Co-administration of attenuated Mycoplasma hyopneumoniae 168 strain with bacterial DNA enhances the local and systemic immune response after intranasal vaccination in pigs

Mycoplasma hyopneumoniae, the primary pathogen of enzootic pneumonia, occurs worldwide and causes major economic losses to the pig industry. M. hyopneumoniae infects pigs at mucosal surfaces of respiratory tract. The aim of the present study was to investigate if the protection rate against M. hyopneumoniae infection following intranasal immunization with attenuated M. hyopneumoniae 168 strain is improved by administration of bacterial DNA containing CpG motifs. Thirty pigs were immunized intranasally or intramuscularly and the levels of local respiratory tract and systemic immune responses were detected. The results showed that the number of intraepithelial lymphocytes in the tracheal fork, the levels of cytokine IL-6, and M. hyopneumoniae specific SIgA in local nasal cavity increased respectively after intranasal vaccination with the attenuated M. hyopneumoniae 168 strain alone. However, the levels of IL-10 and IFN-γ in local nasal cavity, the number of intraepithelial lymphocytes in trachea, CD4(+) and CD8(+) T lymphocytes in the lung and hilar lymph nodes, the specific IgG antibody level in serum on 35 day post immunization were all increased significantly after intranasal vaccination of the attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA. We concluded that intranasal administration of attenuated M. hyopneumoniae 168 strain adjuvanted with bacterial DNA may be effective in evoking the local cellular and humoral immune response in the respiratory tract and the systemic immune response. Intranasal vaccination will be effective in prevention of the transmission and prevalence of MPS.