HLA-B27 polymorphism in patients with juvenile and adult-onset ankylosing spondylitis in Southern China

Spectrum of Spondyloarthritis Among Chinese Populations

Purpose of Review

This review aims to emphasize interesting and important new findings with a focus on the spectrum of spondyloarthritis (SpA) in China.

Recent Findings

Over the past decade, significant advances have been made in the investigation of SpA epidemiology, the exploration of genetic and environmental risk factors, the identification of clinical features, and the updating of treatment protocols in the Chinese population. The prevalence of ankylosing spondylitis (AS) in China is 0.20–0.42%, and the prevalence of HLA-B27 in AS patients is 88.8–89.4%. HLA-B*2704 is the most common subtype in Chinese AS patients, followed by HLA-B*2705. HLA-A*01, more precisely HLA-A*01:01, may be associated with psoriatic arthritis (PsA). Tumor necrosis factor inhibitors and IL-17A inhibitors have been shown to be effective and safe for AS patients in China. Juvenile-onset AS is relatively rare, accounting for only 9.1% of the AS population. The prevalence of arthritis related to inflammatory bowel disease is 6.9 to 7.2%. A Chinese study showed that the most frequently prescribed medication was methotrexate (66.4%). Biological agents were prescribed in only16.4% of patients with PsA.

Summary

This review summarizes the latest research in the epidemiology, pathogenesis, clinical manifestations, and management of SpA among Chinese populations. Multiple HLA associations with SpA have also been described, and it is hoped that discoveries of such ethnic-specific risk factor(s) and understanding of their pathological mechanisms may potentially lead to newer targeted therapies for the Chinese populations worldwide.

Predominant frequency of HLA-B*27 in patients with ankylosing spondylitis in southeastern China

OBJECTIVES

This study was to investigate the polymorphism and distribution of alleles of HLA-B*27 in patients with ankylosing spondylitis (AS) in Han population of southeastern China.

METHODS

A total of 89 peripheral blood samples from southeastern Chinese Han patients with AS that diagnosed according to Modified New York criteria were subtyped using the high-resolution PCR-SSP.Exon 2-3 of HLA-B*27 gene was amplified and sequenced to further confirm the HLA-B*27 subtype.

RESULTS

The frequency of HLA-B*27 was 99.87% in AS patients. Three subtypes, HLA-B*2704, HLA-B*2705, and HLA-B*2706 were identified. The frequencies for these three alleles were HLA-B*2704 in 84/88 (95.46%), HLA-B*2705 in 3/88(3.41%), and HLA-B*2706 in 1/88 (1.13%) of the HLA-B*27 positive patients, respectively.

CONCLUSIONS

Our study shows that HLA-B*2704 has an overwhelming frequency in southeastern Chinese Han AS patients. A combined analysis including previous studies of HLA-B*27-subtype distributions in Chinese Han populations showed that HLA-B*2704 may originate from the southern Han and then migrate and spread to the northern areas, and HLA-B*2705 show the opposite result.

Associations between HLA-B27 subtypes and outcomes in Thai children with enthesitis-related arthritis

OBJECTIVE

Expression of human leukocyte antigen B27 (HLA-B27) has been identified as a predictor of severe disease in enthesitis-related arthritis (ERA) patients. However, the associations between HLA-B27 subtypes and outcomes of this disease are still unclear. Here, we examined the distributions of HLA-B27 subtypes among ERA patients and the associations with disease outcomes.

METHODS

This was a historical cohort study of ERA patients. Patients were followed from diagnosis to the most recent visit. Relationships between outcomes and the HLA-B27 subtype were assessed by mixed-effect regression, Kaplan-Meier survival, and Cox proportional hazards regression analyses.

