The specificity of the antibodies obtained was investigated in detail, particularly since several peptides contain glutamic acid (Glu)-rich sequences which are known to generate cross reactivity among several malarial Glu-rich proteins [15] . Cross-reactions were systematically investigated using each of the 18 affinitypurified antibodies on each of the 18 peptides. Results show thatwith few exceptions-each antibody preferentially recognizes the peptide against which antibodies were affinity-purified, i.e. they are specific for the corresponding peptide (Table S2) . To determine if non-specific antibody binding to solid phase-adsorbed antigens could be responsible for the rare cross-reactivities detected, ELISA competition assays were performed. To this end, binding of antibodies to the solid phase-adsorbed antigen was competed against increasing concentrations of the homologous or cross-reacting peptides. Only homologous peptides competed best whereas peptides having sequence similarity did not (Figures 2A,  2B , and S2B), or at a much higher concentration ( Figure S2A ) including the shorter Glu-rich peptides derived from the Cterminus of peptide 27 and 45 (Figures 2A and 2B) . Finally, the pattern of recognition of peptides by the various sera tested, which differ markedly from one to the other (data not shown), confirms the above results i.e., specificity of antibodies to the corresponding peptide.