Relationship of antibodies to soluble Plasmodium falciparum antigen (Pf70) and protection against malaria in a human population living under intense transmission in Kinshasa, Zaire.

The rapid acquisition of resistance by Plasmodium falciparum to antimalarial drugs has focused worldwide efforts on vaccine development. The definition of critical antigens involved in the induction of protective immunity against disease is essential. Our previous studies have characterized a synthetic peptide complex (SPf70), derived from a 70 kDa P. falciparum exoantigen, in terms of its immunogenicity and antigenic reactivity. In the present study total anti-P. falciparum asexual blood-stage antibodies and antibodies to the Pf70 antigen were measured by immunofluorescence (IFA) and ELISA, respectively, in children and adults (n = 160) of Kinshasa, Zaire, an area with continuous and intense malaria transmission. All of the subjects tested had IFA antibodies and 90% (143/160) had antibodies to Pf70 antigen. Antibody levels against Pf70 were significantly higher among children with low parasitemias (p < 0.05). These results suggest that antibodies to Pf70 antigen may have a protective role against P. falciparum infection. Further studies are needed to define the functional nature of the protective mechanism(s).