Evaluation of immunogenicity and protective efficacy of Actinobacillus pleuropneumoniae HB04C− mutant lacking a drug resistance marker in the pigs

Previously, we reported the construction and characterization of a genetically defined Actinobacillus pleuropneumoniae (A. pleuropneumoniae) apxIIC gene mutant, HB04C−, which conferred protection to mice against infection with A. pleuropneumoniae. In this study, we further evaluated HB04C− for safety and its ability to elicit protective immunity in pigs. It was demonstrated that a dose of 2 × 108 CFU HB04C− was safe to the pigs via intranasal or intramuscular injection. Immunization with a dose of 2 × 108 HB04C− by both intranasal and intramuscular routine could yield equal protective efficacy and elicited significant protection against experiment challenge with homologous or heterologous serotypes of a virulent A. pleuropneumonia. Taken together, HB04C− might serve as a promising vaccine candidate against infection with A. pleuropneumoniae.