A team from Germany investigated the differential genetic determination of immune responsiveness to hepatitis B surface antigen (HbsAg) and to hepatitis A virus (HAV).
They looked at the effect of the HLA-DRB1 locus and other genetic loci unlinked to HLA.
In the open prospective study, 202 twin pairs were vaccinated with a combined recombinant HBsAg/inactivated hepatitis A vaccine.
Antibodies to HBsAg and HAV were measured and HLA-DRB1 alleles were determined.
Heritability was calculated based on variance of antibody response within pairs.
In addition, model-fitting analyses were conducted to analyze genetic and environmental components of vaccine responses.
Anti-HBs and anti-HAV showed heritabilities of 0·61 and 0·36, respectively.
For the anti-HBs immune response, additive genetic effects explained 60% of the phenotypic variance and non-shared environmental effects accounted for 40%.
| Genetic effects accounted for 60% of phenotypic variance of anti-HBs immune response.|
The heritability of the HBsAg vaccine response, accounted for by the DRB1 locus, was estimated to be 0·25. Therefore, the heritability of other gene loci was 0·36.
Dr Thomas Höhler, of Johannes Gutenberg-University, Mainz, said on behalf of his group, "Genetic factors have a strong effect on the immune response to HBsAg."
"Although genes encoded within the major histocompatibility complex are important for this immune response, more than half the heritability is determined outside this complex.
"Identification of these genes will help us to understand regulation of immune responses to viral proteins," he concluded.