Diagnosis of Encephalitozoon cuniculi infection by western blot and the use of cross-reactive antigens for the possible detection of microsporidiosis in humans.

Microsporidia are very primitive, eukaryotic, obligate, intracellular, protozoan parasites. Encephalitozoon cuniculi, a microsporidian originally described from a rabbit infection, has been described in humans as well as in many species of laboratory animals. We report the detection of E. cuniculi by Western blotting in a rabbit with torticollis that was obtained from an Encephalitozoon-free colony. Cross-reactivity of this serum was observed with antigens prepared from several genera of microsporidia. Identical Western blotting patterns were obtained with sera obtained from a rabbit immunized with E. cuniculi that was purified from tissue culture cells. In addition, we were able to demonstrate cross-reactivity between E. cuniculi rabbit antisera and Enterocytozoon bieneusi antigens by indirect immunofluorescent assay techniques in human intestinal biopsy samples. These cross-reactions between microsporidia may be useful in developing diagnostic tests for non-cultivatable microsporidia such as Enterocytozoon bieneusi.