Two-site sandwich ELISA for detection of Plasmodium vivax blood stage antigens using monoclonal and polyclonal antibodies
Khusmith, S.; Intapan, P.; Tharavanij, S.; Tuntrakul, S.; Indravijit, K.A.; Bunnag, D.
Southeast Asian Journal of Tropical Medicine and Public Health 23(4): 745-751
1992
ISSN/ISBN: 0125-1562 PMID: 1298084 Document Number: 395260
Two systems of sandwich enzyme-linked immunosorbent assay (ELISA), a two-site monoclonal antibody sandwich ELISA MAb-MAb sandwich ELISA and a two site polyclonal-monoclonal antibody sandwich ELISA (PAb-MAb sandwich ELISA) for the detection of Plasmodium vivax antigens were developed. The assays showed good correlation with the level of parasitemia when tested against serially diluted P. vivax parasites (r = 0.937, and 0.997 for MAb-MAb and PAb-MAb sandwich ELISA, respectively), with the ability to detect as few as 6.68 parasites/10-6 erythrocytes and 2.69 parasites/10-3 erythrocytes, respectively. The MAb-MAb sandwich ELISA was specific, since it was positive only with P. vivax-infected erythrocytes from vivax malaria patients and negative when erythrocytes from 34 healthy individuals and 30 falciparum malaria cases were tested. In contrast, cross-reaction was found in the PAb-MAb sandwich ELISA when the plates were coated with polyclonal IgG and tested against the serially diluted P. falciparum SO strain antigen prepared from in vitro cultures. Comparison between the two systems of two-site sandwich ELISA showed that the MAb-MAb sandwich ELISA was superior to the PAb-MAb sandwich ELISA: (1) it gave a higher sensitivity when tested with serially diluted P. vivax antigen preparations from vivax malaria patients; (2) it gave a higher specificity when tested with the SO strain of P. falciparum from in vitro cultures. (3) it gave a lower absorbance value when tested with erythrocytes from healthy individuals. All 281 cases of vivax malaria already proven by microscopic examination were positive by MAb-MAb sandwich ELISA. However, the assay showed a poor correlation with parasitemia in infected individuals examined by microscopy (r = 0.117).