Update: the twenty subtypes of HLA-B27

Spondyloarthropathies and arthritis post-infection: a historical perspective

The spondyloarthropathies are a group of conditions characterised by spinal joint pain and have related clinical, epidemiological and genetic-related features. Ankylosing spondylitis, reactive arthritis, the spinal form of psoriatic arthritis and Crohn's and colitis enteropathic arthritis are the major clinical entities of the spondyloarthropathies, and principally occur in HLA-B27 positive individuals. Ankylosing spondylitis is much more common in males than females. Patients are usually seronegative for rheumatoid factor, and extra-articular features including iridocyclitis, mucous membrane and skin lesions: aortitis, may occur in some patients. The reactive arthritis form classically occurs following an infection of the gastrointestinal or genitourinary tract. The Crohn's and colitis enteropathic arthritis forms often have an associated large joint asymmetrical arthritis. Also discussed are acute rheumatic fever and Lyme disease which are conditions where the individual develops arthritis after an infection.

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.

Allelic association with ankylosing spondylitis fails to correlate with human leukocyte antigen B27 homodimer formation

Expression of human leukocyte antigen (HLA)-B27 is strongly associated with predisposition toward ankylosing spondylitis (AS) and other spondyloarthropathies. However, the exact involvement of HLA-B27 in disease initiation and progression remains unclear. The homodimer theory, which proposes that HLA-B27 heavy chains aberrantly form homodimers, is a central hypothesis that attempts to explain the role of HLA-B27 in disease pathogenesis. Here, we examined the ability of the eight most prevalent HLA-B27 allotypes (HLA-B*27:02 to HLA-B*27:09) to form homodimers. We observed that HLA-B*27:03, a disease-associated HLA-B27 subtype, showed a significantly reduced ability to form homodimers compared with all other allotypes, including the non-disease-associated/protective allotypes HLA-B*27:06 and HLA-B*27:09. We used X-ray crystallography and site-directed mutagenesis to unravel the molecular and structural mechanisms in HLA-B*27:03 that are responsible for its compromised ability to form homodimers. We show that polymorphism at position 59, which differentiates HLA-B*27:03 from all other allotypes, is responsible for its compromised ability to form homodimers. Indeed, histidine 59 in HLA-B*27:03 leads to a series of local conformational changes that act in concert to reduce the accessibility of the nearby cysteine 67, an essential amino acid residue for the formation of HLA-B27 homodimers. Considered together, the ability of both protective and disease-associated HLA-B27 allotypes to form homodimers and the failure of HLA-B*27:03 to form homodimers challenge the role of HLA-B27 homodimers in AS pathoetiology. Rather, this work implicates other features, such as peptide binding and antigen presentation, as pivotal mechanisms for disease pathogenesis.

Frequency of Finding Family Donors: A Single Center Experience

OBJECTIVES

Allogeneic hematopoietic stem cell transplant is a curative treatment option for many hematologic diseases. The existence of a fully compatible donor for recipients is the first condition for minimized transplant-related mortality and morbidity. The best donor for hematopoietic stem cell transplant is an HLA-matched sibling donor. The possibility of finding an HLA-matched sibling is less than 30% worldwide. Hematopoietic stem cell transplant is needed for an increasing number of patients every year, but the ability to find a fully compatible donor has limited its use.

MATERIALS AND METHODS

From August 2012 to May 2017, we screened 412 adult patients who required AHSCT and their families for HLA tissue groups who were seen at our center (Baskent University Adana Dr. Turgut Noyan Research and Medical Center Hematology Unit). To screen tissue groups at our center, we perform lowresolution typing for HLA-A, -B, -C, -DRB1, and -DQB. If an HLA genotype cannot be identified, verification typing is done using highresolution testing.

RESULTS

We found matched family donors in 227 (55%) of 412 patients screened at our center. The ratio of HLAmatched related donors was 83% for 279 patients who received allogeneic stem cell transplant.

CONCLUSIONS

The likelihood of finding eligible unrelated donors has been gradually increasing, in part due to the development of the National Bone Marrow Bank. However, a careful screening for related donors is still important. Our findings indicate the importance of careful examination of family genealogy and of careful family screening in our region.

