No abstract

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.Mycoplasma hyopneumoniae is the etiological agent of enzootic porcine pneumonia (PEP), one of the most economically significant diseases in the swine industry worldwide. The disease is characterized by chronic nonproductive cough, retarded growth rate, and inefficient food conversion (29). Adherence of M. hyopneumoniae to the swine respiratory epithelial cells causes reduction of ciliary activity, ciliostasis, and loss of cilia (7), predisposing the swine to secondary infections. For example, it is now clear that M. hyopneumoniae potentiates and exacerbates the severity and duration of pneumonia caused by the porcine reproductive and respiratory syndrome virus (38). After colonizing, M. hyopneumoniae stimulates numerous changes, consisting of infiltrates, mononuclear cells (macrophages and lymphocytes) around bronchi and bronchioles, secretion of proinflammatory cytokines, and lymphoid hyperplasia of bronchus-associated lymphoid tissue (22,26,30). Traditionally, M. hyopneumoniae infection is controlled by the use of antibiotics. However, this practice does not prevent infection, and treatment cost is prohibitive. In addition to the use of antibiotics and animal management procedures, the prevention of PEP through vaccination is needed. The commonly used vaccines against M. hyopneumoniae are in the form of inactivated whole cells or bacterins. These vaccines are efficacious against M. hyopneumoniae challenge (8, 37) but do not prevent colonization by the pathogen or completely eliminate pneumonia (14). In addition, their preparation is very ex...