Title Naturally Acquired Antibody Responses to Plasmodium vivax and Plasmodium falciparum Merozoite Surface Protein 1 ( MSP 1 ) C-Terminal 19 kDa Domains in an Area of Unstable Malaria Transmission in Southeast Asia Permalink

Understanding naturally acquired immunity to infections caused by Plasmodia in different malaria endemicity settings is needed for better vaccine designs and for exploring antibody responses as a proxy marker of malaria transmission intensity. This study investigated the sero-epidemiology of malaria along the international border between China and Myanmar, where malaria elimination action plans are in place. This study recruited 233 P. vivax and 156 P. falciparum infected subjects with acute malaria at the malaria clinics and hospitals. In addition, 93 and 67 healthy individuals from the same endemic region or from nonendemic region, respectively, were used as controls. Acute malaria infections were identified by microscopy. Anti-recombinant PfMSP119 and PvMSP119 antibody levels were measured by ELISA. Antibody responses to respective MSP119 were detected in 50.9% and 78.2% patients with acute P. vivax and P. falciparum infections, respectively. There were cross-reacting antibodies in Plasmodium patients against these two recombinant proteins, though we could not exclude the possibility of submicroscopic mixed-species infections. IgG1, IgG3 and IgG4 were the major subclasses. Interestingly, 43.2% of the healthy endemic population also had antibodies against PfMSP119, whereas only 3.9% of this population had antibodies against PvMSP119. Higher antibody levels were correlated with age and parasite density, but not with season, gender or malaria history. Both total IgG and PLOSONE | DOI:10.1371/journal.pone. 0151900 March 21, 2016 1 / 20 OPEN ACCESS Citation:Wang Q, Zhao Z, Zhang X, Li X, Zhu M, Li P, et al. (2016) Naturally Acquired Antibody Responses to Plasmodium vivax and Plasmodium falciparum Merozoite Surface Protein 1 (MSP1) CTerminal 19 kDa Domains in an Area of Unstable Malaria Transmission in Southeast Asia. PLoS ONE 11(3): e0151900. doi:10.1371/journal.pone. 0151900 Editor: Alister G. Craig, Liverpool School of Tropical Medicine, UNITED KINGDOM Received: July 30, 2015 Accepted: February 29, 2016 Published: March 21, 2016 Copyright: © 2016 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by Grants U19AI089672 to LC and R01 AI099611 to YC from the National Institutes of Health, USA. Competing Interests: The authors have declared that no competing interests exist. individual IgG subclasses underwent substantial declines during the convalescent period in three months. This study demonstrated that individuals in a hypoendemic area with coexistence of P. vivax and P. falciparum can mount rapid antibody responses against both PfMSP119 and PvMSP119. The significantly higher proportion of responders to PfMSP119 in the healthy endemic population indicates higher prevalence of P. falciparum in the recent past. Specific antibodies against PvMSP119 could serve as a marker of recent exposure to P. vivax in epidemiological studies.