F pocket flexibility influences the tapasin dependence of two differentially disease-associated MHC Class I proteins

The human MHC class I protein HLA-B*27:05 is statistically associated with ankylosing spondylitis, unlike HLA-B*27:09, which differs in a single amino acid in the F pocket of the peptide-binding groove. To understand how this unique amino acid difference leads to a different behavior of the proteins in the cell, we have investigated the conformational stability of both proteins using a combination of in silico and experimental approaches. Here, we show that the binding site of B*27:05 is conformationally disordered in the absence of peptide due to a charge repulsion at the bottom of the F pocket. In agreement with this, B*27:05 requires the chaperone protein tapasin to a greater extent than the conformationally stable B*27:09 in order to remain structured and to bind peptide. Taken together, our data demonstrate a method to predict tapasin dependence and physiological behavior from the sequence and crystal structure of a particular class I allotype. Also watch the Video Abstract.

Prevalence and clinical manifestations of ankylosing spondylitis in young Greek males

Increased awareness and sensitivity of general physicians have increased the early diagnoses of seronegative arthritis in young patients, while new agents such as anti-TNF blockers have significantly changed the treatment of the disease. To investigate the prevalence, the clinical manifestations, and the ability for military service of young Greek males (18-30 years old) with ankylosing spondylitis (AS) in the pre-anti-TNF era. We retrospectively studied the AS cases recorded from 1989 to 1995 of the rheumatology department of the largest General Military Hospital in Greece; the diagnosis was based on the modified New York criteria for AS. A total of 285 AS cases were diagnosed among 357,184 young men. The overall prevalence of AS on December 1995 was estimated at 8.2 cases per 10,000 young men (95 % C.I. 7.2-9.2). All the patients had chronic back pain. Two hundred forty (84 %, 95 % C.I. 79-88 %) patients presented sacroiliitis of whom 163 (68 %, 95 % C.I. 62-73 %) were bilateral. Two hundred five patients (72 %, 95 % C.I. 66-77 %) had peripheral joint involvement. Thirty-one patients presented with anterior uveitis (11 %, 95 % C.I. 8-15 %). One patient had IgA nephropathy. None had gut involvement. HLA-B27 antigen was found in 257 patients (90 %, 95 % C.I. 86-93 %). Ninety-one patients (32 %, 95 % C.I. 27-38 %) had permanent discharge from the military service, while 128 (45 %, 95 % C.I. 39-51 %) were able for auxiliaries attendances. The prevalence of AS for the age group 18-30 years old in this young Greek men cohort was significantly lower than in other Caucasian European populations, and the clinical manifestations were considered as mild.

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.

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 30-kDa band from Salmonella typhimurium: IgM, IgA and IgG antibody response in patients with ankylosing spondylitis

OBJECTIVE

To determine the association of Salmonella typhimurium antigens with AS by analysing the IgA, IgG and IgM antibody response to the crude lysate and the 30-kDa band from this micro-organism.

METHODS

Sera from 28 AS patients, 28 HLA-B27+ healthy relatives, 28 unrelated healthy subjects and 14 RA patients were included. Salmonella typhimurium proteins were electrophoretically separated and blotted onto nitrocellulose sheets for immunodetection with sera from AS patients and unrelated healthy subjects. The electroeluted 30-kDa band (p30) and a crude lysat (StCL) from S. typhimurium were used as antigen to evaluate the IgM, IgA and IgG (total and subclasses) antibody levels by ELISA. An inhibition assay was carried out to confirm the specificity of IgG response to the p30.

RESULTS

Twenty out of 28 AS patients (71.4%) and 4 out of 28 unrelated healthy subjects (14.3%) recognized a 30-kDa band from S. typhimurium with IgG antibodies. Six out of 28 AS patients (21.4%) and 4 out of 28 unrelated healthy subjects (14.3%) detected it with IgA antibodies. Recognition of p30 and StCL by both IgA and IgG antibodies was higher in AS patients than in control groups (P = 0.003, <0.001 and 0.003 for IgA and <0.001, 0.003 and 0.006 for IgG). Sera from AS patients have higher percentage of IgG antibodies p30 and IgG3 subclass was higher in AS patients than in control groups. No differences in the IgM response were found.

