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Sterilization of HIV with irradiation: relevance to infected bone allografts
1Royal Adelaide Hospital and Institute of Medical and Veterinary Science, Australia.
Background:
Bone allograft banks commonly sterilize frozen bone by irradiation. The dose-response relationship for HIV is calculated and the dose required to inactivate the bioburden of virus that may be present in allograft bone is determined.
Methods:
A virus titre experiment is performed using irradiated frozen HIV. The virus is maintained on dry ice (approximately -70 degrees C) and is exposed to a cobalt 60 source with 0-40 kGy irradiation at 5 kGy intervals. Lymphocyte cell cultures are exposed to serial dilutions of the irradiated virus. The virus titre is quantified by cytological changes of HIV infection and p24 immunofluorescence.
Results:
There is a linear relationship between the virus titre and the radiation dose delivered. The inactivation rate of irradiated virus was 0.1134 log10 tissue culture infective doses 50/mL per kGy (95% confidence intervals, 0.1248-0.1020). The irradiation dose required to inactivate the HIV bioburden in allograft bone is 35 kGy. The irradiation dose required to achieve a sterility assurance level of 10(-6) is 89 kGy. This dose exceeds current recommendations for sterilizing medical products and the current practice of many bone banks.
Conclusions:
It is concluded that gamma irradiation should be disregarded as a significant virus inactivation method for bone allografts.