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<jats:title>ABSTRACT</jats:title><jats:p><jats:named-content content-type="genus-species">Plasmodium vivax</jats:named-content>is now the dominant<jats:named-content content-type="genus-species">Plasmodium</jats:named-content>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<jats:named-content content-type="genus-species">P. vivax</jats:named-content>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<jats:named-content content-type="genus-species">P. vivax</jats:named-content>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<jats:named-content content-type="genus-species">P. vivax</jats:named-content>free (by quantitative PCR [qPCR] detection,<jats:italic>n</jats:italic>= 31) and another that experienced two or more blood-stage<jats:named-content content-type="genus-species">P. vivax</jats:named-content>infections during the year of follow up (<jats:italic>n</jats:italic>= 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<jats:named-content content-type="genus-species">P. vivax</jats:named-content>infections. In contrast, in the adults with two or more<jats:named-content content-type="genus-species">P. vivax</jats:named-content>infections during the year, IgG positivity was maintained, but the magnitude of the response to<jats:named-content content-type="genus-species">P. vivax</jats:named-content>circumsporozoite protein 210 (CSP210) decreased over time. These findings demonstrate that long-term humoral immunity can develop in low-transmission regions.</jats:p>

Original publication

DOI

10.1128/cvi.00501-15

Type

Journal article

Journal

Clinical and Vaccine Immunology

Publisher

American Society for Microbiology

Publication Date

02/2016

Volume

23

Pages

117 - 124