Differential cellular recognition of antigens during acute Plasmodium falciparum and Plasmodium vivax malaria

Background: Plasmodium falciparum and Plasmodium vivax are co-endemic in the Asia-Pacificregion. Their capacity to induce and sustain diverse T-cell responses underpinsprotective immunity. We compared T-cell responses to the largely conservedmerozoite surface protein-5 (PfMSP5) during acute and convalescent falciparumand vivax malaria.

Methods: Lymphoproliferation and IFN--γ secretion to PfMSP5 and purified protein derivatewere quantified in adults with falciparum (n = 34), and vivax malaria (n = 12)or asymptomatic residents (n = 10) of Papua, Indonesia. Responses werereassessed 7-28 days following treatment.

Results: Thefrequency of IFN-? responders to PfMSP5 was similar in acute falciparum (63%)or vivax (67%) malaria. However, significantly more IFN-γ-secreting cells weredetectable during vivax compared with falciparum infection. Purified proteinderivative responses showed a similarly enhanced pattern. While rapidly lost invivax patients, PfMSP5-specific responses in falciparum malaria remained to day28. By contrast, frequency and magnitude of lymphoproliferation to PfMSP5 weresimilar for falciparum and vivax infections.

Conclusion: CellularPfMSP5-specific responses are most frequent during either acute falciparum orvivax malaria, indicating functional T-cell responses to conserved antigens.Both effector and central memory T-cell functions are increased. Greater IFN-γresponses in acute P. vivax, suggest enhancement of pre-existing effectorT-cells during acute vivax infection.