A recombinant chimera comprising the R1 and R2 repeat regions of M.hyopneumoniae P97 and the N-terminal region of A. pleuropneumoniae ApxIII elicits immune responses

Background: Infection by Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae, either alone or together, causes serious respiratory diseases in pigs. Results: To develop an efficient multi-disease subunit vaccine against these pathogens, we produced a chimeric protein called Ap97, which comprises a deletion derivative of the N-terminal region of the A. pleuropneumoniae ApxIII toxin (ApxN) and the R1 and R2 repeats of M. hyopneumoniae P97 adhesin (P97C), using an E. coli expression system. The levels of both IgG1 and IgG2a isotypes specific for ApxN and P97C in the sera of Ap97-immunized mice increased, and Ap97 induced the secretion of IL-4 and IFN-gamma. by mouse splenocytes. Antisera from mice and pigs immunized with Ap97 readily reacted with both native ApxIII and P97 proteins. In addition, immunization with the Ap97 vaccine effectively protected pigs against challenge with both pathogens. Conclusions: These findings suggest that Ap97 confers immunogenicity, and is an effective vaccine that protects pigs against infection by M. hyopneumoniae and A. pleuropneumoniae.