A sensitive radioimmunoassay was developed for specific detection of IgM antibodies to the hepatitis b virus-associated delta antigen. The test is based on the selective absorption of IgM by anti-IgM fixed on a solid phase. Transient primary IgM anti-delta responses with no conversion to a secondary IgG response were observed in acute self-limited delta infection. IgM anti-delta was invariably found in hepatitis B surface antigen (HBsAg) carriers with active delta infection and liver disease, while it was absent in HBsAg-positive or negative individuals with anti-delta of IgG class but without liver damage or intrahepatic delta antigen. IgM anti-delta appears useful in defining the epidemiology of acute delta infection and in the serological diagnosis of active delta disease from nonpathogenic or past delta infection.
To assess the epidemiology of infection with the delta agent associated with hepatitis B virus, sera from 1314 carriers of the hepatitis B surface antigen (HBsAg) and 687 patients with hepatitis B collected in 1978-1981 from different regions of Italy were tested for delta antigen and antibody to the antigen (anti-delta), and the characteristics of delta-positive patients were analyzed. Anti-delta was found in each center participating in the study, indicating that delta infection has spread throughout Italy. Its prevalence was higher in carriers in southern Italy and in those with chronic hepatitis. In northern Italy, delta infection predominated among southern emigrants in industrial towns but also among parenteral drug addicts with hepatitis B virus infection. The prevalence of delta markers was variable and generally low in acute hepatitis B, suggesting that in Italy self-limited forms of delta infection occur sporadically or by limited outbreaks. Delta infection appears to be endemic in southern Italy but a new epidemiologic event in northern Italy, where it was probably introduced by southern emigrants and is presently exceeding its ethnic confinement to spread selectively in communities of drug addicts. Presumably, the endemicity of delta is maintained by transmission of this agent from carrier to carrier of the HBsAg.
We report a prospective study on infants born to hepatitis B surface antigen (HBsAg) carrier mothers to estimate the incidence of perinatal transmission of HBV and HBV-associated delta agent in Northern Italy. The risk of infection to the infant was related to the presence of the HBe antigen-antibody system, HBV-specific DNA polymerase activity and antibody to delta in maternal sera, and to the titer of anti-HBe in babies at birth. The data of this study indicate: 1. Babies born to HBsAg carrier mothers with HBeAg in serum are at extremely high risk of acquiring HBV infection and of developing a chronic carrier state, whereas those born to anti-HBe-positive mothers are at a lower (P less than .01) yet consistent risk of infection. 2. HBs antigenemia is usually prolonged and symptomatic in babies born to HBeAg-positive mothers while being self-limited and asymptomatic in babies born to anti-HBe-positive mothers. 3. DNA polymerase activity in maternal serum appears to be the most sensitive marker predicting HBV transmission to the infant since it was detected in all the HBeAg-positive mothers and also in two anti-HBe-positive mothers and in one HBeAg/anti-HBe-negative mother who transmitted infection to their babies. 4. High titers of anti-HBe (up to 1:103) do not prevent HBV infection. 5. Vertical transmission of delta infection seems to occur only in circumstances that permit perinatal transmission of HBV infection.
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