Immunoregulatory cytokine polymorphisms in Italian patients affected by paroxysmal nocturnal haemoglobinuria and aplastic anaemia

The relationship between interferon-gamma (INF-γ) single nucleotide polymorphism +874(T/A) and occurrence risk of aplastic anemia: a meta-analysis

Objective: This meta-analysis was designed to investigate the association between interferon-gamma (IFN-γ) polymorphisms and occurrence risk of aplastic anemia.Methods: Literature search was conducted in PubMed, Embase and Cochrane Library up to April 2018. The pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated by R 3.12.Results: Total five studies with 304 aplastic anemia patients and 588 controls were included. The statistically significant results were found in the following models: allele genetic model (T vs A: OR = 2.1749, 95% CI = 1.6825-2.8114, P < 0.01), additive genetic model (TA vs AA: OR = 2.1071, 95% CI = 1.3962-3.1799, P < 0.01; TT vs AA: OR = 4.5788, 95% CI = 2.6606-7.8797, P < 0.01), recessive genetic model (TT vs AA + TA: OR = 2.5579, 95% = 1.6680-3.9226, P < 0.01), dominant genetic model (TT + TA vs AA: OR = 2.5599, 95% = 1.7424-3.7611, P < 0.01), the results suggested that the increased occurrence risk of aplastic anemia is significantly associated with the IFN-γ polymorphism.Conclusions: Patients with IFN-γ genotype carrying allele T have higher occurrence risk of aplastic anemia.

Pathogenesis of aplastic anemia

Aplastic anemia (AA) is a rare and life-threatening bone marrow failure (BMF) that results in peripheral blood cytopenia and reduced bone marrow hematopoietic cell proliferation. The symptoms are similar to myelofibrosis, myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) making diagnosis of AA complicated. The pathogenesis of AA is complex and its mechanism needs to be deciphered on an individualized basis. This review summarizes several contributions made in trying to understand AA pathogenesis in recent years which may be helpful for the development of personalized therapies for AA.

The association of cytokine genes polymorphisms and susceptibility to aplastic anemia in Egyptian patients

BACKGROUND AND OBJECTIVE

Aplastic anemia (AA) remains a rare disease, with very interesting pathophysiology that is being investigated for years now. The present study aimed to determine the association between cytokine gene polymorphisms (TGF-β1 -509 C/T, TNF-α -308 G/A, IFN-γ +874 A/T) and susceptibility to AA in Egyptian patients.

METHODS

The study included 80 participants subjected to determination of gene polymorphisms on genomic DNA using polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS

It was found that IFN-γ +874 A/T gene polymorphism is associated with three-fold increased risk of development of AA (odds ratio (OR) 3.116, P = 0.019), while TNF-α -308 G/A gene polymorphism is associated with decreased risk (OR 0.318, P = 0.026). TGF-β1 -509 C/T gene polymorphism showed comparable risk between patients and controls (P = 0.263).

CONCLUSION

IFN-γ +874 A/T gene polymorphism is associated with the etiology of AA in Egyptian patients.

TNF-α -308 G>A polymorphism and risk of bone marrow failure syndrome: A meta-analysis

The influence of the TNF-α -308 G>A polymorphism on bone marrow failure syndrome susceptibility is unclear. We have conducted a meta-analysis of all relevant published studies. We searched PubMed, Chinese Biomedical Literature and China National Knowledge Infrastructure databases up to February 2015. Odds ratios (ORs) with 95% confidence intervals (CIs) were applied to assess the strength of associations. Eleven case-control studies with a total sample size of 909 cases and 1803 controls were eligible to assess the association between the TNF-α -308 G>A polymorphism and susceptibility to bone marrow failure syndrome. Overall, the TNF-α -308 G>A polymorphism was significantly associated with an increased risk of bone marrow failure syndrome in any genetic model. In stratified analysis by disease type, there was a significant association between the TNF-α -308 G>A polymorphism and increased risk of aplastic anemia but no significant association with myelodysplastic syndrome (AA vs. GG: OR=2.23, 95% CI=1.23-4.05, P=0.006; recessive model: OR=3.52, 95% CI=1.30-9.53, P=0.010). In subgroup analysis by ethnicity, there were significant associations between the TNF-α -308 G>A polymorphism and increased risk of bone marrow failure syndrome for Caucasians in two models, but not in Asian populations (AA vs. GG: OR=2.66, 95% CI=1.36-5.21, P=0.003; recessive model: OR=2.68, 95% CI=1.37-5.24, P=0.002). In conclusion, our meta-analysis suggests that the TNF-α -308 G>A polymorphism may contribute to the risk of bone marrow failure syndrome, particularly among Caucasian and aplastic anemia patients. Further investigations are needed to clarify the role of the TNF-α -308 G>A polymorphism in bone marrow failure syndrome.

