Etiopathogenic role of HLA-B27 alleles in ankylosing spondylitis

Prevalence of HLA-B*27 subtypes in the Tamil population of India with Ankylosing spondylitis and its correlation with clinical features

INTRODUCTION

HLA-B*27 is strongly associated with Ankylosing spondylitis (AS). Its subtypes show considerable geographic and ethnic difference. The main aim of this study was to assess the frequency of subtypes of HLA-B*27 in the Indian Tamil AS patients.

METHODS AND MATERIALS

Adult AS patients positive for HLA-B*27 were considered for the study. The high-resolution typing to define HLA-B*27 subtypes were done using Invitrogen B kits from One Lambda (SeCore® Sequencing Kits, Thermo Fisher, United States).

RESULTS AND CONCLUSION

Prevalence of subtypes identified were HLA-B*27:04 (52.2%), HLA-B*27:05 (41.6%), HLA-B*27:07 (3.5%) and HLA-B*27:02 (2.7%). All subtypes showed disease predisposition for males. The most common extra articular manifestation seen was enthesitis in HLA-B*27:04 and HLA-B*27:05. Uveitis was mainly associated with HLA-B*27:05 and dactylitis with HLA-B*27:04. A significant peripheral joints involvement for female and axial joint involvement for males was seen in HLA-B*27:04. Our study establishes the prevalence of HLA-B*27 subtypes and the associated clinical phenotypes among the Indian Tamil population. Considering the variability of presentation, organ involvement, and disease course in different subtypes and across ethnicities it is critical to define these associations in the ethnic populations we treat for their appropriate care considering the significant negative health and socioeconomic effects of AS.

Usage of Conventional PCR Technology for the Detection of HLA-B27 Allele: A Significant Molecular Marker of Ankylosing Spondylitis

Ankylosing spondylitis is a chronic inflammatory disease that has been linked to the human leukocyte antigen class I allele HLA-B27. More than 90 % of patients with ankylosing spondylitis possess the HLA-B27 allele, but only 1 % of people with HLA-B27 develop the disease. Ankylosing spondylitis predominately affects young males. The present study was planned to find out the involvement of HLA-B27 specific allele in relation to age and sex in symptomatic suspected patients of ankylosing spondylitis using conventional PCR technology. Forty symptomatic patients of ankylosing spondylitis were included in the present study. SSP-PCR technique was used to detect the HLA-B27 specific allele. This study showed (out of 40 symptomatic suspected cases of ankylosing spondylitis only 12 patients were detected positive with HLA-B27 allele, while remaining 28 were negative) that the positivity rate for ankylosing spondylitis with HLA-B27 allele is low. Furthermore, it was observed that the males above 50 years are more prone to develop AS with HLA-B27 specific allele. It could be concluded that the conventional PCR technology is a rapid, sensitive, and confirmatory method for the diagnosis of ankylosing spondylitis.

HLA B27 allele types in homogeneous groups of juvenile idiopathic arthritis patients in Latvia

Juvenile idiopathic arthritis (JIA) is a heterogeneous condition and therapeutic strategies vary in different JIA types. The routinely accepted practice to start with Sulphasalazine (SS) as the first line treatment in patients with HLA B27 positive JIA proves to be ineffective in a large proportion of children.

OBJECTIVE

to investigate HLA B27 positive JIA patients clinical characteristics, determined HLA B27 allele types and their connection with antirheumatic treatment in homogenous patient groups.

MATERIALS AND METHODS

56 patients diagnosed with JIA and observed over the period 2006 to 2009 included in the study. HLAB27 allele types were determined using PCR method.

RESULTS

In HLA B27 positive JIA patients mean disease onset was 12.34 ± 3.3 years. Most common (44%) JIA type was enthesitis related arthritis. Positive response to the treatment with SS was found in 32% of patients, Methotrexate (MTX) - in 43%, combined treatment - SS with MTX was effective in 12.5%. 12.5% of patients required combination MTX with Enbrel.Eight HLA B27 allele types were found in JIA patients in Latvia: *2702, *2703, *2704, *2705, *2710, *2715, *2717, *2728. The most common was *2705 - in 55% of cases. Among all the patients enthesitis related arthritis most commonly occurred in patients with HLAB*2705 allele (OR = 2.01, p < 0.02), oligoarthritis in patients with *2710 allele (OR = 3.0, p < 0.04) and polyarthritis with *2717 allele (OR = 3.0, p < 0.05). In patients with *2705 allele effective treatment was MTX (OR = 1.13, p < 0.03) and MTX with SS (OR = 2.02, p < 0.05), but in patients having *2703 allele - MTX with Enbrel (OR = 2.94, p < 0.02).

CONCLUSIONS

There are 8 different HLA B27 alleles in JIA patients in Latvia and the most common is *2705, but in order to assert them to be disease associated alleles, more extensive studies are needed, including control group of HLA B27 positive healthy individuals. Standard treatment approach with SS proves to be unsatisfactory in the majority of JIA patients. To improve children's quality of life achieving rapid disease control, the first line treatment in HLA B27 positive patients should be MTX. In order to start with the most appropriate drug it is necessary to determine HLAB 27 type at the onset of disease.

Association of CTLA4 gene polymorphism in Iranian patients with ankylosing spondylitis

INTRODUCTION

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a costimulatory molecule expressed by activated T cells. This study was performed to investigate the allele and genotype frequencies of CTLA4 gene polymorphisms in Iranian patients with ankylosing spondylitis (AS).

METHODS

One hundred and fifty-seven patients with AS and 103 controls were included in this study. Polymorphisms of CTLA4 gene at positions +49 (in exon 1), -318, and -1,147 (in the promoter region) were studied on the genomic DNA using PCR restriction fragment-length polymorphism method.

