Anti-histone and anti-nucleosome rather than anti-dsDNA antibodies associate with IFN-induced biomarkers in Sudanese and Swedish Systemic Lupus Erythematosus patients.

OBJECTIVES: In SLE, anti-dsDNA can co-occur with autoantibodies against other chromatin components, like histones and nucleosomes. These antibodies induce type-1 interferon production, a hallmark of SLE. We measured antinuclear antibody (ANA) sub-specificities and investigated their associations to inflammatory biomarkers including interferon-regulated chemokines. METHODS: We included 93 Sudanese and 480 Swedish SLE patients and matched controls (N = 104 + 192). Autoantibodies targeting ANA-subspecificites: dsDNA, Sm, Sm/U1RNPcomplex, U1RNP, SSA/Ro52, SSA/Ro60, SSB/La, ribosomal P, PCNA and histones were quantified in all subjects, anti-nucleosome only in the Swedish patients, with a bead-based multiplex immunoassay. Levels of 72 plasma biomarkers were determined with Proximity Extension Assay technique or ELISA. RESULTS: Among Sudanese patients, the investigated antibodies significantly associated with 9/72 biomarkers. Anti-histone antibodies showed the strongest positive correlations with MCP-3 and S100A12 as well as with interferon I-inducible factors MCP-1 and CXCL10. Anti-dsDNA antibodies associated with CXCL10 and S100A12, but in multivariate analyses, unlike anti-histone, associations lost significance.Among Swedish patients, MCP-1, CXCL10, SA100A12 also demonstrated stronger associations to anti-histone and anti-nucleosome antibodies, compared with anti-dsDNA and other ANA sub-specificities. In multiple regression models, anti-histone/nucleosome retained the strongest associations. When excluding anti-histone or anti-nucleosome positive patients, the associations between MCP-1/CXCL10 and anti-dsDNA were lost. In contrast, when excluding anti-dsDNA positive patients, associations with anti-histone and anti-nucleosome remained significant. CONCLUSION: In two cohorts of different ethnical origin, autoantibodies targeting chromatin correlate stronger with IFN-induced inflammatory biomarkers than anti-dsDNA or other ANA sub-specificities. Our results suggest that anti-histone/nucleosome autoantibodies may be main drivers of type-1 interferon activity in SLE.

Associations with thrombosis are stronger for antiphosphatidylserine/prothrombin antibodies than for the Sydney criteria antiphospholipid antibody tests in SLE.

OBJECTIVES: Antiphosphatidylserine/prothrombin complex antibodies (aPS/PT) are risk factors for thrombosis, yet further validation of their clinical relevance in different ethnic groups is required. We investigated the performance of aPS/PT of IgA/G/M isotypes among Sudanese and Swedish systemic lupus erythematosus (SLE) patients. METHODS: Consecutive SLE patients/matched controls from Sudan (n = 91/102) and Sweden (n = 332/163) were included. All patients fulfilled the 1982 ACR SLE classification criteria. IgA/G/M of aPS/PT, anti-cardiolipin and anti-ß2glycoprotein I (anti-ß2GPI) were tested in both cohorts, and lupus anticoagulant (LA) also in the Swedish cohort. Clinical antiphospholipid syndrome-related events and atherosclerosis, measured as carotid plaques were assessed for associations. Univariate and multivariate analyses adjusting for cardiovascular risk factors were performed. RESULTS: Sudanese SLE patients had higher levels of IgM aPS/PT, but using national cut-offs, the frequency of positivity was similar to Swedish patients for all isotypes. Among Swedish patients, all isotypes of aPS/PT associated with venous thromboembolism (VTE), while only IgA aPS/PT associated with arterial thrombosis (AT). aPS/PT antibodies associated strongly with LA and they were, independently, the best predictor for VTE. Double positivity for aPS/PT and anti-ß2GPI associated with higher VTE risk than the conventional triple positivity. Carotid plaques did not associate with any antiphospholipid antibody. CONCLUSIONS: IgA aPS/PT associated with AT, and the association of IgG/M aPS/PT with VTE outperforms LA and criteria antiphospholipid antibodies in Swedish SLE patients. Furthermore, double positivity for aPS/PT and anti-ß2GPI performed better than conventional triple positivity. Future studies need to address if aPS/PT can replace LA, as this would simplify clinical procedures.

