Cellular immune responses to recombinant Plasmodium vivax tryptophan-rich antigen (PvTRAg) among individuals exposed to vivax malaria.

Plasmodium vivax, the most widespread species of human malaria parasite responsible for 70-80 million cases each year requires a vaccine. In recent years, many potential vaccine candidate antigens have been identified from P. vivax including PvTRAg. We describe here cellular immune response to recombinant PvTRAg expressed in Escherichia coli. The in vitro stimulation of PBMCs derived from P. vivax-exposed individuals (n = 16) showed strong proliferative response (SI > 2.2) to PvTRAg as compared to PBMCs from normal healthy controls (n = 8). Although both Th1 (IFN-gamma, TNF-alpha and IL-12) and Th2 (IL-4 and IL-10) cytokines were secreted by the PBMCs of the P. vivax-exposed individuals in response to PvTRAg, the overall response was more inclined towards Th2. In conclusion, recombinant PvTRAg was found to elicit strong cellular immune response among the P. vivax-exposed individuals.