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

Pediatric Bone Marrow Failure: A Broad Landscape in Need of Personalized Management

Irreversible severe bone marrow failure (BMF) is a life-threatening condition in pediatric patients. Most important causes are inherited bone marrow failure syndromes (IBMFSs) and (pre)malignant diseases, such as myelodysplastic syndrome (MDS) and (idiopathic) aplastic anemia (AA). Timely treatment is essential to prevent infections and bleeding complications and increase overall survival (OS). Allogeneic hematopoietic stem cell transplantation (HSCT) provides a cure for most types of BMF but cannot restore non-hematological defects. When using a matched sibling donor (MSD) or a matched unrelated donor (MUD), the OS after HSCT ranges between 60 and 90%. Due to the introduction of post-transplantation cyclophosphamide (PT-Cy) to prevent graft versus host disease (GVHD), alternative donor HSCT can reach similar survival rates. Although HSCT can restore ineffective hematopoiesis, it is not always used as a first-line therapy due to the severe risks associated with HSCT. Therefore, depending on the underlying cause, other treatment options might be preferred. Finally, for IBMFSs with an identified genetic etiology, gene therapy might provide a novel treatment strategy as it could bypass certain limitations of HSCT. However, gene therapy for most IBMFSs is still in its infancy. This review summarizes current clinical practices for pediatric BMF, including HSCT as well as other disease-specific treatment options.

Human leukocyte antigen-DRB1 gene polymorphism and aplastic anemia: A meta-analysis

BACKGROUND

The human leukocyte antigen-DRB1 (HLA-DRB1) gene plays key roles in mediating immune response and activating autoreactive T-cells during aplastic anemia (AA) etiology. However, inconsistency appeared in the associations between HLA-DRB1 polymorphism and AA. We aimed to comprehensively clarify their associations in the meta-analysis.

METHODS

PubMed, Embase, Web of Science, Science Direct, SinoMed, WanFang Data, China National Knowledge Infrastructure, and Chongqing VIP Chinese Science Database were searched from January 2000 to June 2022. Statistical analysis was performed in STATA 15.0 and Comprehensive Meta-analysis Software 3.0.

RESULTS

A total of 16 studies with 4428 patients were eventually analyzed. The results of the meta-analysis suggested that HLA-DRB1*0301 could decrease the risk of AA (odd ratio (OR) = 0.600, 95% CI: 0.427, 0.843). Besides, HLA-DRB1*0901 and HLA-DRB1*1501 were risk factors of AA (OR = 1.591, 95% CI: 1.045, 2.424; OR = 2.145, 95% CI: 1.501, 3.063; respectively). Sensitivity analysis showed heterogeneity among included studies.

CONCLUSION

HLA-DRB1 polymorphisms could play roles in the occurrence of AA, however more population-based studies with larger sample sizes are required to certify our findings.

Diagnostic Value of a Protocolized In-Depth Evaluation of Pediatric Bone Marrow Failure: A Multi-Center Prospective Cohort Study

Background

Severe multilineage cytopenia in childhood caused by bone marrow failure (BMF) often represents a serious condition requiring specific management. Patients are at risk for invasive infections and bleeding complications. Previous studies report low rates of identifiable causes of pediatric BMF, rendering most patients with a descriptive diagnosis such as aplastic anemia (AA).

Methods

We conducted a multi-center prospective cohort study in which an extensive diagnostic approach for pediatric patients with suspected BMF was implemented. After exclusion of malignant and transient causes of BMF, patients entered thorough diagnostic evaluation including bone marrow analysis, whole exome sequencing (WES) including copy number variation (CNV) analysis and/or single nucleotide polymorphisms (SNP) array analysis. In addition, functional and immunological evaluation were performed. Here we report the outcomes of the first 50 patients (2017-2021) evaluated by this approach.

Results

In 20 patients (40%) a causative diagnosis was made. In this group, 18 diagnoses were established by genetic analysis, including 14 mutations and 4 chromosomal deletions. The 2 remaining patients had short telomeres while no causative genetic defect was found. Of the remaining 30 patients (60%), 21 were diagnosed with severe aplastic anemia (SAA) based on peripheral multi-lineage cytopenia and hypoplastic bone marrow, and 9 were classified as unexplained cytopenia without bone marrow hypoplasia. In total 28 patients had undergone hematopoietic stem cell transplantation (HSCT) of which 22 patients with an unknown cause and 6 patients with an identified cause for BMF.

