The detection of the HLA-B27 antigen by immunomagnetic separation and enzyme-linked immunosorbent assay-comparison with a flow cytometric procedure

Global prevalence of spondyloarthritis in low-income and middle-income countries: a systematic review and meta-analysis protocol

INTRODUCTION

In the past decade, the definition of spondyloarthritis (SpA) has undergone major modifications with respect to new diagnostic tools and classifications. With the advent of biotherapies, treatment possibilities in patients with SpA have substantially improved in the last few years. There is great interest in obtaining accurate data on the disease prevalence, especially in regions where data remains scarce such as low-income and middle-income countries (LMICs), in order to measure and understand the needs of their healthcare systems. Therefore, through a global systematic review and meta-analysis, the current study aims to investigate the prevalence of SpA and human leucocyte antigen B27 (HLAB27) and its association with the risk of SpA in the LMIC population.

METHODS AND ANALYSIS

We will include cohort, case-control and cross-sectional studies performed among adults (>15 years) living in LMICs. EMBASE, Medline, Global Index Medicus and Web of Knowledge will be searched for relevant records published until 30 April 2020, without any language restriction. The review will be reported according to the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. After screening of titles and abstracts, study selection, data extraction and risk of bias assessment by two independent reviewers, we shall assess the studies individually for clinical and statistical heterogeneity. Random-effect meta-analysis will be used to pool studies judged to be clinically homogeneous. Egger's test and visual inspection of funnel plots will be used to assess publication bias. Results will be presented by WHO subregions.

ETHICS AND DISSEMINATION

Since primary data is not collected in this study, ethical approval is not required. This review is expected to provide relevant data on the epidemiology of SpA, HLAB27 and their association in the global population of LMICs. The final report will be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42020163898.

rs657075 (CSF2) Is Associated with the Disease Phenotype (BAS-G) of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a systemic autoimmune disease mainly affecting the lumbar spine and sacroiliac joints, and exhibits peripheral inflammatory arthropathy. More than 25 loci have been identified as associated with AS. Because both AS and rheumatoid arthritis (RA) are autoimmune diseases that may share some common genetic factors, we therefore examined if the newly identified RA genetic polymorphisms were associated with AS in a Taiwanese population. In this study, we enrolled 475 AS patients and 11,301 healthy subjects from a Taiwanese biobank as controls. Although none of single-nucleotide polymorphisms (SNPs) were associated with the susceptibility to AS, the AS disease index Bath AS Global (BAS-G) clinical phenotype was observed as significantly correlated to the AA genotype of rs657075 (CSF2). The significance remains after gender/age/disease duration adjustment and after group categorization by human leukocyte antigen-B 27 (HLA-B27) genotype. We further investigated the possible functions of rs657075 through bioinformatics approaches. Results revealed that polymorphism of rs657075 is able to influence the expression of acyl-CoA synthetase long-chain family member 6 (ACSL6). In conclusion, our study indicated that rs657075 (CSF2) is strongly associated with the AS disease index Bath AS Global (BAS-G) clinical phenotype.

Cardiac Autonomic Function in Patients With Ankylosing Spondylitis: A Case-Control Study

Ankylosing spondylitis (AS) is a chronic inflammatory disease involing spine and enthesis. The primary aim of this study is to investigate the autonomic nervous system (ANS) function and the association between ANS and the functional status or disease activity in AS.The study included 42 AS patients, all fulfilling the modified New York criteria. All the patients are totally symptom free for ANS involvement and had normal neurological findings. These AS patients and 230 healthy volunteers receive analysis of 5 minutes heart rate variability (HRV) in lying posture. In addition, disease activity and functional status of these AS patients are assessed by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Bath Ankylosing Spondylitis Global Score (BAS-G).Both groups were age and sex-matched. Although the HRV analysis indicates that the peaks of total power (TP, 0-0.5 Hz) and high-frequency power (HF, 0.15-0.40 Hz) are similar in both groups, the activities of low-frequency power (LF, 0.04-0.15 Hz), LF in normalized units (LF%), and the ratio of LF to HF (LF/HF) in AS patients are obviously lower than healthy controls. The erythrocyte sedimentation rate and C-reactive protein revealed negative relationship with HF. The AS patients without peripheral joint disease have higher LF, TP, variance, LF%, and HF than the patients with peripheral joint disease. The AS patients without uvetis have higher HF than the patients with uvetis. The total scores of BASDI, BASFI, and BAS-G do not show any association to HRV parameters.AS patients have significantly abnormal cardiac autonomic regulation. This is closely related with some inflammatory activities. Reduced autonomic function may be one of the factors of high cardiovascular risk in AS patients.

