An Insight to Further Malaria Vaccine Development: PfSPZ Vaccine Correlates of Protection Appear to be Cross-Reactive Antibodies to Immunodominant Low-Complexity Epitopes

Abstract

Plasmodium falciparum circumsporozoite protein (PfCSP) coats the sporozoite surface and is the target of multiple malaria vaccines in development. Discovery of additional vaccine candidate antigens beyond PfCSP may lead to improved vaccines. To identify new antigens, we used peptide microarrays to map antibody responses to P. falciparum proteins in adults who received a whole organism sporozoite vaccine, PfSPZ Vaccine, and were protected or unprotected after controlled human malaria infection. We discovered antibody responses that correlate with protection, but further examination, including of two monoclonal antibodies derived from protected PfSPZ Vaccine recipients, suggests that some antibodies elicited by PfCSP cross-react with peptides representing non-CSP proteins, a demonstration of inter-protein cross-reactivity. This work provides evidence that PfSPZ Vaccine elicits inter-protein cross-reactivity, provides amino acid-specific detail of putative epitopes, and introduces opportunities for further exploration that may help to elucidate underexplored immunological mechanisms and inform development of next-generation malaria vaccines.