Malaria is a significant cause of mortality and morbidity globally and has no licensed vaccine to date. Plasmodium falciparum and P. vivax are the parasite species responsible for the majority of malaria cases. Protective immunity to both P. falciparum and P. vivax is mediated by antibodies. Induction of protective antibodies is driven by CD4 T follicular helper cells which activate B cells during infection. To date, no studies have investigated the influence of parasite species on Tfh cell responses during malaria in humans.
We assessed Tfh cell responses in adults with either Plasmodium falciparum (n=8) or Plasmodium vivax (n=8) malaria compared to healthy uninfected endemic controls (n=5). Tfh cell responses were measured ex vivo by flow cytometry and functional capacity measured by intracellular staining of cytokines produced following PMA/Ionomycin stimulation.
We observed significant differences in Tfh cell responses across the species with a more robust Tfh cell activation in Pf than Pv infections. Both Th1 and Th2 – Tfh cell subsets are activated by both species. However, the responses are strongly skewed to Th1- Tfh subset during P. falciparum malaria. Future studies will investigate these differences at the transcriptional level by purifying Tfh cells during infection for RNA sequencing.
This data provides insights into the influence of malaria parasite species on Tfh cell responses and warrants further assessment for strategies targeting Tfh cell responses to improve vaccine efficacy.