Spread of hepatitis-B infections. A seroepidemiologic study.

A solid-phase radioimmunoassay (R.I.A.), allowing simultaneous detection and quantitation either of HB, Ag or of anti-HBs, was applied to check the spread of hepatitis-B virus (H.B.V.) infections in various groups of population. R.I.A. procedures were also used to validate positive reactions and to determine the subtype specificity of sera. The overall prevalence of neutralizing anti-HBs in tested sera was almost 4-fold higher, although generally at rather low titres, than prevalence of HBs Ag. Frequency of HBs Ag and anti-HBs was rather high among healthy individuals from the normal Italian population and was extremely high among individuals from East Africa (Tanzania), as well as among healthy or sub-normal institutionalized subjects, among dialyzed renal patients and unselected blood-donors from 5 Italian towns. 80.2% of HBs Ag and anti-HBs detected in Italy were ay subtype, while most of positive sera from Tanzania (72.3%) were ad, which extends the map of H.B.V. subtypes in Africa. All tested ad antigens, either from Italy and from Tanzania, carried the w secondary determinant. Low-titre neutralizing anti-HBs, predominantly bearing a and d specificity, were also found in almost all examined preparations of standard immunoglobulins, which were imported from U.S.A.