Preliminary observations on the efficacy of a recombinant multistage Plasmodium falciparum vaccine in Aotus nancymai monkeys.

A vaccine trial was conducted to determine the efficacy of a multicomponent candidate vaccine, FALVAC-1, against Plasmodium falciparum in Aotus nancymai monkeys. After two immunizations, animals were challenged intravenously with parasites of the Vietnam Oak Knoll (FVO) strain of P. falciparum. The primary outcome was to determine the protective response of the monkeys to immunization with the FALVAC-1 antigen produced in baculovirus when combined with different adjuvants (alum, QS-21, ASO2a, CRL1005/oil, and CRL1005/saline) as compared with FALVAC-1 with FCA/FIA and antigen alone. When compared with the monkeys immunized with FALVAC-1 alone, FALVAC-1 with FCA/FIA reduced the mean parasite count (to Day 11), reduced the mean accumulated parasitemia (through Day 11), and extended the number of days to treatment. None of the other 5 antigen-adjuvant combinations were able to provide discernable levels of protection based on log(parasitemia) and log(cumulative parasitemia) to Day 11.