IFN-γ causes aplastic anemia by altering hematopoietic stem/progenitor cell composition and disrupting lineage differentiation

Aplastic anemia (AA) is characterized by hypocellular marrow and peripheral pancytopenia. Because interferon gamma (IFN-γ) can be detected in peripheral blood mononuclear cells of AA patients, it has been hypothesized that autoreactive T lymphocytes may be involved in destroying the hematopoietic stem cells. We have observed AA-like symptoms in our IFN-γ adenylate-uridylate-rich element (ARE)-deleted (del) mice, which constitutively express a low level of IFN-γ under normal physiologic conditions. Because no T-cell autoimmunity was observed, we hypothesized that IFN-γ may be directly involved in the pathophysiology of AA. In these mice, we did not detect infiltration of T cells in bone marrow (BM), and the existing T cells seemed to be hyporesponsive. We observed inhibition in myeloid progenitor differentiation despite an increase in serum levels of cytokines involved in hematopoietic differentiation and maturation. Furthermore, there was a disruption in erythropoiesis and B-cell differentiation. The same phenomena were also observed in wild-type recipients of IFN-γ ARE-del BM. The data suggest that AA occurs when IFN-γ inhibits the generation of myeloid progenitors and prevents lineage differentiation, as opposed to infiltration of activated T cells. These results may be useful in improving treatment as well as maintaining a disease-free status.

Immunoregulatory cytokines gene polymorphisms in Egyptian patients affected with acquired aplastic anemia

The immune system is thought to play an important role in aplastic anemia (AA) in light of recent findings of hematologic reconstitution after immunosuppressive therapy. T cell activation, apoptosis, and the cytokines interferon- and TNF-α are suspected to play a role in the suppression of growth of progenitor cells and induced apoptosis in CD34 target cells, TGFβ is a multifunctional peptide, usually produced in latent form and requiring activation to produce a biological response. Also, TGF-β1 has been described as an important negative regulator of haemopoiesis. Over production of IL-6 is described in AA but is of unknown pathophysiological significance. To investigate the role of cytokine gene polymorphisms (IL-6/-174, TNF-α/-308, IFN-γ/+874, and TGFβ1/-509) in patients with acquired AA to assess if genotypes associated with higher or lower production were more prevalent than in established control population and to study the possible association of these genotypes with the disease severity. Fifty AA patients were included in this study. Polymerase chain reaction-amplification refractory mutation system (PCR-ARMS) technique was used to detect INF-γ single nucleotide polymorphism -874A/T, and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to assess IL-6-174 C/G, TNF-α-308G/A, and TGFb1-509C/T gene polymorphisms. Genotypes associated with high production of TNF-α, TGF-β and IFN-γ, and IL-6 were more frequent in patients than in control; no association was found between the presence of hypersecretory genotypes and the disease severity.

Genetic associations in acquired immune-mediated bone marrow failure syndromes: insights in aplastic anemia and chronic idiopathic neutropenia

Increasing interest on the field of autoimmune diseases has unveiled a plethora of genetic factors that predispose to these diseases. However, in immune-mediated bone marrow failure syndromes, such as acquired aplastic anemia and chronic idiopathic neutropenia, in which the pathophysiology results from a myelosuppressive bone marrow microenvironment mainly due to the presence of activated T lymphocytes, leading to the accelerated apoptotic death of the hematopoietic stem and progenitor cells, such genetic associations have been very limited. Various alleles and haplotypes of human leucocyte antigen (HLA) molecules have been implicated in the predisposition of developing the above diseases, as well as polymorphisms of inhibitory cytokines such as interferon-γ, tumor necrosis factor-α, and transforming growth factor-β1 along with polymorphisms on molecules of the immune system including the T-bet transcription factor and signal transducers and activators of transcription. In some cases, specific polymorphisms have been implicated in the outcome of treatment on those patients.

Efficacy of rabbit anti-thymocyte globulin in severe aplastic anemia

BACKGROUND

A combination of horse anti-thymocyte globulin and cyclosporine produces responses in 60-70% of patients with severe aplastic anemia. We performed a phase II study of rabbit anti-thymocyte globulin and cyclosporine as first-line therapy for severe aplastic anemia.

