Enhancement of humoral and cellular immune responses by an oral Salmonella choleraesuis vaccine expressing porcine prothymosin alpha.

Previously, we showed that murine prothymosin alpha (ProT) enhances the efficacy of a pseudorabies DNA vaccine delivered by bacterial vectors. In this study, we cloned and sequenced the cDNA for porcine ProT. The deduced amino acid sequence of porcine ProT exhibited high homology to ProT from other mammals. Oral Salmonella choleraesuis vaccine carrying the ProT eukaryotic expression plasmid protected mice against virulent S. choleraesuis challenge. The adjuvant effect of ProT on humoral and cellular immune responses enhanced protective efficacy of the vaccine. Furthermore, both humoral and cellular immune responses played roles in the protective immune responses induced by the vaccine. Collectively, our results show that delivery of the ProT gene carried by attenuated S. choleraesuis augmented the immunogenicity of oral S. choleraesuis vaccine.