Abstract: Actinobacillus pleuropneumoniae is the causative agent of acute and chronic pleuroneumonia that is responsible for substantial morbidity and mortality in the pig industry. New improved vaccines that can protect against all serotypes and prevent colonization are required. Previous studies showed that whole cells of Propionibacterium acnes protected pigs from A. pleuropneumoniae serotype 1 and 5 and therefore the basis for a promising heterologous vaccine. The aim of this study was to identify those protein antigens of P. acnes responsible for protection against A. pleuropneumoniae infection. Antibodies that are induced by recombinant PASsb cross-react with epitopes in the ApxIV and ZnuA proteins of A. pleuropneumoniae. ZnuA is a known A. pleuropneumoniae immunogenic protein and is required for virulence.