INACTIVATION OF VIRUSES 409 



higher values were obtauied in higher than in lower temperature ranges. 

 Poliovirus seems to fall into the latter category (Lycke, 1958). Thus, temjoera- 

 tures from + 7 to 37°C. yielded approximately linear Arrhenius plots, with 

 slopes corresponding to about 20,000 cal./mole, whereas the inactivation rate 

 at 50°C. indicated a much greater energy of activation. This fact is probably 

 best explained by the assumption that the rate-determinmg factor at tem- 

 peratures below 50°C. is not heat denaturation but a reaction involvmg a 

 single bond. 



This assumption obtains further support from Youngner's (1957) studies 

 on heat-resistant variants of poHoviruses. This author found that a tempera- 

 ture of 36'5°C. did not exert any selective pressure, whereas temperature- 

 resistant variants were regularly segregated by exposure to 50°C. Since no 

 systematic studies of these and similar phenomena seem to have been carried 

 out so far, it cannot yet be stated that the oxidation reduction potential is 

 the rate determining factor at lower temperatures, although this assumption 

 appears highly plausible. 



Ozone is reportedly much more active than oxygen (Kessel et al., 1943). 



3. Hydrogen Peroxide 



Hydrogen peroxide was found to inactivate several viruses (Gordon, 

 1925; Yaoi and Kasai, 1931; Stanley, 1936; Theiler and Gard, 1940), although 

 at comparatively slow rates and only in relatively high concentrations. It is 

 actually to be doubted whether HgOg per se is much more active than plam 

 oxygen. It may participate in various catalyzed reactions, however, often 

 acting indirectly by oxidizing nonviral substances in the medium which in 

 turn act upon the virus. Thus, traces of ferrous ions usually increase its effect. 

 Of considerable interest is the reaction mediated by the leucocyte enzyme 

 myeloperoxidase (Agner, 1950), as this might represent one of the processes 

 by which viruses are eliminated from the living organism. In this case the 

 mechanism is supposedly oxidation of NaCl to hypochlorite, which has a 

 strong virucidal effect. Another type example is the oxidation of ascorbic 

 acid, which was reported to have an inactivating effect (Holden and Resnick, 

 1936; Holden and Molloy, 1937; Kligler and Bernkopf, 1937; Jungeblut, 

 1939; Knight and Stanley, 1944; Klein, 1945). Systematic studies by Lojkin 

 (1937) and by Ericsson and Lundbeck (1955a,b) indicate that ascorbic 

 acid is by itself inactive. However, by rapid oxidation with HgOg in the 

 presence of Cu++, a labile mtermediate of great inactivating capacity is 

 formed. 



Orgaoic peroxides were reported by Latarjet (1956) to inactivate bacterio- 

 phages and Pneumococcus transforming agent and also to sensitize phage to 

 the inactivating effect of ascorbic acid. 