RESULTS

Of the 66 ERA patients, 50 HLA-B27-positive (86% male) and 16 HLA-B27-negative (69% male) patients were included in this study. Patients with HLA-B27-positive were classified into HLA-B*27:04-positive (84%), including combined HLA-B*27:04 and HLA-B*27:07 (2%), and HLA-B*27:04-negative (16%), including HLA-B*27:05 (10%), HLA-B*27:06 (2%), HLA-B*27:07 (2%), and HLA-B*27:15 (2%). HLA-B*27:04-positive (83.3%) and HLA-B*27:04-negative patients (100%) had refractory disease more than HLA-B27-negative patients (37.5%, p = 0.001). HLA-B*27:04-negative patients (57%, 1.73 years) had relapsing disease more and earlier than HLA-B*27:04-positive (35%, 5.54 years) and HLA-B27-negative patients (40%, 6.92 years; p < 0.001). Furthermore, HLA-B*27:04-negative was predictors of refractory disease (HR 4.56, 95%CI 1.40-14.87; p = 0.012) and relapsing disease (HR 3.80, 95% CI 1.18-12.30; p = 0.026). The duration before anti-tumor necrosis factor treatment initiation > 1 year was also a predictor of refractory disease (HR 116.08, 95% CI 14.67-918.26; p < 0.001).

CONCLUSION

HLA-B*27:04 was the most common HLA-B27 subtype in Thai ERA patients. HLA-B*27:04-negative was associated with more unfavorable outcomes than HLA-B*27:04-positive and HLA-B27-negative patients. Key Points • Most ERA patients in Thailand had HLA-B27-positive, and HLA-B*27:04 was the most common HLA-B27 allele in these patients. • The outcomes of ERA were associated with the presence of HLA-B27 and its subtypes. • HLA-B*27:04-negative patients had unfavorable outcomes, including refractory and relapsing disease, compared to HLA-B*27:04-positive and HLA-B27-negative patients.

Spondyloarthritis in North Africa: an update

Spondyloarthritis (SpA) has been less well studied than rheumatoid arthritis in North Africa, due to a belief that it is rare and benign in certain populations. The main genetic trait of SpA is its association with human leukocyte antigen (HLA)-B27. The distribution of this allele largely explains the prevalence and severity of SpA. The prevalence of HLA-B27 in the general population of North Africa is estimated at about 4%, and rises to about 60% among people affected with SpA. Coxitis is one of the main features of North African SpA, but the response to treatment is comparable to the literature from the West. The major challenge in North Africa remains accessibility to specialized care and means of early diagnosis. Prevalent infections in North Africa do not seem to be a major obstacle to optimal treatment strategies.

Comparison of HLA-B*27 subtypes between Chinese patients with ankylosing spondylitis and non-ankylosing spondylitis carriers

Objective

To investigate the distribution of subtypes between HLA-B*27 (+) patients with ankylosing spondylitis (AS) and carriers.

Methods

This case–control study recruited Chinese Han patients with HLA-B*27 (+) AS from six hospitals in Zhejiang Province, China between 2013 and 2018. Patients who were examined for HLA-B*27 because of back pain or arthralgia but who did not have AS or arthritis were recruited as controls. HLA-B*27 target DNA was amplified by amplification refractory mutation systems and HLA-B*27 subtypes were determined by sequencing.

Results

The positive rate of HLA-B*27 was significantly higher in the AS group than in the control group. In AS patients, HLA-B*2704 was predominant at 86.4%, followed by HLA-B*2705 at 12.6%; HLA-B*2704 and HLA-B*2705 were found in 70.0% and 10.0% of controls, respectively. HLA-B*2702 and HLA-B*2706 were detected at low frequencies in the control group, while the rare subtype HLA-B*2715 was only observed in two (1.0%) patients with AS. HLA-B*2707 was not detected in AS or control groups.

Conclusion

HLA-B*2704 is the predominant subtype among patients with AS and carriers in southeast China.

Clinical correlates of HLA-B*27 and its subtypes in enthesitis-related arthritis variant of juvenile idiopathic arthritis in south Indian Tamil patients

AIM

The aim of the study was to assess the distribution of human leukocyte antigen (HLA)-B*27 subtypes and its correlation with disease phenotypes in children with enthesitis-related arthritis variant of juvenile idiopathic arthritis (JIA-ERA).

METHOD

One hundred and sixty patients (132 males, 28 females) satisfying the International League Against Rheumatism (ILAR) classification criteria for JIA-ERA were assessed and relevant demographic, clinical and radiographic data were documented. HLA-B*27 typing was done for all the patients and B*27 positive samples were subjected to high-resolution gene sequencing. The effect of duration of illness, HLA-B*27, its subtypes, and gender on the clinical phenotype were analyzed.