Subclinical sacroiliitis in brucellosis. Clinical presentation and MRI findings

PURPOSE

The aim of this work was to detect subclinical sacroiliac joint involvement in patients with brucellosis and study their clinical and laboratory features.

PATIENTS AND METHODS

The study included 100 brucellosis patients being followed-up in the Gastroenterology and Hepatology Unit, Theodor Bilharz Research Institute and Cairo University outpatient clinics. A thorough history, physical examination, routine laboratory tests, and abdominal ultrasound were obtained for all patients. Extended rheumatological examination was performed including clinical testing for sacroiliitis and enthesitis. None of the patients reported a history of back pain or any symptoms suggestive of sacroiliitis during the course of the infection. Plain x-ray and MRI scan of the sacroiliac joints were performed for all patients.

RESULTS

Asymptomatic sacroiliitis was present in 24 % of the brucellosis patients; none of the patients had tenderness over their spine with preserved lumbar spine mobility. Sacroiliitis was mainly unilateral being bilateral in 20.83 %. There was an obvious relationship with animal contact and occupation of the patients. Osteoarticular involvement was common (67 %) including arthralgias, arthritis, myalgias, spondylitis, enthesitis and bursitis, being clearly higher in those with sacroiliitis. The MRI scan showed blurring of the margins in 66.67 %, widening in 25 %, narrowing in 54.17 %, erosions in 20.83 %, and sclerosis in 12.5 %.

CONCLUSION

Osteoarticular manifestations of brucellosis are prevalent and subclinical sacroiliitis is evident, a finding that may classify these patients as having brucellar spondyloarthropathy (BSA). Referring brucellosis patients for rheumatological assessment has the advantage of early assessment of asymptomatic cases with sacroiliitis which is commonly overlooked.

rs10865331 associated with susceptibility and disease severity of ankylosing spondylitis in a Taiwanese population

Ankylosing spondylitis (AS) is a highly familial rheumatic disorder and is considered as a chronic inflammatory disease. Genetic factors are involved in the pathogenesis of AS. To identify genes which render people susceptible to AS in a Taiwanese population, we selected six single-nucleotide polymorphisms (SNPs) from previous genome-wide association studies (GWASs) which were associated with AS in European descendants and Han Chinese. To assess whether the six SNPs contributed to AS susceptibility and severity in Taiwanese population, 475 AS patients fulfilling the modified New York Criteria and 527 healthy subjects were recruited. We found that rs10865331 was significantly associated with AS susceptibility and with Bath AS Function Index (BASFI). The AA and AG genotypes of rs10865331 were also significantly associated with a higher erythrocyte sedimentation rate. Our findings provided evidence that rs10865331 is associated AS susceptibility and with disease activity (BASFI) in a Taiwanese population.

Higher expression of whole blood microRNA-21 in patients with ankylosing spondylitis associated with programmed cell death 4 mRNA expression and collagen cross-linked C-telopeptide concentration

OBJECTIVE

Bone loss is a recognized feature of ankylosing spondylitis (AS). The binding of microRNA-21 (miR-21) to programmed cell death 4 (PDCD4) could inhibit the expression of PDCD4 and further induce the activation of osteoclasts. In the present study, we compared the difference in miR-21 expression between patients with AS and healthy controls, and evaluated the relationships of miR-21, PDCD4 mRNA, and bone erosion in patients with AS. The influences of nonsteroidal antiinflammatory drugs (NSAID) and disease-modifying antirheumatic drugs (DMARD) on the expressions of miR-21 and PDCD4 mRNA in patients with AS were also assessed.

METHODS

Whole blood miR-21 and PDCD4 mRNA expression were evaluated by quantitative real-time PCR among 122 patients with AS and 122 healthy controls. The serum level of collagen cross-linked C-telopeptide (CTX) was measured using ELISA.

RESULTS

When compared to controls, patients with AS had significantly higher levels of miR-21, PDCD4 mRNA, and CTX. MiR-21 expression was negatively correlated with PDCD4 mRNA expression in patients with AS who were taking neither NSAID nor DMARD. Interestingly, significantly positive correlations between miR-21 expression with PDCD4 mRNA expression (r = 0.33, p = 0.01) and CTX level (r = 0.44, p < 0.01) were observed in patients with AS who were taking sulfasalazine. Positive correlations of miR-21 and CTX level were also observed in AS patients with disease duration < 7.0 years (r = 0.36, p = 0.004) and active disease (r = 0.42, p = 0.001).

