Response to immunosuppressive therapy and an HLA-DRB1 allele in patients with aplastic anaemia: HLA-DRB1*1501 does not predict response to antithymocyte globulin

Association between human leukocyte antigen and immunosuppressive treatment outcomes in Chinese patients with aplastic anemia

Background

Activated cytotoxic T cells (CTLs) recognize the auto-antigens presented on hematopoietic stem/progenitor cells (HSPCs) through class I human leukocyte antigen (HLA) molecules and play an important role in the immune pathogenesis of aplastic anemia (AA). Previous reports demonstrated that HLA was related to the disease susceptibility and response to immunosuppressive therapy (IST) in AA patients. Recent studies have indicated that specific HLA allele deletions, which helped AA patients to evade CTL-driven autoimmune responses and escape from immune surveillance, may lead to high-risk clonal evolution. Therefore, HLA genotyping has a particular predictive value for the response to IST and the risk of clonal evolution. However, there are limited studies on this topic in the Chinese population.

Methods

To explore the value of HLA genotyping in Chinese patients with AA, 95 AA patients treated with IST were retrospectively investigated.

Results

The alleles HLA-B*15:18 and HLA-C*04:01 were associated with a superior long-term response to IST (P = 0.025; P = 0.027, respectively), while the allele HLA-B*40:01 indicated an inferior result (P = 0.02). The allele HLA-A*01:01 and HLA-B*54:01 were associated with high-risk clonal evolution (P = 0.032; P = 0.01, respectively), and the former had a higher frequency in very severe AA (VSAA) patients than that in severe AA (SAA) patients (12.7% vs 0%, P = 0.02). The HLA-DQ*03:03 and HLA-DR*09:01 alleles were associated with high-risk clonal evolution and poor long-term survival in patients aged ≥40 years. Such patients may be recommended for early allogeneic hematopoietic stem cell transplantation rather than the routine IST treatment.

Conclusion

HLA genotype has crucial value in predicting the outcome of IST and long-term survival in AA patients, and thus may assist an individualized treatment strategy.

The similarity of class II HLA genotypes defines patterns of autoreactivity in idiopathic bone marrow failure disorders

Idiopathic aplastic anemia (IAA) is a rare autoimmune bone marrow failure (BMF) disorder initiated by a human leukocyte antigen (HLA)-restricted T-cell response to unknown antigens. As in other autoimmune disorders, the predilection for certain HLA profiles seems to represent an etiologic factor; however, the structure-function patterns involved in the self-presentation in this disease remain unclear. Herein, we analyzed the molecular landscape of HLA complexes of a cohort of 300 IAA patients and almost 3000 healthy and disease controls by deeply dissecting their genotypic configurations, functional divergence, self-antigen binding capabilities, and T-cell receptor (TCR) repertoire specificities. Specifically, analysis of the evolutionary divergence of HLA genotypes (HED) showed that IAA patients carried class II HLA molecules whose antigen-binding sites were characterized by a high level of structural homology, only partially explained by specific risk allele profiles. This pattern implies reduced HLA binding capabilities, confirmed by binding analysis of hematopoietic stem cell (HSC)-derived self-peptides. IAA phenotype was associated with the enrichment in a few amino acids at specific positions within the peptide-binding groove of DRB1 molecules, affecting the interface HLA-antigen-TCR β and potentially constituting the basis of T-cell dysfunction and autoreactivity. When analyzing associations with clinical outcomes, low HED was associated with risk of malignant progression and worse survival, underlying reduced tumor surveillance in clearing potential neoantigens derived from mechanisms of clonal hematopoiesis. Our data shed light on the immunogenetic risk associated with IAA etiology and clonal evolution and on general pathophysiological mechanisms potentially involved in other autoimmune disorders.