RESULTS

The mean age of disease onset was 12.69 ± 2.4 years with a male:female ratio of 4.7:1.0. HLA-B*27 was positive in 109/160 patients and HLA-B*27:04 was detected in 63% followed by B*27:05 (30%). Duration of illness was greater in patients with skeletal deformity, hip arthritis, sacroiliitis, cervical spine involvement and acute anterior uveitis (AAU) (P < 0.05). HLA-B*27 positivity was associated with a prolonged course of disease, higher incidence of AAU (14.7% vs 2%, P = 0.015), family history of spondyloarthritis (21.1% vs 5.9%; P = 0.015) and higher erythrocyte sedimentation rate as compared to HLA-B*27 negative patients (P < 0.01). The HLA-B*27:04 and *27:05 positive patients had similar clinical phenotypes.

CONCLUSION

Presence of HLA-B*27 and long duration of illness results in skeletal deformity, hip arthritis, sacroiliitis, cervical spine involvement and AAU. HLA-B*27:04 followed by B*27:05 are the most common HLA-B*27 subtypes in our study population and both have a similar clinical phenotype.

Optimization of an in-house PCR method for the detection of HLA-B*27 alleles

The association of spondyloarthropathies with different alleles of human leukocyte antigen (HLA) B*27 is well established. Different subtypes of HLA-B*27 may be linked with different ethnic groups, distinct clinical manifestations, specific age of onset and different prognoses. Polymerase chain reaction with sequence specific primers (PCR-SSP) is the most frequently adapted molecular method used for the recognition of HLA-B*27-specific DNA sequences. The aim of the present study was to standarise an in-house protocol of PCR-SSP for HLA-B*27 allele detection for use in the Armed Forces Institute of Pathology (AFIP), Pakistan, with consideration of its cost effectiveness. A total of 49 individual samples were included, comprising 10 transplant samples determined to be HLA-B*27-negative by PCR-SSP and 39 HLA-B*27-positive samples determined by flow cytometry, obtained from patients who were symptomatic and referred for HLA-B*27 testing. By altering each variable individually, an in-house PCR-SSP protocol was optimized to amplify common HLA-B*27 alleles (2701-2721, 2723-2730). To discriminate B*27 from all other HLA-B alleles, a low-resolution HLA-B typing set with a 96 PCR-SSP primer mixture was used in conjunction. Among the 39 HLA-B*27-positive specimens, 31 (79%) were detected as positive by PCR-SSP, with the remaining samples failing due to a sub-optimized protocol and/or low DNA concentration. Additionally, there was complete concordance between flow cytometry and in-house PCR, and the sensitivity and specificity of the PCR-SSP were determined to be 100%. In conclusion, in-house SSP-PCR is, standard method for the detection of HLA-B*27 alleles. The determination of associations between specific HLA-B*27 alleles and AS may aid to identify individuals at higher risk of developing the disease. Furthermore, the identification of individuals at risk may aid to adapt preventive strategies.

HLA-B27 testing: A journey from flow cytometry to molecular subtyping

BACKGROUND

Determination of HLA-B27 status plays an important role as adjuvant in suspected cases for diagnosis of Ankylosing Spondilytis (AS). Objectives of this study were to evaluate (i) flow cytometry method in comparison with DNA microarray for HLA-B27 typing and (ii) EUROArray HLA-B27 Direct assay for HLA-B27 allele detection along with discrimination of AS/non-AS subtypes in Indian population.

METHODS

A total of 7543 patients with a presumptive clinical diagnosis of AS were referred for screening of HLA-B27. All samples were initially tested by flow cytometry, and based on its findings, 1560 samples were analyzed for the presence of HLA-B27 allele by microarray technology. A subset of samples (n = 200) were further tested by DNA sequencing for identification of HLA-B27 subtypes.

RESULTS

Screening of HLA-B27 by flow cytometry reported 1551 positive (20.56%) and 5556 negative (73.65%) cases. Remaining 436 (5.78%) samples were identified within equivocal zone. Of cases (n = 1560) analyzed by microarray method, 1333 (85.44%) and 227 (14.55%) were detected microarray positive and negative, respectively. DNA sequencing identified HLA-B*27:07 as the predominant subtype among cases showing ex2 positivity by microarray method. Of 200 cases, 20 cases (14 of HLA-B*07 and 6 of HLA-B*37) of HLA-B27 cross-reactive subtypes were also identified.

