Enzyme-linked staining method for light microscopic detection of antibodies to parasite antigens on the membrane of Plasmodium falciparum infected erythrocytes

Abstract

Indirect erythrocyte membrane immunofluorescence (EMIF), a standard method for detection of antibodies to the P. falciparum blood stage vaccine candidate antigen Pf155/RESA, has been adapted to light microscopy by enzyme-linked immunostaining of the erythrocyte membrane, using alkaline phosphatase and chromogenic substrate. This method gives a dark blue staining of the membranes of ring infected erythrocytes. Results obtained with 70 African sera in EMIF and in enzyme immunostaining correlated well although the enzyme based method sometimes resulted in higher antibody titers and appeared to be slightly more sensitive. Similar results were obtained when comparing immunofluorescence with enzyme immunostaining for detection of antibodies to intraerythrocytic parasite antigens. The enzyme linked immunostaining described is simple and fast and does not require expensive equipment and should, thus, be well suited for use in laboratories with limited resources or under field conditions.