Conclusion

We conclude that a standardized in-depth diagnostic protocol as presented here, can increase the frequency of identifiable causes within the heterogeneous group of pediatric BMF. We underline the importance of full genetic analysis complemented by functional tests of all patients as genetic causes are not limited to patients with typical (syndromal) clinical characteristics beyond cytopenia. In addition, it is of importance to apply genome wide genetic analysis, since defects in novel genes are frequently discovered in this group. Identification of a causal abnormality consequently has implications for the choice of treatment and in some cases prevention of invasive therapies.

Antigen presentation safeguards the integrity of the hematopoietic stem cell pool

Hematopoietic stem and progenitor cells (HSPCs) are responsible for the production of blood and immune cells. Throughout life, HSPCs acquire oncogenic aberrations that can cause hematological cancers. Although molecular programs maintaining stem cell integrity have been identified, safety mechanisms eliminating malignant HSPCs from the stem cell pool remain poorly characterized. Here, we show that HSPCs constitutively present antigens via major histocompatibility complex class II. The presentation of immunogenic antigens, as occurring during malignant transformation, triggers bidirectional interactions between HSPCs and antigen-specific CD4⁺ T cells, causing stem cell proliferation, differentiation, and specific exhaustion of aberrant HSPCs. This immunosurveillance mechanism effectively eliminates transformed HSPCs from the hematopoietic system, thereby preventing leukemia onset. Together, our data reveal a bidirectional interaction between HSPCs and CD4⁺ T cells, demonstrating that HSPCs are not only passive receivers of immunological signals but also actively engage in adaptive immune responses to safeguard the integrity of the stem cell pool.

PNH Clones for Aplastic Anemia with Immunosuppressive Therapy: A Systematic Review and Meta-Analysis

OBJECTIVES

PNH clones, also aptly called "escape clones," are evidence of acquired immune-mediated bone marrow failure and have a high prevalence in patients with aplastic anemia (AA). Several studies have reported contradictory results regarding the impact of PNH clones on AA patients with immunosuppression treatment, and PNH clones have not been confirmed as positive predictors of response in the AA guidelines of the British Society for Standards in Haematology.

METHODS

We performed a meta-analysis to address this issue by searching for articles in PubMed, EMBASE, The Coch-rane Library, Web of Science, and ClinicalTrials.gov, and for abstracts from the annual meetings of the American Society of Hematology and the European Hematology Association. We included 1,236 participants from 11 cohort-controlled studies. Our primary outcome was the 6-month hematologic response with a secondary outcome of the mortality rate within 3 months.

RESULTS

A better response rate was observed in the PNH+ group than in the PNH- group (odds ratio [OR] 2.85; 95% confidence interval [CI] 2.17-3.75; p < 0.00001), and further subgroup analysis strengthened the outcome, with minor heterogeneity in non-Asian countries. In contrast, the early mortality was not significantly different between the PNH+ and PNH- groups (OR 0.54; 95% CI 0.26-1.10; p = 0.09).

CONCLUSIONS

The meta-analysis suggested an evidence-based role for PNH clones in predicting a better response in AA patients with immunosuppression.

Association of HLA class II (-DRB1,-DQB1,-DPB1) alleles and haplotypes on susceptibility to aplastic anemia in northern Chinese Han

