V delta 2+T cell response to malaria correlates with protection from infection but is attenuated with repeated exposure

Abstract

V delta 2(+) gamma delta T cells are semi-innate T cells that expand markedly following P. falciparum (Pf) infection in naive adults, but are lost and become dysfunctional among children repeatedly exposed to malaria. The role of these cells in mediating clinical immunity (i.e. protection against symptoms) to malaria remains unclear. We measured V delta 2(+) T cell absolute counts at acute and convalescent malaria timepoints (n = 43), and V delta 2(+) counts, cellular phenotype, and cytokine production following in vitro stimulation at asymptomatic visits (n = 377), among children aged 6 months to 10 years living in Uganda. Increasing age was associated with diminished in vivo expansion following malaria, and lower V delta 2 absolute counts overall, among children living in a high transmission setting. Microscopic parasitemia and expression of the immunoregulatory markers Tim-3 and CD57 were associated with diminished V delta 2(+) T cell pro-inflammatory cytokine production. Higher V delta 2 pro-inflammatory cytokine production was associated with protection from subsequent Pf infection, but also with an increased odds of symptoms once infected. V delta 2(+) T cells may play a role in preventing malaria infection in children living in endemic settings; progressive loss and dysfunction of these cells may represent a disease tolerance mechanism that contributes to the development of clinical immunity to malaria.