Viral hepatitis type B: propects for active immunization.

Studies conducted in 1970 and 1971 with heat-inactivated MS-2 serum revealed that this active immunizing procedure was associated with a protective effect, a more attenuated hepatitis B infection and a decreased hepatitis B carrier rate. More recent studies have revealed striking differences in the response of unimmunized and immunized persons following a parenteral exposure to the MS-2 strain of hepatitis B virus. Serial tests for the detection of hepatitis B surface antigen (HBsAg), DNA polymerase activity, serum transaminase (SGOT), antibody to HBsAg (anti-HBs) and antibody to hepatitis B core antigen (anti-HBc) revealed the following findings. In serosusceptible unimmunized persons HBsAg was detectable about 4 weeks after exposure, DNA polymerase activity at about 6 weeks, abnormal SGOT levels at about 8 weeks, anti-HBc at about 8-10 weeks, and anti-HBs usually after 20 weeks. In successfully immunized persons HBsAg, DNA polymerase activity, abnormal SGOT levels, and anti-HBc were not detectable, evidence of a booster response of pre-existing or non-detectable anti-HBs was observed one to two weeks after exposure. Studies by various investigators have revealed that anti-HBs is associated with protection and resistance to reinfection. In contrast, anti-HBc is not protective and does not correlate positively with either resistance to infection or recovery from infection. The availability of sophisticated biophysical and biochemical techniques has enabled several investigators to prepare candidate inactivated hepatitis B vaccines from purified preparations of HBsAg. The successful propagation of hapatitis B virus infection to susceptible chimpanzees has provided an excellent animal model for the evaluation of hepatitis B vaccines. At the present time various investigators are studying the immunogenic and protective effect of the vaccine in these animals. Prospects for the development of a vaccine for the prevention of viral hepatitis type B are encouraging. It is extraordinary that this objective will be achieved in spite of the failure to isolate the etiologic agent in tissue culture.