Association of human leukocyte antigen DRB1 with anti-cyclic citrullinated peptide autoantibodies in Saudi patients with rheumatoid arthritis

Association of Hematological and Biochemical Parameters and HLA-DRB1 Alleles With Anti-cyclic Citrullinated Peptide Autoantibodies in Sudanese Rheumatic Patients

Introduction Anti-citrullinated protein/peptide antibodies (ACPA) are crucial for the diagnosis and prognosis of rheumatoid arthritis (RA) and are associated with class II HLA-DRB1 alleles. The study's goal was to determine how DRB1 alleles and hematological and biochemical parameters affect ACPA production in RA patients from Sudan. Methods The study analyzed the hematological and biochemical parameters and the frequency of HLA-DRB1 alleles in 120 RA patients and 100 controls. Automated analyzers, ELISA, the latex agglutination test, and the Westergren method were utilized for hematological and biochemical testing. HLA class II alleles were genotyped using polymerase chain reaction-sequence-specific primers (PCR-SSP). The student's t-test and the chi-square (Χ2) test were employed to identify significant alterations between the examined parameters and allele frequencies. Results A total of 51.7% of 120 RA patients tested positive for ACPA (ACPA+). Among those patients, the DRB1*04 and *10 alleles were significantly more prevalent (22.2% vs. 8.9%, P = 0.048 and 23.8% vs. 8.9%, P = 0.030, respectively). RA patients had significantly higher counts of platelet count test (PLT; P = 0.011), lymphocytes (LY; P = 0.000), neutrophils (NE; P = 0.025), monocytes (MO; P = 0.000), eosinophils (EO; P = 0.000), neutrophil-to-lymphocyte ratio (NLR; P = 0.006), C-reactive protein (CRP; P = 0.000), and erythrocyte sedimentation rate (ESR; P = 0.000) than controls. Patients also showed low counts of red blood cells (RBC; P = 0.003), hemoglobin (Hb; P = 0.024), mean platelet volume (MPV; P = 0.000), and basophils (BA; P = 0.048). ACPA+ RA patients had elevated white blood cells (WBC; P = 0.046), PLT (P = 0.029), and low mean corpuscular hemoglobin concentration (MCHC; P = 0.022). The hematological and biochemical parameters of ACPA+ RA patients with the DRB1*04 or *10 alleles did not differ significantly. Conclusions We found significant differences in hematological and biochemical parameters between RA patients and controls that had nothing to do with ACPA positivity or the frequency of DRB1*04 or *10 alleles.

The Association of Human Leukocyte Antigen Genotyping Among Sudanese Patients With Rheumatoid Arthritis: Reference to Ethnicity

INTRODUCTION

 Human leukocyte antigens (HLA) account for up to one-half of the total genetic contribution to rheumatoid arthritis (RA) risk. The study investigated the association of HLA class II genotyping with RA susceptibility in Sudanese ethnic groups.

METHODS

 The DRB1 and DQB1 alleles and haplotypes were determined in 122 RA patients (i.e., Gaalia = 54, Johayna = 24, Baggara = 17, Nile Nubian = 12, and others = 15) and 120 healthy controls of ethnic groups (i.e., Gaalia = 44, Johayna = 11, Baggara = 15, Nile Nubian = 9, and others = 21) using a polymerase chain reaction with sequence-specific primers method.

RESULTS

Susceptibility to RA was associated with a high frequency of DRB1*04 (P = 0.04), DRB1*10 (P = 0.04), and DQB1*03 (P = 2.2 x 10-8/Pc = 6.6 x 10-8) between study ethnic groups, while protective effects were shown with DRB1*07 (P = 0.01), DQB1*02 (P = 0.02), and DQB1*06 (P = 2.2 x 10-6/Pc = 6.6 x 10-6), with an inconsistent frequency between study ethnic groups. The HLA haplotypes that were high in frequency among RA ethnic groups and showed susceptibility associations were DRB1*03-DQB1*03, DRB1*04-DQB1*03, DRB1*08-DQB1*03, DRB1*13-DQB1*02, and DRB1*13-DQB1*03 (P = 0.00003/Pc = 0.0003, P = 0.0001/Pc = 0.0001, P = 0.03, P = 0.004/Pc = 0.03, and P = 3.79x10-8/Pc = 3.3x10-9, respectively). On the contrary, DRB1*03-DQB1*02, DRB1*07-DQB1*02, and DRB1*13-DQB1*06 were lower in frequency in the ethnic groups with RA and may confer protection (P = 0.004/Pc = 0.032, P = 0.002/Pc = 0.02, and P = 0.01, respectively).