CONCLUSION

We recommend DNA typing as a complementary tool along with flow cytometry to accomplish successful HLA-B27 phenotype determination. This is the first study among Indian population to evaluate efficacy of EUROArray to detect B27 allele and its potential to indicate the presence of nondisease-associated alleles in Indian population.

Does HLA-B27 Status Influence Ankylosing Spondylitis Phenotype?

The association of HLA-B27 with ankylosing spondylitis (AS) remains as one of the intriguing models that could exist between a molecule and human disease in medicine. Although it was reported in 1973, its contribution to AS and related spondyloarthritis continues to be a major challenge for scientific community. It is important to understand its etiopathogenic mechanism and its functions in these diseases. Although the diagnostic and prognostic roles of HLA-B27 in AS are still debated, there is an increasing interest for HLA-B27–based effects especially in HLA-B27(+) patients with AS. This review will focus in the examination of published reports regarding the influence of HLA-B27 status on the demographic and clinical features in AS, with specific interest to its role on AS severity.

Polymorphisms of human leukocyte antigen B*27 on clinical phenotype of spondyloarthritis in Chinese

BACKGROUND

In recent years, an ever-increasing number of alleles of human leukocyte antigen B*27 (HLA-B*27) have been identified. This study aimed to establish an updated method for HLA-B*27 subtyping, and to investigate the impact of HLA-B*27 polymorphisms on the clinical phenotype of spondyloarthritis (SpA).

METHODS

Overall, 184 SpA patients were recruited for analyzing diversity of HLA-B*27 via an updated high-resolution polymerase chain reaction amplification with sequence specific primers (PCR-SSP).

RESULTS

The prevalence of HLA-B*27 was 94.0%, and four subtypes were identified including HLA-B*2704 (77.5%), B*2705 (20.2%), B*2707 (1.7%), and B*2724 (0.6%). There was an obvious male predominance (P=.05) and markedly elevated C-reaction protein (CRP) in B*27 positive SpA (P<.01). In multivariate linear regression analysis, the elevated CRP was positively associated with HLA-B*27 positivity (regression coefficient B=46.1, P=.0003), grade of sacroiliitis (B=47.5, P=.0032), and male gender (B=20.4, P=.0041). Notably, a male predilection was also found in B*2705 positive SpA while B*2707 was associated with older age, higher positive family history, and higher prevalence of extra-articular features (all P<.05).

CONCLUSIONS

In this study, an updated PCR-SSP technique to identify increasing alleles of HLA-B*27 was developed and their different effects on clinical manifestations of SpA were demonstrated. Genotyping of HLA-B*27 would shed light on our understanding of the pathogenesis of SpA.

Clinical Features in Juvenile-Onset Ankylosing Spondylitis Patients Carrying Different B27 Subtypes

Background. Ankylosing spondylitis (AS) is a common rheumatic disease and is characterized by inflammation of the axial skeleton. HLA-B27 is strongly associated with AS. Juvenile-onset AS (JAS) with disease onset before 16 years of age differs from adult-onset AS (AAS) in many respects. Objective. To compare the clinical features in JAS with different B27 subtypes and analyze the differences between JAS and AAS. Methods. 145 JAS and 360 AAS patients were included. The demographic data, clinical manifestations, laboratory markers, Bath AS indices, and B27 subtypes were recorded. Results. Peripheral arthritis, enthesitis, BASDAI, ESR, and CRP were significantly higher in JAS patients with HLA-B^*2704 than those with B27-negative. Enthesitis and ESR were significantly higher in patients with HLA-B^*2705 than those with B27-negative. The onset age of HLA-B^*2715 group was much earlier than the other groups. The peripheral arthritis, enthesitis, and hip joint involvement in JAS with HLA-B^*2704 were significantly higher than those in AAS with HLA-B^*2704. Conclusion. JAS with different B27 subtypes had similar features in most of manifestations; JAS and AAS patients with the same subtype could have distinctive courses. Early diagnosis, hip detection, and control of systemic active inflammation in JAS patients will be helpful for improving the prognosis.

