Identification and characterization of novel antigenic vaccine candidates of Actinobacillus pleuropneumoniae.

Actinobacillus pleuropneumoniae is an important respiratory pathogen of swine, for which there is no highly effective vaccine. A phage expression library of the A. pleuropneumoniae genome was constructed and screened to identify potential vaccine components. Open reading frames within immuno-reactive phage were analyzed in silico to identify conserved outer membrane proteins. Four ORFs, named comL, lolB, lppC and ompA were chosen for further study. The four encoded proteins were shown experimentally to be antigenic, highly conserved, outer membrane, in vivo-expressed proteins. In pig protection studies, none of the proteins was individually capable of protecting pigs from colonization and infection with the homologous A. pleuropneumoniae strain, despite a detectable specific antibody response being induced.