INACTIVATION OF VIRUSES 411 



E. Alkylating Agents 



In this group are included a number of biologically active compounds, of 

 particular interest because they possess carcinogenic, mutagenic, and pro- 

 phage-inducing capacity. These biologically active substances fall mainly 

 into the following classes: sulfur and nitrogen mustards, epioxides, and 

 ethyleneimines. They are characterized by their instabihty in aqueous 

 solutions and their tendency to polymerize. They either contain hetero- 

 cyclic rings or form on hydrolysis intermediates containing ring structures 

 that are supposed to represent the active principle. They react primarily with 

 ionized acid groups, carboxyl, hydroxy, phenoHc, sulfydryl, and phosphoric 

 acid groups, or noniom'zed amino and thio-ether groups. They generally 

 display a somewhat higher affinity to nucleic acids than to proteins. The 

 reactions of alkylating agents with macromolecules was reviewed by Alex- 

 ander (1954). 



Herriott et at. (1946; Herriott, 1948), compared the sensitivity to mustards 

 of various biologically active agents. Most easily inactivated was the Pnemno- 

 coccus transforming prmciple and then, in order of decreasing sensitivity, 

 DNA-containing, RNA-containing viruses, and enzymes. Since subsequently 

 the question of the chemical nature of some of the viruses studied by Herriott 

 has been revised — Newcastle disease virus (NDV), for instance, is now con- 

 sidered to contain only ENA and no DNA — the validity of the general rule 

 suggested by Herriott appears questionable. A theoretical treatment of the 

 problem of the kinetics of inactivation was also attempted, the conclusion 

 being that the experimental data satisfied a reaction equation of the first 

 order. The activity range studied was, however, too narrow to lend too much 

 weight to this conclusion. Actually, "membrane effects" are to be expected; 

 as mustards are capable of forming crosslinks as well as spHtting peptide 

 bonds, the type of effect can hardly be predicted, however. Kmetic studies 

 meet in fact with great technical difficulties. The process is extremely rapid, 

 the reaction proceeding to completion in a few minutes. No reliable method of 

 prompt interruption of the reaction seems to exist. Fong and NematoUahi 

 (1954) found that thiosulfate, recommended for such purposes, in reahty 

 seemed to have less competitive power than the virus. According to Fong 

 (1955), mustards are considerably more active at sHghtly acid than at alka- 

 line pH. The limited solubility of mustards and their rapid hydrolysis in 

 aqueous media create great difficulties in the estabfishment of reproducible 

 experimental conditions (Schwerdt et al., 1951); m the last few years these 

 substances have not attracted much interest as virus-inactivating agents. 



Ethylene oxide has been used in both gaseous (Philfips and Kaye, 1949; 

 Klarenbeek and van Tongeren, 1954) and fiquid form (Wilson and Bruno, 

 1950; Ginsberg and Wilson, 1950) for sterilization of food, milk, serum, 

 growth media, etc. It has the advantage over most other disuifectants of 



