Genetic characterisation of protective vaccine responses in sheep using multi-valent Dichelobacter nodosus vaccines

Protective vaccine responses to nine distinct serogroups of Dichelobacter n odosus (serogroups A-I) can be readily measured by serogroup-specific K-agg lutinating antibody titres. On the basis of a large quantitative genetic ex periment (1200 progeny from 129 sire groups), it was shown that variation i n antibody responses following Vaccination with a multi-valent pilus antige n D. nodosus vaccine (serogroups A-I) is, in part, under genetic control an d thus heritable. Based on the genetic relationships between antibody respo nses to all nine antigens, results suggested that both genes for a broad-ba sed and genes for serogroup-specific response contributed to genetic variat ion in vaccine response. Furthermore, preliminary data in 389 progeny showe d that polymorphism within the ovine major histocompatibility (MHC) based o n serological classification accounted for a significant proportion of the Variation in Vaccine responses. In subsequent experimentation, we examined the importance of genetic polymorphism within the ovine MHC, and the possib ility of genes outside the MHC for their involvement in antigen-specific an d broad-based vaccine response. Within two large half sib families (131, an d 143 progeny), four MHC haplotypes were investigated and found to be assoc iated with differential antibody responses to six out of eight distinct vac cine-antigens presented to the host in a multi-valent vaccine. The model us ed here shows how well characterised immunogens, quantitative genetic exper imentation, and molecular gene mapping tools can be used to unravel genetic differences in host responses to commercial vaccines. (C) 1999 Elsevier Sc ience B.V. All rights reserved.