CONCLUSIONS

Data presented suggest the association between the p30 and AS.

Identification of previously unrecognized predisposing factors for ankylosing spondylitis from analysis of HLA-B27 extended haplotypes in Sardinia

OBJECTIVE

To define the contribution of HLA genes other than HLA-B27 in conferring susceptibility to ankylosing spondylitis (AS), through analysis of HLA-B27 haplotypes in Sardinian subjects.

METHODS

Ninety-eight patients with AS, 133 HLA-B27-positive controls (of whom 33 were positive for HLA-B*2709), and 190 randomly selected controls were genotyped for microsatellites and single-nucleotide polymorphisms (SNPs) spanning the HLA region.

RESULTS

Haplotypes carrying either the B*2705 or the B*2709 allele were found to share a conserved region downstream of the HLA-B gene and a functional polymorphism in the HLA-E gene (R128G), while differing in all other markers. Notably, the presence of an A at SNP rs1264457, encoding for Arg-128, was significantly increased in the cohort of patients (P = 6 x 10(-6), corrected P = 3 x 10(-5)) but not in B*2705- or B*2709-positive controls. Comparing the alleles co-occurring at each HLA marker, we identified a region differentiating patients with AS and B*2705-matched controls. In particular, there was a markedly increased prevalence of heterozygosity at rs1264457 among B27-positive controls (74%, versus 47% in patients and 54% in random controls), suggesting a protective role of G128 in AS. Moreover, other markers around the HLA-B gene were also differentially represented.

CONCLUSION

These results demonstrate a significant difference in the frequency of some HLA markers between AS patients and B*2705-positive controls, which could be attributed to the opposite chromosome. In particular, the differential distribution of a functional polymorphism in the HLA-E gene suggests a possible role of natural killer function in AS pathogenesis.

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.

Acute anterior uveitis and HLA-B27

Acute anterior uveitis is the most common form of uveitis. HLA-B27-associated acute anterior uveitis is a distinct clinical entity that has wide-ranging medical significance due to its ocular, systemic, immunologic, and genetic features. The association between HLA-B27 and the spectrum of HLA-B27-associated inflammatory diseases remains one of the strongest HLA-disease associations known to date. This review examines acute anterior uveitis with particular focus on HLA-B27-associated acute anterior uveitis, including the epidemiology, immunopathology, association with HLA-B27 and its subtypes, clinical features, complications, prognosis, and potential new therapies such as anti-TNFalpha therapy and oral HLA-B27-peptide tolerance. There have been substantial recent advances in both clinical and basic scientific research in this field, including studies of the various animal models of acute anterior uveitis and the HLA-B27 transgenic animals, and these are summarized in this review. To the ophthalmologist, HLA-B27-associated acute anterior uveitis is an important clinical entity that is common, afflicts relatively young patients in their most productive years, and is associated with significant ocular morbidity due to its typically recurrent attacks of inflammation and its potentially vision-threatening ocular complications. Furthermore, to the ophthalmologist and the internist, HLA-B27-associated acute anterior uveitis is also of systemic importance due to its significant association with extraocular inflammatory diseases.

HLA-B27 polymorphism in Mumbai, Western India

Human leucocyte antigen (HLA)-B27 encompasses an increasing number of subtypes that show diverse racial/ethnic prevalence in the world. One thousand-one-hundred and seventy unrelated individuals from Mumbai, Maharashtra, Western India were typed for HLA-B27 antigen by serological methods. HLA-B27 positivity was confirmed by polymerase chain reaction using sequence specific primers. High-resolution typing using sequence specific primers for HLA-B27 alleles (B*2701 - B*2721) was carried out in 70 HLA-B27-positive individuals. The frequency of B27 ranged between 1.48 and 9.6% among the caste groups studied. HLA-B27 subtyping identified B*2702 (1.43%), B*2704 (14.29%), B*2705 (70%), B*2707 (12.86%) and B*2718 (1.43%), respectively. The findings illustrate substantial genetic variation and heterogeneity within population groups from India. Extensive subtyping in other Indian caste groups will be necessary to resolve the evolutionary implications of HLA-B27 subtypes and their relationship to disease association in the Indian context.

