Molecular and immunological characterization of Mycobacterium avium 65 kDaheat shock protein (Hsp65)

The heat shock protein Hsp65 has been characterized previously in several m ycobacterial species. This is the first report of the complete sequence of the coding region of the Mycobacterium avium homologue. The sequence was hi ghly homologous to the Hsp65 of other mycobacterial species, as well as bei ng related closely to the murine and human homologues. Recombinant Hsp65 (r Hsp65) was expressed in Escherichia coli to high levels and the recombinant protein tested for its immunogenicity in a murine model of M. avium infect ion. Although mice infected with M. avium produced antibodies that reacted with rHsp65, they showed low proliferative T-cell responses and no cytokine production in response to the same antigen. However, immunization with rHs p65 in the adjuvant dimethydioctadecylammonium bromide (DDA), induced T cel ls that responded to native Hsp65 with proliferation and IFN-gamma producti on, indicating that the recombinant and native forms of the protein were an tigenically similar. Therefore, the findings indicate that Hsp65 is not a d ominant T-cell antigen during M. avium infection.