Development of immunoradiometric assay for detection of Plasmodium falciparum antigen in blood using monoclonal antibody.

Abstract

Specific monoclonal antibody (MAB) F2W22C1) produced by hybridoma technology against blood stage common antigens shared by almost all isolates of P. falciparum was selected. The 125I-labelled prepared from this MAB (125I-MIgG) was used as probe for detection of low grade P. falciparum infection. Recently, a two-site monoclonal antibody sandwich immunoradiometric assay (Mab-IRMA) has been developed. The assay showed good correlation with parasitaemia with the ability to detect as few as 2.4 parasites/10(8) erythrocytes. Two surveys were made in people living in a malaria endemic area during transmission and non-transmission season to detect the antigen of Plasmodium falciparum by using the Mab-IRMA. In the first survey involving 101 people, the IRMA positive rate was 56.4% and then significantly declined to 16.5% during the second survey involving 79 people of the same group. The parasitological positive rates were likewise decreased from 11.9% to 1.3% (p = 0.015) during these two seasons. IRMA positive rates were significantly higher than the corresponding parasitological positive rates (p less than 0.0001 and less than 0.002 for the first and the second surveys respectively). Regression analysis showed that IRMA activities were linearly correlated with the parasite counts by microscopic examinations (r = 0.629, p = 0.022). IRMA was specific for P. falciparum since all 30 healthy controls and six of seven vivax malaria cases were negative. IRMA has potential for use to monitor the malaria control and to assess the efficacy of the future field trial of malaria vaccine.