Association of Human Leukocyte Antigen DRB1*15 and DRB1*15:01 Polymorphisms with Response to Immunosuppressive Therapy in Patients with Aplastic Anemia: A Meta-Analysis

This study aimed to review and quantitatively analyze (1) the association of aplastic anemia (AA) with human leukocyte antigen (HLA)-DRB1*15 and HLA-DRB1*15:01 polymorphisms and (2) the association of HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms with response to immunosuppressive therapy (IST) in AA. Published studies have reported conflicting and heterogeneous results regarding the association of HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms with response to IST in AA. The PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, Chinese BioMedical Literature, Wangfang and Chinese Social Sciences Citation Index databases were searched. All relevant publications were searched through December 2015. Odds ratio (OR), risk ratio (RR), and 95% confidence intervals (CI) for the comparison between case–control or cohort studies were evaluated. Finally, 24 articles were identified. For HLA-DRB1*15 and HLA-DRB1*15:01, the OR (95% CI) was 2.24(1.33–3.77), P < 0.01 and 2.50(1.73–3.62), P < 0.01, respectively; and the overall pooled RR was 1.72 (1.30–2.29), P < 0.01 and 1.59 (1.29–1.96), P < 0.01, respectively. Statistical evidence showed no publication bias (P > 0.05). Sensitivity analyses revealed that the results were statistically robust. The meta-analysis suggested that HLA-DRB1*15 and HLA-DRB1*15:01 polymorphisms might be associated with increased AA risk in Asians. IST might be more effective in HLA-DRB1*15⁺ and HLA-DRB1*15:01⁺ Asian patients with AA than in HLA-DRB1*15− and HLA-DRB1*15:01− Asian patients with AA. Future studies with adequate methodological quality on gene–gene and gene–environment interactions and gene treatment may yield valid results.

The complex pathophysiology of acquired aplastic anaemia

Immune-mediated destruction of haematopoietic stem/progenitor cells (HSPCs) plays a central role in the pathophysiology of acquired aplastic anaemia (aAA). Dysregulated CD8(+) cytotoxic T cells, CD4(+) T cells including T helper type 1 (Th1), Th2, regulatory T cells and Th17 cells, natural killer (NK) cells and NK T cells, along with the abnormal production of cytokines including interferon (IFN)-γ, tumour necrosis factor (TNF)-α and transforming growth factor (TGF)-β, induce apoptosis of HSPCs, constituting a consistent and defining feature of severe aAA. Alterations in the polymorphisms of TGF-β, IFN-γ and TNF-α genes, as well as certain human leucocyte antigen (HLA) alleles, may account for the propensity to immune-mediated killing of HSPCs and/or ineffective haematopoiesis. Although the inciting autoantigens remain elusive, autoantibodies are often detected in the serum. In addition, recent studies provide genetic and molecular evidence that intrinsic and/or secondary deficits in HSPCs and bone marrow mesenchymal stem cells may underlie the development of bone marrow failure.

Association of human leukocyte antigen class II alleles with response to immunosuppressive therapy in Korean aplastic anemia patients

HLA-DR15 (DR2) is overrepresented in aplastic anemia (AA) patients, and its presence is associated with a better response to cyclosporine-based immunosuppressive therapy (IST). However, little is known about other human leukocyte antigen (HLA) alleles affecting therapy response. We investigated 37 Korean patients with severe AA for the association of HLA class II alleles with response to IST: cyclosporine A combined with antithymocyte globulin or antilymphocyte globulin. Molecular or serologic typing of HLA-DR and HLA-DQ alleles was performed. In responders (13/37, 35.1%), the frequency of HLA-DR15 was increased (69.2% vs 8.3%, p = 0.0002) and that of DR4 was decreased (7.7% vs 66.7%, p = 0.0007) compared with nonresponders. The response rate was significantly higher in DR15(+) than in DR15(-) (81.8% vs 15.4%, p = 0.0002) and in DR4(-) than in DR4(+) patients (60.0% vs 5.9%, p = 0.0007). The response rates in the best (DR15(+)/DR4(-)), intermediate, and poor response groups (DR15(-)/DR4(+)) were 88.9, 38.5, and 0%, respectively (p = 0.00001). At the allelic level, DRB1*1501 and closely linked DQB1*0602 were associated with a good response and DRB1*0405 and closely linked DQB1*0401 with a poor response to IST. HLA-DR typing may be useful for predicting a response to IST in AA patients.

