SummaryThe mechanisms causing non-responsiveness to hepatitis B surface antigen (HBsAg) vaccines in man remain elusive. The increased incidence of nonresponsiveness in subjects with HLA-DR3 + + + + NR were able to present HBsAg. In the present paper we demonstrate that six DR0301 + + + + NR, five of which are homozygous for this marker, were able to take up, process and present HBsAg to HBsAg-specific, DR0301-restricted T cell lines. Non-fractionated peripheral blood mononuclear cells (PBMC) from the DR0301 + + + + NR did not proliferate to HBsAg in vitro , whereas they proliferated vigorously upon stimulation with tetanus toxoid, thus ruling out the presence of a generalized immunodeficiency. We therefore conclude that HLA-DR0301 + + + + NR vaccinees are not deficient in their HBsAgpresentation. Because it was demonstrated that recently activated T cells can apparently bypass the requirement for B7, we may have overlooked the role of the B7-co-stimulation in our set-up that used HBsAg-specific T cell lines. Therefore we examined the expression of B7 co-stimulatory molecules on NR-APC. CD86 was normally present on these cells and was not down-regulated after culturing the PBMC in the presence of HBsAg. We conclude that CD86 expression on CD14 + + + + monocytes of DR0301-and DR07-homozygous poor responders is not deficient and cannot be the mechanism underlying the nonresponsiveness of these subjects.Keywords: antigen presentation, DRB1*0301, HBsAg, hepatitis B vaccines, non-response
I ntroductionFor nearly two decades, vaccines against hepatitis B virus (HBV) have been administered routinely and the antibodies to the hepatitis B surface antigen (HBsAg) they elicit are clearly effective in preventing infections with HBV. About 5% of healthy vaccine recipients fail to produce protective levels of antibodies (defined as an antibody level £ 10 IU/l) to the hepatitis B vaccine after standard immunization. This phenomenon has been observed in all surveys of vaccine effectiveness, irrespective of the HBsAg vaccine employed [1][2][3], and its cause remains largely unknown.Variations in immune response are often associated with polymorphism of the major histocompatibility complex (MHC). The suggestion that MHC-linked immune response genes may control the human response to HBsAg was first made in 1981 by Walker et al . [4], who observed a significant excess of HLA-DR7 and a total absence of HLA-DR1 in hepatitis B non-responders (NR). Subsequent studies demonstrated that HLA class II alleles that are associated strongly with high response (or protect from non/poor response) are: DRB1*01 ( DR1 ), DRB1*11 ( DR5 ), DRB1*15 ( DR2 ), DQB1*0501, DPB1*0401, whereas alleles strongly associated with non/poor response are: DRB1*03, DRB1*07, DQB1*02, ,9,13-18] and, in particular, homozygotes for these extended haplotypes were seen more frequently [1,19,20]. In our studies, for example, six of seven DRB1*07 homozygous individuals and five of six DRB1*0301 homozygous individuals were found to be NR.We and other groups have reported t...