A New Method for the Production of Potent Inactivated Vaccines with Ultraviolet Irradiation

Abstract

A new method has been developed for completely killing or inactivating turbid suspensions of bacteria and viruses in less than one second by exposing continuously flowing thin films to far and extreme ultraviolet irradiation. Intensity, film thickness, time of exposure and distance have been so standardized that experiments could be duplicated with consistent results. By means of this new technic, suspensions containing approximately one billion organisms per ml of the following bacteria were completely killed in 0.17 to 0.33 seconds exosure to ultraviolet rays: (1) Bacterium coli, (2) Eberthella typhi (strain 58), (3) Salmonella enteritidis, (4) Staphylococcus aureus, (5) Streptococcus viridans, and (6) Diplococcus pneumoniae (type I). Four per cent uncentrifuged brain tissue suspensions infected with fixed rabies or lymphocytic choriomeningitis virus were completely inactivated by irradiation for 0.17 to 0.33 seconds; an exposure twice this length was necessary to inactivate lightly centrifuged four per cent suspensions of St. Louis encephalitis virus. Several lots of rabies vaccine inactivated by this irradiation technic consistently induced a higher degree of immunity in mice than control phenolized vaccines. The irradiated rabies vaccines exhibited no significant loss of potency after six months storage at 5 C. Two lots of St. Louis encephalitis vaccine inactivated by this irradiation technic conferred a high degree of immunity in mice. Irradiation of rabies or St. Louis encephalitis viruses beyond the optimal time necessary for complete inactivation causes progressive diminution of antigenicity.