Clinical impact of HLA-DR15, a minor population of paroxysmal nocturnal haemoglobinuria-type cells, and an aplastic anaemia-associated autoantibody in children with acquired aplastic anaemia

Aplastic anaemia (AA) is defined as a pancytopenia caused by bone marrow failure, and its pathogenesis is thought to involve autoimmune processes. Several predictive markers of the response to immunosuppressive therapy (IST) have been proposed, which appear to reflect the immune pathophysiology. We prospectively investigated the presence of human leucocyte antigen (HLA)-DR15, a minor population of paroxysmal nocturnal haemoglobinuria (PNH)-type cells, and antibodies to the recently identified autoantigen postmeiotic segregation increased 1 (PMS1) in 103 children with AA enrolled in a multicentre study. In contrast to adults, children with AA did not show an increased frequency of HLA-DR15. In addition, a sensitive flow cytometric assay revealed that children with AA have a much lower prevalence of PNH-type cells (21.4%) than reported for adults with this disease. An immunoblotting assay detected anti-PMS1 antibody in 15 of 103 (14.6%) of the children. Finally, the response rate to IST was not significantly different between patients with and without DR15 (45.5% vs. 54.0%), PNH-type cells (68.2% vs. 53.1%) or anti-PMS1 antibody (40.0% vs. 59.1%). The current study did not confirm a correlation between these markers and the response to IST, suggesting that there is a difference in the pathophysiologies of adult and paediatric AA.

Low IPSS score and bone marrow hypocellularity in MDS patients predict hematological responses to antithymocyte globulin

Immunosuppressive therapy has been shown to induce sustained hematological responses in a subset of patients with myelodysplastic syndromes (MDS). In particular, antithymocyte globulin (ATG), a polyclonal immunoglobulin induces hematological responses in up to 60% of MDS patients. We report herein on the results of a retrospective multicenter study on the use of ATG in the treatment of 96 patients with MDS. Patients were evaluated for duration of response to ATG, as well as survival after administration of ATG. The median age of the cohort was 54.7 years (range: 19-75 years), with a median follow-up of 33.8 months (range: 0.8-133 months). A total of 40 patients (42%) achieved a hematological response, of which 30 patients (75%) had a durable hematological response lasting a median duration of 31.5 months (range: 6-92 months). On multivariate analysis, both low International Prognostic Scoring System (IPSS) and bone marrow (BM) hypocellularity were independent predictive factors for improved response to ATG (IPSS Int-2/high: odds ratio (OR) 0.08, P=0.018 and BM normo/hypercellularity: OR 0.49, P=0.012). In addition, IPSS was the sole predictor of overall survival, with Int-2/high risk patients having a significantly poorer survival outcome (OR 0.08, P<0.01). In conclusion, this study identifies BM hypocellularity and a low IPSS as important factors predicting response to ATG.

Roles of DRB1 *1501 and DRB1 *1502 in the pathogenesis of aplastic anemia

OBJECTIVE

Although a number of reports have documented a significantly increased incidence of HLA-DR15 in aplastic anemia (AA), the exact role of HLA-DR15 in the immune mechanisms of AA remains unclear. We herein clarify the difference between DRB1( *)1501 and DRB1( *)1502, the two DRB1 alleles that determine the presentation of HLA-DR15, in the pathophysiology of AA.

MATERIALS AND METHODS

We investigated the relationships of the patients( *) HLA-DRB1 allele with both the presence of a small population of CD55(-)CD59(-) (PNH-type) blood cells and the response to antithymocyte globulin (ATG) plus cyclosporin (CsA) therapy in 140 Japanese AA patients.

RESULTS

Of the 30 different DRB1 alleles, only DRB1( *)1501 (33.6% vs 12.8%, p(c) < 0.01) and DRB1( *)1502 (43.6% vs 24.4%, p(c) < 0.01) displayed significantly higher frequencies among the AA patients than among a control. AA patients possessing HLA-DR15 tended to be old, and especially, the frequency of DRB1( *)1502 in patients 40 years of age and older (52.4%) was markedly higher than that in those younger than 40 years old (16.2%, p(c) < 0.01). Only DRB1( *)1501 was significantly associated with the presence of a small population of PNH-type cells and it also showed a good response to ATG plus CsA therapy in a univariate analysis. A multivariate analysis showed only the presence of a small population of PNH-type cells to be a significant factor associated with a good response to the immunosuppressive therapy (p < 0.01).

CONCLUSIONS

Although both DRB1( *)1501 and DRB1( *)1502 contribute to the development of AA, the methods of contribution differ between the two alleles.

HLA association is different in children and adults with severe acquired aplastic anemia

BACKGROUND

Severe aplastic anemia (SAA) is defined as pancytopenia caused by bone marrow failure. The pathogenesis of SAA is thought to involve autoimmune processes. Increased susceptibility to autoimmunity has been shown to be associated with several different HLA alleles. In SAA, few large studies based on data mainly from adults describe a positive HLA correlation with HLA-DR2 (DRB1*15) and HLA-B14.

