Lymphocyte Responsiveness to a Candidate Malaria Sporozoite Vaccine (R32tet32) of Individuals with Naturally Acquired Plasmodium Falciparum Malaria

Lymphocyte proliferative responses to the candidate malaria sporozoite vaccine antigen R32tet32 were evaluated in 29 patients with acute Plasmodium falciparum malaria, 20 convalescent patients, 11 nonimmune individuals, and 22 healthy residents of two endemic malarious areas in Thailand. The results indicate that 14 of 20 (70%) convalescent patients and 14 of 22 (64%) residents of endemic areas responded to the R32tet32 antigen. However, only 8 of 29 (28%) patients with acute P. falciparum malaria responded. When 4 of the convalescent patients who remained in a malaria-free area were restudied 5-10 months after the acute infection, they were either not responsive or their responses had greatly diminished. These findings show that sensitization to R32tet32 occurs following a natural P. falciparum infection, but the cellular immune response to sporozoite antigens may be short-lived and may be suppressed during acute P. falciparum malaria.