CONCLUSIONS

Our findings indicate an association between HLA-DRB1 and DQB1 genotypes and the susceptibility to RA in the Sudanese population, with a moderate frequency between our ethnic groups.

Association of Human Leukocyte Antigen (HLA) class II (DRB1 and DQB1) alleles and haplotypes with Rheumatoid Arthritis in Sudanese patients

The aim of this study was to determine the Human Leukocyte Antigen (HLA) class II (DRB1 and DQB1) alleles and haplotype frequency in Rheumatoid Arthritis (RA) in the Sudanese population. The frequency of HLA-DRB1 and -DQB1 alleles and DRB1-DQB1 haplotypes were determined in 122 RA patients and 100 controls. HLA alleles were genotyped by the polymerase chain reaction-sequence specific primers (PCR-SSP) method. In RA patients, HLA-DRB1*04 and *10 alleles were high in frequency (9.6% vs 14.2%, P = 0.038 and P = 0.042, respectively), and dependently on anti-citrullinated protein antibodies (ACPAs) seropositivity (P = 0.044 and P = 0.027, respectively). In contrast, the frequency of the HLA-DRB1*07 allele was significantly low in patients than in controls (11.7% vs 5.0%, P = 0.010). Moreover, the HLA-DQB1*03 allele was strongly associated with RA risk (42.2%, P = 2.2x10^-8), whereas, HLA-DQB1*02 and *06 showed protective effects against RA (23.1% and 42.2%, P = 0.024 and P = 2.2x10^-6, respectively). Five different HLA haplotypes, DRB1*03-DQB1*03 (P = 0.00003), DRB1*04-DQB1*03 (P = 0.00014), DRB1*08-DQB1*03 (P = 0.027), DRB1*13-DQB1*02 (P = 0.004), and DRB1*13-DQB1*03 (P = 3.79x10^-8) were significantly associated with RA risk, while 3 protective haplotypes, DRB1*03-DQB1*02 (P_c = 0.008), DRB1*07-DQB1*02 (P_c = 0.004), and DRB1*13-DQB1*06 (P_c = 0.02) were identified. This is the first study determining the association between HLA class II alleles and haplotypes and RA risk in our population.

The spectrum of association in HLA region with rheumatoid arthritis in a diverse Asian population: evidence from the MyEIRA case-control study

BACKGROUND

Fine-mapping of human leukocyte antigen (HLA) region for rheumatoid arthritis (RA) risk factors has identified several HLA alleles and its corresponding amino acid residues as independent signals (i.e., HLA-A, HLA-B, HLA-DPB1, and HLA-DQA1 genes), in addition to the well-established genetic factor in HLA-DRB1 gene. However, this was mainly performed in the Caucasian and East Asian populations, and data from different Asian regions is less represented. We aimed to evaluate whether there are independent RA risk variants in both anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative RA patients from the multi-ethnic Malaysian population, using the fine-mapping of HLA region strategy.

METHODS

We imputed the classical HLA alleles, amino acids, and haplotypes using the Immunochip genotyping data of 1260 RA cases (i.e., 530 Malays, 259 Chinese, 412 Indians, and 59 mixed ethnicities) and 1571 controls (i.e., 981 Malays, 205 Chinese, 297 Indians, and 87 mixed ethnicities) from the Malaysian Epidemiological Investigation of Rheumatoid Arthritis (MyEIRA) population-based case-control study. Stepwise logistic regression was performed to identify the independent genetic risk factors for RA within the HLA region.

