Protective effects of Mycoplasma pneumoniae live vaccine or its hyperimmune serum on the experimental infection in mice

Abstract

SPF-BALB/c mice in which Mycoplasma pneumoniae cell proliferation accompanied by immunological responses had been confirmed, were immunized with live vaccines or with hyperimmune sera of M. pneumoniae FH-P24 and its mutant strains (P24-S1, P24-S11), were then assayed for infection-protection. Eight weeks after the last vaccination, 70 percent protection was obtained by inoculation once or twice with live FH-P24 and P24-S1 vaccines, respectively. After 12 weeks, 80% protection was achieved by FH-P24 and 60% by P24-S1 live vaccine, while protectivity was not obtained by P24-S11 live vaccine. In case of passively immunized mice, IgG antibody titers and protective effect were not always found to be parallel. Namely, mice which were passively immunized with anti-FH-P24 serum, showed only 20% protection. However to get the above results, it was necessary that the anti-mutant strain serum be ten times higher than anti-FH-P24 serum in IgG titer. In the immunoblot analysis, sera from patients infected with M. pneumoniae immunoblotted the 168-KDa (P1 protein) and the 85-KDa protein of FH-P24 and P24-S1, but not the 85-KDa protein of P24-S11.