Virocidal Cleavage of Disulphide Bonds within Structural Proteins of Sendai Virus

Department of Research and Development, Wyeth Laboratories, Philadelphia, Pennsylvania 19101, U.S.A. Dithiothreitol (DTT), a reagent which cleaves disulphide bonds, destroyed the haemagglutinin, neuraminidase and ‘haemolysin’ of Sendai virus. The treated virus particles appeared morphologically intact. They failed to bind haemagglutination-inhibiting (HI) and neuraminidase-inhibiting (NI) antibodies. Antisera against DTT-treated virus inhibited haemolysis induced by intact virus, although they did not contain detectable HI, NI or virus-neutralizing antibodies. Treated and untreated virus particles were labelled with [ 14 C]-iodoacetamide or with [ 14 C]- N -ethylmaleimide, disrupted with SDS and subsequently electrophoresed in polyacrylamide gels. Thus, polypeptide species with accessible cysteinyl residues, either originally present in intact virus or resulting from reduction of disulphide bonds, were distinguished. The significance of these findings is discussed. * Present address: Virus Laboratory, The New York Blood Center, 310 East 67th Street, New York, N.Y. 10021, U.S.A. Received 3 August 1972; accepted 15 November 1972.