Immune Responses to Hepatitis B Vaccine With and Without the Pre-S2 Antigen in Children With Type 1 Diabetes

This study involved 20 patients (10 males and 10 females) with type 1 diabetes who were seronegative for hepatitis B surface-antigen (HBsAg) and other hepatitis B (HB) viral markers and had no diabetic complications. As patients were recruited over a period of several months, each patient was alternatively assigned to one of two vaccination groups (A or B). There was no significant difference between groups A and B in terms of age, sex, duration of diabetes, and levels of HbA_1c. Written informed parental consent was obtained for all patients. Patients in groups A (mean age 12.7 ± 2.6 years, mean duration of diabetes 5.1 ± 2.6 years, mean HbA_1c level 8.6 ± 0.7%) received three doses of 10 or 20 μg (the lower dose was given to patients aged <10 years, as recommended by the manufacterer) of a recombinant DNA HB vaccine (Engerix B; Smith-Kline Beecham, Rixensart, Belgium) by intramuscular injections in the left thigh at 0, 1, and 2 months. Patients in group B (mean age 13.8 ± 5.7 years, mean duration of diabetes 6.3 ± 3.6 years, mean HbA_1c level 8.4 ± 0.5%) were given three doses of 20-μg recombinant DNA HB vaccine that included pre-S1 and -S2 proteins encoded by the HB viral genome (GenHevac B; Pasteur Vaccins, Pasteur-Mérieux, Marcy l’Etoile, France). We adopted this schedule of vaccinations to induce early immunization because children with type 1 diabetes are considered to be at increased risk of infection by HB virus (1). A sample of venous blood (10 ml) was taken from each child in group A and group B at 4–5 weeks after the first, second, and third injection of HB vaccine to determine the serum concentrations of HBsAg, HBsAg–specific antibodies (HBsAb), and other common markers of infection by HB virus (Ausria II, Corab and Ausab; Abbott Laboratories, Chicago). Moreover, HLA class I antigens were analyzed by serological typing, whereas HLA class II antigens (DR3, DR4, DR7, and DQ2) were analyzed by polymerase chain reaction (Amplicor HLA DRB test; Roche, Monza, Italy). The HLA class II antigens DR3, DR4, DR7, and DQ2 were equally distributed in both groups of children. Both vaccines were well tolerated, and no immediate adverse reactions were observed in any of the 20 patients.

Table 1 shows the means of the titers of antibodies (MTAs) against HB virus in the children of groups A and B after each of the three doses of HB vaccine. The MTAs against HB virus in the patients of group B were higher than those of group A after each dose of vaccine. The difference between the groups was statistically significant (P = 0.014) after the administration of the third dose of the vaccine. However, the MTAs against HB virus of the patients in group B were lower than those determined in other young patients with type 1 diabetes who received three doses of HB vaccine at 0, 1, and 6 months (2). This difference was probably attributable to the schedule of vaccinations, which induced earlier immunization (3), albeit with lower titers of antibodies. Douvin et al. (4) found that the choice of the HB vaccine has little influence on the immune response to HB vaccine administered at 0, 1, 2, 4, and 12 months in adults with type 1 or type 2 diabetes. However, in patients vaccinated with GenHevac B, HBsAbs appeared earlier than in patients vaccinated with Engerix B. The different results in the two studies could be due to both the age of the patients and the schedule of vaccinations. It seems that the immune response to HB vaccine is poorer in adults (5); this could explain the low HBsAb titers found by Douvin et al. (4) after three doses of both vaccines administered at 0, 1, and 2 months. As we did not give a fourth dose at 12 months, we cannot exclude that we could have found a similar immune response to both vaccines after a fourth dose at 12 months.

The hyporesponsiveness and poorer immune response of the children in group A did not seem to correlate with the distribution of HLA class II antigens, nor did they appear to be due to age, sex, level of HbA_1c, or duration of diabetes. The better immune response of children who were given three doses of GenHevac B was probably a result of the formulation of the vaccine (6). It has been demonstrated that in mice, the pre-S2 region of HBsAg is more immunogenic than the S region in regard to induction of antibodies (7), probably because the pre-S2 region of HbsAg is able to recruit helper T-cells that circumvent nonresponsiveness to the S region. We suggest that when HB vaccine is administered to children with type 1 diabetes, a vaccine that includes the pre-S2 antigen is preferable because it may guarantee a more adequate and longer-lasting protection against infection by HB virus.