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Paracoccidioides brasiliensis: attenuation of yeast cells by gamma irradiation
Marina Cortez Demicheli1, Bernardo Sgarbi Reis, Alfredo Miranda Goes
1Laboratório de Radiobiologia, Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, MG, Brazil.
Abstract:
Paracoccidioides brasiliensis is the agent of paracoccidioidomycosis, the most prevalent mycosis in Latin America, and currently there is no effective vaccine. The aim of this study was to attenuate the yeast form of P. brasiliensis by gamma irradiation for further studies on vaccine research. Paracoccidioides brasiliensis (strain Pb 18) cultures were irradiated at doses between 0.5 and 8.0 kGy. After each dose the viability, reproductive ability and protein metabolism were evaluated. The comparison between the antigenic profile of irradiated and control yeast was made by Western blot and the virulence evaluated by the inoculation in C(57)Bl/J6 mice. At 6.5 kGy the yeast lost its reproductive capacity. The viability and the incorporation of [L-(35)S]-methionine were the same in control and up to 6.5 kGy irradiated cells, but 6.5 kGy-irradiated yeast secreted 40% less proteins. The Western blot profile was clearly similar in control and 6.5 kGy-irradiated yeast. No colony-forming unit (CFU) could be recovered from the tissues of the mice infected with the radioattenuated yeast. We concluded that for P. brasiliensis yeast it is possible to find a dose in which the pathogen loses its reproductive ability and virulence, while retaining its viability, metabolic activity and the antigenic profile.
Insights
Gamma irradiation effectively attenuated Paracoccidioides brasiliensis, the fungus causing paracoccidioidomycosis. This radioattenuated yeast retained key characteristics while losing virulence, paving the way for vaccine development.
Area of Science:
- Mycology
- Infectious Diseases
- Vaccine Development
Background:
- Paracoccidioidomycosis is a prevalent fungal infection in Latin America caused by Paracoccidioides brasiliensis.
- There is currently no effective vaccine available for paracoccidioidomycosis.
- Developing a safe and effective vaccine is crucial for controlling this mycosis.
Purpose of the Study:
- To attenuate the yeast form of Paracoccidioides brasiliensis using gamma irradiation.
- To evaluate the potential of radioattenuated P. brasiliensis as a candidate for vaccine research.
- To determine the optimal gamma irradiation dose for attenuating P. brasiliensis while preserving essential characteristics.
Main Methods:
- Cultures of Paracoccidioides brasiliensis (strain Pb 18) were subjected to gamma irradiation at doses ranging from 0.5 to 8.0 kGy.
- Evaluated parameters included yeast viability, reproductive ability, and protein metabolism ([L-(35)S]-methionine incorporation).
- Antigenic profiles were compared using Western blot, and virulence was assessed in C57BL/6 mice.
Main Results:
- A dose of 6.5 kGy resulted in the loss of reproductive capacity in P. brasiliensis yeast.
- Viability and [L-(35)S]-methionine incorporation remained comparable between control and irradiated cells up to 6.5 kGy.
- Irradiated yeast at 6.5 kGy secreted 40% fewer proteins but maintained a similar antigenic profile to the control.
- No colony-forming units (CFU) were recovered from mice infected with 6.5 kGy-irradiated yeast, indicating complete attenuation.
Conclusions:
- Gamma irradiation can effectively attenuate Paracoccidioides brasiliensis yeast.
- A specific dose (6.5 kGy) eliminates virulence and reproductive ability while preserving viability, metabolic activity, and antigenic profile.
- Radioattenuated P. brasiliensis shows promise as a live vaccine candidate for paracoccidioidomycosis.