HLA and disease

Association of HLA and diseases is well known. Several population studies are available suggesting evidence of association of HLAs in more than 40 diseases. HLA found across various populations vary widely. Some of the reasons attributed for such variation are occurrence of social stratification based on geography, language and religion, consequences of founder effect, racial admixture or selection pressure due to environmental factors. Hence certain HLA alleles that are predominantly associated with disease susceptibility or resistance in one population may or may not show any association in other populations for the same disease. Despite of these limitations, HLA associations are widely studied across the populations worldwide and are found to be important in prediction of disease susceptibility, resistance and of evolutionary maintenance of genetic diversity. This review consolidates the HLA data on some prominent autoimmune and infectious diseases among various ethnic groups and attempts to pinpoint differences in Indian and other population.

HLA-B27 typing: evaluation of an allele-specific PCR melting assay and two flow cytometric antigen assays

BACKGROUND

Human leukocyte antigen B27 (HLA-B27) is a major histocompatibility complex class 1 molecule that is strongly associated with the disease ankylosing spondylitis. Testing for HLA-B27 is of diagnostic value because 90% of patients with ankylosing spondylitis have the B27 antigen. Two commonly used HLA-B27 flow cytometric assays are commercially available.

METHODS

An allele-specific polymerase chain reaction (PCR) melting assay for HLA-B27 was compared with two available antigen assays on 371 clinical samples. The accuracy of the assays was measured by receiver operating characteristic analysis using the PCR method and sequencing as the reference standard.

RESULTS

When PCR results were compared with those of the antigen assays, complete concordance was observed except for five discrepant results that were resolved by sequence analysis. Using DNA sequencing as the gold standard, the sensitivity and specificity of PCR were 99.6 and 100.0, those of the best single antigen assay were 98.2 and 97.6, and those of a reflex combination of both antigen assays were 98.8 and 97.6.

CONCLUSIONS

The allele-specific PCR melting assay for HLA-B27 genotyping is easy to perform and has better sensitivity and specificity than antigen assays. The performance of the two flow cytometric antigen assays depends on the antibody used and the positive cutoff values assigned.

HLA-B27 polymorphism in the Malays

The frequency of HLA-B27 and its subtypes was determined in 878 Malay subjects. Thirty-five of the subjects typed for HLA-A, -B and -DR were found to be positive for HLA-B27. The frequency of this allele in the Malay population was found to be 3.99%. The subtypes observed and their frequencies are: HLA-B*2704 (19.4%), HLA-B*2705 (5.6%), HLA-B*2706 (72.2%) and HLA-B*2707 (2.8%).

Juvenile spondyloarthropathies: the Chinese experience

The data presented here show that in Chinese juvenile-onset AS patients, their clinical features were similar to those reported by Burgos-Vargas and other researchers looking at other ethnic groups. For most JSpA patients, its relation to HLA-B27, basic clinical expression, anatomic substrate, histopathologic nature of the lesion, and response to treatment are the same or similar to those of adult-onset SpA patients. Current treatments provide relief but do not alter the natural course of the disease. New treatments that target immune responses and cellular inflammatory processes, which play a part in the pathogenesis of SpA, are under investigation. TNF-alpha has been identified as a predominant proinflammatory cytokine in synovial tissue of patients who have SpA. Clinical, histologic, and immunohistochemical findings of studies of anti-TNF-alpha antibody therapy in adult SpA patients suggest the possibility of altering the progression of disease coincident with clinical improvement. These findings in adult SpA patients suggest that anti-TNF-alpha therapy might confer similar benefits to JSpA patients.

Six-month results of a double-blind, placebo-controlled trial of etanercept treatment in patients with active ankylosing spondylitis

OBJECTIVE

There is increasing evidence that tumor necrosis factor alpha (TNFalpha) is centrally involved in the pathogenesis of ankylosing spondylitis (AS) and other spondylarthritides. This study was designed to investigate the efficacy of anti-TNFalpha therapy with etanercept, a 75-kd receptor fusion protein, in active AS.

