Immune responses induced by replication-defective adenovirus expressing the C-terminal portion of the Mycoplasma hyopneumoniae P97 adhesin.

Mycoplasma hyopneumoniae, the causative agent of porcine enzootic pneumonia, colonizes the respiratory cilia of affected swine, causing significant economic losses to swine production worldwide. Vaccination is the most cost-effective strategy for the control and prevention of this disease. The goal of this study was to design and evaluate a replication-defective recombinant adenovirus, rAdP97c, expressing the C-terminal portion of P97 adhesin (P97c), an important pathogenesis-associated protein of M. hyopneumoniae, as a new vaccine candidate against M. hyopneumoniae infection. P97c-specific immune responses were evaluated in BALB/c mice following intranasal and intramuscular inoculation with rAdP97c. Mice inoculated by both routes of immunization produced significant levels of specific immunoglobulin G (IgG) antibodies in the serum and in bronchoalveolar lavage fluids (BALs). Animals immunized intranasally also produced a significant level of P97c-specific IgA in BALs. Intramuscular inoculation of rAdP97c induced a systemic and mucosal Th1-type biased response, evidenced by the predominance of IgG2a in the serum and BALs, whereas intranasal inoculation resulted in a mixed Th1/Th2-type response (balanced levels of IgG1 and IgG2a) in both sytemic and mucosal compartments. P97c-specific antibodies were able to inhibit the growth of M. hyopneumoniae cells in vitro. These data suggest that rAdP97c vaccine may represent a new strategy for controlling infection by M. hyopneumoniae.