Virus neutralizing antibodies against a panel of 18 BVDV isolates in calves vaccinated with Rispoval RS-BVD

Seven of nine colostrum-deprived calves, free from infection with bovine virus diarrhoea virus (BVDV), were vaccinated with Rispoval RS-BVD on two occasions, 21 days apart, while the other two were kept as BVDV infection controls. The virus neutralizing (VN) serum antibodies induced by vaccination were tested for their ability to neutralize 18 European BVDV isolates, including laboratory reference strains and recent field isolates, both cytopathic and non-cytopathic biotypes as well as genotypes I and II. The strains were isolated in Belgium, France, Germany and the United Kingdom. While there were large variations in the vaccine-induced VN titres of the individual calves against all the strains, e.g. the titres against Osloss NCP, the European reference strain ranged from 1.7 to 6.7 (1:log2), serum from each animal was capable of neutralizing between nine and all 18 of the strains tested. Nevertheless, from the results of this study, it can be concluded that in colostrum-deprived BVDV seronegative calves, Rispoval RS-BVD can stimulate the production of VN antibodies capable of neutralizing a wide range of antigenically diverse European isolates of BVDV, including genotypes I and II.     

Canine distemper virus neutralising antibodies in vaccinated dogs

The associations between the levels of canine distemper virus neutralising antibodies and vaccination history, age and gender were investigated in a cross-sectional study of a sample of 4627 dogs from the Finnish urban dog population. Dogs vaccinated with either Canlan (Langford Laboratories) or Dohyvac (Solvay Animal Health) or with both, had significantly lower titres than those vaccinated with Candur (Behringwerke), Duramune (Fort Dodge Laboratories) or Nobivac (Intervet), or with combinations including at least one of these. The vaccines were classified as having low and high immunogenicity on the basis of the geometric mean titre achieved by the vaccine when compared with the geometric mean titre of the entire dataset. The low geometric mean titre of Canlan, Dohyvac and their combination groups resulted from the large proportion of dogs without detectable titres, especially dogs under one year of age, rather than from uniformly low titres. An age-stratified comparison of vaccine usage and titres showed that the division of the vaccines into low and high immunogenicity vaccines was apparent in the dogs less than two years of age but not in the older dogs. The first vaccination with the high immunogenicity vaccines resulted in a higher proportion of dogs with detectable antibodies than even repeated vaccination with the low immunogenicity vaccines. Neither the time elapsed since the most recent vaccination nor the gender of the dogs was associated with the titre of antibody.     

Epitopic characterisation of Turkish bovine viral diarrhoea virus (BVDV) isolates using monoclonal antibodies

In this study, 15 bovine viral diarrhoea viruses (BVDV) isolated from the field in Turkey were characterised for their biotype, cloned and eventually analysed for their epitopic composition in terms of glycoprotein E2. Immunoplaque assay, plaque assay, limiting dilution and streptavidin-biotin-peroxidase techniques were used for biotype characterisation, cloning of cytopathic (cp) and noncytopathic (ncp) biotypes and epitope analysis, respectively. While 14 out of 15 BVDV isolates were distinguished as ncp biotype, 1 isolate was found to be containing both biotypes (cp + ncp). According to the reactivity patterns of isolates with 15 monoclonal antibodies, 4 different antigenic groups could be formed. There were no antigenic differences between the isolates derived from the same animal with various time intervals. On the other hand, biotype clones isolated from the same animal exhibited difference in one epitope. This is the first study describing antigenic characterisation of BVDV field isolates in Turkey.     

Genetic typing of bovine viral diarrhoea virus isolates from India

Thirteen BVDV isolates collected in four geographic regions of India between 2000 and 2002 were typed in 5'-UTR. To confirm results of genetic typing, selected viruses were also analysed in the N(pro) region. Phylogenetic analysis revealed that all Indian BVDV isolates belong to BVDV-1b (Osloss-like group). Despite a long distance between the farms from which the viruses were isolated there was no correlation between the origin of viral isolates and their position in a phylogenetic tree. Higher genetic similarity of Indian BVDV isolates was observed most probably due to the uncontrolled movement of cattle as well as the uncontrolled use of semen from bulls for breeding of local and farm cattle in different states of India.     

