Application of yeast enolase as antigen for immunodiagnosis of malaria.

In 1998, we reported that Plasmodium falciparum (Pf) enolase was useful as the capture antigen for the immunodiagnosis of malaria. In the present study, we modified a fluorescence-ELISA for the diagnosis of malaria by applying yeast enolase or rabbit muscle enolase as antigen. Sera from 67 falciparum malaria patients and 15 vivax malaria patients were tested by the method. Positivity rates of the former was 82.1% against yeast enolase antigen and 90.5% against rabbit muscle enolase antigen, and those of latter was 93.3% against both enolase antigens. Mean antibody level (RFU values) of sera from falciparum and vivax malaria patients were significantly higher than those from healthy individuals. There was a significant correlation between anti-yeast and anti-rabbit muscle enolase antibody level (RFU values) in the group of falciparum subjects (r = 0.401, p<0.001). A significant correlation between RFU values against yeast enolase antigen and indirect fluorescent antibody titers against crude Pf antigen in the same subjects was recognized (r = 0.518, p<0.001). Longitudinal changes of RFU values against yeast enolase for the following 4 weeks after admission were also examined for sera from falciparum malaria patients. Patients with more severe malaria showed increasing RFU values as the clinical courses progressed. However, in the mild cases, each RFU value stayed unchanged during the course. We concluded that yeast and rabbit muscle enolase could be appropriately used as antigen for the immunodiagnosis of malaria.