PROCEDURE

This study explored the HLA constitution of 181 children with SAA who were enrolled in the prospective multi-center study SAA94 between January 1994 and January 2002. The control group consisted of 303 healthy individuals of comparable demographic background. Allelic frequencies between patients and controls are compared using Fisher's exact test.

RESULTS

In our pediatric cohort, we describe a positive association with HLA-B14 (P = 0.0039), but no association of HLA-DR2 with SAA.

CONCLUSION

HLA associations appear to be different in children and adults with SAA. This might point towards a difference in pathophysiology between at least part of the children and adults.

Immunosuppressive therapy for myelodysplastic syndrome: efficacy of methylprednisolone pulse therapy with or without cyclosporin A

We investigated whether immunosuppressive therapy using methylprednisolone (mPSL) with or without cyclosporin A (CsA) could benefit patients with myelodysplastic syndrome (MDS). Eligibility criteria for this study were a clinical diagnosis of MDS with less than 5% blast in peripheral blood, less than 10% blast in bone marrow and advanced cytopenia. Among 73 patients with MDS, 18 eligible and consecutive patients (8 men and 10 women), aged 48 to 87 years (median: 66.5 years) were assigned to receive mPSL pulse therapy (1,000 mg daily for 3 consecutive days, followed by tapering oral prednisolone; n= 12) or mPSL pulse with CsA therapy (4 to 5 mg/kg administered twice daily; n= 6). Six of 18 patients (33.3%; 3 of 10 patients with RA, 2 of 6 patients with RAEB, 1 of 2 patients with CMMoL) responded to immunosuppressive therapy. Four patients responded to mPSL pulse alone, and two patients responded to mPSL pulse with CsA. One of 6 patients with hypocellular bone marrow and 5 of 12 patients with normocellular or hypercellular marrow responded to immunosuppressive therapy. No patient with myelofibrosis responded to the therapy. The duration of response ranged from 4 to 59 months (median: 14 months). Although a significant difference was observed between responders and nonresponders in the survival rate ( P<0.05), no significant difference was found in clinical characteristics at entry between responders and nonresponders. In responders, mean hemoglobin levels were significantly increased ( P<0.01), and the required red cell transfusion dose was significantly reduced ( P<0.01). It is possible that immunosuppressive therapy might be effective for a certain subset of patients with MDS.

HLA-DR15 (DR2) is overrepresented in myelodysplastic syndrome and aplastic anemia and predicts a response to immunosuppression in myelodysplastic syndrome

The extent and importance of autoimmune mechanisms in myelodysplastic syndrome (MDS) and the role of immunosuppression in the treatment of this disease are not well defined. We report overrepresentation of HLA-DR2 and its serologic split HLA-DR15 in both MDS and aplastic anemia (AA). Four clinically and ethnically defined patient groups were analyzed. The HLA-DR15 antigen frequencies among North American white MDS patients (n = 72) and AA patients (n = 59), who received immunosuppressive treatment at the National Institutes of Health (NIH), were 36% and 42%, respectively. These antigen frequencies were significantly higher than that of the control population of 240 North American white NIH blood donors typed for HLA antigens by the same molecular technique (HLA-DR15, 21.3%,P = .01 for MDS, P < .001 for AA). Among North American white patients reported in the International Bone Marrow Transplant Registry (IBMTR), 30% of 341 MDS patients and 33% of 364 AA patients were positive for HLA-DR2. These antigen frequencies were higher than those reported for the general North American white population (HLA-DR2, 25.3%, P = .089 for MDS,P = .01 for AA). The DR15 and DR2 frequencies were significantly increased in MDS refractory anemia (RA) (P = .036 and P = .01, respectively) but not MDS refractory anemia with excess blasts. In the NIH MDS patients, HLA-DR15 was significantly associated with a clinically relevant response to antithymocyte globulin (ATG) or cyclosporine immunosuppression (multivariate analysis, P = .008). In MDS with RA, DR15 may be useful as a guide to pathophysiology, prognosis, and treatment.

