New B cell epitopes in the Plasmodium falciparum malaria circumsporozoite protein

Abstract

Most antibodies directed against the Plasmodium falciparum circumsporozoite (CS) protein react with its central domain, which contains about 40 repeats of the tetrapeptide Asn-Ala-Asn-Pro (NANP). To search for new epitopes in the non-repetitive part of the CS protein, we expressed the non-repetitive regions of the protein in E. coli as fusion proteins with mouse dihydrofolate reductase linked to six adjacent histidine residues. These fusion proteins were obtained at greater than 70% purity by a single Ni-chelate affinity chromatography step. Of the new epitopes defined in the C-terminal portion of the CS protein, three are located in a stretch of 65 amino acids immediately C-terminal of the protein's central repetitive domain. Pooled sera from inhabitants of a malaria-endemic area reacted with epitopes in this region of the molecule, and four mouse monoclonal antibodies to this region also reacted with the native CS protein on sporozoites. Two of the monoclonal antibodies reacted with a peptide PNDPNRNVD derived from a conserved region of the CS protein. The other two antibodies showed different reactivities to sporozoites of the NF54 and Ro59 parasite isolates. One, which reacted with a peptide ENANANNAV, recognized Ro59 but not NF54 sporozoites, while the other reacted with a small percentage of NF54 but not Ro59 sporozoites. Antibodies which react with non-repetitive regions of the CS protein could contribute to maintaining its genetic variability.

Multiple Antigen Peptide Vaccines againstPlasmodium falciparumMalaria

“…This sequence was identified as a B-cell epitope in two independent studies in Africa (9, 47) but was found to be nonresponsive in C57BL/6 mice when delivered in complete Freund's adjuvant (9). The second epitope (S-11b) was first identified based on its reactivity with an anti-CSP MAb generated in BALB/c mice (53) and recognition by sera from individuals living in Papua New Guinea and Brazil (47). Our studies suggest that while these B-cell epitopes are individually recognized by some individuals living in areas where malaria is endemic, when presented as a combination epitope in a MAP vaccine, they are not effective B-cell epitopes in mice.…”

Interethnic differences in the humoral response to non-repetitive regions of the Plasmodium falciparum circumsporozoite protein.

“…Moreover, our results confirmed the presence of B cell epitopes in the non-repetitive regions of the Pf CSP. [10][11][12][13][14][15][16][17]27 However, in all three ethnic groups, the seroprevalence for both the N-and C-terminal regions of Pf CSP was lower than that recorded for the central repetitive domain.…”

“…[5][6][7][8] The involvement of CSP in the invasion of sporozoites into hepatocytes has been shown by Cerami and others. 9 The flanking non-repeat regions of CSP contain several epitopes recognized not only by antibodies, [10][11][12][13][14][15][16][17] but also by CD4 ϩ T helper cells [18][19][20] and CD8 ϩ cytotoxic T lymphocytes. [21][22][23][24] Vaccine candidates based on the immunodominant, repetitive domain of the P. falciparum CSP (Pf CSP) gave unsatisfactory results in terms of protection of human volunteers.…”

A Role for Apical Membrane Antigen 1 during Invasion of Hepatocytes by Plasmodium falciparum Sporozoites

“…Antibodies and Inhibitors-We used previously characterized anti-P. falciparum AMA-1 (PfAMA-1) domain III monoclonal antibody (mAb) DV5 (8), anti-PfAMA-1 prodomain mAb 5G8 (9), anti-PfAMA-1 domain I mAb 1F9 (9), anti-3D7 strain PfAMA-1 polyclonal rabbit IgG (10), anti-FVO strain PfAMA-1 polyclonal rabbit IgG (11), anti-PfTRAP mAb SSP2.2 (12), and anti-PfCSP mAb E9 (13). For liver schizont counting, we used anti-Plasmodium HSP-70 sera obtained from mice immunized with i72 recombinant protein (gift from D. Mattei, Institut Pasteur, Paris, France).…”