Plasmodium chabaudi antigen Pch105, Plasmodium falciparum antigen Pf155, and erythrocyte band 3 share cross-reactive epitopes.

By immunoblotting with a number of monoclonal antibodies raised in human and murine malaria systems, we have been able to establish the presence of cross-reactive epitopes on the Plasmodium falciparum vaccine candidate antigen Pf155/RESA and its proposed Plasmodium chabaudi analog Pch105. These findings were confirmed when the same antibodies were tested in an immunofluorescence assay. By using short synthetic peptides corresponding to repeated sequences in the C terminus of the Pf155 and enzyme-linked immunosorbent assays, the cross-reacting epitope was found to be localized to this repeat segment. Furthermore, a monoclonal antibody to murine erythrocyte band 3 which also cross-reacted with human band 3 bound to both Pch105 and Pf155 as well as to the synthetic peptides, suggesting that these proteins share a related epitope. The cross-reactions reflect the existence of sequence homologies of band 3 with these plasmodial proteins. This molecular similarity may be used by the parasite to disturb the rigidity of the erythrocyte membrane, thereby facilitating its entrance into the cell.