RESULTS

The frequencies of the T allele at position -1147 in the patients with AS was significantly increased in comparison with the control group (11% vs. 5%, P = 0.004); whereas the frequencies of C allele at the same position were significantly decreased in the patient group (89% vs. 95%, P = 0.004). Comparison of genotype frequencies at this position showed that the frequency of CT genotype in comparison with other genotypes was overrepresented in the patient group (20% vs. 8%, P = 0.012), while the CC genotype in comparison with other genotypes was decreased (79% vs. 91%, P = 0.012). There was no significant difference on frequencies of genotypes at the positions -318 and +49.

CONCLUSION

This study could suggest an association between specific allele in the promoter region of CTLA4 gene and AS disease.

The association of HLA-B*27 subtypes with ankylosing spondylitis in Wuhan population of China

The aim of this study was to investigate the association of the B27 subtypes with ankylosing spondylitis (AS) in the Wuhan population of China. We selected 317 HLA-B27-positive individuals (145 controls and 172 patients with ankylosing spondylitis). The B27 subtypes were characterized using a PCR-SSP method. Six B27 subtypes were determined: B*2702, 03, 04, 05, 06 and B*13. HLA-B*2704 and HLA-B*2705 were the two high frequency genotypes in controls and patients. Compared with the controls, the AS patients had high frequency of B*2704 (patients 69.2% vs. controls 53.8%) and low frequency of B*2705 (patients 23.8% vs. controls 33.1%). B*2703 was detected in 10 (5.8%) patients and in 13 (8.9%) controls. B*2702, 06 and B*2713 were relatively rare. Our results show that the allele conferring risk to AS in the Wuhan population of China was B*2704 and B*2705. B*2704 is strongly associated with AS.

The interplay between the geographic distribution of HLA-B27 alleles and their role in infectious and autoimmune diseases: a unifying hypothesis

Due to its strong association with Ankylosing Spondylitis and the other Spondyloarthropathies, the HLA-B27 family of alleles and, in particular, the ancestral HLA-B*2705, has been the object of numerous studies. More recently, some novel interesting features have emerged such as the ability of HLA-B27 to confer resistance to the progression of HIV infection and to promote a spontaneous CD8+ T cell-mediated viral clearance of HCV. The co-occurrence of these protective and pathogenic features suggests a common ground, i.e. to promote a more pronounced immune/inflammatory response leading to an effective clearance of some pathogens on one side and to autoimmunity on the other. This might be due to the antigen presenting properties and/or to the co-inheritance of gene variants that contribute to an altered homeostasis in case of microbial infections or tissue injury. The existence of conserved HLA haplotypes have since long been thought to result from a selective pressure by some pathogens that have edited the immune response genes. The peculiar distribution of the ancestor HLA-B*2705 along a latitude-dependent gradient and the opposite distribution of their variants have suggested a correlation with endemic malaria. In this respect, Sardinia, a small Mediterranean island plagued by malaria, represents an interesting laboratory since its population is enriched in conserved HLA haplotypes and several genetic studies have disclosed their correlation with infectious and autoimmune diseases.

The study of the extended haplotypes of rare HLA-B*2730 allele using microsatellite loci

The aim of the present study was to compare haplotypes of the most frequent B*27 alleles among Croatians (B*2702 and *2705) and the rare B*2730 allele. For this purpose, 37 families with members carrying human leukocyte antigen (HLA)-B27 were selected. All individuals were analysed for eight microsatellites (Msats): D6S2927, short tandem repeat - MHC class I-related gene (STR_MICA), D6S2793, D6S2811, tumor necrosis factor a (TNFa), tumor necrosis factor d (TNFd), D6S273 and D6S1014, while individuals carrying the HLA-B27 specificity were subtyped. Of 39 analysed haplotypes, 20 individuals had B*2702, 15 subjects were positive for the B*2705 allele, the B*2730 allele was found in three haplotypes from different families, while one individual carried the B*2703 allele. HLA-A3 and -DRB1*16 were shared by all three B*2730 haplotypes. The DRB1*16 allele was also observed in the majority of B*2702 haplotypes (76.5%), while HLA-A3 was, after HLA-A2, the second most frequent HLA-A specificity in B*2702 haplotypes. No such correlation was found for the B*2705 haplotypes. Msat analysis showed that B*2730 haplotypes also share the same allele at all tested Msats. The D6S2927, D6S2793, MICA and TNFd Msats were not useful in distinguishing B*2702 and B*2705 alleles because D6S2927-213bp, STR_MICA-179bp, D6S2793-206bp, D6S2811-83bp and TNFd-130bp were detected in almost all cases. Conversely, for the TNFa, D6S273 and D6S1014 loci, haplotypes carrying B*2702 and B*2730 shared a single Msat allele in the majority of cases (TNFa-113bp, D6S1014-134bp and D6S273-134bp), which was not observed for B*2705 haplotypes. In conclusion, the similarity between B*2702 and B*2730 DNA sequences as well as their sharing of the same haplotypic combinations corroborates the proposed mechanism of B*2730 evolution from B*2702 by interallelic recombination.

The pathogenetic role of HLA-B27 and its subtypes

The strong association between HLA-B27 and ankylosing spondylitis has been known for more than 33 years, but the enigma of the pathogenetic role of the gene and its product has not yet been solved. Ongoing studies have produced evidence supporting different theories to explain this association, and structural and functional studies of HLA-B27 allele products at molecular level have provided information of broad and multidisciplinary value and disclosed new avenues leading to autoimmunity and immune disregulation.