METHODS

This multicenter trial had 2 phases: an initial placebo-controlled period of 6 weeks' duration and an observational phase lasting 24 weeks. Thirty patients with active AS were included. They were randomized into 2 groups, which received either etanercept (25 mg twice weekly) (n = 14) or placebo (n = 16) for 6 weeks. Then both groups were treated with etanercept. Nonsteroidal antiinflammatory drug (NSAID) treatment could be continued, but disease-modifying antirheumatic drugs (DMARDs) and steroids had to be withdrawn prior to the study. All patients received etanercept for a total of 12 weeks and were followed up for at least 24 weeks. The Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index, Bath AS Metrology Index, pain level on a numeric rating scale, quality of life by the Short Form 36, and C-reactive protein (CRP) level were assessed. The primary outcome parameter was a >or=50% improvement in the BASDAI.

RESULTS

Treatment with etanercept resulted in at least a 50% regression of disease activity in 57% of these patients at week 6, versus 6% of the placebo-treated patients (P = 0.004). After the placebo-treated patients switched to etanercept, 56% improved. The mean +/- SD BASDAI improved from 6.5 +/- 1.2 at baseline to 3.5 +/- 1.9 at week 6 in the etanercept group, with no improvement in the placebo group (P = 0.003 between groups). Similarly, pain, function, mobility, and quality of life improved with etanercept but not with placebo at week 6 (P < 0.05). Mean CRP levels decreased significantly with etanercept but not with placebo (P = 0.001). There was ongoing improvement in all parameters in both groups until week 12 and week 18, respectively (i.e., throughout the period of etanercept treatment). Disease relapses occurred a mean +/- SD of 6.2 +/- 3.0 weeks after cessation of etanercept. No severe adverse events, including major infections, were observed during the trial.

CONCLUSION

This study shows that on a short-term basis (3 months), treatment with etanercept is clearly efficacious in patients with active AS who are receiving NSAID therapy but not DMARDs or steroids. After cessation of therapy, almost all patients experienced a relapse within a few weeks. Thus, it seems probable that etanercept must be administered continuously in most AS patients to achieve permanent inhibition of the inflammatory process.

Ankylosing spondylitis in a Malawian

I report a case of ankylosing spondylitis in a Malawian patient. I believe this is the first reported case of ankylosing spondylitis in a Malawian. Ankylosing spondylitis is rare in black Africans when compared with the Caucasian population. The clinical features of this disease are also different in these different racial groups. I will present a brief clinical history and a review of ankylosing spondylitis with special reference to the black African.

HLA-B27 Subtypes Differentially Associated with Disease Exhibit Subtle Structural Alterations

The reasons for the association of the human major histocompatibility complex protein HLA-B27 with spondyloarthropathies are unknown. To uncover the underlying molecular causes, we determined the crystal structures of the disease-associated B*2705 and the nonassociated B*2709 subtypes complexed with the same nonapeptide (GRFAAAIAK). Both differ in only one residue (Asp(116) and His(116), respectively) in the F-pocket that accommodates the peptide C terminus. Several different effects of the Asp(116) --> His replacement are observed. The bulkier His(116) induces a movement of peptide C-terminal pLys(9), allowing the formation of a novel salt bridge to Asp(77), whereas the salt bridge between pLys(9) and Asp(116) is converted into a hydrogen bond with His(116). His(116) but not Asp(116) adopts two alternative conformations, one of which leads to breakage of hydrogen bonds. Water molecules near residue 116 differ with regard to number, position, and contacts made. Furthermore, F-pocket atoms exhibit higher B-factors in B*2709 than in B*2705, indicating an increased flexibility of the entire region in the former subtype. These changes induce subtle peptide conformational alterations that may be responsible for the immunobiological differences between these HLA-B27 subtypes.

Mechanisms of bone resorption and new bone formation in spondyloarthropathies

Spondyloarthropathies (SpA) share clinical features such as sacroiliitis, axial immobility, and peripheral arthropathies. They also share a strong association with human leukocyte antigen-B27, implicating T cells and antigen-presenting cells in the disease process. Inflammation seems to underlie the pathogenesis of SpA, particularly in the axial skeleton and entheses. Pathologic bone loss and formation occur simultaneously in inflamed regions, suggesting an inflammation-induced dysregulation of osteoclast and osteoblast activity. Pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNFa) appear to be central to the disease, because TNFa blockade has been shown to effectively improve clinical outcome. Other cytokines such as transforming growth factor-beta, interferon-gamma (IFNg), and interleukin-18 are also likely to be important in SpA. Activated T cells have been shown to produce cytokines such as IFNg and receptor activator of nuclear-factor- kappaB ligand, with direct effects on osteoclastogenesis. The dual role of T cells in immunobiology and skeletal biology provides a possible link between human leukocyte antigen-B27, pro-inflammatory cytokines, and bone cells in SpA.

