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In vitro and in vivo investigations of human microsporidia
1Department of Biology, Imperial College of Science, Technology and Medicine, London, United Kingdom.
Abstract:
The numerous infections of microsporidia which have been diagnosed in patients with AIDS have revealed the potential of these organisms for establishing themselves when the immune status of the host is compromised. Two species of Encephalitozoon, E. cuniculi and E. hellem, have been diagnosed in man, the former infecting a variety of tissues, the latter restricted to the corneal and conjunctival epithelia. These species are morphologically indistinguishable even at the ultrastructural level but can be separated biochemically. Two human sera were found to react with equal intensity in the ELISA on spores of E. cuniculi and E. hellem purified from in vitro cultures, and gave similar binding patterns in Western blots on SDS-PAGE protein profiles of the two species. This has raised questions about the identity of Encephalitozoon infections diagnosed previously in man. The diagnosis of Enterocytozoon bieneusi, which infects the intestinal enterocytes of AIDS patients and is associated with chronic diarrhoea, requires observation of smears or sections of biopsies or specialist observation of stool preparations. In vitro cultures, which would facilitate the raising of specific antisera, have proved difficult to establish. In vitro and in vivo systems for assaying drugs for microsporidia have revealed that albendazole has a marked effect on parasite numbers and morphology but does not eliminate infection, which resurges when drug pressure is removed.
Insights
Microsporidia infections are common in immunocompromised patients, particularly those with AIDS. Morphologically identical Encephalitozoon species (E. cuniculi and E. hellem) show similar reactions to human sera, questioning previous diagnoses.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Parasitology
Background:
- Microsporidia infections pose significant risks to immunocompromised individuals, notably patients with Acquired Immunodeficiency Syndrome (AIDS).
- Two Encephalitozoon species, Encephalitozoon cuniculi and Encephalitozoon hellem, have been identified in human infections, affecting various tissues or ocular epithelia, respectively.
- These species are morphologically indistinguishable, even ultrastructurally, complicating accurate diagnosis and identification.
Purpose of the Study:
- To investigate the serological relationship between Encephalitozoon cuniculi and Encephalitozoon hellem in human infections.
- To address the diagnostic challenges posed by morphologically similar microsporidian species in immunocompromised patients.
- To evaluate the efficacy of albendazole in treating microsporidian infections.
Main Methods:
- Enzyme-Linked Immunosorbent Assay (ELISA) was used to detect antibody responses in human sera against purified spores of E. cuniculi and E. hellem.
- Western blot analysis was performed on SDS-PAGE protein profiles of the two species to compare antibody binding patterns.
- In vitro and in vivo drug assays were conducted to assess the impact of albendazole on microsporidian infections.
Main Results:
- Human sera exhibited similar reactivity patterns against both E. cuniculi and E. hellem in ELISA and Western blot analyses.
- This serological cross-reactivity raises questions regarding the specific identification of previously diagnosed Encephalitozoon infections in humans.
- Albendazole demonstrated a significant effect on reducing parasite load and altering morphology but did not eradicate the infection, with parasites reappearing after drug withdrawal.
Conclusions:
- The study highlights the difficulty in differentiating between E. cuniculi and E. hellem infections based on current serological methods due to cross-reactivity.
- Accurate diagnosis of microsporidiosis, including Enterocytozoon bieneusi, often relies on specialized microscopic examination of patient samples.
- Albendazole shows potential as a therapeutic agent but is not curative for microsporidian infections, necessitating further research into more effective treatments.