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Delayed-type hypersensitivity responses in infected mice elicited by cytoplasmic fractions of Cryptococcus neoformans
Abstract:
Four subcellular fractions of Cryptococcus neoformans prepared by differential centrifugation of disrupted whole yeast and a 3-day culture filtrate were examined for their ability to elicit delayed-type hypersensitivity in sensitized animals. The methods used to detect sensitization were (i) the footpad swelling test and inhibition of peritoneal macrophage migration in mice and (ii) skin testing in guinea pigs. Two entities, the post-mitochondrial supernatant and the culture filtrate, showed considerable activity in the footpad test, with 26- and 30-microliter 24-h swellings, respectively, at 6 weeks after infection. With the latter there was interference from a strong antibody-mediated 4-h skin reaction. The post-mitochondrial supernatant produced strong delayed-type hypersensitivity in guinea pigs at a dose of 69 microgram, and there was no demonstrable cross-reactivity in animals sensitized with heterologous fungi. The footpad swelling in mice correlated well with the macrophage migration inhibition test, with 71% inhibition in mice infected subcutaneously with C. neoformans at 6 weeks. However, mice infected intravenously developed poorer cell-mediated immunity than the subcutaneously infected mice. The post-mitochondrial supernatant was found to contain detectable amounts of cryptococcal capsular polysaccharide.
Insights
Researchers identified specific Cryptococcus neoformans fractions that effectively trigger delayed-type hypersensitivity in animal models. The post-mitochondrial supernatant demonstrated significant immune response, indicating its potential as a diagnostic or therapeutic target.
Area of Science:
- Immunology
- Mycology
- Cell Biology
Background:
- Cryptococcus neoformans is a significant fungal pathogen causing life-threatening infections, particularly in immunocompromised individuals.
- Understanding the immune response to C. neoformans is crucial for developing effective diagnostics and therapeutics.
- Cell-mediated immunity plays a vital role in controlling cryptococcal infections.
Purpose of the Study:
- To investigate the immunogenic properties of subcellular fractions of Cryptococcus neoformans.
- To identify specific components of C. neoformans that elicit delayed-type hypersensitivity (DTH).
- To evaluate the efficacy of these fractions in animal models of sensitization.
Main Methods:
- Differential centrifugation was used to isolate four subcellular fractions from disrupted C. neoformans yeast and culture filtrate.
- Delayed-type hypersensitivity was assessed using the footpad swelling test and macrophage migration inhibition assay in mice.
- Skin testing in guinea pigs was also employed to evaluate sensitization.
- Specific fractions, including the post-mitochondrial supernatant and culture filtrate, were analyzed for their immunogenicity.
Main Results:
- The post-mitochondrial supernatant and culture filtrate demonstrated significant activity in the footpad swelling test.
- The post-mitochondrial supernatant induced strong delayed-type hypersensitivity in guinea pigs without cross-reactivity with other fungi.
- Footpad swelling in mice correlated with macrophage migration inhibition, showing 71% inhibition in subcutaneously infected mice.
- Intravenously infected mice exhibited weaker cell-mediated immunity compared to subcutaneously infected mice.
- The post-mitochondrial supernatant contained detectable levels of cryptococcal capsular polysaccharide.
Conclusions:
- The post-mitochondrial supernatant of Cryptococcus neoformans is a potent elicitor of delayed-type hypersensitivity.
- This fraction holds promise for further investigation as a component in diagnostic tools or immunotherapies for cryptococcosis.
- The route of infection significantly influences the development of cell-mediated immunity against C. neoformans.