DESIGN AND METHODS

Twenty patients with severe aplastic anemia treated with rabbit anti-thymocyte globulin were compared to 67 historical control cases with matched clinical characteristics treated with horse anti-thymocyte globulin.

RESULTS

Response rates at 3, 6 and 12 months were similar for patients treated with rabbit anti-thymocyte globulin or horse anti-thymocyte globulin: 40% versus 55% (P=0.43), 45% versus 58% (P=0.44) and 50% versus 58% (P=0.61), respectively. No differences in early mortality rates or overall survival were observed. We then performed multivariable analyses of response at 6 months and overall survival and identified the presence of a paroxysmal nocturnal hemoglobinuria clone (P=0.01) and a pretreatment absolute reticulocyte count greater than 30×10(9)/L (P=0.007) as independent predictors of response and younger age (P=0.003), higher pretreatment absolute neutrophil (P=0.02) and absolute lymphocyte counts (P=0.03) as independent predictors of overall survival. None of the immunogenetic polymorphisms studied was predictive of response to immunosupressive therapy.

CONCLUSIONS

Despite reports suggesting differences in biological activity of different anti-thymocyte globulin preparations, rabbit and horse anti-thymocyte globulin appear to have a similar efficacy for up-front treatment of severe aplastic anemia. Clinicaltrial.gov: NCT01231841).

Inflammatory signals regulate hematopoietic stem cells

Hematopoietic stem cells (HSCs) are the progenitors of all blood and immune cells, yet their role in immunity is not well understood. Most studies have focused on the ability of committed lymphoid and myeloid precursors to replenish immune cells during infection. Recent studies, however, have indicated that HSCs also proliferate in response to systemic infection and replenish effector immune cells. Inflammatory signaling molecules including interferons, tumor necrosis factor-α and Toll-like receptors are essential to the HSC response. Observing the biology of HSCs through the lens of infection and inflammation has led to the discovery of an array of immune-mediators that serve crucial roles in HSC regulation and function.

Impact of cytokine gene polymorphisms on risk and treatment outcomes of aplastic anemia

Autoreactive cytotoxic T cells play a key role in the pathogenesis of aplastic anemia (AA) by myelosuppressive cytokines including interferon-gamma, tumor necrosis factor alpha, and transforming growth factor beta. The purpose of this study is to determine which single nucleotide polymorphisms (SNPs) in cytokine genes were relevant to AA risk and whether the relevant SNPs were associated with response to immunosuppressive therapy (IST). Among 84 screened patients, 80 patients confirmed as having acquired AA, and 84 age- and sex-matched healthy controls were analyzed consecutively. We genotyped ten polymorphisms in three cytokine genes (IFNG, TNF, and TGFB1) and FAS gene. We assessed the association between polymorphisms and AA risk, and the association between polymorphisms and response to IST in three genetic models (dominant, recessive, and additive). The IFNG -2,353 T allele (dominant model, OR = 0.43, p = .012) and TCA haplotype (dominant model, OR = 0.50, p = .038) were significantly associated with the development of AA. In addition, this relevant IFNG -2,353 T allele and TCA haplotype were related to the response of IST (dominant model, OR = 0.076, p = .034). Concerning TGFB1, although its polymorphisms are not related to AA susceptibility, P10L T allele (recessive model, OR = 0.18, p = .038) and CT haplotype (dominant model, OR = 5.68, p = .038) were associated with response to IST. This exploratory study concurred with prior studies indicating that polymorphisms in IFNG are related to AA susceptibility. In addition, it was found that polymorphisms in IFNG and TGFB1 are associated with response to IST.

Abnormal immunity and stem/progenitor cells in acquired aplastic anemia

Acquired aplastic anemia (AA) is considered as an immune-mediated bone marrow failure syndrome, characterized by hypoplasia and pancytopenia with fatty bone marrow. Abnormal immunity is the major factor mediating the pathogenesis of acquired AA. Activated DCs might promote the polarization to Th1 cells, and activate CD8(+) T cells. A variety of immune molecules including IFN-gamma, TNF-alpha, MIP-1alpha and IL-2, 8, 12, 15, 17, 23, produced by them and stromal cells, compose a cytokine network to destruct stem/progenitor cells as well as hematopoietic stem/progenitor cells, mesenchymal stem cells (MSCs) and angioblasts/endothelial progenitor cells. Inversely, deficient MSCs, CD4(+)CD25(+) T cells, NK cells, NKT cells and early hematopoietic growth factors diminish the capacity of immune regulation and the support of hematopoiesis. As a result, stem/progenitor cells are significantly impaired to be disabled cells with markedly deficient proliferation, differentiation, induced apoptosis and dysfunctional response to growth factor stimuli, together with rare normal ones. Although some patients can be ameliorated by stem-cell transplantation or immunosuppressive therapy, more effective and convenient therapies such as patient-specific pluripotent iPS cells based on definite pathogenesis are expected.

