Characterization of a human reference standard for antibody to Plasmodium falciparum merozoite surface protein 142

Abstract

Volunteers vaccinated with a candidate malaria vaccine containing merozoite surface protein I42 (MSP-142) exhibit antibodies to MSP-142 that are measured by enzyme-linked immunosorbent assay (ELISA). The purpose of this study was to make a human reference standard for MSP-142 antibody measured in absolute quantity units using pooled plasma samples known to contain high titers of MSP-142 antibody based on previous ELISA results. Immobilized metal affinity chromatography was used to determine the amount of MSP-142 antibody in this plasma pool. Hexahistidine-tagged MSP-142 antigen adsorbed to nickel-chelating resin was used to capture MSP-142 antibody from the plasma pool. The intact MSP-142 antibody-antigen complexes were eluted and total IgG was measured by an ELISA standardized against purified human IgG. In this way, the human reference standard was determined to contain 48.3 μg/mL of MSP-142 antibody. This reference standard may be useful as a quantitative working standard for measuring MSP-142 antibody response in future vaccine clinical trials involving MSP-1. Copyright © 2005 by The American Society of Tropical Medicine and Hygiene.