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The human isolate of Brachiola algerae (Phylum Microspora): development in SCID mice and description of its fine
B Koudela1, G S Visvesvara, H Moura
1Institute of Parasitology, Academy of Sciences of the Czech Republic, Ceské Budejovice. koudelab@vfu.cz
Abstract:
Ocular, peroral, intraperitoneal, intramuscular, and subcutaneous inoculation of severe combined immunodeficient (SCID) mice with spores of the human isolate (CDC: V404) of Brachiola algerae (syn. Nosema algerae) (Phylum Microspora) revealed that the microsporidium develops in viscera of the immunodeficient mouse host, but only after the ocular administration of spores. It is hypothesized that the physico-chemical milieu of the conjunctiva and cornea helped to adapt the originally 'poikilothermic microsporidian' to the conditions within the homoiothermic organism. Ocular application of spores caused no clinical signs of disease at the application site. However, severe infection in the liver was found 60 days after infection, manifested as hepatosplenomegaly and multifocal miliary necroses and granulomas containing parasites. No microsporidia were found in any other tissues. Transmission electron microscopy revealed characteristic tubulovesicular 'secretory materials' on the plasma membrane of all developmental stages of B. algerae except sporoblasts and spores. These formations increase the parasite surface and allow more efficient metabolic communication of the parasite with the host cell. It is hypothesized that the presence of these structures is a factor helping the parasite to grow in a variety of hosts and tissues. Ultrastructural characters support the likelihood that B. algerae and B. vesicularum are conspecific, and that there exists a relationship between species of the genera Brachiola and Anncaliia.
Insights
Ocular inoculation of Brachiola algerae spores in immunodeficient mice led to liver infection, suggesting the eye
Area of Science:
- Parasitology
- Immunology
- Microbiology
Background:
- Microsporidia are obligate intracellular parasites.
- Brachiola algerae (formerly Nosema algerae) is a microsporidian parasite.
- Severe combined immunodeficient (SCID) mice are a model for studying host-parasite interactions.
Purpose of the Study:
- To investigate the infectivity and development of Brachiola algerae in SCID mice.
- To determine the role of the ocular route in microsporidian infection.
- To examine the ultrastructure of Brachiola algerae during infection.
Main Methods:
- Inoculation of SCID mice via ocular, peroral, intraperitoneal, intramuscular, and subcutaneous routes with Brachiola algerae spores.
- Clinical observation and histopathological examination of infected mice.
- Transmission electron microscopy (TEM) of Brachiola algerae developmental stages.
Main Results:
- Ocular inoculation led to visceral development, specifically in the liver, 60 days post-infection.
- Infected livers showed hepatosplenomegaly, necroses, and granulomas containing parasites.
- Ultrastructural analysis revealed tubulovesicular 'secretory materials' on parasite membranes, potentially aiding host cell interaction.
Conclusions:
- The ocular route is critical for initiating visceral infection of Brachiola algerae in SCID mice.
- The conjunctival/corneal environment may facilitate parasite adaptation to a mammalian host.
- Ultrastructural features suggest Brachiola algerae may be conspecific with B. vesicularum, indicating a relationship with Anncaliia.