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Identification of the microsporidian Encephalitozoon hellem using immunoglobulin G monoclonal antibodies
G P Croppo1, G S Visvesvara, G J Leitch
1Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, Ga 30341-3724, USA.
Objective:
Microsporidia isolated from clinical specimens so far have been identified to level of species by electron microscopy, indirect immunofluorescence (IIF), western blot (WB), and genetic analysis. Recent studies, however, indicate extensive serologic cross-reactions among microsporidian species involved in human disease.
Design And Setting:
In this study, we used IIF and WB techniques to evaluate the reactivity of six different immunoglobulin G monoclonal antibodies (MAbs) raised against Encephalitozoon hellem with six isolates of E hellem that originated from patients with acquired immunodeficiency syndrome. A rabbit isolate of Encephalitozoon cuniculi, and an isolate of Encephalitozoon intestinalis, which was established in cultures from the urine of a patient with acquired immunodeficiency syndrome were also used for comparison.
Results:
Five of the six antibodies, when analyzed by both IIF and WB assays, specifically identified six isolates of E hellem originating from three patients with acquired immunodeficiency syndrome. The sixth MAb, however, reacted with all of the E hellem isolates in the WB assay, but failed to react with them in the IIF assay. Using the IIF test, five of the six MAbs failed to react with E cuniculi and E intestinalis, even at a dilution of 1:50. The MAbs also did not react in the IIF test with Enterocytozoon bieneusi, Giardia, and Cryptosporidium. These MAbs did react with E cuniculi and E intestinalis in the WB assay, but the banding patterns were very different from those of E hellem, thus facilitating the identification of E hellem from the other microsporidia. The MAbs also reacted, in the IIF test, with E hellem spores in formalin-fixed tissue sections that were heated in a microwave oven.
Conclusions:
Identification of microsporidian agents to the species level is important. Since certain therapeutic agents (eg, fumagillin, albendazole) are efficacious in treating E hellem infections of the cornea, as well as urogenital and respiratory infections caused by E hellem, a quick and definitive identification of the organism is important so that successful therapy may be instituted. An IIF test using the MAbs described here would therefore be invaluable in the quick identification of this parasite.
Insights
Monoclonal antibodies (MAbs) can accurately identify Encephalitozoon hellem (E. hellem) infections. This specific indirect immunofluorescence (IIF) test aids in rapid diagnosis for effective treatment of microsporidiosis.
Area of Science:
- Medical Microbiology
- Immunology
- Parasitology
Background:
- Accurate species-level identification of microsporidia is crucial for diagnosing human infections.
- Previous identification methods like electron microscopy and genetic analysis can be time-consuming.
- Serologic cross-reactivity among microsporidian species complicates accurate diagnosis.
Purpose of the Study:
- To evaluate the diagnostic utility of immunoglobulin G monoclonal antibodies (MAbs) against Encephalitozoon hellem (E. hellem).
- To assess the specificity and sensitivity of indirect immunofluorescence (IIF) and Western blot (WB) assays using these MAbs for E. hellem identification.
- To compare the reactivity of MAbs against E. hellem with other microsporidian species and protozoa.
Main Methods:
- Six immunoglobulin G (IgG) monoclonal antibodies (MAbs) against E. hellem were tested.
- Indirect immunofluorescence (IIF) and Western blot (WB) assays were employed.
- Isolates of E. hellem, Encephalitozoon cuniculi, and Encephalitozoon intestinalis were used for reactivity testing.
Main Results:
- Five of six MAbs specifically identified E. hellem isolates using both IIF and WB.
- One MAb showed reactivity in WB but not IIF against E. hellem isolates.
- MAbs demonstrated minimal cross-reactivity with E. cuniculi and E. intestinalis in IIF, aiding species differentiation.
Conclusions:
- Monoclonal antibodies provide a valuable tool for specific E. hellem identification.
- The developed indirect immunofluorescence (IIF) assay using MAbs enables rapid and definitive diagnosis.
- Accurate diagnosis is essential for timely and effective treatment of E. hellem infections.