Germline gain-of-function (GOF) mutations in the signal transducer and activator of transcription 1 (STAT1) gene cause a dominantly inherited inborn error of immunity (IEI) characterized by chronic mucocutaneous candidiasis, autoimmunity, severe opportunistic infections and an increased risk of malignancy. Allogeneic hematopoietic stem cell (HSC) transplantation (HSCT) is curative but is associated with increased risk of morbidity and mortality in STAT1 GOF patients compared to other IEI. To develop a curative, autologous alternative to HSCT, we evaluated gene editing strategies in STAT1 GOF model cell lines, primary T cells, and patient-derived HSCs. Universal and mutation-specific strategies using CRISPR/Cas-mediated homology-directed repair (HDR) were limited by low efficacy (<25%), poor viability, and a lack of allele-specificity. In contrast, adenine base editing corrected the recurrent and highly pathogenic p.T385M mutation with upwards of 90% efficiency in patient T cells and HSCs without significant unintended on- or off-target genomic aberrations. Gene editing functionally restored total STAT1 expression (p<0.0217), STAT1 phosphorylation (p<0.0056), interferon-stimulated gene expression (OAS1; p=0.0005) and improved IL-17 production (p<0.0001). Edited HSCs retained multilineage differentiation capacity and sustained engraftment with persistence of the corrected allele at 16 weeks in humanized immunodeficient mice. These data demonstrate efficient and precise correction of STAT1 GOF mutations by base editing, with maintenance of the correction through long-term engraftment in vivo. This represents the first application of gene editing to correct a dominant gain-of-function mutation causing immunodeficiency, with potential applicability to other genetic disorders associated with heterozygous and gain-of-function mutations.

Outcomes following international MDT assessment of adult IEI patients for allogeneic HSCT suggest early referral is vital: patients considered too high risk for transplant have poor outcomes with a 3-year overall survival of 31%.

ABSTRACT:Signal transduction and activator of transcription 3 hyperimmunoglobulin E syndrome (STAT3-HIES) is a multisystem disorder causing recurrent skin and respiratory infection with bronchiectasis, pneumatoceles, and aspergillosis; lymphoma; and extraimmune manifestations including fractures and vasculopathy. Published data on immune and extraimmune hematopoietic stem cell transplant (HSCT) outcomes focus on case reports or small cohorts. We conducted an international multicenter retrospective study of HSCT in STAT3-HIES. Primary end points were overall survival (OS) and event-free survival (EFS; events were death, graft failure, chronic graft-versus-host disease [GVHD]). We identified 41 patients over a 28-year period. HSCT indication was infection (93%) or lymphoma (7%). Median age at HSCT was 14 years (range, 4-45). Most patients had pre-HSCT respiratory disease (93%), including parenchymal lung disease (68%), and prior suspected/confirmed pulmonary fungal infection (32%). Patients received peripheral blood stem cells (51%) or marrow (49%) from HLA 10/10-matched unrelated donors (44%), matched family donors (44%), mismatched family donors (10%), or 1 9/10-mismatched unrelated donor (2%). Conditioning regimens were predominantly treosulfan-based (59%; with thiotepa, 34%); other patients received busulfan-based (24%) or melphalan-based (17%) regimens. Median follow-up for surviving patients was 5 years (0.8-28). The 5-year OS was 93%, and 5-year EFS 90%. Cumulative incidence of grade 2 to 4 acute GVHD was 22%. Median whole blood donor chimerism at latest follow-up was 100%. Eighty-seven percent of patients have reduced or no bacterial or fungal respiratory infection. After HSCT, 20% developed new skeletal fractures. This worldwide study expanded data on HSCT for STAT3-HIES to 41 patients; despite significant pre-HSCT pulmonary morbidity, OS was high, and patients have improved skin and respiratory disease though the impact on extraimmune manifestations appears limited.