Increased frequency of HLA-DR2 in patients with paroxysmal nocturnal hemoglobinuria and the PNH/aplastic anemia syndrome

Many autoimmune diseases are associated with HLA alleles, and such a relationship also has been reported for aplastic anemia (AA). AA and paroxysmal nocturnal hemoglobinuria (PNH) are related clinically, and glycophosphoinositol (GPI)-anchored protein (AP)-deficient cells can be found in many patients with AA. The hypothesis was considered that expansion of a PNH clone may be a marker of immune-mediated disease and its association with HLA alleles was examined. The study involved patients with a primary diagnosis of AA, patients with myelodysplastic syndrome (MDS), and patients with primary PNH. Tests of proportions were used to compare allelic frequencies. For patients with a PNH clone (defined by the presence of GPI-AP-deficient granulocytes), regardless of clinical manifestations, there was a higher than normal incidence of HLA-DR2 (58% versus 28%; z = 4.05). The increased presence of HLA-DR2 was found in all frankly hemolytic PNH and in PNH associated with bone marrow failure (AA/PNH and MDS/PNH). HLA-DR2 was more frequent in AA/PNH (56%) than in AA without a PNH clone (37%; z = 3.36). Analysis of a second cohort of patients with bone marrow failure treated with immunosuppression showed that HLA-DR2 was associated with a hematologic response (50% of responders versus 34% of nonresponders; z = 2.69). Both the presence of HLA-DR2 and the PNH clone were independent predictors of response but the size of PNH clone did not correlate with improvement in blood count. The results suggest that clonal expansion of GPI-AP-deficient cells is linked to HLA and likely related to an immune mechanism.

HLA-DR2 Frequency Increase in Severe Aplastic Anemia Patients is Mainly Attributed to the Prevalence of DR15 Subtype

The association between severe aplastic anemia (AA) and DR2 antigen seems to be well established. However, since discrimination between two DR2-associated splits, namely DR15 and DR16, rarely was performed, it remains unclear whether one or both of these subvariants are responsible for AA susceptibility. In this study, we have analyzed the HLA-DR allelic distribution in a group of 37 AA patients of slavic origin from North-Western Russia. The experimental design included PCR-based amplification of DRB-specific sequences, followed by reverse dot-blot hybridization of the biotinylated PCR-product with the set of sequence-specific oligonucleotide probes. HLA-DRB alleles were identified by non-radioactive enzymatic reaction, then standard serological specificities of HLA-DR antigen were estimated according to the WHO nomenclature. Whereas DR15 subtype occurred more often in the patients (23.0% vs. 13.3%, p< 0.05), DR16 split did not show the same tendency. The results, show the overall predominance of HLA-DR2 specificity (DR15+DR16) did not reach statistical significance (24.4% vs.17.5%, p<0.2). Thus, we conclude that repeatedly reported DR2 frequency increase in AA patients is mainly attributed to the prevalence of DR15 subtype.

Study of the association between cytochromes P450 2D6 and 2E1 genotypes and the risk of drug and chemical induced idiosyncratic aplastic anaemia

A genetic susceptibility to drug or chemical toxicity may provide a basis for an increased risk of idiosyncratic aplastic anaemia (AA). The cytochrome P450 enzymes are responsible for the metabolism of many drugs, some of which have been linked to AA. Mutations in the cytochrome P450 CYP2D6 gene result in absent or impaired enzyme activity in about 7% of Caucasians, whereas a specific mutation in the 5'-regulatory region of the CYP2E1 gene causes overexpression of the gene. We evaluated the frequency of allelic variants of CYP2D6 and CYP2E1 using allele-specific PCR amplification and restriction enzyme analysis of blood mononuclear cell DNA among 54 Caucasian AA patients. CYP2D6 and CYP2E1 were chosen because of the link between AA and the antipsychotic drug remoxipride (CYP2D6 substrate) and benzene (CYP2E1 substrate), respectively. Results were compared with 53 controls matched for age, sex and ethnicity. The percentage of AA patients homozygous for the CYP2D6*3, CYP2D6*4 alleles (poor metabolizer phenotype) and the CYP2E1 mutant allele (overexpression) was 0%, 4% and 0%, respectively, and the percentage of heterozygotes was 2%, 28% and 15%, respectively. For normal controls the corresponding results for homozygous mutants were 0%, 4% and 0% and for heterozygotes 4%, 25% and 6%, respectively. We concluded that there were no major differences in the frequencies of the genetic polymorphisms between this series of AA patients and controls, but due to the low number of cases with the poor metabolizer phenotype and those with a history of drug exposure, the power of the study was too low to disprove an interaction.