Swine fever: influence of passive immunity on pig immune response following vaccination with a live virus vaccine (Thiverval strain)

Abstract

The influence of passive immunity on the immune response to swine fever virus (S.F.V.) was investigated in pigs injected with variable amounts of S.F.V. antibodies instead of piglets from immune sows. The passive immunity suppresses the primary serum antibody response normally observed after vaccination with the Thiverval strain of S.F.V. This inhibition is either partial or complete depending on the amount of injected antibodies. Whatsoever the passive immunity intensity, a priming occurred (even in absence of any detectable primary response). This priming was evidenced by the clinical signs and the type of immune response following a virulent challenge. Two vaccination routes were tested: intramuscular and intranasal: 48 pigs were checked and no significant differences established, concerning protective efficiency. Intranasal vaccination induced local antibody production in pharyngeal secretions. Even in the absence of any detectable immunoglobulin transudation from serum to these secretions, local antibody synthesis was completely inhibited in passively immunized animals.