CONCLUSION

The expression of miR-21 might have a role in the development of AS.

Genetic polymorphisms of stromal interaction molecule 1 associated with the erythrocyte sedimentation rate and C-reactive protein in HLA-B27 positive ankylosing spondylitis patients

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. The development of ankylosing spondylitis is still unclear. Genetics factors such as human leukocyte antigen HLA-B27 and ERAP1 have been widely reported to associate to AS susceptibility. In this study, we enrolled 361 AS patients and selected four tagging single nucleotides polymorphisms (tSNPs) at STIM1 gene. The correlation between STIM1 genetic polymorphisms and AS activity index (BASDAI, BASFI, BAS-G) as well as laboratory parameters of inflammation (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)) were tested. Our results indicated that HLA-B27 positive AS patients who are carrying the minor allele homozygous G/G genotype of SNP rs3750996 significantly associated with a higher level of ESR in serum. Furthermore, rs3750996/rs3750994 pairwise allele analysis indicated that G-C haplotypes also significantly correlated with higher level of ESR as well as CRP. These findings provide a better understanding of STIM1 genetic contribution to the pathogenesis of AS.

Use of immunomagnetic reduction for C-reactive protein assay in clinical samples

BACKGROUND

Magnetic nanoparticles biofunctionalized with antibodies are able to recognize and bind to the corresponding antigens. In this work, anti-C-reactive protein (CRP) antibody was covalently conjugated onto the surface of magnetic nanoparticles to label CRP specifically in serum.

METHODS

The level of serum CRP was detected by immunomagnetic reduction (IMR) assay, which identifies the changes in the magnetic signal representing the level of interaction between antibody-conjugated magnetic nanoparticles and CRP proteins. To investigate the feasibility of IMR for clinical application, pure CRP solutions and 40 human serum samples were tested for IMR detection of CRP to characterize sensitivity, specificity, and interference.

RESULTS

In comparison with the immunoturbidimetry assay, the results of the IMR assay indicated higher sensitivity and had a high correlation with those of the current immunoturbidimetry assay.

CONCLUSION

We have developed a novel and promising way to assay CRP in human serum using immunomagnetic reduction in clinical diagnosis.

Association of IL-12B genetic polymorphism with the susceptibility and disease severity of ankylosing spondylitis

OBJECTIVE

Interleukin 23 (IL-23) stimulates the differentiation of T helper 17 (Th17) cells, which are involved in the pathogenesis of ankylosing spondylitis (AS). Binding of IL-23 to the IL-23 receptor complex activates Janus kinases 2 and tyrosine kinase 2, which phosphorylate IL-23R and subsequently promote the transcription of the IL-17 gene. IL-12B encodes a p40 subunit common to IL-12 and IL-23. We evaluated the effects of IL-12B and IL-23R genotype on the occurrence and clinical features of AS.

METHODS

A total of 362 patients with AS and 362 healthy controls were enrolled in the study. Genotypes of IL-12B A1188C (rs3212227) and IL-23R C2370A (rs10889677) were identified by polymerase chain reaction/restriction fragment-length polymorphism. Disease activity and functional status were assessed by Bath AS indices.

RESULTS

Subjects carrying IL-12B CC [matched relative risk (RR(m)) 1.93, 95% CI 1.23-3.03] and IL-12B AC (RR(m) 1.73, 95% CI 1.21-2.46) genotypes had a significantly greater risk of developing AS than subjects with the IL-12B AA genotype. Subjects carrying both IL-12B CC and IL-23R AA genotypes also had a significantly higher risk (RR(m) 2.98, 95% CI 1.51-5.89) of developing AS compared to those with IL-12B AA and IL-23R CC/CA genotypes, and this interaction between IL-12B and IL-23R was significant. Patients with AS who had IL-12B CC and IL-12B AC genotypes had an obviously increased Bath Ankylosing Spondylitis Disease Activity Index score compared to those who carried the IL-12B AA genotype (4.3 vs 3.7).

CONCLUSION

The IL-12B A1188C genotype was associated with the development and disease severity of AS.