Juvenile onset spondyloarthropathies: therapeutic aspects

Juvenile onset spondyloarthropathy (SpA) is a term that refers to a group of human leucocyte antigen (HLA)-B27 associated inflammatory disorders affecting children under the age of 16 years, producing a continuum of clinical symptoms through adulthood. This disease is characterised by enthesopathy and arthropathy affecting the joints of the lower extremities and seronegativity for IgM rheumatoid factor and antinuclear antibodies. Children usually present with undifferentiated SpA and progress to differentiated forms over time. Except for the prevalence of some clinical features at onset, the pathogenic and clinical aspects of juvenile onset SpAs resemble those of the adult disease. Thus application of the same or similar therapeutic measures for both juvenile and adult onset SpAs seems logical. Current treatments for juvenile onset SpA provide symptomatic improvement, but do not alter disease progression. The increased expression of tumour necrosis factor alpha (TNFalpha) in synovial tissue of patients with adult and juvenile onset SpA and its correlation with infiltration of inflammatory mediators into the synovia suggest a significant pathogenic role of this cytokine. Clinical trials of anti-TNFalpha antibody (infliximab) therapy in patients with adult onset SpA have demonstrated significant clinical improvement in inflammatory pain, function, disease activity, and quality of life in correlation with histological and immunohistochemical evidence of modulation of synovial inflammatory processes. These promising findings suggest that anti-TNFalpha therapy may confer similar benefits in patients with juvenile onset SpA.

High variability of HLA-B27 alleles in ankylosing spondylitis and related spondyloarthropathies in the population of northern Spain

The distribution of B27 alleles (B*2701-23) was characterized by PCR-SSP in ankylosing spondylitis and related spondyloarthropathies (SpA) in a sample of B27 positive patients from northern Spain. Six B27 alleles were identified: B*2705,02,03,07,08 and B*2713. B*2705 and 02 were the most common alleles in the SpA studied: ankylosing spondylitis (AS) (n = 89), reactive arthritis (ReA) (n = 11), psoriatic arthritis (PsA) (n = 29), and inflammatory bowel disease (IBD) (n = 21). B*2707 and B*2708 were found in PsA patients and B*2703 in one patient with IBD. B*2713 was identified in a healthy control family. B*2713 has not been reported to be represented in either ethnic group. Thus, this population shows higher levels of B27 diversity than other Caucasian groups.

Identification and sequencing of HLA-B*0714 and B*2718 alleles and novel exon 1 sequences of B*0709 and B*2714 alleles in potential bone marrow donors

Sequence specific oligonucleotide probe hybridization and sequence specific primer PCR typing of volunteer bone marrow donors suggested the presence of variants of known HLA-B alleles in two individuals. PCR products encompassing HLA-B locus exons 1, 2, and 3 were prepared, subcloned and sequenced. A Hispanic individual had a novel B*07 allele (B*0714) and a Chinese individual had a novel B*27 allele (B*2718). In two other individuals, a previously unknown sequence of exon 1 was determined for HLA-B*0709 (African American) and B*2714 (Native American). These findings further illustrate the substantial genetic variation present at the HLA-B locus within human populations. We discuss the structural variation in the protein sequence for these HLA-B alleles and its potential functional effects.

Treatment of active ankylosing spondylitis with infliximab: a randomised controlled multicentre trial

BACKGROUND Treatment options for patients with ankylosing spondylitis are few. We aimed to assess the effectiveness of infliximab, an antibody to tumour necrosis factor (TNF)-alpha, in treatment of such patients.