Allogeneic haematopoietic stem cell transplantation (alloHSCT) is safe and effective for adolescents and adults with inborn errors of immunity (IEI) with severe disease manifestations of their disease. The haematopoietic cell transplantation comorbidity index (HCT-CI) score predicts transplant survival in non-malignant diseases, including IEIs. We hypothesised that immune dysregulation pre-transplant may also influence transplant outcomes. We calculated the pre-transplant immune dysregulation and disease activity score (IDDA v2.1) for 82 adolescent and adult IEI patients (aged ≥ 13 years). Three-year overall survival (OS) for the whole cohort was 90

Inborn errors of immunity (IEIs), also known as primary immunodeficiencies, are a group of rare inherited disorders that affect the immune system. They result in severe, opportunistic infections, severe autoimmune manifestations and a predisposition to malignancy. The only curative treatment for many years has been allogenic haematopoietic stem cell transplantation (alloHSCT). However, this requires the availability of a suitable donor and has risks of morbidity and mortality. Autologous gene therapy (GT) abrogates the immunological complications of alloHSCT and uses the patient's own cells, removing the need for a donor. Preclinical proof-of-concept and clinical trials in humans have demonstrated that GT is safe and effective and can be used to correct a variety of IEIs. In this review, we outline the progress in developing GT for IEIs over the last four decades. We describe the gene editing technologies available to correct IEIs and their current applications. We also examine advances in GT development, the challenges to its application, and discuss future developments in the field, including emerging in vivo approaches.

Effective gene therapy approaches have been developed for many rare diseases, including inborn errors of immunity and metabolism, haemoglobinopathies and inherited blindness. Despite successful pre-clinical and clinical results, these gene therapies are not widely available, primarily for non-medical reasons. Lack of commercial interest in therapies for ultra-rare diseases, costs of development and complex manufacturing processes required for advanced therapy medicinal products (ATMPs) are some of the main problems that are restricting access. The complexities and costs of navigating the regulatory environments in different jurisdictions for treatments that affect small numbers of patients is a problem unique to ATMPS for rare and ultra-rare diseases. In this Perspective, we outline some of the challenges and potential solutions that, we hope, will improve access to gene therapy for rare diseases.

Background: Cytotoxic T-lymphocyte antigen 4 (CTLA-4) insufficiency causes a primary immune regulatory disorder characterized by lymphoproliferation, dysgammaglobulinemia, and multiorgan autoimmunity including cytopenias and colitis. Objective: We examined the outcome of hematopoietic stem cell transplantation (HSCT) for CTLA-4 insufficiency and study the impact of pre-HSCT CTLA-4 fusion protein (CTLA-4-Ig) therapy and pre-HSCT immune dysregulation on survival and immunologic outcome. Methods: This was a retrospective study of HSCT for CTLA-4 insufficiency and 2q33.2-3 deletion from the European Society for Blood and Marrow Transplantation Inborn Errors Working Party. Primary end points were overall survival (OS) and disease- and chronic graft-versus-host disease-free survival (DFS). Secondary end point was immunologic outcome assessed by immune dysregulation disease activity (IDDA) score. Results: Forty patients were included over a 25-year period. Before HSCT, 60% received CTLA-4-Ig, and median (range) IDDA score was 23.3 (3.9-84.0). Median (range) age at HSCT was 14.2 (1.3-56.0) years. Patients received peripheral blood stem cell (58%) or marrow (43%) from a matched unrelated donor (75%), mismatched unrelated donor (12.5%), or matched family donor (12.5%). Median (range) follow-up was 3 (0.6-15) years, and 3year OS was 76.7% (58-87%) and DFS was 74.4% (54.9-86.0%). At latest follow-up, disease of 28 of 30 surviving patients was in disease-free remission with median IDDA reduction of 16. Probability of OS and DFS was greater in patients with lower disease activity before HSCT (IDDA < 23, P = .002 and P = .006, respectively). CTLA-4-Ig receipt did not influence OS or DFS. Cause of death was transplant related in 7 of 8 patients. Conclusion: HSCT is an effective therapy to prevent ongoing disease progression and morbidity, with improving survival rates over time and in patients with lower pre-HSCT disease activity.

