Detection of antibodies to Blastocystis hominis in immunised mice using counterimmunoelectrophoresis (CIE) and enzyme-linked immunosorbent assay (ELISA)

Abstract

Blastocystis hominis can cause diarrhoea in both immunocompetent and immunocompromised patients. Laboratory confirmation of the infection is usually based on detection of the parasite directly in stools or after in vitro culture. As these may not detect all cases, various immunological and molecular tests are being developed to increase the sensitivity and specificity of laboratory detection of infection. The indirect fluorescence antibody assay (IFA), counterimmunoelectrophoresis (CIE) and enzyme-linked immunosorbent assay (ELISA) are being evaluated for the detection of parasite antigens or specific B. hominis antibodies. The present study seeks to determine if homologous and heterologous antigens can be used in the CIE and ELISA to detect antibodies in mice immunised differently with an axenic B. hominis isolate (isolate C), xenic isolates (isolate H7 and RN), and an Escherichia coli isolate (Bac2). The granular form of the parasite isolates was used for antigen preparation. In the CIE, sera of mice immunised with isolate C reacted only with antigen C but not with H7, RN or Bac2 antigens. However, antigen C reacted with sera of all mice immunised with isolate RN, 37.5% of those immunised with H7, but not Bac2. Sera of mice immunised with RN and H7 all reacted with RN, H7 and Bac2 antigens. It is believed that the cross-reactions of sera from mice immunised with the xenic B. hominis isolates are due to antibodies against E. coli. Mean antibody levels detected in the ELISA with homologous and heterologous antigens followed closely the CIE results.