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


RESULTS
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
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.
Center for Innovation Development and Technology Transfer, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand.
Kulachart
K
Jangpatarapongsa
Hui
H
Xia
Qiang
Q
Fang
Kaiming
K
Hu
Yuanying
Y
Yuan
Meiyu
M
Peng
Qi
Q
Gao
Jetsumon
J
Sattabongkot
Liwang
L
Cui
Baiqing
B
Li
Rachanee
R
Udomsangpetch
D000328:Adult; D015496:CD4-Positive T-Lymphocytes / Q000469:parasitology; D016022:Case-Control Studies; D049109:Cell Proliferation; D002681:China; D018920:Coculture Techniques; D003430:Cross-Sectional Studies; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007107:Immune System; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000469:parasitology; D008137:Longitudinal Studies; D016780:Malaria, Vivax / Q000453:epidemiology / Q000276:immunology* / Q000469:parasitology*; D008875:Middle Aged; D010641:Phenotype; D010966:Plasmodium vivax / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology
D053645:Interleukin-2 Receptor alpha Subunit