Genetics of ankylosing spondylitis: An update

Association of rs11209032 and rs1004819 Polymorphisms in Interleukin-23 Receptor Gene With Ankylosing Spondylitis

Objectives

This study aims to investigate the distribution of human leukocyte antigen B27 (HLA-B27) alleles (+/-) and interleukin-23 receptor (IL-23R) gene rs11209032 and rs1004819 polymorphisms among ankylosing spondylitis (AS) patients in a Turkish cohort.

Patients and methods

The study sample comprised 106 AS patients (89 males, 18 females; mean age 38.9±10 years; range 19 to 65 years) and 82 healthy controls (70 males, 12 females; mean age 32.15±7.07 years; range 19 to 51 years). Distribution of HLA-B27 alleles (+)/(-) in AS patients were observed by reverse hybridization technique. Genotyping of IL-23R rs11209032 and rs1004819 polymorphisms of AS patients and healthy controls were performed by real time polymerase chain reaction.

Results

Of the AS patients, 69 (65.1%) were HLA-B27 positive. Distribution of rs11209032 genotype frequencies in AS group were 31.1% for GG, 50.9% for GA, and 17.9% for AA; while in control group, it was 34.1% for GG, 53.7% for GA, and 12.2% for AA. Distribution of rs1004819 genotype frequencies in AS group were 30.2% for CC, 52.8% for CT, and 17.0% for TT; while in control group, it was 42.7% for CC, 46.3% for CT, and 11.0% for TT. There was no significant difference between AS patients and controls in terms of genotype frequencies of IL-23R gene rs11209032 and rs1004819 polymorphisms.

Conclusion

No association was found between AS and IL23R rs11209032 and rs1004819 polymorphisms in this Turkish AS cohort.

The PADI4 gene does not contribute to genetic susceptibility to rheumatoid arthritis in Chinese Han population

The Peptidyl arginine deiminase, type IV (PADI4) gene has been suggested to have an association with rheumatoid arthritis (RA) in several populations. But its role in Chinese RA is not clarified. We investigated five single-nucleotide polymorphisms (SNPs) of PADI4 as PADI4-89 (rs11203366), PADI4-90 (rs11203367), PADI4-92 (rs874881) PADI4-94 (rs2240340), and PADI4-104 (rs1748033) in Chinese Han population. A total of 378 unrelated RA patients and 204 healthy controls were genotyped for the five SNPs. Individual allele, genotype and haplotype frequencies were compared between patients and controls. No significant differences in the frequency of PADI4 alleles, genotypes and haplotypes were observed between the patients and controls except PADI4-92. These data indicated that PADI4 polymorphisms were unlikely to play an important role in the susceptibility to RA in Chinese Han population.

The immunobiology of viral arthritides

A large range of human viruses are associated with the development of arthritis or arthralgia. Although there are many parallels with autoimmune arthritides, there is little evidence that viral arthritides lead to autoimmune disease. In humans viral arthritides usually last from weeks to months, can be debilitating, and are usually treated with non-steroidal anti-inflammatory drugs, but with variable success. Viral arthritides likely arise from immunopathological inflammatory responses directed at viruses and/or their products residing and/or replicating within joint tissues. Macrophages recruited by monocyte chemoattractant protein-1 (MCP-1/CCL2) and activated by interferon, and proinflammatory mediators like tumour necrosis factor alpha, interferon gamma, interleukin-6 and interleukin-1beta appear to be common elements in this group of diseases. The challenge for new treatments is to target excessive inflammation without compromising anti-viral immunity. Recent evidence from mouse models suggests targeting MCP-1 or complement may emerge as viable new treatment options for viral arthritides.

One-tube HLA-B27/B2708 typing by flow cytometry using two "Anti-HLA-B27" monoclonal antibody reagents

BACKGROUND

Flow cytometry-based methods are widely used to detect the ankylosing spondylitis-associated HLA-B27/B2708 antigens. However, the generally used "HLA-B27" monoclonal antibodies (moabs) cross-react with many HLA specificities, including the common HLA-B7 antigen. Thus, using two "B27" moabs is highly recommended.

METHODS

The assay used two "HLA-B27" reagents, FITC and PE conjugated, respectively and a PE-Cy5 anti-CD3 antibody. Assay verification used 51 reference subjects possessing B*2705, B*2702, and B*2708 and a range of cross-reactive HLA antigens. A total of 1,006 consecutive patients' samples, referred for "HLA-B27 typing", were assayed alongside our standard flow cytometry method. A further 12 low frequency HLA-B*27 specificities were tested. Samples reacting with one "B27" moab only were B*27 allele typed by PCR using sequence-specific primers.

RESULTS

All patient B27/B2708 positives (28.3%) were identified by our one-tube method which detected B*2705, B*2702, B*2708, and 8/12 other B*27 specificities. It was unaffected by HLA-B7 and other cross-reactive antigens but required a minor adjustment, a reduction in the volume of one of the "B27" moabs used, to avoid detecting a minority of HLA-B57 subjects.

CONCLUSIONS

Our one-tube B27/B2708 assay is simple, robust, uses two "B27" moabs for typing precision and security, does not suffer from interference by HLA-B7 or other cross-reactive antigens and has the obvious advantage of using a single tube per typing.