V_H and V_L region structure of antibodies that recognize the (NANP)₃ dodecapeptide sequence in the circumsporozoite protein of Plasmodium falciparum

The sporozoite form of Plasmodium falciparum displays on its surface the circumsporozoite (CS) protein. The central domain of this protein possesses a reiterated tetrapeptide sequence Asn‐Ala‐Asn‐Pro (NANP), and > 90% of the sporozoite‐specific antibodies obtained from individuals living in malaria endemic areas recognize epitopes within this repeat sequence. Considering the highly repetitive structure of this naturally occurring antigen and its immunodominance, we were interested in analyzing the structural diversity of antibodies that bind to the (NANP)₃ sequence. Molecular characterization of immunoglobulin heavy and light chain mRNA was performed for five hybridomas that produce antibodies with binding specificity for the dodecapeptide (NANP)₃. These hybridomas were produced in BALB/c mice by inoculation with whole P. falciparum sporozoites. Sequence analysis and Northern blotting showed that for heavy chain, three hybridomas used V_H elements that belong to the V_HIX family and two to the V_HJ558 family. Four different V_χ subgroups were represented among the light chains. Different D and J_χ segments are also utilized, while four heavy chain gene rearrangements involved the J_H4 segment. These results indicated that multiple V_H‐V_L gene combinations can code for reactivity to the (NANP)₃ sequence, demonstrating that the murine antibody response to this immunodominant region is structurally heterogeneous.