IMMUNOGENICITY OF CHIMERIC MULTIPLE ANTIGEN PEPTIDES BASED ON PLASMODIUM-FALCIPARUM ANTIGENS - IMPACT OF EPITOPE ORIENTATION

Assembly of B and T epitopes in multiple antigen peptides (MAP) can by pass genetically predisposed unresponsiveness to B epitopes. Although the underlying mechanisms are unknown, B-cell responses to such diepit ope MAP are influenced by intramolecular epitope orientation. In this study, MAP constructs were synthesized, encompassing two epitopes deri ved from the Plasmodium falciparum antigens circumsporozoite protein ( CS) and Pf332. In addition to B epitopes, the sequences comprised T ep itopes restricted to mouse H-2(b) (CS) or to H-2(d) and H-2(k) (Pf332) haplotypes. Congenic H-2(b), H-2(d) and H-2(k) Balb mice were immuniz ed with MAP in which the two epitopes were arranged either tandemly or in parallel. Tandemly arranged (B-T)(4) MAP in which the relevant T e pitope was positioned adjacent to the lysine core [(Pf332-CS)(4)-core for H-2(b) mice and (CS-Pf332)(4)-core for H-2(d) and H-2(k) mice], el icited the most potent antibody responses in terms of reactivity to bo th epitopes. Additionally, the (B-T)(4) constructs were generally most efficient in recalling proliferative T-cell responses in vitro, irres pective of the MAP used for in vivo priming. As high antibody titers w ere generated to both epitopes, the position of B epitopes in the cons tructs does not appear to be critical for an efficient B-cell response . Rather, the association of strong B-and T-cell responses to the (B-T )(4) MAP constructs suggests that the intramolecular position of the r elevant T epitope determines the magnitude of specific antibody produc tion. (C) 1997 Elsevier Science Ltd.