Changes of serum levels of MMP-3, sRANKL, and OPG in juvenile-onset ankylosing spondylitis patients carrying different HLA-B27 subtypes

Ankylosing spondylitis (AS) patients whose symptom onset occurs before 16 years of age are termed juvenile-onset ankylosing spondylitis (JAS). Investigations suggested that JAS had worse functional outcome, and abnormality of bone metabolism can appear in early stage of AS. The objectives of this study are to compare changes of serum inflammatory and bone metabolic markers and to explore the relationship between these biomarkers and disease activity in JAS with different HLA-B27 subtypes. Serum matrix metallopeptidase-3 (MMP-3), soluble receptor activator of nuclear factor-κB ligand (sRANKL), and osteoprotegerin (OPG) were detected by ELISA in 56, 62, and 68 JAS patients, respectively, and 32 healthy individuals were as controls. Serum MMP-3 and sRANKL were significantly higher and OPG in JAS was slightly higher than those in controls. There was no significant difference in the level of MMP-3, sRANKL, and OPG among JAS patients with B27 negativity, B*2704, B*2705, and B*2715, respectively. Serum levels of MMP-3 showed positive correlation with BASDAI and BASFI (Bath Ankylosing Spondylitis Disease Activity Index and Functional Index). Serum level of sRANKL showed positive correlation with MMP-3 and negative correlation with disease duration. The significantly higher sRANKL expression suggested the enhanced osteoclast function and imbalance of RANKL/OPG system in the inflammatory process of JAS patients carrying different B27 subtypes. It should be paid attention to the abnormality of bone metabolism during the treatment of JAS.

Association of HLA-B27 genetic polymorphisms with ankylosing spondylitis susceptibility worldwide: a meta-analysis

OBJECTIVES

Many publications have evaluated the correlation between HLA-B27 polymorphisms and ankylosing spondylitis (AS), with conflicting results. We carried out this new meta-analysis in order to collect all the relevant studies to further clarify the association of HLA-B27 polymorphisms with AS susceptibility.

METHODS

Relevant published data were retrieved through Medline, PubMed, Web of Science, CNKI, and the Chinese BioMedical Literature Database on disc. The statistical analysis was conducted using Review Manager Version 5.0 and STATA 11.0. From these data, the odds ratio (OR) with a 95 % confidence interval (95 % CI) was calculated.

RESULTS

(1) A total of 38 studies, including 3,410 AS cases and 1,735 healthy controls, were collected in this meta-analysis. (2) Our results showed that B2704 was a risk factor but B2703, B2706, B2707, B2727, B2729, and B2747 may be protective factors for AS worldwide. (3) These subtypes, such as B2701, B2702, B2705, B2708-15, B2717-20, B2723-24, B2733, B2735, B2740, B2746, B2749, and B2767, showed no association with susceptibility to AS. There was a huge difference with previous reports for B2702 and B2705. (4) The B2702, B2704 and B2705 subtypes have existed high heterogeneity but no publication bias.

CONCLUSIONS

This meta-analysis in our study suggested that B2704 might be a potential risk factor, however, B2703, B2706, and B2707 might be potential protective factors of AS, especially in Asia.

Polymorphism of HLA-B27: 105 subtypes currently known

HLA-B27 has a high degree of genetic polymorphism, with 105 known subtypes, named HLA-B*27:01 to HLA-B*27:106, encoded by 132 alleles. The most common subtypes associated with ankylosing spondylitis are HLA-B*27:05 (Caucasians), HLA-B*27:04 (Chinese), and HLA-B*27:02 (Mediterranean populations). For Chinese populations, HLA-B*27:04 is associated with a greater ankylosing spondylitis risk than HLA-B*27:05. Two subtypes, HLA-B27*06 and HLA-B27*09, seem to have no disease association. These differential disease associations of HLA-B27 subtypes, and the recent discovery that ERAP1 is associated with ankylosing spondylitis for patients with HLA-B27, have increased attempts to determine the function of HLA-B27 in disease pathogenesis by studying hemodynamic features of its protein structure, alterations of its peptidome, aberrant peptide handling, and associated molecular events. However, after 40 years we still do not fully know how HLA-B27 predisposes to ankylosing spondylitis and related spondyloarthritis.

