Factors influencing the effects of gamma, irradiation on influenza A(PR8) virus suspensions have been investigated. In purified virus suspensions in physiological saline, the hemagglutinin was destroyed more rapidly than the infectivity. The addition of reagents such as histidine, sodium p-aminohippurate, ascorbic acid, or cystine to the saline suspension reversed this effect. It was also found that the effect of a given amount of gamma radiation on the infectivity and hemagglutinin was similar regardless of whether the radiation was administered as a single dose or as two or four divided doses on different days. It is possible to calculate the amount of radiation required to destroy the infectivity and yet retain most of the hemagglutinin content, If a given dose of radiation has been insufficient to produce complete virus inactivation, the suspension can be subjected to a further dose, the amount of which can be exactly calculated, without destroying the hemagglutinin. These experiments were repeated with other strains of influenza A and B with similar results. The application of this work to the preparation of virus vaccines is being investigated and will be reported later.

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A protective agent such as histidine or sodium p-aminohippurate was added to purified suspensions of influenza and mumps viruses. It was then possible to inactivate them in about an hour with gamma radiation while retaining most of the hemagglutination titer. It was demonstrated in mice that a vaccine prepared from a mouse-adapted virus (Shope's swine influenza strain of influenza A) conferred protection against challenge by the live virus and produced an antibody response as measured by the hemagglutination–inhibition technique. Vaccines prepared with the viruses of influenza A(PR8), influenza B, and mumps were shown to produce antibody responses in guinea pigs as measured by the hemagglutination–inhibition and serum neutralization techniques. With gamma radiation it was possible to prepare influenza and mumps virus vaccines quickly and with precise control of the inactivation. This work is being continued with other viruses.

The use of gamma radiation from a cobalt-60 cell for the preparation of non-infective diagnostic antigens for influenza A, influenza B, mumps, smallpox, and herpes simplex has been investigated. It was found possible to destroy the infectivity while retaining most of the complement-fixing activity of all these antigens. The degree of purity of the antigen had no apparent effect on the rate of inactivation, as is the case when formaldehyde is used. Under the experimental conditions described, the degree of inactivation depended on the total amount of radiation applied and not on the dose rate. The kinetics of virus inactivation make it possible to calculate the amount of radiation required to destroy infectivity completely and yet retain most of the antigenicity. If necessary it is possible to apply an additional calculated amount of radiation to destroy residual infectivity without causing loss of antigenicity. Gamma radiation appears to be superior to formaldehyde treatment for the preparation of the herpes simplex antigen which is particularly sensitive to heat and to formaldehyde.

The ability of crude, semi-purified, and purified rubella antigens to elicit a specific and significant blast cell transformation of lymphocytes from immune individuals was investigated in 25 seronegative and 25 seropositive young adults. The type of preparation and the purity of the antigens were critical. Titration of the antigens by complement fixation or hemagglutination was of little value for selecting the best antigen which was a whole virion-purified antigen.