Characterisation of subtype- and variant-specific antigen regions of the P1 adhesin of Mycoplasma pneumoniae

Distinct sequence differences within the repetitive elements (RepMP) of the Mycoplasma pneumoniae P1 adhesin are the only targets to discriminate patient isolates with molecular approaches into subtypes and variants. Since the P1 protein is also one of the most immunodominant proteins of the bacterium, the antigenic regions of the differing repetitive sequences might be of epidemiological significance for the observation of time-dependent outbreaks due to defined subtypes and variants of M. pneumoniae in the human population. By establishing a set of four subtype- and variant 2-specific recombinant proteins, we investigated the antigenicity of the variable P1 protein regions with sera of subtype- and variant-specific immunised animals and sera of M. pneumoniae-positive pneumonia patients. The results of the ELISA experiments confirmed the immunogenic character of the differing parts of the P1 adhesin and the occurrence of a specific immune response of the immunised animals. The detection of subtype- and variant-specific antibodies in the investigated sera strongly support the hypothesis of a selective immune response. It might be indicative for the partial protection of the host to a defined endemic or epidemic strain and therefore also the reason for a reduced protection against secondary infections with a differing subtype and variant of M. pneumoniae strains compared to the first contact.