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Resistance of vaccinated mice to typical and atypical strains of Coccidioides immitis
Abstract:
In earlier reports, it was shown that mice and monkeys could be immunized against otherwise lethal challenge doses of Coccidioides immitis arthrospores. The vaccine was composed of Formalin-killed, in vitro grown, endosporulating spherules of C. immitis strain Silveira. In this study, mice were immunized as in the earlier work and then challenged intranasally with arthrospores from seven heterologous strains of C. immitis. Two of these strains were typical of the species, and five were atypical with respect to their cultural characteristics and morphology of microscopic structures. The vaccinated animals were well protected against challenge doses that were lethal to a majority of the control animals, regardless of the strain of fungus employed. The infection ratios among surviving vaccinated and control animals were comparable, but demonstrable lesions were generally smaller and less numerous in the vaccinated groups. It is suggested that these strains are at least immunogenically similar, although not necessarily identical, and that a vaccine prepared from a single strain of C. immitis would be practical for an immunization program.
Insights
A Coccidioides immitis vaccine using killed spherules protected mice against various fungal strains. This suggests a single-strain vaccine could be effective for immunization programs.
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- Coccidioides immitis causes coccidioidomycosis.
- Previous studies demonstrated successful immunization in mice and monkeys against C. immitis using a formalin-killed spherule vaccine.
Purpose of the Study:
- To evaluate the protective efficacy of a C. immitis vaccine against challenge with heterologous strains.
- To determine the immunogenic similarity among different C. immitis strains.
Main Methods:
- Mice were immunized with a formalin-killed, in vitro grown C. immitis spherule vaccine.
- Vaccinated mice were challenged intranasally with arthrospores from seven different C. immitis strains (two typical, five atypical).
- Protection was assessed by survival rates, infection ratios, and lesion development compared to control groups.
Main Results:
- Vaccinated mice showed significant protection against lethal doses of all tested C. immitis strains.
- Survival rates were higher in vaccinated groups compared to controls, irrespective of the challenge strain.
- While infection ratios were similar in survivors, vaccinated animals exhibited smaller and fewer demonstrable lesions.
Conclusions:
- The tested strains of Coccidioides immitis are immunogenically similar.
- A vaccine developed from a single strain of C. immitis could be practical for widespread immunization.
- The vaccine demonstrates broad protective potential against diverse C. immitis strains.