[Protective immune responses induced by intranasal immunization with Mycoplasma pneumoniae P1C-IL-2 fusion DNA vaccine in mice].

OBJECTIVE

To investigate the immune responses and immune protections of a DNA vaccine constructed by fusing Mycoplasma pneumoniae (M. pneumoniae) p1 gene car boxy terminal region (p1c gene) with interleukin-2 (IL-2) gene.

METHODS

BALB/c mice were immunized by intranasal inoculation of P1C-IL-2 fusion DNA vaccine. Levels of serum IgG, IgG isotypes, BAL fluids IgA, IFN-γ and IL-4 were detected by ELISA. We established the mouse models infected with M. pneumoniae, and then observed the histopathological changes in lungs and counted colonies in bronchoalveolar lavage fluid (BALF) after challenged intranasally with M. pneumoniae.

RESULTS

Serum total IgG, IgG1 and IgG2a isotypes, levels of IFN-γ and IL-4 in BALF increased significantly in the group inoculated with P1C-IL-2 fusion DNA vaccine as compared with the one with P1C DNA vaccine (P<0.05), while there was no significant difference in BALF IgA between the two groups (P>0.05). The lung tissue inflammation was aggravated and the histopathologic score (HPS) of P1C-IL-2 DNA vaccine immunized mice significantly increased as compared with those in P1C DNA vaccine immunized mice at 1, 3, 6 d after challenged intranasally with M. pneumoniae (P<0.05). The P1C-IL-2 fusion DNA vaccine did not show significant difference from P1C DNA vaccine in the detectable number of M. pneumoniae strain in BALF(P>0.05).

CONCLUSION

IL-2 can enhance the systemic immune responses of P1C DNA vaccine, but it also can develop a severe histopathological change in early days after infection of M. pneumoniae.