ABSTRACT
The bovine viral diarrhea virus (BVDV) infection control should be based on elimination of persistently infected animals and on immunization through vaccination, to prevent fetal infection. However, the efficacy of inactivated BVDV vaccines is variable due to its low immunogenicity. This study evaluated the humoral immune response against homologous and heterologous strains of 7 inactivated BVDV vaccines, in bovines and two experimental models (ovine and guinea pig) which might be used to test candidate vaccines. Vaccines formulated with BVDV Singer, Oregon, NADL, and multivalent, induced seroconversion in the three animal models studied, reaching antibody titres higher than 2. Vaccine containing 125C -genotype 2- only induced a low antibody response in ovine, while VS-115 NCP vaccine was not immunogenic. Furthermore, bovine sera at 60 dpv presented homologous as well as heterologous antibody response, indicating a high degree of cross-reactivity among the strains studied. However, when bovine sera were tested against the Argentine field strain 00-693, they showed the lowest levels of cross-reactivity, suggesting the need of continued surveillance to identify and characterize emerging field BVDV strains. Finally, optimal correlations between bovine-ovine and bovine-guinea pig models were observed, indicating that two alternative species could replace bovines when testing the immunogenicity of BVDV candidate vaccines.
El control del virus de la diarrea viral bovina (VDVB) se basa en la eliminación de animales persistentemente infectados, y la inmunización de hembras para prevenir infecciones fetales. La eficiencia de estas vacunas es variable por su baja inmunogenicidad. Se evaluó la respuesta inmune humoral contra virus homólogos y heterólogos de 7 vacunas experimentales inactivadas del VDVB en bovinos y en dos modelos experimentales (ovinos y cobayos). Las vacunas conteniendo VDVB Singer, Oregon, NADL y polivalentes indujeron seroconversión en los tres modelos y se alcanzaron títulos de anticuerpos mayores de 2. La vacuna con VDVB genotipo 2 VS-115, NCP, no resultó inmunogénica. La vacuna genotipo 2 125C sólo indujo baja respuesta humoral en ovinos, mientras que la VS-115, NCP, no resultó inmunogénica. En bovinos se determinó la respuesta a virus homólogos y heterólogos a 60 dpv, lo que indica un alto grado de inmunidad cruzada entre la mayoría de las cepas estudiadas. Cuando los sueros bovinos fueron ensayados con la cepa de campo de Argentina 00-693, los niveles de reacción cruzada fueron más bajos; esto sugiere la necesidad de una vigilancia epidemiológica sostenida a fin de identificar y caracterizar las cepas emergentes del VDVB. La óptima correlación en el modelo bovino-ovino y bovino-cobayo indica su utilidad para evaluar la inmunogenicidad de vacunas inactivadas de VDVB.
Subject(s)
Animals , Cattle , Guinea Pigs , Diarrhea Viruses, Bovine Viral/immunology , Viral Vaccines/immunology , Antibodies, Viral/biosynthesis , Antibodies, Viral/immunology , Dose-Response Relationship, Immunologic , Diarrhea Viruses, Bovine Viral/genetics , Genotype , Models, Animal , Neutralization Tests , Sheep , Species Specificity , Vaccines, Inactivated/immunologyABSTRACT
Group A Bovine Rotavirus (BRV) has been identified as a major cause of neonatal diarrhea in cattle. The study was aimed to determine the prevalence of BRV and to antigenically characterize the G-types of circulating strains in dairy and beef herds in Argentina. A total of 1129 stool samples from diarrheic calves was analyzed from 1994 to 1999. The samples were initially screened for RV by ELISA and PAGE, and then G-typed using monoclonal antibodies (Mab) directed against G1, G2, G3, G6 and G10-specific epitopes. Forty percent (452/1129) of the samples were positive for RV by ELISA, while 24.7 (279/1129) were also positive for PAGE. VP7 was detected in the 70.5 (319/452) of the positive samples using a broadly reactive Mab (C60); 32.6 (104/319) were G6, 15.4 (49/319) were G10, and 6 (19/319) were G1. However, 46.1 (147/319) of the samples remained untypable. Rotavirus diarrhea prevalences were comparable in beef and dairy herds (87.3 and a 74.4, respectively). Finally, G6 was the most prevalent G-type circulating in beef herds while G10 prevailed in dairy herds. A better understanding of RV epidemiology will contribute to the optimization of current vaccines and prevention programs of RV diarrhea in calves.
Subject(s)
Animals , Cattle , Diarrhea , Cattle Diseases/virology , Rotavirus Infections/veterinary , Rotavirus , Antibodies, Monoclonal , Antibodies, Viral , Argentina , Diarrhea , Cattle Diseases/epidemiology , Electrophoresis, Polyacrylamide Gel , Enzyme-Linked Immunosorbent Assay , Feces , Rotavirus Infections/epidemiology , Rotavirus Infections/virology , Prevalence , Viral Proteins/immunology , RotavirusABSTRACT
Two handred and ninety five faecal samples from 45 days old calves with and without diarrhoea were processed using the ELISA, PAGE, and IFT techniques for rotavirus detection. Ninety one sample (31%) proved to be positive bu at least one of the techniques used. ELISA detected 93%, PAGE 84% and IFT 67%. Fifteen per cent of the samples were positive using ELISA and negative using PAGE, The reverse situation appeared in 5% of the samples. In 5%, 4% and 1% only of the techniques used showed the presence of the virus (ELISA, PAGE and IFT, respectively). ELISA proved to be the most sensitive technique for the detection of rotavirus in the faeces of calves. No relationship could be established between detection of rotavirus by any one of teh techniques used and age, imptomatology, geographical distribution, and electrophoretic pattern. Rotavirus was detected more frequently in diarrheic than in non-diarrheic calves