Cross protection of a Haemophilus parasuis serotype 12 vaccine (Parapac ) against serotype 4

摘要

Haemophilus parasuis is the primary eciological agent associated with porcine polyserositis (Glasser's disease). There is considerable heterogeneity among H. parasuis strains isolated through out the world. Heterogeneity among isolates is confirmed byseveral mediods including morphology , immunodiffusion test with heat stable antigens and outer membrane proteins profile. Fifteen serovars have been identified based on heat stable antigens. There are number of isolates which are non-typable suggesting the existence of other serovars. Some serovars appear to be more prevalent than others depending on the geographic locations. In the United States, serotype 4 appears to be most predominant (25%) followed by serotype 12 (23%) and serotype 5 (15%). The virulence factors associated with Glasser's disease have not been fully understood and are not well characterized. Some antigens are shared by a number of isolates and it is not clear which antigens are involved with cross protection. A bacterin containing serovar 4 has been shown to provide protection against serovar 5 but the converse is not true. A bacterin containing serovars 4 and 5 provided protection against challenge with serovars 13 and 14 and the same bacterin failed to provide protection against serovars 2 and 12. A bacterin containing serovar 12 provided protection against challenge with serovar 5. A bacterin containing serovar 2 failed to protect pigs against serovar 5 challenge. Similarly, a serovar 5 bacterin failed to provide protection against serovar 2 challenge. It is not easy to predict which serovar provides heterologous protection without conducting actual vaccination challenge studies. The purpose of this study was to evaluate whether serovar 12 bacterin provides protection following challenge with serovar 4.