Patients with haematological malignancies are more likely to have poor responses to vaccination. Here we provide detailed analysis of the humoral and cellular responses to COVID-19 vaccination in 69 patients with B-cell malignancies. Measurement of anti-spike IgG in serum demonstrated a low seroconversion rate with 27.1% and 46.8% of patients seroconverting after the first and second doses of vaccine, respectively. In vitro pseudoneutralisation assays demonstrated a poor neutralising response, with 12.5% and 29.5% of patients producing a measurable neutralising titre after the first and second doses, respectively. A third dose increased seropositivity to 54.3% and neutralisation to 51.5%, while a fourth dose further increased both seropositivity and neutralisation to 87.9%. Neutralisation titres post-fourth dose showed a positive correlation with the size of the B-cell population measured by flow cytometry, suggesting an improved response correlating with recovery of the B-cell compartment after B-cell depletion treatments. In contrast, interferon gamma ELISpot analysis showed a largely intact T-cell response, with the percentage of patients producing a measurable response boosted by the second dose to 75.5%. This response was maintained thereafter, with only a small increase following the third and fourth doses, irrespective of the serological response at these timepoints.

We assessed a cohort of people living with human immunodeficiency virus (PLWH) (n = 110) and HIV negative controls (n = 64) after 1, 2 or 3 SARS-CoV-2 vaccine doses. At all timepoints, PLWH had significantly lower neutralizing antibody (nAb) titers than HIV-negative controls. We also observed a delayed development of neutralization in PLWH that was underpinned by a reduced frequency of spike-specific memory B cells (MBCs). Improved neutralization breadth was seen against the Omicron variant (BA.1) after the third vaccine dose in PLWH but lower nAb responses persisted and were associated with global MBC dysfunction. In contrast, SARS-CoV-2 vaccination induced robust T cell responses that cross-recognized variants in PLWH. Strikingly, individuals with low or absent neutralization had detectable functional T cell responses. These PLWH had reduced numbers of circulating T follicular helper cells and an enriched population of CXCR3(+)CD127(+)CD8(+)T cells after two doses of SARS-CoV-2 vaccination.

Allogeneic hematopoietic stem cell transplantation (alloSCT) is curative for severe inborn errors of immunity (IEIs), with recent data suggesting alloSCT in adulthood is safe and effective in selected patients. However, questions remain regarding the indications for and optimal timing of transplant. We retrospectively compared outcomes of transplanted vs matched nontransplanted adults with severe IEIs. Seventy-nine patients (aged >= 15 years) underwent alloSCT between 2008 and 2018 for IEIs such as chronic granulomatous disease (n = 20) and various combined immune deficiencies (n = 59). A cohort of nontransplanted patients from the French Centre de R ' ef ' erence D ' eficits Immunitaires H ' er ' editaires registry was identified blindly for case-control analysis, with <= 3 matched controls per index patient, without replacement. The nontransplanted patients were matched for birth decade, age at last review greater than index patient age at alloSCT, chronic granulomatous disease or combined immune deficiencies, and autoimmune/lymphoproliferative complications. A total of 281 patients were included (79 transplanted, 202 nontransplanted). Median age at transplant was 21 years. Transplant indications were mainly lymphoproliferative disease (n = 23) or colitis (n = 15). Median follow-up was 4.8 years (interquartile range, 2.5-7.2). One-year transplant-related mortality rate was 13%. Estimated disease-free survival at 5 years was higher in transplanted patients (58% vs 33%; P = .007). Nontransplanted patients had an ongoing risk of severe events, with an increased mean cumulative number of recurrent events compared with transplanted patients. Sensitivity analyses removing patients with common variable immune deficiency and their matched transplanted patients confirm these results. AlloSCT prevents progressive morbidity associated with IEIs in adults, which may outweigh the negative impact of transplant-related mortality.

