Studies on antibody production against peptides derived from malaria parasite antigens in balb/c mice

Abstract

Peptideslinked to carrier proteins are widely used to produce anti-peptide antibodies for experimentalpurposes. Since peptide vaccines are relatively inexpensive and antipeptideantibodiesare able to react specifically with the corresponding native protein in manyinstances,there is considerable interest in using peptide-carrier conjugates as vaccines against human and veterinary diseases including malaria. Peptides correspondingto known and predicted Band T cell epitopes of the antigens of human malaria parasite Plasmodium falciparum were synthesized. A 45kDa merozoite surfaceglycoprotein(GYMSSA), a precursor to the major merozoite surface antigen (PMMSA),an antigen present in the rhoptry-microneme complex (RAP), a serine rich antigen (SERA) present largely in the parasitophorous vacuole and a protein containing acidic and basic amino acid repeats also present largely in the parasitophorousvacuole (ABRA) were used in the study. The studies were performed in four stages. Firstly, peptides from GYMSSA and PMMSA were conjugated through6-maleimido caproic acyl N-succinimide ester to bovine serum albumin. The conjugateswere used to immunize Balb/c mice in saline and with different adjuvants. Freund's adjuvant, two muramyl dipeptide derivatives (murabutide and muramatide) andaluminiumhydroxide. Three injections of antigen were given intra muscularly at 2ld intervals and sera obtained after each injection. Antibody levels against peptides were measured by ELISA. Freund's adjuvant produced the highest titer of 10-4. Antibody levels obtained with alum absorbed antigen reached titers of 10-3- 10-4 while antigen administered in saline alone yielded titers of 10-3. The synthetic adjuvantsmaramyl dipeptide derivatives did not produce higher antibody levels than