Accumulation of antinuclear associated antibodies in circulating immune complexes is more prominent in SLE patients from Sudan than Sweden.

The role of anti-nuclear autoantibody (ANA) specificities in immune complexes (IC) formation has been studied to a limited extent in SLE, and not at all in African SLE patients. We compared ANA in IC from Sudanese and Swedish SLE patients. We included 93 Sudanese and 332 Swedish SLE patients fulfilling the 1982 ACR criteria. IC were captured using C1q-coated beads. ANA specificities were quantified in sera and IC. Results were related to modified SLEDAI. Whereas serum levels of anti-Sm, anti-dsDNA and anti-ribosomal P were higher in Swedish patients, IC levels of most ANA specificities were higher among Sudanese patients. This difference was especially prominent for anti-chromatin antibodies, which remained after adjustment for age, disease duration and treatment. Total levels of C1q-binding IC correlated with levels of specific ANA in IC, with highest correlations for anti-chromatin antibodies among Sudanese patients. Whereas occurrence of anti- SSA/Ro60, anti-histone and anti-U1RNP in both serum and IC associated with high SLEDAI score, anti-dsDNA in IC but not in serum associated with high SLEDAI. ANA, especially antibodies targeting chromatin, accumulate more in IC from Sudanese SLE patients. If the autoantibody fraction forming IC is pathogenically important, this might explain the generally described severe SLE in black populations.

High IgA antiphospholipid autoantibodies in healthy Sudanese explain the increased prevalence among Sudanese compared to Swedish systemic lupus erythematosus patients.

OBJECTIVES: IgA antiphospholipid antibodies (aPL) are prevalent in systemic lupus erythematosus (SLE) patients of African American, Afro-Caribbean and South African origin. Nevertheless, data from North Africa are lacking, and most studies use manufacturer-suggested cut-offs based on Caucasian controls. Therefore, we compared aPL isotypes in Sudanese and Swedish SLE patients using nation-based cut-offs. METHODS: Consecutive SLE patients and age- and sex-matched controls from Sudan (N = 115/106) and Sweden (N = 340/318) were included. All patients fulfilled the 1982 American College of Rheumatology SLE classification criteria. Antiphospholipid syndrome-related events were obtained from patients' records. IgA/G/M anticardiolipin and anti-ß2 glycoprotein I (ß2GPI) were analysed with two independent assays. IgA anti-ß2GPI domain 1 (D1) was also investigated. Manufacturers' cut-offs and the 95th and 99th percentile cut-offs based on national controls were used. RESULTS: Sudanese patients and controls had higher levels and were more often positive for IgA aPL than Swedes when using manufacturers' cut-offs. In contrast, using national cut-offs, the increase in IgA aPL among Sudanese patients was lost. Occurrence of IgA anti-D1 did not differ between the countries. Venous thromboses were less common among Sudanese patients and did not associate with aPL. No clinical associations were observed with IgA anti-ß2GPI in Sudanese patients. Thromboses in Swedes were associated with IgG/M aPL. Fetal loss was associated with aPL in both cohorts. CONCLUSIONS: IgA anti-ß2GPI prevalence was higher among Sudanese compared to Swedish patients when manufacturers' cut-offs were used. This situation was reversed when applying national cut-offs. Anti-D1 was not increased in Sudanese patients. Previous studies on populations of African origin, which demonstrate a high prevalence of IgA aPL positivity, should be re-evaluated using a similar cut-off approach.

Sudanese and Swedish patients with systemic lupus erythematosus: immunological and clinical comparisons.

