Distribution of IgG subclasses after anti-hepatitis B virus immunization with a recombinant vaccine

To assess whether a different IgG subclass distribution was elicited in "low" and "high responders" after vaccination with recombinant hepatitis B virus surface antigen, we selected from 360 vaccine recipients 30 "low-responder" subjects, with anti-HBs levels of 10-160 mIU/ml, and 40 "high-responder" subjects, with anti-HBs levels greater than 10,000 mIU/ml. In both groups all IgG subclasses were elicited in the anti-HBs response and the greatest contribution was that of IgG1, followed by IgG2. IgG1 was significantly less represented after the second (58%) and third doses (61%) of vaccine in "low responders" compared with "high responders" (65% and 69%). The relative percentage of IgG2 was significantly higher after the second (33%) and third (30%) doses of vaccine in "low responders" than in "high responders" (29% and 26%). In "low responders" the age of vaccine recipients significantly influenced the anti-HBs IgG subclass distribution: IgG2 and IgG4 production was positively correlated with age, whereas the opposite was observed for IgG1. These data support the evidence that: (1) IgG1 and IgG2 subclasses are mainly involved in the specific anti-HBs response both in "high" and "low responders"; (2) the relative contribution of specific IgG2 to vaccination is higher in low responders and progressively increases with age.