In vitro inactivation of the rabies virus by ascorbic acid

Objective: The current recommended inactivating agent for the rabies virus, beta propiolactone (BPL) is very expensive and potentially carcinogenic. There is a need to evaluate alternative chemicals, which will inactivate the virus without affecting its antigenicity. In this study the effect of ascorbic acid on the infectivity of the rabies virus has been investigated. Method: Vero cell grown fixed rabies virus CVS strain was treated with 0.1 mg/ml, 0.5 mg/ml and 1 mg/ml final concentrations of ascorbic acid and 5 mug/ml of copper sulfate and kept at 4 degreesC along with untreated virus material. Each aliquot was titrated after various intervals for viral infectivity using both mice inoculation and titration in vero cells. The antigenicity of the virus material was determined by antibody induction in mice and modified NIH tests in parallel with virus material inactivated with a 1:4000 concentration of BPL. Results: An optimal concentration of 0.5 mg/ml of ascorbic acid and 5 mug/ml of copper sulfate completely inactivated the virus after 72 hours. The inactivated virus retained good antigenicity and potency value, which was comparable with using BPL. Conclusion: These findings suggest that ascorbic acid can be used as an inactivating agent for fixed rabies virus grown in cell culture particularly for the preparation of diagnostic reagents. Further studies are required to evaluate its effect on the cell associated virus, probable therapeutic potential and feasibility of replacing BPL in production of inactivated rabies vaccine. (C) 2003 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.