B-Cell Epitope Mapping of the <i>Plasmodium falciparum</i> Malaria Vaccine Candidate GMZ2.6c in a Naturally Exposed Population of the Brazilian Amazon
Barbara de Oliveira Baptista,
Ana Beatriz Lopes de Souza,
Luana Santos de Oliveira,
Hugo Amorim dos Santos de Souza,
Jenifer Peixoto de Barros,
Lucas Tavares de Queiroz,
Rodrigo Medeiros de Souza,
Linda Eva Amoah,
Susheel Kumar Singh,
Michael Theisen,
Rodrigo Nunes Rodrigues-da-Silva,
Evelyn Kety Pratt Riccio,
Paulo Renato Rivas Totino,
Josué da Costa Lima-Junior,
Cláudio Tadeu Daniel-Ribeiro,
Lilian Rose Pratt-Riccio
Affiliations
Barbara de Oliveira Baptista
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Ana Beatriz Lopes de Souza
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Luana Santos de Oliveira
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Hugo Amorim dos Santos de Souza
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Jenifer Peixoto de Barros
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Lucas Tavares de Queiroz
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Rodrigo Medeiros de Souza
Centro de Pesquisa em Doenças Infecciosas, Universidade Federal do Acre–Campus Floresta (UFAC), Cruzeiro do Sul 69895-000, AC, Brazil
Linda Eva Amoah
Immunology Department, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra P.O. Box LG 25, Ghana
Susheel Kumar Singh
Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, DK-2200 Copenhagen, Denmark
Michael Theisen
Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, University of Copenhagen, DK-2200 Copenhagen, Denmark
Rodrigo Nunes Rodrigues-da-Silva
Laboratório de Tecnologia Imunológica, Instituto de Tecnologia em Imunobiológicos (Bio-Manguinhos), Fiocruz, Rio de Janeiro 21040-900, RJ, Brazil
Evelyn Kety Pratt Riccio
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Paulo Renato Rivas Totino
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Josué da Costa Lima-Junior
Laboratório de Imunoparasitologia, IOC, Fiocruz, Rio de Janeiro 21040-900, RJ, Brazil
Cláudio Tadeu Daniel-Ribeiro
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
Lilian Rose Pratt-Riccio
Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro 21040-900, RJ, Brazil
The GMZ2.6c malaria vaccine candidate is a multi-stage P. falciparum chimeric protein that contains a fragment of the sexual-stage Pfs48/45-6C protein genetically fused to GMZ2, an asexual-stage vaccine construction consisting of the N-terminal region of the glutamate-rich protein (GLURP) and the C-terminal region of the merozoite surface protein-3 (MSP-3). Previous studies showed that GMZ2.6c is widely recognized by antibodies from Brazilian exposed individuals and that its components are immunogenic in natural infection by P. falciparum. In addition, anti-GMZ2.6c antibodies increase with exposure to infection and may contribute to parasite immunity. Therefore, identifying epitopes of proteins recognized by antibodies may be an important tool for understanding protective immunity. Herein, we identify and validate the B-cell epitopes of GMZ2.6c as immunogenic and immunodominant in individuals exposed to malaria living in endemic areas of the Brazilian Amazon. Specific IgG antibodies and subclasses against MSP-3, GLURP, and Pfs48/45 epitopes were detected by ELISA using synthetic peptides corresponding to B-cell epitopes previously described for MSP-3 and GLURP or identified by BepiPred for Pfs48/45. The results showed that the immunodominant epitopes were P11 from GLURP and MSP-3c and DG210 from MSP-3. The IgG1 and IgG3 subclasses were preferentially induced against these epitopes, supporting previous studies that these proteins are targets for cytophilic antibodies, important for the acquisition of protective immunity. Most individuals presented detectable IgG antibodies against Pfs48/45a and/or Pfs48/45b, validating the prediction of linear B-cell epitopes. The higher frequency and antibody levels against different epitopes from GLURP, MSP-3, and Pfs48/45 provide additional information that may suggest the relevance of GMZ2.6c as a multi-stage malaria vaccine candidate.
