Hazliza binti Hussin1, Mak JW1,2, lnit 12 and Ngah Z1
1. Faculty of Medical and Health Sciences, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
2. lnstitute for Medical Research, Kuala Lumpur, Malaysia
Correspondence: Dr Mak JW; e-mail
CITATION: Hazliza binti Hussin, Mak JW, lnit I, Ngah Z. Detection of antibodies to Blastocystis hominis in immunised mice using counterimmunoelectrophoresis (CIE) and enzyme-linked immunosorbent assay (ELISA). International Medical Research Journal. 2000;4(1):37–43.
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. Immune sera against isolate C had significantly higher OD levels in the ELISA with antigen C at week 2 to 6 post-immunisation than sera of mice immunised against the xenic isolates (RN and H7) and Bac2 (P < 0.005). ELISA OD levels in sera of mice immunised with xenic isolates were higher with homologous antigens. OD values were higher against other xenic isolate antigens and Bac2 antigen than with isolate C. All antigens induced significantly higher antibody levels than preimmunisation sera in the sera of immunised mice at week 2 to 6 post-immunisation (P < 0.005). It is concluded that both the CIE and ELISA can be used to detect B. hominis antibodies. It is recommended that the antigen for these assays be from axenic isolates of B. hominis to avoid cross-reactions with antibodies directed against E. coli. The CIE is technically simpler and quicker to carry out than the ELISA but uses more antigens.
KEYWORDS: Blastocystis hominis, antibodies, ELISA, CIE