RESULTS

We confirmed that the HLA-DRB1 amino acid at position 11 with valine residue conferred the strongest risk effect for ACPA-positive RA (OR = 4.26, 95% CI = 3.30-5.49, P_GWAS = 7.22 × 10^-29) in the Malays. Our study also revealed that HLA-DRB1 amino acid at position 96 with histidine residue was negatively associated with the risk of developing ACPA-positive RA in the Indians (OR = 0.48, 95% CI = 0.37-0.62, P_GWAS = 2.58 × 10^-08). Interestingly, we observed that HLA-DQB1*03:02 allele was inversely related to the risk of developing ACPA-positive RA in the Malays (OR = 0.17, 95% CI = 0.09-0.30, P_GWAS = 1.60 × 10^-09). No association was observed between the HLA variants and risk of developing ACPA-negative RA in any of the three major ethnic groups in Malaysia.

CONCLUSIONS

Our results demonstrate that the RA-associated genetic factors in the multi-ethnic Malaysian population are similar to those in the Caucasian population, despite significant differences in the genetic architecture of HLA region across populations. A novel and distinct independent association between the HLA-DQB1*03:02 allele and ACPA-positive RA was observed in the Malays. In common with the Caucasian population, there is little risk from HLA region for ACPA-negative RA.

Association of anti-cyclic citrullinated peptide antibodies and rheumatoid factor isotypes with HLA-DRB1 shared epitope alleles in Egyptian rheumatoid arthritis patients

INTRODUCTION

The most common genetic risk factor for rheumatoid arthritis (RA) is human leucocyte antigen DRB1 (HLA-DRB1) shared epitope (SE).

AIM

To investigate the relationship between anti-cyclic citrullinated peptide (anti-CCP), rheumatoid factor (RF), immunoglobulin (Ig)G, IgM and IgA and HLA-DRB1 SE among Egyptian patients with RA.

METHODS

Serum levels of anti-CCP antibodies and RFIgG, RFIgM, RFIgA were assayed using enzyme-linked immunosorbent assay for 157 Egyptian RA patients and 150 healthy controls attending the outpatient clinics of National Research Center and Kasr El Aini Hospital. HLA-DRB1 genotyping was performed by the DynalAllSetTM polymerase chain reaction (PCR) single specific primer low-resolution typing kits. Amplified PCR product was checked using 3% agarose gel.

RESULTS

HLA-DRB1-SE was found among 129 (82.2%) RA patients and 67 (44.7%) controls (odds ratio [OR] 5.7, CI 3.4-9.6, P < .0001). The risk of RA development was higher with the presence of SE two alleles (OR 11.6, P < .0001), while the OR for 1 copy SE allele was 4.4 (P < .0001). HLA-DRB1-SE was significantly associated with positive as well as negative anti-CCP and RF isotypes. The stronger association was with anti-CCP positivity with OR 11 (5.1-23.6), P < .0001. Furthermore, the risk of development of positive anti-CCP and RF isotypes was higher with the presence of 2 copies of SE alleles than with 1 copy.

CONCLUSION

The prevalence of HLA-DRB1-SE is high in Egyptian RA patients. The role of SE in RA patients is most probably related to the development of anti-CCP positive RA rather than the development of anti-CCP positivity.

An Overview of the Intrinsic Role of Citrullination in Autoimmune Disorders

A protein undergoes many types of posttranslation modification. Citrullination is one of these modifications, where an arginine amino acid is converted to a citrulline amino acid. This process depends on catalytic enzymes such as peptidylarginine deiminase enzymes (PADs). This modification leads to a charge shift, which affects the protein structure, protein-protein interactions, and hydrogen bond formation, and it may cause protein denaturation. The irreversible citrullination reaction is not limited to a specific protein, cell, or tissue. It can target a wide range of proteins in the cell membrane, cytoplasm, nucleus, and mitochondria. Citrullination is a normal reaction during cell death. Apoptosis is normally accompanied with a clearance process via scavenger cells. A defect in the clearance system either in terms of efficiency or capacity may occur due to massive cell death, which may result in the accumulation and leakage of PAD enzymes and the citrullinated peptide from the necrotized cell which could be recognized by the immune system, where the immunological tolerance will be avoided and the autoimmune disorders will be subsequently triggered. The induction of autoimmune responses, autoantibody production, and cytokines involved in the major autoimmune diseases will be discussed.