Title: Effects of radiation type and delivery mode on a radioresistant eukaryote Cryptococcus neoformans
Citation: NUCLEAR MEDICINE AND BIOLOGY vol. 42 no. 6 p. 515-523
Publication Year: 2015
JRC N°: JRC92421
ISSN: 0969-8051
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC92421
DOI: 10.1016/j.nucmedbio.2015.02.006
Type: Articles in periodicals and books
Abstract: Introduction: Most research on radioresistant fungi, particularly on human pathogens such as Cryptococcus neoformans, involves sparsely-ionizing radiation. Consequently, fungal responses to densely-ionizing radiation, which can be harnessed to treat life-threatening fungal infections, remain incompletely understood. Methods: We addressed this issue by quantifying and comparing the effects of densely-ionizing α-particles (delivered either by external beam or by 213Bi-labeled monoclonal antibodies), and sparsely-ionizing 137Cs γ-rays, on Cryptococus neoformans. Results: The best-fit linear-quadratic parameters for clonogenic survival were the following: α = 0.24 × 10− 2 Gy− 1 for γ-rays and 1.07 × 10− 2 Gy− 1 for external-beam α-particles, and β = 1.44 × 10− 5 Gy− 2 for both radiation types. Fungal cell killing by radiolabeled antibodies was consistent with predictions based on the α-particle dose to the cell nucleus and the linear-quadratic parameters for external-beam α-particles. The estimated RBE (for α-particles vs. γ-rays) at low doses was 4.47 for the initial portion of the α-particle track, and 7.66 for the Bragg peak. Non-radiological antibody effects accounted for up to 23% of cell death. Conclusions: These results quantify the degree of C. neoformans resistance to densely-ionizing radiations, and show how this resistance can be overcome with fungus-specific radiolabeled antibodies.
JRC Directorate:Nuclear Safety and Security

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