Dataset Information

Immunity to malaria in Plasmodium vivax infection: a study in central China.

ABSTRACT:

Background

P. vivax infection is characterised by relapsing fever, indicating reinfection by previously hidden parasites in the host. Relapsed infection can lead to the activation of the memory T cell pool, which may lead to protective immunity. This study aims to characterise immune responses in acute P. vivax-infected patients living in an area of central China characterised by only P. vivax infection.

Methodology/principal findings

We conducted a cross-sectional immune-phenotypic analysis of adults using the following inclusion criteria: acute P. vivax infection (N=37), a history of P. vivax infection (N=17), and no known history of P. vivax infection (N=21). We also conducted a 2-week longitudinal analysis following acute P. vivax infection, in which PBMC proliferation was measured in response to P. vivax and P. falciparum blood stage lysates. Using flow cytometry, we showed elevated memory T cells in the blood during acute P. vivax infection. The levels of γδ T cells were two-fold higher than those measured in naive controls. This result suggested that in the two populations, memory and γδ T cells promptly responded to P. vivax parasites. Interestingly, P. falciparum antigens stimulated T cells obtained from P. vivax-infected patients during a day 14-convalescence, whereas lymphocytes from the naïve control group responded to a lower degree of convalescence.

Conclusions/significance

Cell-mediated immunity during the convalescent period of the P. vivax-infected hosts was comprised of T cells that were specifically able to recognise P. falciparum antigens. Although the magnitude of the response was only half that measured after stimulation with P. vivax antigens, the matter of cross-antigenic stimulation is of great interest.

SUBMITTER: Jangpatarapongsa K

PROVIDER: S-EPMC3457974 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:In Central China the declining incidence of Plasmodium vivax has been interrupted by epidemic expansions and imported cases. The impact of these changes on the local parasite population, and concurrent risks of future resurgence, was assessed.Plasmodium vivax isolates collected from Anhui and Jiangsu provinces, Central China between 2007 and 2010 were genotyped using capillary electrophoresis at seven polymorphic short tandem repeat markers. Spatial and temporal analyses of within-host and population diversity, population structure, and relatedness were conducted on these isolates.Polyclonal infections were infrequent in the 94 isolates from Anhui (4%) and 25 from Jiangsu (12%), with a trend for increasing frequency from 2008 to 2010 (2 to 19%) when combined. Population diversity was high in both provinces and across the years tested (H(E)?=?0.8 - 0.85). Differentiation between Anhui and Jiangsu was modest (F'(ST)?=?0.1). Several clusters of isolates with identical multi-locus haplotypes were observed across both Anhui and Jiangsu. Linkage disequilibrium was strong in both populations and in each year tested (I(A)(S)?=?0.2 - 0.4), but declined two- to four-fold when identical haplotypes were accounted for, indicative of occasional epidemic transmission dynamics. None of five imported isolates shared identical haplotypes to any of the central Chinese isolates.The population genetic structure of P. vivax in Central China highlights unstable transmission, with limited barriers to gene flow between the central provinces. Despite low endemicity, population diversity remained high, but the reservoirs sustaining this diversity remain unclear. The challenge of imported cases and risks of resurgence emphasize the need for continued surveillance to detect early warning signals. Although parasite genotyping has potential to inform the management of outbreaks, further studies are required to identify suitable marker panels for resolving local from imported P. vivax isolates.