The Human Leukocyte Antigen (HLA) genes, playing key roles in mediating the immune response, especially HLA class II alleles were suggested to play a role in the activation of autoreactive T-cells in aplastic anemia (AA). Previous studies in different ethnic groups have indicated that some of HLA-A,-B,-DRB1 alleles had a protective or susceptive association with the prevalence, pathogenesis and development of AA. HLA class II genes, especially HLA-DQB1 and -DPB1 alleles or haplotypes at high-resolution level associated with AA have not been fully identified in northern Chinese Han populations. The aim of this study was to identify association of the variations in HLA class II region with AA in northern Chinese Han population. A recent case-control study, including 96 AA patients and 824 healthy controls was performed. The high-resolution HLA genotyping was conducted by PCR-SBT, -SSO and NGS-ION S5^TM platform. Based on genotypic data of the three loci, haplotype estimation was carried out. HLA-DRB1*15:01 (Pc = 2.87 × 10^-3; OR = 2.11, 95% CI = 1.45-3.07) and HLA-DQB1*06:02 (Pc = 1.86 × 10^-2; OR = 2.01, 95% CI = 1.32-3.06) were the risk and predisposition alleles to AA in northern Chinese Han after considering multiple testing. Moreover, the HLA-DRB1*15:01-DQB1*06:02 (Pc = 4.90 × 10^-3; OR = 2.09, 95% CI = 1.37-3.19) and HLA-DRB1*14:05-DQB1*05:03 (Pc = 2.65 × 10^-2; OR = 2.82, 95%CI = 1.45-5.50) haplotypes had direct strong relevance to AA and were the susceptible haplotypes. HLA-DPB1 alleles and 23 polymorphic amino acid residues spanning exon 2 ~ 4 of DPβ1 molecules have showed no statistically significant associations between AA and controls. The present findings establish a novel link between inherited HLA-DRB1,-DQB1,-DPB1 risk alleles and haplotypes in northern Chinese Han with AA, and open new avenues for development of targeted therapies to prevent or redirect immunopathology in AA.

HLA-DRB1 polymorphisms and alopecia areata disease risk: A systematic review and meta-analysis

BACKGROUND

Published studies have reported conflicting and heterogeneous results regarding the association between human leukocyte antigen (HLA)-DRB1 polymorphisms and alopecia areata (AA). This study aimed to review and quantitatively analyze the association between HLA-DRB1 polymorphisms and AA.

METHODS

In this study, all relevant publications were searched through December 2016. Odds ratios (ORs) and confidence intervals (CIs) for comparisons between case and control groups were calculated. Stata 14.0 software was used to perform statistical analysis. This research does not require formal ethical approval because the data used in this analysis do not involve personal information and thus do not affect privacy.

RESULTS

Twelve articles were identified. For HLA-DRB1*04 and HLA-DRB1*16 polymorphisms, the OR (95% CIs) was 1.49 (1.24-1.78) and 1.61 (1.08-2.41), and P was <.01 and <.01, respectively. For HLA-DRB1*0301, HLA-DRB1*09, and HLA-DRB1*13 polymorphisms, the OR (95% CIs) was 0.42 (0.28-0.63), 0.74 (0.55-0.99), and 0.62 (0.40-0.98), and P was <.01, <.01, and <.01, respectively. Statistical evidence revealed no publication bias (P > .05).

CONCLUSION

The present meta-analysis suggested that HLA-DRB1*04 and HLA-DRB1*16 polymorphisms might be associated with increased AA risk, while HLA-DRB1*0301, HLA-DRB1*09, and HLA-DRB1*13 polymorphisms might decrease the AA risk. Studies with adequate methodological quality on gene-gene and gene-environment interactions are needed to validate the results in the future.

Associations between the HLA-A/B/DRB1 polymorphisms and aplastic anemia: evidence from 17 case-control studies

OBJECTIVE

To estimate the associations between HLA-A/B/DRB1 polymorphisms and aplastic anemia (AA), we carried out the meta-analysis.

METHODS

In this meta-analysis, all publications in English and Chinese were considered up to 30 September 2015. The electronic databases we searched were Pubmed, Science Direct, Embase, Web of Science, CNKI, Wanfang Data and VIP. We conducted all statistical data analyses in the Stata11.0 software.

RESULTS

A total of 17 studies including 9164 subjects (containing 1372 cases and 7792 controls) were retrieved, which studied the relationship between HLA-A/B/DRB1 and AA. Odds ratios (ORs) with 95% confidence intervals (CIs) for the comparisons between cases and controls were calculated. The result revealed that HLA-A*02 and HLA-DRB1 (*0407, *15 and *1501) polymorphisms might increase the risk of AA. Otherwise, HLA-DRB1 (*0301, *04, *0406, *0802, *1301, *1302 and *14) were protective against AA. But, other sites of HLA-A/B/DRB1 in our study had no correlations with AA (all P_c > 0.05).

CONCLUSION

In conclusion, HLA-A/B/DRB1 polymorphisms may play an important role in AA, but higher quality and larger sample studies are needed to confirm.