Alterations of Immunologic Responses of Calves Experimentally Infected with Virulent Either Type I or 2 Non-Cytopathogenic Strains of Bovine Viral Diarrhea Virus
Alterations of Immunologic Responses of Calves Experimentally Infected with Virulent Either Type I or 2 Non-Cytopathogenic Strains of Bovine Viral Diarrhea Virus
Ahmed Abd El-Samie H. Ali
ABSTRACT
Bovine viral diarrhea virus (BVDV) is a worldwide pathogen infecting cattle. Eleven Holstein calves between 6-8 months of age that were seronegative to BVDV were divided into three groups (n=4 for NY-1, n=4 for 890 and n=3 control). Fibroblast cells were prepared from calves' skin biopsies by trypsin digestion. Using immunofluorescence. the percentages of infected cells and MHC antigens expression were evaluated. fibroblast and peripheral blood mononuclear (PBMC) cells were in vitro infected and stained by direct double staining with both human and bovine anti-MHC class I and II antibodies labeled with phycoerythrin (pink) 1:20 and anti-BVDV polyclonal antibodies labeled with fluorescein isothiocyanate. FITC (green) 1:60. There was a reduction in the percentages of infected fibroblasts and PBMC expressing both MHC-I and Il. While mild reduction was observed in the percentages of PBMC expressing MHC-I molecules. Eight calves of the two groups were infected intranasally with a virulent NCP BVDV type I (NY-I) and 2 (890) biotypes and kinetic evaluation of its effect of in vivo infection on clinical and immunological parameters. All virus-inoculated calves developed a fever on days 3-7-post infection. BVDV antigens were detected in the buffy coat cells on days 3, 5, and 7 post infections. Most calves developed low neutralizing antibody titers as type I (3, 12, 18 and 44) and type-2 (6, 16, 20 and 48) on days 5, 7, 10 and 15 post infection, respectively. There was a significant and minor diminution in the expression of the MHC-II and MHC-I molecules respectively in virus infected calves on days 3-, 5-, 7-, and 10-days post infection when compared to control calves. There was close correlation between both in vitro and in vivo of virus immunodown regulatory effects associated with blocking the transport of MHC complexes and prevention or antigen presentation to the immune cells associated with eventual dysregulation and/or impairment of immunological functions accompanied with immunosuppression.
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