OBJECTIVE: SLE is known to have an aggressive phenotype in black populations, but data from African cohorts are largely lacking. We therefore compared immunological and clinical profiles between Sudanese and Swedish patients using similar tools. METHODS: Consecutive SLE patients from Sudan (n = 115) and Sweden (n = 340) and from 106 Sudanese and 318 Swedish age- and sex-matched controls were included. All patients fulfilled the 1982 ACR classification criteria for SLE. Ten ANA-associated specificities and C1q-binding immune complexes (CICs) were measured. Cut-offs were established based on Sudanese and Swedish controls, respectively. Disease activity was measured with a modified SLEDAI and organ damage with the SLICC Damage Index. In a nested case-control design, Swedish and Sudanese patients were matched for age and disease duration. RESULTS: Females constituted 95.6% and 88.1% of Sudanese and Swedish patients, respectively (P = 0.02), with younger age at inclusion (33 vs 47.7 years; P < 0.0001) and shorter disease duration (5 vs 14 years; P < 0.0001) among Sudanese patients. Anti-Sm antibodies were more frequent in Sudanese patients, whereas anti-dsDNA, anti-histone and CICs were higher in Swedish patients. In the matched analyses, there was a trend for higher SLEDAI among Swedes. However, Sudanese patients had more damage, solely attributed to high frequencies of cranial/peripheral neuropathy and diabetes. CONCLUSION: While anti-Sm is more common in Sudan than in Sweden, the opposite is found for anti-dsDNA. Sudanese patients had higher damage scores, mainly because of neuropathy and diabetes. Sudanese patients were younger, with a shorter SLE duration, possibly indicating a more severe disease course with impact on survival rates.

Occurrence of anti-CCP2 and RF isotypes and their relation to age and disease severity among Sudanese patients with rheumatoid arthritis.

OBJECTIVE: Anti-cyclic citrullinated peptide 2 antibodies (anti-CCP2) and rheumatoid factor (RF) in rheumatoid arthritis (RA) has been extensively assessed in industrialized countries. We investigated the diagnostic and prognostic impact of anti-CCP2 and RF isotypes in a Sudanese cross-sectional RA cohort. METHODS: Consecutive RA patients (n = 281) diagnosed according to the 1987 ACR criteria were included 2008-2010. Anti-CCP2 and RF isotypes (IgA, IgM, and IgG) were measured by enzyme immunoassay in 262 patients, with reference intervals aligned to the same diagnostic specificity as for anti-CCP2 (97.6%) using national controls. RESULTS: IgA RF was the predominant RA-associated autoantibody (56%), followed by IgM RF and anti-CCP2 (both 52%) and IgG RF (49%). In receiver operator characteristic analysis, IgA RF also showed the largest area under the curve. Patients with IgG RF were younger and had 8 years lower median age of disease onset compared to antibody negative patients (p < 0.0001). IgG RF was the only marker associated with a high number of involved joints (p = 0.028), and together with anti-CCP2 were the strongest markers for finger deformities (p = 0.016 and p = 0.012), respectively. No statistical differences were found for disease duration, ESR and Hb levels, and occurrence of erosions/osteopenia for any of the investigated autoantibodies. CONCLUSION: Whereas IgA RF showed the best diagnostic performance, IgG RF associated with low age of RA onset, high number of involved joints, and finger deformities. These findings indicate that RA-associated antibodies other than conventional IgM RF and anti-CCP2 might be informative in non-Caucasian RA populations.

Active Rheumatoid Arthritis in Central Africa: A Comparative Study Between Sudan and Sweden.

OBJECTIVE: To compare clinical characteristics and treatment between simultaneously investigated Sudanese and Swedish outpatients with rheumatoid arthritis (RA). METHODS: Outpatients with RA from Sudan (n = 281) and Sweden (n = 542) diagnosed according to the 1987 American College of Rheumatology criteria were recruited between December 2008 and September 2010 and compared concerning clinical presentation, treatment, and laboratory findings, including immunoglobulin M with rheumatoid factor (IgM-RF). RESULTS: Sudanese patients had lower inclusion age (median 49 vs 68 yrs), disease duration (48 vs 107 mos), and disease onset age (43 vs 56 yrs) as compared with Swedish patients (p < 0.0001 for all). When stratified concerning the age of inclusion, Swedish patients between 41-50 years had, however, a significantly lower age of onset, with a similar trend for all age groups above 30 years. The female preponderance was higher among Sudanese patients (89.3% vs 72.5%, p < 0.0001), and smoking was nonexistent among Sudanese female patients (p < 0.0001). Erythrocyte sedimentation rate levels and number of tender joints were significantly higher among Sudanese patients. The proportion of IgM-RF positivity was lower among Sudanese patients with RA (52.4% vs 75.5%, p < 0.0001). Higher proportions of Sudanese patients with RA were treated with methotrexate (MTX) and disease-modifying antirheumatic drug combinations, but none of them used biologics. Sudanese patients used lower doses of MTX and sulfasalazine (p < 0.0001) and higher doses of prednisolone (p < 0.0001) than Swedish patients. CONCLUSION: Sudanese patients with RA have significantly higher disease activity and are often IgM-RF-seronegative. Together with reports from Uganda and Cameroon, our data indicate a cluster of highly active and often seronegative RA in central Africa.

