Bovine adenoviruses. VI. An enzyme-linked immunosorbent assay for detection of antibodies to bovine adenovirus types belonging to subgroups I and II.

An enzyme-linked immunosorbent assay (ELISA) was developed for detection of antibodies against the officially recognized bovine adenoviruses (BAV). Soluble antigens of adenoviruses were extracted from bovine kidney (BAV-1 and BAV-3) or bovine testicle (BAV-4, -6, and -7) cell cultures, respectively. Presence of the major hexon antigen, known to be the most essential compound for serological cross-reactivity, was demonstrated on a discontinuous sodium-dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). The relatively crude polypeptide preparations were coated onto microelisa plates and tested for specific reactivity with available type-specific antisera of calves. Plates coated with BAV-1 showed reactivity with antibodies against types 1 and 3, but did not react with hyperimmune serum against BAV-4. Soluble antigens of BAV-4 react to a high extent with homologous antiserum but did not cross-react with a hyperimmune serum against BAV-1. Both these hyperimmune sera had been prepared in colostrum-free calves. Several calf sera produced by cooperating researches in colostrum-free calves were tested for homologous and cross-reactivity. In addition, ELISA plates coated with BAV-4 were tested on 33 sera of conventionally reared calves, earlier infected experimentally with homologous BAV-4. ELISA titres correlated well in 28 of them with seroneutralization titres; in 5 other sera correlation was poor, but in no case to a degree which would have resulted in a dissenting diagnosis. The use of BAV types 1 and 4 as representatives of bovine adenovirus subgroup I and II will allow easy and economical surveillance of these frequently occurring antibodies in diagnostic laboratories.