Conserved repetitive epitope recognized by CD4+ clones from a malaria-immunized volunteer.

T cell clones obtained from a human volunteer immunized with Plasmodium falciparum sporozoites specifically recognized the native circumsporozoite (CS) antigen expressed on P. falciparum sporozoites, as well as bacteria- and yeast-derived recombinant falciparum CS proteins. The response of these CD4+ CD8- cells was species-specific, since the clones did not proliferate or secrete gamma interferon when challenged with sporozoites or recombinant CS proteins of other human, simian, or rodent malarias. The epitope recognized by the sporozoite-specific human T cell clones mapped to the 5' repeat region of the CS protein and was contained in the NANPNVDPNANP sequence.