A heat shock-like protein from the human malaria parasite Plasmodium falciparum induces autoantibodies.

The humoral immune response to a 72-kDa heat shock-like protein of Plasmodium falciparum has been analyzed using mouse monoclonal antibodies (mAb) and human immune sera. Three regions of the molecule containing B cell epitopes were identified by screening a sublibrary encoding the COOH-terminal half of the antigen with the mAb. One B cell epitope mapped to a region poorly conserved between the parasite 72-kDa polypeptide and mammalian heat-shock proteins (Hsp 70). Another mAb, G10C9, reacted with an amino acid region that has a high degree of homology with mouse (87.5%) and human (81.2%) Hsp 70. Both mouse and human cells were recognized by this mAb when analyzed by indirect immunofluorescence and by two-dimensional immunoblots. Sera from humans infected with malaria also recognized the human Hsp 70. Thus, our results indicate that autoantibodies directed against host Hsp 70 can be induced by the homologous parasite protein.