Alteration of Hepatitis B Antigen (HB Ag) Determinants by Reduction and Alkylation

Previous studies have demonstrated that sulphydryl groups and/or disulphide bonds play an important role in the tertiary structure of a number of animal viruses since biological activities such as infectivity and haemagglutination are destroyed by treatment with either alkylating (sulphydryl binding) or reducing reagents (Allison, Buckland & Andrewes, 1962; Carver & Seto, 1968; Hare & Chan, 1968; Neurath & Rubin, 1968) The differential effect of these different reagents is illustrated by the fact that a reducing agent such as dithiothreitol (DTT) destroys the infectivity of many enteroviruses, but these same viruses are unaffected by treatment with sulphydryl binding reagents (Allison et al. 1962; Carver & Seto, 1968).

Amino acid analyses of highly purified preparations of hepatitis B antigen (HB Ag) have shown that the 20 to 25 nm particles contain increased levels of cysteine (or cystine) amino acid residues (4.8% molar concentration) when compared to other animal viruses (0.3 to 2.0%) (Dreesman et al. 1972a).