Association of ORAI1 haplotypes with the risk of HLA-B27 positive ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammation of the sacroiliac joints, spine and peripheral joints. The aetiology of ankylosing spondylitis is still unclear. Previous studies have indicated that genetics factors such as human leukocyte antigen HLA-B27 associates to AS susceptibility. We carried out a case-control study to determine whether the genetic polymorphisms of ORAI1 gene, a major component of store-operated calcium channels that involved the regulation of immune system, is a susceptibility factor to AS in a Taiwanese population. We enrolled 361 AS patients fulfilled the modified New York criteria and 379 controls from community. Five tagging single nucleotides polymorphisms (tSNPs) at ORAI1 were selected from the data of Han Chinese population in HapMap project. Clinical statuses of AS were assessed by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), and Bath Ankylosing Spondylitis Global Index (BAS-G). Our results indicated that subjects carrying the minor allele homozygote (CC) of the promoter SNP rs12313273 or TT homozygote of the SNP rs7135617 had an increased risk of HLA-B27 positive AS. The minor allele C of 3′UTR SNP rs712853 exerted a protective effect to HLA-B27 positive AS. Furthermore, the rs12313273/rs7135617 pairwise allele analysis found that C-G (OR 1.69, 95% CI 1.27, 2.25; p = 0.0003) and T-T (OR 1.75, 95% CI 1.36, 2.27; p<0.0001) haplotypes had a significantly association with the risk of HLA-B27-positive AS in comparison with the T-G carriers. This is the first study that indicate haplotypes of ORAI1 (rs12313273 and rs7135617) are associated with the risk of HLA-B27 positive AS.

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.

Long-term stabilized blood samples as controls for flow cytometric HLA-B27 screening: a feasibility study

BACKGROUND

Long-term stabilized blood samples are potentially useful as positive or negative procedure controls for flow cytometric HLA-B27 screening, and could serve as test samples in an external quality assessment (EQA) scheme. We evaluated long-term stabilized whole blood specimens as prepared for the UK NEQAS for Leucocyte Immunophenotyping EQA scheme (Sheffield, UK).

METHODS

Peripheral blood samples were obtained from nine blood bank donors with known HLA-B typing. Short-term stabilization with Trans-FIXtrade mark was performed before shipment to Sheffield. Thereafter, long-term stabilization was performed. Commercially available HLA-B27 mAb were tested periodically between 1 week and 12 months on (i) fresh, (ii) short-term stabilized, and (iii) long-term stabilized blood samples using a stain, lyse, and wash technique. We compared the forward scatter (FSC), sideward scatter (SSC), and fluorescence signals of lymphocytes as a function of time. Furthermore, a pilot send-out with stabilized blood samples of four blood bank donors was distributed among the participants to the Benelux EQA scheme for HLA-B27 screening, and results were compared with historical EQA data obtained using nonstabilized blood samples from the same donors.

RESULTS

There were no major effects on FSC and SSC characteristics of lymphocytes. Background fluorescence of stabilized samples increased and specific fluorescence of stabilized HLA-B27 positive samples decreased as compared with fresh samples. However, discrimination between the investigated HLA-B27 positive and HLA-B27 negative samples remained feasible poststabilization. In the pilot send-out, the results obtained with stabilized samples were less concordant than with the corresponding fresh samples due to variable quality of the stabilized samples.

CONCLUSION

Long-term stabilized whole blood samples are potentially useful as true HLA-B27 positive and true HLA-B27 negative control cells for daily and longitudinal quality control of flow cytometric HLA-B27 screening. In the same way, long-term stabilized samples may be used for EQA purposes. However, these samples are currently not feasible for reagent validation purposes. Extensive quality control of long-term stabilized samples is necessary before distribution in multicenter surveys.

Usefulness of human leucocyte antigen-B27 subtypes in predicting ankylosing spondylitis: Taiwan experience

BACKGROUND

Genetic factors are clearly attributed to the susceptibility of ankylosing spondylitis (AS). The human leucocyte antigen (HLA)-B27 proved to be the very useful marker for diagnosing AS. The aim of this study was to determine the prevalence of HLA-B27 subtypes in Taiwan and to investigate whether these subtypes may be of help in predicting the diagnosis of AS.

METHODS

A total of 314 patients with AS and a control group of 71 subjects positive for HLA-B27 detected by flow cytometry analysis were recruited for the study. HLA-B27 subtypes were confirmed by the polymerase chain reaction-sequence-specific primers and sequence-specific oligonucleotide probing.