Natural killer (NK) cell subsets with adaptive properties are emerging as regulators of vaccine-induced T and B cell responses and are specialized towards antibody-dependent functions contributing to SARS-CoV-2 control. Although HIV-1 infection is known to affect the NK cell pool, the additional impact of SARS-CoV-2 infection and/or vaccination on NK cell responses in people living with HIV (PLWH) has remained unexplored. Our data show that SARS-CoV-2 infection skews NK cells towards a more differentiated/adaptive CD57 + FcεRIγ − phenotype in PLWH. A similar subset was induced following vaccination in SARS-CoV-2 naïve PLWH in addition to a CD56 bright population with cytotoxic potential. Antibody-dependent NK cell function showed robust and durable responses to Spike up to 148 days post-infection, with responses enriched in adaptive NK cells. NK cell responses were further boosted by the first vaccine dose in SARS-CoV-2 exposed individuals and peaked after the second dose in SARS-CoV-2 naïve PLWH. The presence of adaptive NK cells associated with the magnitude of cellular and humoral responses. These data suggest that features of adaptive NK cells can be effectively engaged to complement and boost vaccine-induced adaptive immunity in potentially more vulnerable groups such as PLWH.

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Purpose Allogeneic hematopoietic stem cell transplant (HSCT) remains the treatment of choice for patients with inborn errors of immunity (IEI). There is little published medical outcome data assessing late medical complications following transition to adult care. We sought to document event-free survival (EFS) in transplanted IEI patients reaching adulthood and describe common late-onset medical complications and factors influencing EFS. Methods In this landmark analysis, 83 adults surviving 5 years or more following prior HSCT in childhood for IEI were recruited. The primary endpoint was event-free survival, defined as time post-first HSCT to graft failure, graft rejection, chronic infection, life-threatening or recurrent infections, malignancy, significant autoimmune disease, moderate to severe GVHD or major organ dysfunction. All events occurring less than 5 years post-HSCT were excluded. Results EFS was 51% for the whole cohort at a median of 20 years post HSCT. Multivariable analysis identified age at transplant and whole blood chimerism as independent predictors of long-term EFS. Year of HSCT, donor, conditioning intensity and underlying diagnosis had no significant impact on EFS. 59 events occurring beyond 5 years post-HSCT were documented in 37 patients (45% cohort). A total of 25 patients (30% cohort) experienced ongoing significant complications requiring active medical intervention at last follow-up. Conclusion Although most patients achieved excellent, durable immune reconstitution with infrequent transplant-related complications, very late complications are common and associated with mixed chimerism post-HSCT. Early intervention to correct mixed chimerism may improve long-term outcomes and adult health following HSCT for IEI in childhood.

Inborn errors of immunity (IEIs) are a heterogeneous group of inherited disorders of the immune system. Many IEIs have a severe clinical phenotype that results in progressive morbidity and premature mortality. Over 450 IEIs have been described and the incidence of all IEIs is 1/1,000–10,000 people. Current treatment options are unsatisfactory for many IEIs. Allogeneic haematopoietic stem cell transplantation (alloHSCT) is curative but requires the availability of a suitable donor and carries a risk of graft failure, graft rejection and graft-versus-host disease (GvHD). Autologous gene therapy (GT) offers a cure whilst abrogating the immunological complications of alloHSCT. Gene editing (GE) technologies allow the precise modification of an organisms’ DNA at a base-pair level. In the context of genetic disease, this enables correction of genetic defects whilst preserving the endogenous gene control machinery. Gene editing technologies have the potential to transform the treatment landscape of IEIs. In contrast to gene addition techniques, gene editing using the CRISPR system repairs or replaces the mutation in the DNA. Many IEIs are limited to the lymphoid compartment and may be amenable to T cell correction alone (rather than haematopoietic stem cells). T cell Gene editing has the advantages of higher editing efficiencies, reduced risk of deleterious off-target edits in terminally differentiated cells and less toxic conditioning required for engraftment of lymphocytes. Although most T cells lack the self-renewing property of HSCs, a population of T cells, the T stem cell memory compartment has long-term multipotent and self-renewal capacity. Gene edited T cell therapies for IEIs are currently in development and may offer a less-toxic curative therapy to patients affected by certain IEIs. In this review, we discuss the history of T cell gene therapy, developments in T cell gene editing cellular therapies before detailing exciting pre-clinical studies that demonstrate gene editing T cell therapies as a proof-of-concept for several IEIs.

