SUMMARYThe determination of serum levels of antibodies against hepatitis B virus surface antigen (anti-HBs) after hepatitis B vaccination is currently the only simple test available to predict the decay of protection and to plan the administration of booster doses. A total of 3085 vaccine recipients of plasma-derived and recombinant vaccine have been followed for 10 years to determine the kinetics of anti-HBs production and to construct a mathematical model which could efficiently predict the anti-HBs level decline. The anti-HBs peak level was reached 68 days after the last dose of recombinant vaccine and 138 days after the last dose of plasma-derived vaccines. The age of vaccinees negatively influenced the anti-HBs levels and also the time necessary to reach the anti-HBs peak. A bilogarithmic mathematical model (log 10 level, log 10 time) of anti-HBs decay has been constructed on a sample of recombinant vaccine recipients and subsequently validated on different samples of recombinant or plasma-derived vaccine recipients. Age, gender, type of vaccine (recombinant or plasma-derived), number of vaccine doses (three or four) did not influence the mathematical model of antibody decay. The program can be downloaded at the site: http://www2.stat.unibo.it/palareti/vaccine.htm. Introducing an anti-HBs determination obtained after the peak, the program calculates a prediction of individual anti-HBs decline and allows planning of an efficient booster policy.

Electron microscopy examination of liver biopsies from 8 patients with chronic non-A, non-B hepatitis revealed ultrastructural changes similar to those previously described in chimpanzees with experimentally induced acute non-A, non-B hepatitis. These changes consisted of intranuclear clusters of electron-dense, 15-27-nm particles that were detected in five out of the eight patients and of circular cytoplasmic structures that were present in seven cases. Other cytoplasmic abnormalities found in our patients related to the presence of curved membranes apparently developing from apposition of two cisternae of endoplasmic reticulum. In contrast with what has been reported in infected chimpanzees, the nuclear and cytoplasmic changes were not mutually exclusive in our patients, but coexisted in four of them.

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