To study the pathogenicity of the Brazilian bovine viral diarrhea virus (BVDV) type 1a 241.10 isolate, four calves were intranasally inoculated with a viral suspension containing 107.2 TCID50 mL-1. One calf was left uninoculated and kept in contact with the other calves to investigate viral transmissibility. After inoculation, the animals were monitored daily for clinical signs of infection. The presence of the virus in the blood and nasal secretions was confirmed by virus isolation in cell culture. White blood cells were quantified prior to and every 3 days after infection, and the presence of antibodies was checked every 7 days, starting at day 0 until day 42 post-inoculation (pi). After infection, nasal and ocular serous secretions were observed between days 1 and 5 pi, along with a mild cough from days 2 to 4 pi; however, no severe clinical signs were present. Body temperature was slightly elevated between days 4 and 6 pi. The control calf did not develop any of the signs observed in the infected animals. Cell culture-mediated virus isolation confirmed viremia between days 4 and 8 pi and the presence of the virus in the nasal secretions between days 1 and 10 pi. All infected animals showed a decrease in white blood cell count. Antibodies could be detected from day 14 pi, and these levels remained high until day 35 pi. The control calf had no viremia, viral presence in nasal secretions, or positive serology, indicating the absence of viral transmission. Thus, isolate BVDV 1a 241.10 has low pathogenicity and transmissibility but retains immunosuppressive capacity.
Resumo O objetivo do estudo foi produzir anticorpos policlonais para vírus bovino e testar a reatividade em imunoensaios como imunofluorescência, imunoperoxidase e slot blot. Como imunógeno utilizou-se cepas e/ou isolados dos herpesvírus bovino tipo 1, 2 e 5 (BoHV-1, BoHV-2 e BoHV-5), vírus da diarreia viral bovina (BVDV), vírus respiratório sincicial bovino (BRSV), vírus da língua azul (BTV) e vírus vaccina (VACV) amplificados em cultivo celular. Os coelhos foram imunizados em intervalos regulares e o soro hiperimune produzido foi utilizado como anticorpo primário nos imunoensaios. A diluição de trabalho para cada antissoro foi determinada por diluição seriada limitante e variaram entre 1:800 e 1:51.200. As maiores diluições foram observadas para imunoperoxidase, quando comparadas com a imunofluorescência e slot blot. Diluições menores que 1:800 foram associadas com aumento de reações inespecíficas. Os antissoros anti-BoHV-1, -BoHV-5, -BVDV e -BRSV reagiram frente a isolados heterólogos em ensaios de imunofluorescência e imunoperoxidase. Conclui-se que os antissoros produzidos possuem elevadas concentrações de anticorpos específicos para os vírus e é uma alternativa para a utilização em imunoensaios.
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