INDUCTION OF ANTIBODIES AGAINST THE PLASMODIUM-FALCIPARUM P126 ANTIGEN IN NONRESPONDER H-2(B) AND PARTIAL-RESPONDER H-2(D) MICE USING SYNTHETIC PEPTIDES

The p126 Plasmodium falciparum antigen is processed into two fragments , p50 and p73, the latter one containing the sub-fragments p47 and p18 when the schizonts rupture. An absence of antibody response against t he p126 antigen has been reported recently in H-2(b) mice and limited to the p73 processed fragment in H-2(d) mice. Synthetic peptides corre sponding to various domains of the molecule have been used to immunize mice in order to overcome the absence of an immune response. Syntheti c peptides corresponding to the N-terminus of p50 or p18 as well as to the C-terminus of p47 were unable to induce anti-peptides antibodies when injected carrier-free or coupled to ovalbumin. Synthetic peptides corresponding to the C-terminus of p18 or composed of 6 or 9 serines were able to induce anti-peptide antibodies when injected coupled to a carrier protein. However, none of these antibodies was able to recogn ize the native p126 molecule. Various synthetic peptides corresponding to the 6-octapeptide [Nt47(6x8)] or the 4-octapeptide [Nt47(4x8)] rep eat sequence localized at the N-terminus of the p47 have also been use d to immunize mice. No antibodies were generated using a carrier-free [Nt47(6x8)-Cys](2) or [Nt47(4x8)-Cys](2) peptide, an octameric multipl e antigen peptide construct [Nt47(6x8)]-MAP or the [Nt47(6x8)] coupled to one or two palmitic acids. In contrast, [Nt47(6x8)]-Cys coupled to either tetanus toxoid (TT) or ovalbumin (OVA) and [Nt47(4x8)]-Cys cou pled to OVA induced antibodies against the synthetic peptide and the n ative p126 molecule in both H-2(d) and H-2(b) mice. A multiple antigen peptide construct [Nt47(4x8)-MSP-3b]-MAP containing 4 [Nt47(4x8)] and 4 [MSP-3b] also induced antibodies against the synthetic peptide [Nt4 7(4x8)-Cys](2) and the native p126 molecule in both H-2(d) and H-2(b) mice.