Immunogenetic factors determining the evolution of T-cell large granular lymphocyte leukaemia and associated cytopenias

T-cell large granular lymphocyte leukaemia (T-LGL) is a chronic clonal proliferation of cytotoxic T lymphocytes (CTL). T-LGL presents with cytopenias, often accompanied by autoimmune diseases, suggesting clonal transformation arising from an initially polyclonal immune response. Various immunogenetic predisposition factors, previously described for both immune-mediated bone marrow failure and autoimmune conditions, may promote T-LGL evolution and/or development of cytopenias. The association of T-LGL was analysed with a number of immunogenetic factors in 66 patients, including human leucocyte antigen (HLA) and killer-cell immunoglobulin-like receptor (KIR) genotype, KIR/KIR-L mismatch, CTLA-4 (+49 A/G),CD16-158V/F, CD45 polymorphisms, cytokine single nucleotide polymorphisms including: TNF-alpha (-308G/A), TGF-beta1 (codons 10 C/T, 25 G/C), IL-10 (-1082 G/A), IL-6 (-174 C/G), and IFN-gamma(+874 T/A). A statistically significant increase in A/A genotype for TNF-alpha-308, IL-10-1082, andCTLA-4 +49 was observed in T-LGL patients compared with control, suggesting that the G allele serves a protective role in each case. No association was found between specific KIR/HLA profile and disease. KIR/KIR-L analysis revealed significant mismatches between KIR3DL2 and KIR2DS1 and their ligands HLA-A3/11 and HLA-C group 2 (P = 0.03 and 0.01 respectively); the biological relevance of this finding is questionable. The significance of additional genetic polymorphisms and their clinical correlation to evolution of T-LGL requires future analysis.

Interferon-gamma-induced gene expression in CD34 cells: identification of pathologic cytokine-specific signature profiles

Hematopoietic effects of interferon-gamma (IFN-gamma) may be responsible for certain aspects of the pathology seen in bone marrow failure syndromes, including aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and some forms of myelodysplasia (MDS). Overexpression of and hematopoietic inhibition by IFN-gamma has been observed in all of these conditions. In vitro, IFN-gamma exhibits strong inhibitory effects on hematopoietic progenitor and stem cells. Previously, we have studied the transcriptome of CD34 cells derived from patients with bone marrow failure syndromes and identified characteristic molecular signatures common to some of these conditions. In this report, we have investigated genome-wide expression patterns after exposure of CD34 and bone marrow stroma cells derived from normal bone marrow to IFN-gamma in vitro and have detected profound changes in the transcription profile. Some of these changes were concordant in both stroma and CD34 cells, whereas others were specific to CD34 cells. In general, our results were in agreement with the previously described function of IFN-gamma in CD34 cells involving activation of apoptotic pathways and immune response genes. Comparison between the IFN-gamma transcriptome in normal CD34 cells and changes previously detected in CD34 cells from AA and PNH patients reveals the presence of many similarities that may reflect molecular signature of in vivo IFN-gamma exposure.

Aplastic Anemia: Management of Adult Patients

The primary therapeutic approach to acquired aplastic anemia (AA) in older adults differs from the primary approach used in children and younger adults because in the former group, the results of allogeneic bone marrow transplantation (BMT) are less favorable. With increasing age of the patients, immunosuppressive therapy with antithymocyte globulin (ATG) and cyclosporine (CsA) constitutes the primary treatment option and may be better than BMT. There are very few clinical clues as to the selection of patients likely to respond to immunosuppression. Repeated ATG/CsA cycles are often used as salvage regimens, but in refractory patients BMT may be the best treatment option, as the prognosis for non-responders is poor without definitive treatment. Conservative therapy such as intense immunosuppression is associated with a high relapse rate but does not impact the survival and overall prognosis. The inability to eliminate autoimmune T cell clones using current therapeutic strategies suggests that prolonged immunosuppressive maintenance therapy may be needed for a substantial proportion of patients. Late clonal complications of conservatively treated patients include evolution to myelodysplasia and paroxysmal nocturnal hemoglobinuria and may develop in 20% of the patients. However, BMT also has several sequelae including an increased frequency of solid tumors. Novel immunosuppressive and immunomodulatory agents and constantly improving results of allogeneic BMT will further improve the survival rate of adult patients with AA.