Antigenic characterization of bovine viral diarrhoea virus isolates from Spain with a panel of monoclonal antibodies

A group of 47 bovine viral diarrhoea virus (BVDV) strains isolated from a variety of bovine tissues from eight different geographical areas of Spain and two BVDV strains isolated from a cell line were characterized antigenically with a panel of 23 monoclonal antibodies (mAbs). The mAbs were directed at one of three viral proteins: E2, Erns and NS2-3. A peroxidase-linked assay was used to test the mAbs for reactivity against infected cell monolayers. The data were analysed by two computational methods: the Antigenic Distance Program (MAP) and the Phylogeny Inference Package (PHYLIP), and compared with those obtained previously using the same mAbs with other pestiviruses, including reference strains and UK field isolates. All the Spanish field strains studied appeared to be broadly similar to reference strains of BVDV and were included in the subgroup of classical BVDV, meanwhile the two strains isolated from a cell line were included in the subgroup of atypical pestiviruses.     

Expression of the E2 envelope glycoprotein of bovine viral diarrhoea virus (BVDV) elicits virus-type specific neutralising antibodies

A region of genome from the NADL strain of BVDV corresponding to the coding sequence for the E2 glycoprotein has been molecularly cloned using RT-PCR. The viral cDNA sequence was used to construct vaccinia virus recombinants that expressed either the entire E2 coding sequence or fragments of it. These recombinants were used to immunise mice of three H-2 haplotypes to investigate their ability to elicit a neutralising antibody response against BVDV. Sera from mice immunised with the recombinant expressing full length E2 contained high levels of virus neutralising antibodies that in addition to giving neutralisation of the homologous NADL strain were also able to neutralise the Oregon C24V reference strain. These sera failed to give any neutralisation of the Osloss reference strain providing evidence for the division of BVDV isolates into at least two distinct E2 serotypes. These results were confirmed in gnotobiotic lambs. Expression of E2 fragments revealed the presence of at least two distinct neutralising epitopes, one of which was localised within the carboxy terminal 90 amino acids of the protein.     

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

OBJECTIVE: To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. ANIMALS: 1,782 calves from 61 beef herds. PROCEDURES: Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. RESULTS: There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. CONCLUSIONS AND CLINICAL RELEVANCE: BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.     

Lack of virus transmission from bovine viral diarrhoea virus infected calves to susceptible peers

None of 14 calves not previously exposed to BVDV became infected after being forced to have nose-to-nose contact with a group of 5 calves primarily infected with BVDV. These were 5 male calves primarily infected with a type I BVDV strain, after nose-to-nose contact with a persistently viraemic calf. All 5 became infected and were clinically affected. They were slightly depressed and pyretic at 8-9 days post-infection, with a body temperature of up to 41.6 degrees C, but no medical treatment was required. Seroconversions to BVDV were detected in these calves at 14 to 21 days post-infection. The 14 healthy calves, proved to be free from BVD virus--as well as antibodies, were introduced 2 by 2 into the group of 5 primarily infected calves on days 4, 7, 14, 21, 28, 35 and 42 after the 5 calves had been in contact with the persistently BVDV-infected calf. Each pair of calves stayed within the primarily infected group for 2 days. None of these 14 calves seroconverted to BVDV.     

The pathology of concurrent bovine viral diarrhoea and infectious bovine rhinotracheitis virus infection in newborn calves

Concurrent bovine viral diarrhoea (BVD) and systemic infectious bovine rhinotracheitis (IBR) are reported from two neonatal (11 and 15 days old) calves. The diseases occurred sporadically in a large-scale herd which may have been due to the calves' heterogeneous immunobiological status. Gross pathological and histopathological examinations revealed focal interstitial pneumonia with acidophilic intranuclear inclusions in the alveolar epithelial cells and necrotic foci in the liver with a few intranuclear inclusions in the hepatocytes. There were subserous haemorrhages in the forestomachs and intestine, necrotic changes in the rumen, enteritis, lymphocytic necrosis in the Peyer's patches, and fibrinoid necrosis in the wall of some of the neighbouring blood vessels. BVD virus was demonstrated by immunofluorescence (IF), whereas IBR virus by electron microscopy, immunofluorescence and virus isolation.     