Mycophenolate mofetil versus azathioprine for maintenance treatment of lupus nephritis.

To compare the efficacy of mycophenolate mofetil (MMF) with that of azathioprine (AZA) drugs in the maintenance therapy of lupus nephritis (LN) patients, we studied 81 Sudanese patients with LN (32 in Class III, 34 in Class IV, and 15 in combined Class V + IV of the ISN/RPS 2003 Classification). All patients received induction therapy consisting of monthly intravenous pulse doses of cyclophosphamide (CYC) (500 mg/m 2 of body-surface area) for six months, plus three consecutive pulses of intravenous methylprednisolone 15 mg/kg/day of body weight (maximum 500 mg). Subsequently, 41 (50.6%) patients were randomized into a group that received oral MMF (22 mg/kg/day), and 40 (49.4%) patients randomized to a group that received oral AZA (2 mg/kg/day). All patients initially received oral prednisone (1 mg/kg of body weight daily) for four weeks. The baseline characteristics of the two groups were similar. Total remission rate was 75.3% (80.5% in MMF and 70% in AZA), complete remission rate of 54.3% (56.1% with MMF and 52.5% with AZA), and a partial remission rate of 21% (24.4% with MMF and 17.5% with AZA) over 29 months. During maintenance therapy, six patients died (four in the AZA group and two in the MMF group), and end-stage renal disease (ESRD) developed in five patients (three in the AZA group and two in the MMF group). During the 36-months of the study, both groups had comparable event-free survival rate for the composite end point of death or ESRD and rate of relapse-free survival. Furthermore, both groups had no significant differences in terms of frequency of hospitalization, amenorrhea, infection, nausea, and vomiting. We conclude that our study showed that short-term therapy with intravenous CYC followed by maintenance therapy with oral MMF or AZA had similar efficacy and safety for the treatment of patients with moderate to severe LN.

Anticorpos antipeptídeos citrulinados e fator reumatoide em pacientes sudaneses com infecção por Leishmania donovani / Anti-citrullinated peptide antibodies and rheumatoid factor in Sudanese patients with Leishmania donovani infection

OBJETIVO: Este estudo avaliou a presença de anticorpos antipeptídeos citrulinados cíclicos (anti-CCP), fator reumatoide (FR) e imunocomplexos circulantes (ICC) em pacientes sudaneses infectados por Leishmania donovani. PACIENTES E MÉTODOS: Os soros foram coletados de pacientes infectados por Leishmania (n = 116) e de sudaneses saudáveis (n = 93). Dezenove pacientes sudaneses com artrite reumatoide (AR) e anti-CCP+ foram incluídos como controles positivos. Os níveis de ICC e anti-CCP foram medidos por ELISA. Para avaliar a reatividade citrulina-específica foi usada a placa-controle com peptídeos-controle cíclicos contendo arginina em vez de citrulina. RESULTADOS: Entre os pacientes infectados por Leishmania e os pacientes com AR e anti-CCP+, a maioria (86%) era positiva para FR, enquanto a frequência de positividade para ICC foi maior entre pacientes com leishmaniose visceral (LV) (LV 38%; AR e anti-CCP+ 24%). Quando foi analisada a reatividade anti-CCP, 12% dos pacientes com LV foram positivos. Os níveis de anti-CCP entre os pacientes com LV correlacionaram-se bem com os níveis de ICC encontrados (r = 0,65; P < 0,0001). No grupo de AR não foi encontrada associação entre ICC e anti-CCP. A possibilidade de que a positividade para anti-CCP se deva a reações cruzadas com ICC foi descartada experimentalmente. Ao contrário do que foi visto no soro dos sudaneses com AR, a reatividade anti-CCP não se restringiu à citrulina, mas houve reação igual com os peptídeos-controle com arginina. CONCLUSÃO: O fato de a reatividade CCP não se ter restringido à citrulina comprova tratar-se mais de um efeito de inflamação extensa e ativação imune do que de um sinal de características patogênicas compartilhadas com artrite anti-CCP. Nossos achados ressaltam a importância de se interpretar um teste CCP positivo com cuidado ao se avaliar condições não reumáticas ou em áreas onde tais infecções predominam.