People living with HIV (PLWH) on suppressive antiretroviral therapy (ART) can have residual immune dysfunction and often display poorer responses to vaccination. We assessed in a cohort of PLWH (n=110) and HIV negative controls (n=64) the humoral and spike-specific B-cell responses following 1, 2 or 3 SARS-CoV-2 vaccine doses. PLWH had significantly lower neutralizing antibody (nAb) titers than HIV-negative controls at all studied timepoints. Moreover, their neutralization breadth was reduced with fewer individuals developing a neutralizing response against the Omicron variant (BA.1) relative to controls. We also observed a delayed development of neutralization in PLWH that was underpinned by a reduced frequency of spike-specific memory B cells (MBCs) and pronounced B cell dysfunction. Improved neutralization breadth was seen after the third vaccine dose in PLWH but lower nAb responses persisted and were associated with global, but not spike-specific, MBC dysfunction. In contrast to the inferior antibody responses, SARS-CoV-2 vaccination induced robust T cell responses that cross-recognized variants in PLWH. Strikingly, a subset of PLWH with low or absent neutralization had detectable functional T cell responses. These individuals had reduced numbers of circulating T follicular helper cells and an enriched population of CXCR3 + CD127 + CD8 + T cells after two doses of SARS-CoV-2 vaccination, which may compensate for sub-optimal serological responses in the event of infection. Therefore, normalisation of B cell homeostasis could improve serological responses to vaccines in PLWH and evaluating T cell immunity could provide a more comprehensive immune status profile in these individuals and others with B cell imbalances.

We report a case of FLT3-mutated AML with t(6;9) in which induction chemotherapy with DA and midostaurin failed to achieve complete cytogenetic or molecular remission. Due to the COVID-19 pandemic and co-existing cellulitis, monotherapy with the selective FLT3-inhibitor gilteritinib was used as an alternative consol-idation treatment option rather than further intensive chemotherapy. Gilteritinib was able to achieve complete molecular and cytogenetic remission despite the additional cytogenetic abnormality. This case provides supporting evidence for the use of single agent gilteritinib in high-risk primary refractory FLT3-mutated AML with t(6;9) prior to transplantation.

Heterozygous mutations in CTLA-4 result in an inborn error of immunity with an autoimmune and frequently severe clinical phenotype. Autologous T cell gene therapy may offer a cure without the immunological complications of allogeneic hematopoietic stem cell transplantation. Here, we designed a homology-directed repair (HDR) gene editing strategy that inserts the CTLA-4 cDNA into the first intron of the CTLA-4 genomic locus in primary human T cells. This resulted in regulated expression of CTLA-4 in CD4 + T cells, and functional studies demonstrated CD80 and CD86 transendocytosis. Gene editing of T cells isolated from three patients with CTLA-4 insufficiency also restored CTLA-4 protein expression and rescued transendocytosis of CD80 and CD86 in vitro. Last, gene-corrected T cells from CTLA-4 −/− mice engrafted and prevented lymphoproliferation in an in vivo murine model of CTLA-4 insufficiency. These results demonstrate the feasibility of a therapeutic approach using T cell gene therapy for CTLA-4 insufficiency.