[Specific immunological profile of candidates for hepatitis A]

Blood samples were taken from 1,279 healthy adults for radioimmunological studies before their collective departure to an endemic area and received an administration of polyvalent immunoglobin for hepatitis A prophylaxis. On the 120th day, 1,220 subjects were in good health and their serum was studied again. Hepatitis A was observed in 59 cases, confirmed either by the presence of virus in the stool or by the demonstration of anti-HAV IgM, when other causes of hepatitis had been excluded. The following results were observed in the two groups: a) Subjects having HAV antibodies with a titre of about 1:100 in the initial blood samples had a reduced risk of hepatitis. Subjects with lower titres and, paradoxically, with higher titres, had a significantly higher risk. b) Markers of HBV were less commonly present in the initial blood samples of subjects who did not develop hepatitis. c) Low titres of HAV antibodies (less than 20) were commonly associated with markers of HBV in the initial samples of subjects who developed hepatitis. This suggests either a congenital susceptibility to infection to both viruses or that prior HBV infection increases the risk of HAV infection.