Longley Rhea J, Reyes-Sandoval Arturo, Montoya-Díaz Eduardo, Dunachie Susanna, Kumpitak Chalermpon, Nguitragool Wang, Mueller Ivo, Sattabongkot Jetsumon
Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia Department of Medical Biology, University of Melbourne, Melbourne, Australia.
The Jenner Institute, Nuffield Department of Medicine, The Henry Wellcome Building for Molecular Physiology, University of Oxford, Oxford, United Kingdom.
Clin Vaccine Immunol. 2015 Dec 9;23(2):117-24. doi: 10.1128/CVI.00501-15. Print 2016 Feb.
Plasmodium vivax is now the dominant Plasmodium species causing malaria in Thailand, yet little is known about naturally acquired immune responses to this parasite in this low-transmission region. The preerythrocytic stage of the P. vivax life cycle is considered an excellent target for a malaria vaccine, and in this study, we assessed the stability of the seropositivity and the magnitude of IgG responses to three different preerythrocytic P. vivax proteins in two groups of adults from a region of western Thailand where malaria is endemic. These individuals were enrolled in a yearlong cohort study, which comprised one group that remained P. vivax free (by quantitative PCR [qPCR] detection, n = 31) and another that experienced two or more blood-stage P. vivax infections during the year of follow up (n = 31). Despite overall low levels of seropositivity, IgG positivity and magnitude were long-lived over the 1-year period in the absence of qPCR-detectable blood-stage P. vivax infections. In contrast, in the adults with two or more P. vivax infections during the year, IgG positivity was maintained, but the magnitude of the response to P. vivax circumsporozoite protein 210 (CSP210) decreased over time. These findings demonstrate that long-term humoral immunity can develop in low-transmission regions.
间日疟原虫现已成为泰国导致疟疾的主要疟原虫种类，但在这个低传播地区，人们对针对这种寄生虫的自然获得性免疫反应知之甚少。间日疟原虫生命周期的前红细胞期被认为是疟疾疫苗的一个绝佳靶点，在本研究中，我们评估了泰国西部一个疟疾流行地区两组成年人中，针对三种不同间日疟原虫前红细胞期蛋白的血清阳性稳定性和IgG反应强度。这些个体参加了一项为期一年的队列研究，其中一组始终未感染间日疟原虫（通过定量聚合酶链反应[qPCR]检测，n = 31），另一组在随访的一年中经历了两次或更多次间日疟原虫血期感染（n = 31）。尽管总体血清阳性水平较低，但在没有qPCR检测到的间日疟原虫血期感染的情况下，IgG阳性及其强度在1年期间保持稳定。相比之下，在一年中感染过两次或更多次间日疟原虫的成年人中，IgG阳性得以维持，但对间日疟原虫环子孢子蛋白210（CSP210）的反应强度随时间下降。这些发现表明，在低传播地区可以产生长期的体液免疫。