METHODS

In this 12-week placebo-controlled multicentre study, we randomly assigned 35 patients with active ankylosing spondylitis to intravenous infliximab (5 mg/kg) and 35 to placebo at weeks 0, 2, and 6. One patient in the infliximab group was withdrawn from the study. Our primary outcome was regression of disease activity of at least 50%. To assess response, we used validated clinical criteria from the ankylosing spondylitis assessment working group, including disease activity (BASDAI), functional indices (BASFI), metrology (BASMI), and quality of life (short form 36). Analyses were done by intention to treat.

FINDINGS

18 (53%) of 34 patients on infliximab had a regression of disease activity at week 12 of at least 50% compared with three (9%) of 35 on placebo (difference 44% [95% CI 23-61], p<0.0001). Function and quality of life also improved significantly on infliximab but not on placebo (p<0.0001 and p<0.0001, respectively). Treatment with infliximab was generally well tolerated, but three patients had to stop treatment because of systemic tuberculosis, allergic granulomatosis of the lung, or mild leucopenia.

INTERPRETATION

Our results show that treatment with infliximab is effective in patients with active ankylosing spondylitis. Since there are some potentially serious adverse effects, we recommend that this treatment mainly be used in co-operation with rheumatological centres.

HLA-B27 polymorphism

HLA-B27 is a serologic specificity that encompasses 25 different alleles that encode 23 different products (proteins): HLA-B*2701 to B*2723. These alleles are also called subtypes of HLA-B27, and they may have evolved from the most widespread subtype, B*2705. These subtypes are distinguished from changes mostly in exons 2 and 3, which encode the alpha 1 and alpha 2 domains of the B27 molecule, respectively. Occurrence of ankylosing spondylitis (AS) or related spondyloarthropathy (SpA) has thus far been documented in subjects possessing any one of the first ten (B*2701 to B*2710) subtypes studied. However, B*2706 in Southeast Asian and B*2709 in the Italian island population of Sardinia seem not to be associated with AS. The 13 most recent subtypes have not yet been studied for disease association. It is important to investigate which of them are and are not associated with AS and related SpA, and whether certain subtypes show any preferential association with some of the clinical features or forms of these diseases among the various ethnic/racial populations and geographic regions of the world. This is expected to provide clues as to the mechanism of disease association, and one of the strongest reasons to study the B27 subtypes is to learn the effects of the sequence variations on the peptide-binding specificity of the molecule. Among these peptides may be the putative arthritogenic peptide(s).

Identification of novel HLA-B27 ligands derived from polymorphic regions of its own or other class I molecules based on direct generation by 20 S proteasome

HLA-B27 is strongly associated with ankylosing spondylitis. Natural HLA-B27 ligands derived from polymorphic regions of its own or other class I HLA molecules might be involved in autoimmunity or provide diversity among HLA-B27-bound peptide repertoires from individuals. In particular, an 11-mer spanning HLA-B27 residues 169-179 is a natural HLA-B27 ligand with homology to proteins from Gram-negative bacteria. Proteasomal digestion of synthetic substrates demonstrated direct generation of the B27-(169-179) ligand. Cleavage after residue 181 generated a B27-(169-181) 13-mer that was subsequently found as a natural ligand of B*2705 and B*2704. Its binding to HLA-B27 subtypes in vivo correlated better than B27-(169-179) with association to spondyloarthropathy. Proteasomal cleavage generated also a peptide spanning B*2705 residues 150-158. This region is polymorphic among HLA-B27 subtypes and class I HLA antigens. The peptide was a natural B*2704 ligand. Since this subtype differs from B*2705 at residue 152, it was concluded that the ligand arose from HLA-B*3503, synthesized in the cells used as a source for B*2704-bound peptides. Thus, polymorphic HLA-B27 ligands derived from HLA-B27 or other class I molecules are directly produced by the 20 S proteasome in vitro, and this can be used for identification of such ligands in the constitutive HLA-B27-bound peptide pool.

