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COMPARISON OF IgG REACTIVITIES TO PLASMODIUM VIVAX MEROZOITE INVASION ANTIGENS IN A BRAZILIAN AMAZON POPULATION

Naturally acquired antibody reactivity to two major Plasmodium vivax vaccine candidates was investigated in 294 donors from three malaria-endemic communities of Rondônia state, Brazil. Antibody recognition of recombinantly expressed antigens covering five different regions of P. vivax reticulocyte binding protein 1 (PvRBP1) and region II of P. vivax Duffy binding protein (PvDBP-RII) were compared. Positive IgG responses to these antigens were significantly related to the level of malaria exposure in terms of past infections and years of residence in the endemic area when corrected for age. The highest prevalence of anti-PvRBP1 total IgG antibodies corresponded to the amino acid regions denoted PvRBP1_431-748 (41%) and PvRBP1_733-1407 (47%). Approximately one-fifth of positively responding sera had titers of at least 1:1,600. Total IgG responses to PvDBP-RII were more prevalent (67%), of greater magnitude, and acquired more rapidly than those to individual PvRBP1 antigens. Responses to both PvRBP1 and PvDBP-RII were biased toward the cytophilic subclasses IgG1 and IgG3. These data provide the first insights on acquired antibody responses to PvRBP1 and a comparative view with PvDBP-RII that may prove valuable for understanding protective immune responses to these two vaccine candidates as they are evaluated as components of multitarget blood-stage vaccines.

View larger version (21K): [in this window] [in a new window]       SUPPLEMENTAL FIGURE 1. Anti-penta-His Western blot of recombinant Plasmodium vivax reticulocyte binding protein 1 (PvRBP1) and P. vivax Duffy binding protein region II (PvDBP-RII) proteins. Approximately 2 µg of each protein were run on a 10% polyacrylamide gel and transferred to a nitrocellulose membrane. Western blot was performed using an anti-penta-His monoclonal antibody (Qiagen, Valencia, CA) according to the manufacturer’s specifications. See "Materials and Methods" for details on expression and purification of proteins. Molecular weights in kilodaltons (kDa) are indicated.

View larger version (14K): [in this window] [in a new window]       SUPPLEMENTAL FIGURE 2. Immunoglobulin G subclass calibration curves. Ninety-six well plates were coated with serial dilutions of purified human IgG1, IgG2, IgG3, and IgG4 myeloma proteins (The Binding Site, San Diego, CA). Enzyme-linked immunosorbent assay was performed with the corresponding anti-IgG subcalss monoclonal antibody (Sigma, St. Louis, MO) as described in "Materials and Methods." Points represent experimental data points. Lines correspond to sigmoidal curves representing the best-fit equation for each subclass.

Received October 7, 2004. Accepted for publication March 18, 2005.

Acknowledgments: The authors thank the Fundação Nacional de Saude (Brazilian Ministry of Health) and the Secretary of Health of Rondônia for providing fieldwork support and K.B. Anderson for help with statistical analyses. We are grateful to all donors who participated in this study.

Financial support: This research is supported by the National Institute of Allergy and Infectious Diseases, National Institutes of Health, grant no. R01AI247-18. Tuan M. Tran was also a recipient of an American Society of Tropical Medicine and Hygiene Benjamin H. Kean Fellowship in Tropical Medicine. Chetan E. Chitnis is a Wellcome Trust International Senior Research Fellow and Howard Hughes International Research Scholar.

^* Address correspondence to Mary R. Galinski, Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd., Atlanta, Georgia 30329. E-mail: galinski{at}rmy.emory.edu

Note: Supplemental figures 1 and 2 appear online at www.ajtmh.org.

Authors’ addresses: Tuan M. Tran, Alberto Moreno, John D. Altman, Esmeralda V-S. Meyer, and Mary R. Galinski, Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Rd., Atlanta GA 30329. Joseli Oliveira-Ferreira, Laboratorio de Pesquisas em Malaria, Fundação Oswaldo Cruz –FIOCRUZ, Av. Brasil, 4365 – Manguinhos, Rio de Janeiro, RJ, Brazil. Fatima Santos, Fundação Nacional de Saúde, Av George Teixeira S/N, Porto Velho, Rondônia, Brazil. Syed S. Yazdani and Chetan E. Chitnis, Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India. John W. Barnwell, Malaria Branch, Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, MS F-36, Atlanta, GA 30341.

Reprint requests: Mary R. Galinski, Emory Vaccine Center at Yerkes, Emory University, 954 Gatewood Rd., Atlanta, GA 30329, Telephone: 404-727-7214, Fax: 404-727-8199, E-mail: galinski{at}rmy.emory.edu.