HLA homozygosity does not adversely affect measles vaccine-induced cytokine responses

The association between HLA homozygosity and measles-specific Th1 (IFN-γ, IL-2 and IL-12p40) and Th2 (IL-4 and IL-10) cytokine responses were assessed in a group of 339 healthy schoolchildren 12–18 years of age previously immunized with two doses of live-attenuated measles virus vaccine. No associations were observed between class I HLA homozygosity and measles-specific cytokine levels. Children who were homozygous at the class II DRB1, DQA1, DPA1 and DPB1 loci had higher median IFN-γ secretion levels compared with children who were heterozygous for DRB1 (77.7 vs. 39.5 pg/ml, p = 0.05), DQA1 (60.9 vs. 36.6 pg/ml, p = 0.03), DPA1 (46.1 vs. 27.1 pg/ml, p = 0.01) and DPB1 (61.5 vs. 36.0 pg/ml, p = 0.01) loci, respectively. Homozygosity at increasing numbers of HLA loci ( >= 4) was associated with increased IFN-γ secretion levels (test for trend p-value = 0.01). Our results suggest that HLA homozygosity showed no disadvantage for measles-specific cytokine responses and instead was associated with increased IFN-γ levels.