RESULTS

Four B27 alleles were identified: B*2704, B*2705, B*2706 and B*2707. HLA-B*2704 was the predominant allele. There were significant differences in the distribution of HLA-B27 subtypes between patients with AS and controls. Five of them who were homozygous for the B*2704 allele were solely found in AS group but not in controls. Statistical analysis showed that B*2704 was positively associated with AS, which suggested an increased possibility of having AS. Other HLA-B27 subtypes showed no strong correlation with AS.

CONCLUSION

In the Taiwanese population, susceptibility to AS was determined by the presence of HLA-B*2704. Although B*2706 was reported to have a negative association with AS in Taiwanese, Thai and Chinese Singaporean populations, we report, in our study, two AS patients with B*2706 (0.6%). Disease heterogeneity suggests that other than genetic background, many pathogenic factors could be associated with AS. This may need to be investigated with a larger group of patients with AS and controls.

Replication of association of IL1 gene complex members with ankylosing spondylitis in Taiwanese Chinese

OBJECTIVE

To test the association of interleukin 1 (IL1) gene family members with ankylosing spondylitis (AS), previously reported in Europid subjects, in an ethnically remote population.

METHODS

200 Taiwanese Chinese AS patients and 200 ethnically matched healthy controls were genotyped for five single nucleotide polymorphisms (SNPs) and the IL1RN.VNTR, markers previously associated with AS. Allele, genotype, and haplotype frequencies were compared between cases and controls.

RESULTS

Association of alleles and genotypes of the markers IL1F10.3, IL1RN.4, and IL1RN.VNTR was observed with AS (p<0.05). Haplotypes of pairs of these markers and of the markers IL1RN.6/1 and IL1RN.6/2 were also significantly associated with AS. The strongest associations observed were with the marker IL1RN.4, and with the two-marker haplotype IL1RN.4-IL1RN.VNTR (both p = 0.004). Strong linkage disequilibrium was observed between all marker pairs except those involving IL1B-511 (D' 0.4 to 0.9, p<0.01).

CONCLUSIONS

The IL1 gene cluster is associated with AS in Taiwanese Chinese. This finding provides strong statistical support that the previously observed association of this gene cluster with AS is a true positive finding. These authors contributed equally to the study.

Flow cytometric HLA-B27 screening: cross-reactivity patterns of commercially available anti-HLA-B27 monoclonal antibodies with other HLA-B antigens

BACKGROUND

Some 50 clinical laboratories in the Benelux perform flow cytometric HLA-B27 screening and participate in the Benelux external quality assessment scheme operational since 1995. Results from this scheme indicate that cross-reactivity of HLA-B27 monoclonal antibodies (mAbs) is a major problem.

METHODS

We analyzed cross-reactivity patterns of commercially available mAbs for HLA-B27 screening. Three clones of HLA-B27 mAb (ABC-m3, n = 3; FD705; and GS145.2) from five manufacturers were evaluated. Test cells were selected as to express HLA-B antigens with known serologic cross-reactions (HLA-B7, B12, B13, B16, B17, B22, B37, B40, B41, B42, B47, and B48). Cells without B27 cross-reactive antigens (B5, B8, B14, B15, B21, and B35) and cells positive for B27 were included as controls. All tests were performed and interpreted as recommended by the manufacturers. Cross-reactivity was defined as increased fluorescence intensity in comparison with the baseline reactivity observed with the corresponding immunoglobulin G isotype control mAb.

RESULTS AND CONCLUSIONS

All mAbs tested showed cross-reactivity, ranging from weak (+/-) to strong (+), with different antigens and different degrees of intensity-ABC-m3: (+/-) B12, B16, B17, B41, B47, and B48 and (+) B7, B13, B22, B37, B40, and B42; GS145.2: (+/-) B13, B17, B22, B40, and B47 and (+) B7, B16, B37, B42, and B48; FD705: (+/-) B12, B13, B16, and B48 and (+) B17, B37, and B47. If one mAb had been used for HLA-B27 screening, ABC-m3 would have yielded nine false-positive B27 assignments, FD705 would have yielded seven, and GS145.2 would have yielded two. This problem largely canbe avoided by the combined use of two different mAb clones. The combination of FD705 and GS145.2 yielded the best results, with one false-positive HLA-B27 assignment among the 99 HLA-B27(-) samples of this highly selected panel.