OBJECTIVE: The present study evaluated the presence of anti-cyclic citrullinated peptides antibodies (anti-CCP), rheumatoid factor (RF), and circulating immune complexes (CIC) in Sudanese patients infected with the Leishmania donovani parasite. PATIENTS AND METHODS: Sera were collected from Leishmania infected patients (n = 116) and healthy Sudanese (n = 93). Nineteen Sudanese anti-CCP+ RA patients were included as positive controls. Levels of CIC and anti-CCP were measured by ELISA. Control plate with cyclic control peptides containing arginine instead of citrulline was used to evaluate citrulline specifi c reactivity. RESULTS: Among Leishmania-infected patients and anti-CCP+ RA patients, most were RF positive (86%), while the frequency of CIC positivity was higher among visceral leishmaniasis (VL) patients (VL 38%; anti-CCP+ RA 24%). When anti-CCP reactivity was analysed, 12% of VL patients were found to be positive. The levels of anti-CCP among VL patients correlated well with the CIC levels found (r = 0.65, P < 0.0001). In RA group, no association was found between CIC and anti-CCP. The possibility that anti-CCP positivity was due to cross reactions with CIC was experimentally ruled out. Contrary to what was seen in Sudanese RA sera, the CCP reactivity was not restricted to citrulline but reacted equally well with the arginine control peptide. CONCLUSION: The finding that CCP reactivity was not restricted to citrulline argues that this is more an effect of extensive inflammation and immune activation than a sign of shared pathogenic characteristics with anti-CCP arthritis. Our fi ndings stress the importance to interpret a positive CCP test carefully when evaluated in non-rheumatic conditions or in areas where such infections predominate.

Anti-citrullinated peptide antibodies and rheumatoid factor in Sudanese patients with Leishmania donovani infection.

OBJECTIVE: The present study evaluated the presence of anti-cyclic citrullinated peptides antibodies (anti-CCP), rheumatoid factor (RF), and circulating immune complexes (CIC) in Sudanese patients infected with the Leishmania donovani parasite. PATIENTS AND METHODS: Sera were collected from Leishmania infected patients (n = 116) and healthy Sudanese (n = 93). Nineteen Sudanese anti-CCP+ RA patients were included as positive controls. Levels of CIC and anti-CCP were measured by ELISA. Control plate with cyclic control peptides containing arginine instead of citrulline was used to evaluate citrulline specifi c reactivity. RESULTS: Among Leishmania-infected patients and anti-CCP+ RA patients, most were RF positive (86%), while the frequency of CIC positivity was higher among visceral leishmaniasis (VL) patients (VL 38%; anti-CCP+ RA 24%). When anti-CCP reactivity was analysed, 12% of VL patients were found to be positive. The levels of anti-CCP among VL patients correlated well with the CIC levels found (r = 0.65, P < 0.0001). In RA group, no association was found between CIC and anti-CCP. The possibility that anti-CCP positivity was due to cross reactions with CIC was experimentally ruled out. Contrary to what was seen in Sudanese RA sera, the CCP reactivity was not restricted to citrulline but reacted equally well with the arginine control peptide. CONCLUSION: The finding that CCP reactivity was not restricted to citrulline argues that this is more an effect of extensive inflammation and immune activation than a sign of shared pathogenic characteristics with anti-CCP arthritis. Our fi ndings stress the importance to interpret a positive CCP test carefully when evaluated in non-rheumatic conditions or in areas where such infections predominate.