Serum hepatitis as a persistent infection.

Large amounts of serum hepatitis virus are circulating in the blood of about 50 000 healthy persons in this country, and every year this agent causes at least 2 000 cases of acute infection in adults. Superficially at least this resembles the ecological situation in a mouse colony recently affected by lymphocytic choriomeningitis. In situations where the carrier rate is 10 or even 100 times higher than in Britain, clinical serum hepatitis is reputed to be uncommon (Cheru-bin, 1971) suggesting an ecological comparison with a mouse colony where lymphocytic choriomeningitis is well established. Is there also a useful analogy to be drawn between the pathogenesis of lymphocytic choriomeningitis in the mouse and serum hepatitis in man? While lymphocytic choriomeningitis can be grown in tissue culture and in eggs, and antibody to it measured in a variety of ways, the serum hepatitis virus has not yet been cultivated in vitro, nor is there any satisfactory test of immunity. The discovery of Australia antigen by Blumberg, Alter, and Visnich in 1965, and the subsequent realization that its presence in the blood correlated closely with viraemia (Prince, 1968) has provided the first useful laboratory marker for the study of serum hepatitis. Acute Infection After inoculation of a susceptible adult both serum hepatitis virus and Australia antigen disappear and have not been identified in blood or tissues during the long incubation period. This stage varies from about four to 20 weeks, and its duration does not seem to be closely related either to the size of the infecting dose 1954). Australia antigen, and infectivity, tend to appear in the blood a few days before the onset of illness, and this viraemic phase may persist for weeks or even months, especially in immunosuppressed individuals. Characteristically joint pain and swelling and a diffuse skin rash also appear at this stage, but these 'allergic' symptoms subside asjaundice develops. The titre of the antigen in the blood rises very 22 rapidly and has usually reached its maximum by the time the first serum sample is obtained from a patient with hepatitis. Titres of 1/1024 or 1/2048 in the complement-fixation test are not unusual, and correspond to infectivity titres of about 106 ID50 per millilitre of blood The exact nature of Australia antigen remains unknown but its morphological appearance in the electron microscope is sufficiently characteristic to provide a useful diagnostic feature (Bayer, Blumberg, and Werner, 1968). Three types …