Evaluation of protection against virulent bovine viral diarrhea virus type 2 in calves that had maternal antibodies and were vaccinated with a modified-live vaccine

OBJECTIVE: To evaluate the efficacy of an adjuvanted modified-live bovine viral diarrhea virus (BVDV) vaccine against challenge with a virulent type 2 BVDV strain in calves with or without maternal antibodies against the virus. DESIGN: Challenge study. ANIMALS: 23 crossbred dairy calves. PROCEDURES: Calves were fed colostrum containing antibodies against BVDV or colostrum without anti-BVDV antibodies within 6 hours of birth and again 8 to 12 hours after the first feeding. Calves were vaccinated with a commercial modified-live virus combination vaccine or a sham vaccine at approximately 5 weeks of age and challenged with virulent type 2 BVDV 3.5 months after vaccination. Clinical signs of BVDV infection, development of viremia, and variation in WBC counts were recorded for 14 days after challenge exposure. RESULTS: Calves that received colostrum free of anti-BVDV antibodies and were vaccinated with the sham vaccine developed severe disease (4 of the 7 calves died or were euthanatized). Calves that received colostrum free of anti-BVDV antibodies and were vaccinated and calves that received colostrum with anti-BVDV antibodies and were vaccinated developed only mild or no clinical signs of disease. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the modified-live virus vaccine induced a strong protective immune response in young calves, even when plasma concentrations of maternal antibody were high. In addition, all vaccinated calves were protected against viral shedding, whereas control calves vaccinated with the sham vaccine shed virus for an extended period of time.     

Preliminary serological characterization of bovine viral diarrhoea virus strains using monoclonal antibodies

Five monoclonal antibodies against the bovine viral diarrhoea (BVD) viral strain NADL were isolated and characterized by an indirect immunofluorescence assay. Extensive cross-reactions were detected when the antibodies were tested with 12 heterologous BVD and four hog cholera (HC) viral strains. One antibody reacted with all strains tested. Two antibodies were specific for cytopathogenic BVD viruses, but failed to react with HC virus. The other antibodies reacted to varying degrees with BVD and HC viral strains.     

Primary bovine viral diarrhoea virus infection in calves following direct contact with a persistently viraemic calf.

Six calves, aged 24 to 58 days and not previously exposed to bovine viral diarrhoea virus (BVDV), were infected with this agent by nose-to-nose contact with a persistently BVDV viraemic calf. The study was conducted in two trials, using 3 calves in each. All 6 calves showed a peak interferon level in serum at 4 days post infection (dpi), and they seroconverted to BVDV at 16-21 dpi. The calves in trial 1 had diarrhoea for 2 or 3 days between 2 and 6 dpi and one calf again from 9 to 11 dpi. During the periods of fever, the calves were slightly depressed. Those in trial 2 were more depressed and their oral and nasal mucous membranes were reddened but they never had diarrhoea. In both trials, fever (up to 41.3 degrees C) was a prominent symptom at 8 to 9 dpi and 2 calves showed a diphasic fever course. Respiratory affection was mild and no medical treatment was required. Haematological assessment demonstrated a transient but significant leukopenia and lymphopenia at 4 dpi (P less than 0.01 and P less than 0.05 respectively) and 11 dpi (P less than 0.05 and P less than 0.01 respectively). A significant decrease in thrombocyte count was seen at 4 dpi (P less than 0.05, n = 3). This study has demonstrated that nose-to-nose contact is an effective way of transmitting BVDV from persistently infected to susceptible cattle.     