Immunogenetic study in Chinese population with ankylosing spondylitis: are there specific genes recently disclosed?

Purpose. Ankylosing spondylitis (AS) is a systemic, autoimmune disease resulting in the destruction of the affected joints. Over the past 5 years, several new genes or genetic regions associated with AS have been identified in the Chinese population. This paper aims to discuss the major findings and related potential mechanisms of these studies in our population. Recent Findings. In recent years, due to the rapid advances in computational genetics and technology, there has been an increasing list of well-validated genes or genetic regions associated with AS susceptibility. So far, several genes or genetic regions have now been reported in the Han ethnic Chinese population, containing the major histocompatibility complex (MHC), ERAP1, IL-23R, 12q12, 2p15, 5q14.3, and so on. Different hypotheses for disease mechanisms have been investigated on the basis of the functional studies of these genes or genetic regions. Summary. This paper tries to summarize the association of several candidate genes with risk for AS in the Han ethnic Chinese population and aims to identify the novel inflammatory pathways and provide potential strategies for better therapies.

Rapid and reliable genotyping of HLA-B*27 in the Chinese Han population using a duplex real-time TaqMan PCR assay

OBJECTIVES

To develop a duplex real-time TaqMan PCR assay for genotyping HLA-B*27 in the Chinese Han population.

DESIGN AND METHODS

A standard curve was constituted to deduce amplification efficiency, dynamic range and detection limit of the duplex real-time TaqMan PCR assay, whereas PCR-SBT (PCR with sequence-based typing) was used to evaluate the accuracy of the assay.

RESULTS

A linear standard curve for determining HLA-B*27 was obtained within the range of 10(1)-10(9) copies per reaction with the correlation coefficient of 0.99 and amplification efficiency of 98.30%. The detection limit was 3.09 copies per reaction. Complete concordance was found between the results obtained by the duplex real-time TaqMan PCR assay and PCR-SBT. Fifty-nine of the 178 genomic samples were HLA-B*27 positive and the other 119 were HLA-B*27 negative.

CONCLUSIONS

The duplex real-time TaqMan PCR approach appears to be a reliable, sensitive, rapid and high-throughput method to genotype HLA-B*27 in the Chinese Han population.

SLA-DRB1 and -DQB1 genotyping by the PCR-SSOP-Luminex method

A simple and novel genotyping method was developed to detect alleles at the swine leukocyte antigen (SLA)-DRB1 and -DQB1 class II loci by using polymerase chain reaction (PCR)-fluorescently labeled sequence-specific oligonucleotide probes (SSOPs) and Luminex 100 xMAP detection. The PCR-SSOP-Luminex method exhibited accuracy of 95% for both SLA-DRB1 and -DQB1 in 6 homozygous and 16 heterozygous pig samples as confirmed by sequencing the PCR products of the same samples. In addition, 12 low-resolution SLA class II haplotypes consisting of 7 and 9 DRB1 and DQB1 alleles were identified, respectively, in one population of 283 Landrace pigs. This genotyping method facilitates the rapid and accurate identification of two- or four-digit alleles at the SLA-DRB1 and -DQB1 loci.

Remarkable polymorphism of HLA-B27: an ongoing saga

Histocompatibility antigen HLA-B27 is a normal gene that is distributed worldwide with variable prevalence and shows a remarkable association with ankylosing spondylitis and related spondyloarthropathies. The precise biological explanation for this remarkable association remains elusive. HLA-B27 represents a family of closely related proteins encoded by an ever-increasing number of alleles; there are 75 alleles of HLA-B27 known thus far, based on nucleotide sequence differences, but at the translated protein level, there are 62 known subtypes of HLA-B27. Not all subtypes are disease associated. Moreover, existence of a possible hierarchical ranking among some of the subtypes for their disease association has been observed.

HLA-B27 and ankylosing spondylitis: tales from China

The two most frequent HLA-B27 subtypes worldwide are B*2704 and B*2705. In the Han population of China B*2704 and, to a lower extent, B*2705 are found with significant frequency, and both are associated to ankylosing spondylitis (AS). Two articles in this issue report that the association to AS in this ethnic group is stronger for B*2704 than for B*2705. Thus, at least among the Han, B*2704 would be the strongest known susceptibility factor for AS.