HLA-B27 and genetic predisposing factors in spondyloarthropathies

With the mapping of the human genome having been completed, our ability to investigate and ideally better understand the genetic basis of rheumatic diseases is advancing at a rapid pace. Substantial evidence strongly favors a direct role for HLA-B27 in genetic susceptibility to ankylosing spondylitis and related spondyloarthropathies, although the underlying molecular basis has yet to be identified. HLA-B27 contributes only 16 to 50% of the total genetic risk for the disease, clearly indicating that other genes must be involved. However, no other putative disease genes have yet been absolutely proven. Potential genes include MHC (HLA class II, low molecular weight proteasome [LMP], transporter associated with antigen processing (TAP), tumor necrosis factor [TNF]-alpha, and major histocompatibility complex class I chain-related gene A (MICA), as well as non-MHC genes (IL-1RA, IL-6, IL-10, and CYP2D6). Genome-wide screens have identified other chromosomal areas of interest: 1p, 2q, 6p, 9q, 10q, 16q, and 19q. However, different studies have given conflicting results. HLA-B27 itself is a serologic specificity, which encompasses 25 different alleles that encode 23 different products (proteins): HLA-B*2701 to B*2723. These alleles may have evolved from the most widespread subtype, B*2705, and two of them, B*2706 in Southeast Asia and B*2709 in Sardinia, seem not to be associated with ankylosing spondylitis. The distinction between the disease associated and nonassociated subtypes may provide clues to the actual role of B27 in disease pathogenesis.

Spondyloarthropathies in eastern Asia

The association between HLA-B27 and the spondyloarthropathies (SpAs) is so strong that it is supposed that the HLA-B27 molecule plays a pathogenetic role. In whites and Indonesians, the frequency of HLA-B27 is about 10%; in Chinese it is about 8%; and in Japanese it is only about 1%. The prevalence of SpA in the Chinese is at least 0.2%, but in native Indonesians, Philippinos, and Malaysians, SpA is rarely seen. Twenty-three subtypes (B*2701-B*2723) have been distinguished. These subtypes are not equally distributed over the world. In most countries the distribution of the subtypes among HLA-B27 SpA patients is the same as that among the normal HLA-B27-positive population. In China, the subtype B*2704 is frequent and the prevalence of SpA is high. Native Indonesians, however, mostly have subtype B*2706, and SpA is rarely seen in this population. It was shown that B*2706, probably like B*2709 in Sardinia, is not associated with SpA. The difference between the SpA-associated and non-SpA-associated subtypes is limited to only two amino acid residues (114 and 116) at the bottom of the peptide-binding groove of HLA-B27. This small difference between health and disease rewards studies for different peptide-binding capacities and may help us characterize the peptides that are involved in the pathogenesis of SpA. The differences in disease associations in these countries also have clinical implications. In Southeast Asia, HLA-B27 typing without subtyping has less clinical usefulness than in parts of the world where B*2706 is rarely seen. When native Indonesians, Malaysians, or Philippinos are suspected of having ankylosing spondylitis or a related SpA, it is worth asking if they had white or Chinese ancestors. If native HLA-B27-positive Indonesians (with subtypes other than B*2706) develop SpA, the clinical features are not different from those in other parts of the world. In the Chinese population on the mainland and in Taiwan, juvenile SpA is frequently seen. The onset is often a peripheral arthritis or enthesitis.

Therapeutic advances in ankylosing spondylitis

Ankylosing spondylitis (AS) is a systemic inflammatory rheumatic disease involving spinal and sacroiliac joints. This condition is responsible for back pain, stiffness, but also loss of functional capacity with socio-economic consequences. The management of AS includes patient education, rest, a programme of regular physical exercise, together with the use of NSAIDs. Second-line treatments are required in cases of severe or refractory AS, however only sulfasalazine has proven to benefit AS patients with peripheral arthritis. In spite of this management, the disease may not be adequately controlled, mainly for patients with refractory axial disease, enthesopathy or extra-articular features. Thus, new innovative treatments are needed for AS. It is likely that the new NSAIDs or COX-2 specific inhibitors will certainly take the place of the conventional NSAIDs, with regard to their superior tolerability. Methotrexate is a therapeutic option for AS treatment, but its usefulness in this disease remains to be established in adequate controlled studies. Finally, the TNF-alpha targeting drugs, namely thalidomide and the anti-TNF-alpha mAb, infliximab, have given promising results in the treatment of severe and/or refractory AS patients, however further controlled studies are required. In addition, the long-term use (efficacy and tolerability) of these two agents deserves attention.