Cytopathogenicity markers in the genome of Hungarian cytopathic isolates of bovine viral diarrhoea virus

Since genetic recombination is a major factor in the evolution of the cytopathogenic (cp) bovine viral diarrhoea virus (BVDV) biotypes, in this study the cytopathogenicity markers were investigated in the genomes of two cp BVDV strains recently isolated from mucosal disease (MD) cases in Hungary. In the genome of strain H4956, a Jiv-like insertion was found similar to those described in reference strain NADL and in other BVDV 1, BVDV 2 and border disease virus (BDV) strains. The 133 amino acid Jiv-like sequence is inserted at nucleotide position 4984 (amino acid position 1533), 9 nucleotides upstream of that of strain NADL. The insertion showed 96% amino acid sequence identity with the cellular Jiv protein. In the genome of cp BVDV strain H115/PCR, an ubiquitin-containing duplication was found. The duplicated sequence started at nucleotide position 7978 (amino acid 2531) in the NS4B gene. The duplication contained a complete ubiquitin monomer of 76 amino acids and the complete NS3 gene starting at nucleotide position 5153 (amino acid 1589), which corresponds to the first N-terminal amino acid of NS3. The duplication was located further downstream of the known ubiquitin-containing genomic regions of cp BVDV strains, and it consisted of the shortest inserted nucleotide sequence. The insertions and duplication of strains H4956 and H115/PCR further confirmed that recombinations occurring at positions A and B are the most common mechanisms leading to the development of BVDV cytopathogenicity.     

Spread of bovine virus diarrhoea virus in a herd of heifer calves.

A calf persistently infected and immunotolerant to Bovine Virus Diarrhoea virus (BVD virus) was, on purpose, introduced to a herd of heifer calves over 4 months of age that had been reared as recipients for embryo transplantation. All calves were brought in contact with the persistently infected animal. In total, 240 calves were involved in this experiment, 22 of which were serologically negative when introduced. These serologically negative animals developed antibodies against BVD virus within 5 months after introduction. At short distances from the persistently infected BVD virus shedder, negative calves seroconverted within 2 months, but at greater distances the moment of seroconversion was unpredictable. The calves that had undergone a natural infection with BVD virus received embryos after transportation to an allied farm. In total, 14 calves were born after embryo transplantation, all of which were free of BVD virus, in spite of the presence of BVD-virus on the latter farm.     

Vaccination of cattle against bovine viral diarrhoea

This brief review describes types and quality (efficacy and safety) of bovine viral diarrhoea virus (BVDV) vaccines that are in the market or under development. Both conventional live and killed vaccines are available. The primary aim of vaccination is to prevent congenital infection, but the few vaccines tested are not highly efficacious in this respect, as shown in vaccination-challenge experiments. Vaccination to prevent severe postnatal infections may be indicated when virulent BVDV strains are prevalent. Live BVDV vaccines have given rise to safety problems. A complication for the development of BVDV vaccines is the wide antigenic diversity among wild-type BVDV. There is ample room for improvement of both the efficacy and safety of BVDV vaccines, and it may be expected that better vaccines, among which marker vaccines, will be launched in the future.     

ELISA detection of bovine viral diarrhoea virus specific antibodies using recombinant antigen and monoclonal antibodies

A panel of monoclonal antibodies was prepared by immunization of BALB/c mice with Moredun (BD) virus strains. These antibodies were characterized by immunofluorescence and seroneutralization against BD, BVD and hog cholera (HC) virus strains, and radioimmunoprecipitation of BVD-infected cells extracts. The MAbs reacting with the majority of the Pestivirus strains recognize the 80 kDa antigen of the BVD cytophathic strains. The 80 kDa antigen of the BVD/Osloss virus strain has been cloned and expressed in E. coli as a fusion protein with beta-galactosidase. The fusion protein has been purified from inclusion bodies and used successfully as an antigen for ELISA detection of BVDV specific antibodies in bovine sera. A competitive ELISA using MAbs is more specific than a direct assay. These results compare well with the ones obtained with antigen extracted from BVDV-infected cells.