378 S. GARD AND O. MAAL0E 



Bawden and Kleczkowski (1953, 1955) demonstrated photo-reactivation 

 in bushy stunt, tobacco necrosis, and, particularly strongly, in potato X virus. 

 Five strains of TMV gave consistently negative results. 



Along with theoretical studies a considerable amount of work has been 

 done to test the usefulness of UV as a bactericidal and virus inactivating 

 agent, e.g., in barracks and laboratories. Thus, WeUs and Brown (1936), de- 

 monstrated the effects of UV on air-borne influenza virus and extensive 

 studies of a similar kind are reported by Edwards et al. (1944). Inactivation 

 by UV has also been considered in connection with vaccine production; e.g., 

 by Levinson et al. (1945) for rabies vaccine, and by Taylor et al. (1957) for 

 polio vaccine. In the latter case, safe and highly antigenic preparations are 

 said to have been obtained by UV treatment and subsequent storage for 

 a week at 37-40°C. Another combined treatment, with UV and ^-propio- 

 lactate, was suggested by Smolenz and Stokes (1954) for sterilizing hepatitis- 

 contaminated sera. 



Like X-rays, UV has been used to test for inactivation of properties other 

 than infectivity. Salk et al. (1940) fomid that the antigenicity of UV-inacti- 

 vated influenza virus was considerably reduced. Stanley (1945), in studies of 

 the UV inactivation of purified PR8 influenza virus, noted that the loss of 

 virus infectivity greatly preceded that of red cell agglutinating activity and 

 that a fully potent non-infectious vaccine could be produced by using an 

 amount of irradiation sufficient to cause loss of infectivity, but insufficient 

 to cause a marked decrease in red cell agglutinating activity. A more thorough 

 study of influenza viruses was made by Henle and Henle (1947). The proper- 

 ties examined were affected in this order: (1) infectivity; (2) toxicity to mice; 



(3) interfering property and inhibition of the development of the chick embryo; 



(4) hemagglutinating cajiacity (including the adsorption-elution mechanism, 

 the ability to block red ceU agglutmation, and the adsorption onto allantoic 

 cells); and (5) complement-fixmg capacity. The immunizing capacity could 

 not be definitely placed according to sensitivity to UV; certain differences 

 between A and B strains were noticed, but, generally, antigenicity was at 

 least as stable as the hemagglutinating capacity. 



The action spectrum for the destruction of the interfering property of 

 influenza virus has been established by PoweU and Setlow (1956) and com- 

 pared with the sjjectrum for the loss of infectivity. The spectrum for destruc- 

 tion of interference was found to have a broad maximum, extending to 

 about 2800 A, as compared with the usual, weU-defined maximum at 2600 A 

 in the action spectrum for inactivation. This was taken to mean that, prob- 

 ably, absorption of UV by protein plays a significant role in destroying the 

 interfering property. 



•Interference between plant viruses after UV treatment was demonstrated 

 by Bawden and Kleczkowski (1953) and heat inactivation of preirradiated 



