Host factors affecting the homologous and heterologous immune response of cattle to FMDV: genetic background, age, virus strains and route of administration.

Sixty bulls were tested for antibodies to the heterologous serotype C1 of FMDV following repeatable vaccinations with a commercial trivalent vaccine (O1, A22, Asia1). Six (10%) bulls were found to possess rather high levels of heterologous neutralizing antibodies which showed accumulative trend with age. Two high positive and two negative bulls for the heterologous serotype C1 were selected for progeny test involving ten daughters of each bull. The four bulls, either positive or negative for the heterologous serotype C1, showed significant phenotypic correlation between their heterologous and homologous titers (O1, A22, Asia1). This correlation between heterologous and homologous antibody titers was not found in the daughters of these bulls. However, two of ten daughters of one positive bull, to C1 showed individual high titers (> or = 1.5). The intradermal (ID) as compared to subcutaneous (SC) route of administration resulted in higher rate of responders to both heterologous serotypes C1 and SAT1. The heterologous immune response to FMDV in Israeli-Friesian cattle was found to be related to the age of the host, multiplicity of vaccinations, route of vaccination, kind and numbers of the antigens used in the vaccine. The homologous immune response is also controlled by genetic factors.