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Ultrastructural changes in Paracoccidioides brasiliensis yeast cells attenuated by gamma irradiation
Marina Cortez Demicheli1, Alfredo Miranda Goes, Antero Silva Ribeiro de Andrade
1Laboratório de Radiobiologia, Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, MG, Brazil.
Abstract:
Paracoccidioides brasiliensis is a thermally dimorphic fungus agent of paracoccidioidomycosis, a deep-seated systemic infection of humans with high prevalence in Latin America. Until now no vaccine has been reported. Ionizing radiation can be used to attenuate pathogens for vaccine development and we have successfully attenuated yeast cells of P. brasiliensis by gamma irradiation. The aim of the present study was to examine at ultrastructural level the effects of gamma irradiation attenuation on the morphology of P. brasiliensis yeast cells. Paracoccidioides brasiliensis (strain Pb-18) cultures were irradiated with a dose of 6.5 kGy. The irradiated cells were examined by scanning and also transmission electron microscopy. When examined 2 h after the irradiation by scanning electron microscopy, the 6.5 kGy irradiated cells presented deep folds or were collapsed. These lesions were reversible since when examined 48 h after irradiation the yeast had recovered the usual morphology. The transmission electron microscopy showed that the irradiated cells plasma membrane and cell wall were intact and preserved. Remarkable changes were found in the nucleus that was frequently in a very electrondense form. An extensive DNA fragmentation was produced by the gamma irradiation treatment.
Insights
Gamma irradiation attenuates Paracoccidioides brasiliensis yeast cells, causing temporary morphological changes and nuclear DNA fragmentation. This research explores potential vaccine development strategies against paracoccidioidomycosis.
Area of Science:
- Mycology
- Infectious Diseases
- Vaccine Development
Background:
- Paracoccidioides brasiliensis causes paracoccidioidomycosis, a prevalent systemic infection in Latin America.
- No vaccine is currently available for paracoccidioidomycosis.
- Pathogen attenuation using ionizing radiation is a viable strategy for vaccine creation.
Purpose of the Study:
- To investigate the ultrastructural effects of gamma irradiation on Paracoccidioides brasiliensis yeast cells.
- To assess the potential of gamma irradiation as an attenuation method for P. brasiliensis vaccine development.
Main Methods:
- Paracoccidioides brasiliensis (strain Pb-18) yeast cells were exposed to a 6.5 kGy dose of gamma irradiation.
- Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine cell morphology.
- Cells were analyzed at 2 hours and 48 hours post-irradiation.
Main Results:
- SEM revealed temporary cell surface folding and collapse 2 hours after irradiation.
- TEM showed intact plasma membranes and cell walls in irradiated cells.
- Significant nuclear electron density increase and extensive DNA fragmentation were observed post-irradiation.
Conclusions:
- Gamma irradiation induces reversible morphological changes and significant nuclear damage in P. brasiliensis yeast cells.
- The observed ultrastructural alterations suggest gamma irradiation as a potential method for attenuating P. brasiliensis for vaccine purposes.
- Further studies are warranted to confirm the efficacy and safety of this attenuation strategy for vaccine development.
