Proteomic scan for tyrosinase peptide antigenic pattern in vitiligo and melanoma: role of sequence similarity and HLA-DR1 affinity.

Immune responses contribute to the pathogenesis of vitiligo and target melanoma sometimes associated with vitiligo-like depigmentation in some melanoma patients. We analyzed the sera from patients with vitiligo and cutaneous melanoma for reactivity toward tyrosinase peptide sequences 1) endowed with low level of similarity to human proteome, and 2) potentially able to bind HLA-DR1 Ags. We report that the tyrosinase autoantigen was immunorecognized with the same molecular pattern by sera from vitiligo and melanoma patients. Five autoantigen peptides composed the immunodominant anti-tyrosinase response: aa95-104FMGFNCGNCK; aa175-182 LFVWMHYY; aa176-190FVWMHYYVSMDALLG; aa222-236IQKLTGDENFTIPYW, and aa233-247 IPYWDWRDAEKCDIC. All of the five antigenic peptides were characterized by being (or containing) a sequence with low similarity level to the self proteome. Sera from healthy subjects were responsive to aa95-104FMGFNCGNCK, aa222-236IQKLTGDENFTIPYW, and aa233-247 IPYWDWRDAEKCDIC, but did not react with the aa175-182LFVWMHYY and aa176-190FVWMHYYVSMDALLG peptide sequences containing the copper-binding His180 and the oculocutaneous albinism I-A variant position F176. Our results indicate a clear-cut link between peptide immunogenicity and low similarity level of the corresponding amino acid sequence, and are an example of a comparative analysis that might allow to comprehensively distinguish the epitopic peptide sequences within a disease from those associated to natural autoantibodies. In particular, these data, for the first time, delineate the linear B epitope pattern on tyrosinase autoantigen and provide definitive evidence of humoral immune responses against tyrosinase.

Association of rheumatoid arthritis with HLA-DR1 and HLA-DR4 in Hungary.

Susceptibility to and outcome for rheumatoid arthritis (RA) have been associated with particular HLA-DR alleles, but these alleles vary among ethnic groups and geographic areas. The frequency of HLA-DR1 (HLA-DRB1*0101, DRB1*0102) and HLA-DR4 (DRB1*0401, DRB1*0404) alleles is elevated among Caucasian patients with RA. We studied a northeastern Hungarian population of RA patients to determine the frequency of HLA-DR1 and HLA-DR4 phenotypes in this population and to compare it with healthy control subjects, as well as to investigate whether the presence of these alleles could be a marker for RA. We performed HLA-DRB1 genotyping (DRB1*01-DRB1*16) in 83 RA patients and 55 healthy controls using polymerase chain reaction with sequence-specific primers (PCR-SSP). In the case of HLA-DR1- or HLA-DR4-positive patients, the DR1 and DR4 subtypes were also determined. The frequency of HLA-DR4 alleles was significantly higher in RA patients than in controls (31.3 vs. 10.9%; P <.05). HLA-DR1, in particular, tended to be more frequent in patients than in controls (32.5 vs. 18.1%). Among the HLA-DR4 subtypes, DRB1*0401 and DRB1*0404 were the most common alleles found in both groups. However, no significant differences were seen in the frequency of HLA-DRB1*0401 and HLA-DRB1*0404 between RA patients and controls. In contrast, HLA-DRB1*0405 and HLA-DRB1*0408 were significantly more common in RA patients than in control subjects. Among HLA-DR1 subtypes, the DRB1*0101 allele was most commonly detected, but HLA-DRB1*0101 as well as DRB1*0102 and DRB1*0105 were similarly frequent in RA patients and controls. HLA-DR12 was more common among controls than in RA patients (18.1 vs. 0%; P <.05). Our results generally agree with the findings in other Caucasian populations. Nonetheless, we found differences in the frequency of HLA-DR1 and HLA-DR4 subtypes among Hungarian patients compared with reports from other geographic regions (e.g., Finland and Asia). Our data suggest that in northeastern Hungary, HLA-DR4 as well as its subtypes DRB1*0405 and DRB1*0408 may be involved in susceptibility to RA, but HLA-DR1 may not. In addition, the presence of HLA-DR12, at least in Hungary, may protect from this disease.

Discrimination between HLA-DR1 (DRB1*0101) and DR'Br' (DRB1*0103) using sequence-specific oligonucleotide probes.

Serological identification of the HLA-DQw1(w5)-associated or HLA-DQw3(w7)-associated DR'Br' (DRB1*0103) allele cannot be accomplished in the presence of a second DQw1(w5)-positive or DQw3(w7)-positive haplotype, respectively. DNA-restriction fragment length polymorphism (RFLP) analysis assists in identification of DR'Br', though not in the presence of DR1. We describe an alternative or complementary method for identification of DR'Br' using two oligonucleotide probes which target HLA-DRB1 gene HV3 regions.