic potential since an array of primer pairs, each specific for a different pathogen, can be used with a diagnostic sample without inter-pair interactions that plague the development of multiplex PCRs. As a result, one assay should be able to determine which of multiple pathogens are present and which are absent in each sample. As test material, we examined the specificity of detection of the RNA-containing bovine viral diarrhea virus (BVDV) and two DNA-containing bovine herpesviruses 1 and 2 (BHV-1 and BHV-2). Nylon membranes with two spots of UV-immobilized primer pairs--one for BVDV and one for BHV--were used in amplification with both corresponding templates, with each template singly and with no template. When amplification was assayed by chemiluminescent detection of incorporated DIG-nucleotides, the expected amplification patterns were obtained.