Laboratory of Parasitology, Department of Infection-Immunology, Division of Biotechnology, Statens Seruminstitut, Liberian Institute for Biomedical Research, Chemical Institute, Royal Veterinary and Agricultural University, Copenhagen, Denmark
A Plasmodium falciparum antigen gene coding for a 220-kD glutamate-rich protein (GLURP) has been cloned, and the 783 C-terminal amino acids of this protein (GLURP489–1271) have been expressed as a β-galactosidase fusion protein in Escherichia coli. The encoded 783 amino acid residues contain two areas of repeated amino acid sequences. Antibodies against recombinant GLURP489–1271, as well as against a synthetic peptide corresponding to GLURP899–916, and against a synthetic peptide representing the major glutamate rich repeat sequence from the P. falciparum ring erythrocyte surface antigen (Pf155/RESA) (EENV)6 were examined in 423 individuals (age range 30 days-78 years) living in a malaria holoendemic area of Liberia. In the 5–9-year-old age group, subjects with anti-GLURP489–1271 antibody concentrations greater than the mean value of the group had lower parasite densities than those with low antibody concentrations (P = 0.0151). High levels of anti-GLURP899–916 antibodies did not correlate with low parasite densities. However, high levels of anti-(EENV)6 antibodies were associated with significantly lower parasite densities in the 2–4-year-old age group (P = 0.0189). There was no correlation between the anti-GLURP489–1271 and anti-(EENV)6 antibody responses. The data provide indirect evidence for a protective role of antibodies reacting with recombinant GLURP489–1271 as well as with the synthetic peptide (EENV)6 from the Pf155/RESA.