Human CARMIL2 deficiency underlies a broader immunological and clinical phenotype than CD28 deficiency

Human immunity to fungal infections

Fungi increasingly threaten health globally. Mycoses range from life-threatening, often iatrogenic conditions, to enigmatic syndromes occurring without apparent immunosuppression. Despite some recent advances in antifungal drug development, complementary therapeutic strategies are essential for addressing these opportunistic pathogens. One promising avenue is leveraging host immunity to combat fungal infections; this necessitates deeper understanding of the molecular immunology of human fungal susceptibility to differentiate beneficial versus harmful immunopathological responses. Investigating human models of fungal diseases in natural settings, particularly through genetic immunodeficiencies and ethnographic-specific genetic vulnerabilities, reveals crucial immune pathways essential for fighting various yeasts and molds. This review highlights the diversity in intrinsic fungal susceptibility across individuals and populations, through genetic- and autoantibody-mediated processes, complementing previous principles learned from animal studies and iatrogenic contexts. Improved understanding of human immunity to fungal diseases will facilitate the development of host-directed immunotherapies and targeted public health interventions, paving the way for precision medicine in fungal disease management.

Human Immune Responses to Epstein-Barr Virus Highlighted by Immunodeficiencies

Inborn errors of immunity (IEIs) represent unique in natura models that uncover key components of immunity in humans, in particular those that predispose to infections. Epstein-Barr virus (EBV) is one of the most common opportunistic infectious agents in humans and is responsible for several diseases, including infectious mononucleosis, nonmalignant and malignant lymphoproliferative disorders, hemophagocytic lymphohistiocytosis, and smooth muscle and epithelial tumors. For most individuals, EBV infection persists for life without pathological consequences. IEIs that do not predispose to EBV infection suggest that innate and humoral responses are not necessary or redundant for the immune response to EBV. IEIs associated with high susceptibility to EBV infection provide unequivocal genetic proof of the central role of CD8+ T cell responses in immunity to EBV. They also highlight the distinct steps and pathways required for, on the one hand, the effector cytotoxic functions of CD8+ T cells and, on the other hand, the expansion and maturation of cytotoxic CD8+ T cells.

Genomic profiling at a single center cracks the code in inborn errors of immunity

Inborn errors of immunity (IEI) entail a diverse group of disorders resulting from hereditary or de novo mutations in single genes, leading to immune dysregulation. This study explores the clinical utility of next-generation sequencing (NGS) techniques in diagnosing monogenic immune defects. Eight patients attending the immunodeficiency clinic and with unclassified antibody deficiency were included in the analysis. Clinical records, immune characteristics, and family histories were reviewed, and a target gene panel (TGP) sequencing was performed to identify pathogenic variants. TGPs identified seven variants in TNFRSF13B (TACI), CARMIL2, STAT1, STAT3, and ORAI1 genes. These findings provided definitive diagnoses and proper prognostic assessment. Patients exhibited a wide range of clinical manifestations, including recurrent infections, autoimmune cytopenias, and organ-specific complications. The genetic diversity observed highlights the importance of genetic testing in diagnosing IEIs and tailoring treatments. This study underscores the role of TGPs in diagnosing IEIs, revealing significant genetic heterogeneity and phenotypic variability. They offer a precise tool for identifying underlying genetic defects, facilitating personalized medicine approaches, and eventually improving patient outcomes. The findings emphasize the need for comprehensive genetic testing to uncover novel pathogenic variants, enhancing our understanding of immune system dysfunction. NGS is a critical tool for the management of IEI, enabling precise diagnosis and personalized treatment strategies. Despite resource limitations, the progressive affordability is likely to expand its clinical utility, ultimately improving patient care and advancing the field of immunology. In the meantime, accurate phenotypic assessment is essential for resource optimization and case prioritization.

The monogenic landscape of human infectious diseases

The spectrum of known monogenic inborn errors of immunity is growing, with certain disorders underlying a specific and narrow range of infectious diseases. These disorders reveal the core mechanisms by which these infections occur in various settings, including inherited and acquired immunodeficiencies, thereby delineating the essential mechanisms of protective immunity to the corresponding pathogens. These findings also have medical implications, facilitating diagnosis and improving the management of individuals at risk of disease.

Recurrent eosinophilia with a novel homozygous ARPC1B mutation

Cytoskeletal network dysregulation is a pivotal determinant in various immunodeficiencies and autoinflammatory conditions. This report reviews the significance of actin remodeling in disease pathogenesis, focusing on the Arp2/3 complex and its regulatory subunit actin related protein 2/3 complex subunit 1B (ARPC1B). A spectrum of cellular dysfunctions associated with ARPC1B deficiency, impacting diverse immune cell types, is elucidated. The study presents a patient featuring recurrent and persistent eosinophilia attributed to homozygous ARPC1B mutation alongside concomitant compound heterozygous cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. We used ARPC1B antibody to stain the patient's peripheral blood lymphocytes and those of the control. The defect in the ARPC1B gene in the present patient caused absent/low expression by immunofluorescence microscopy. The intricate interplay between cytoskeletal defects and immunological manifestations underscores the complexity of disease phenotypes, warranting further exploration for targeted therapeutic strategies.

Impaired development of memory B cells and antibody responses in humans and mice deficient in PD-1 signaling

T follicular helper (Tfh) cells abundantly express the immunoreceptor programmed cell death protein 1 (PD-1), and the impact of PD-1 deficiency on antibody (Ab)-mediated immunity in mice is associated with compromised Tfh cell functions. Here, we revisited the role of the PD-1-PD-L1 axis on Ab-mediated immunity. Individuals with inherited PD-1 or PD-L1 deficiency had fewer memory B cells and impaired Ab responses, similar to Pdcd1-/- and Cd274-/-Pdcd1lg2-/- mice. PD-1, PD-L1, or both could be detected on the surface of human naive B cells following in vitro activation. PD-1- or PD-L1-deficient B cells had reduced expression of the transcriptional regulator c-Myc and c-Myc-target genes in vivo, and PD-1 deficiency or neutralization of PD-1 or PD-L1 impeded c-Myc expression and Ab production in human B cells isolated in vitro. Furthermore, B cell-specific deletion of Pdcd1 prevented the physiological accumulation of memory B cells in mice. Thus, PD-1 shapes optimal B cell memory and Ab-mediated immunity through B cell-intrinsic and B cell-extrinsic mechanisms, suggesting that B cell dysregulation contributes to infectious and autoimmune complications following anti-PD-1-PD-L1 immunotherapy.

Expanding the spectrum of IPEX: from new clinical findings to novel treatments

PURPOSE OF REVIEW

This review aims to provide an overview of recent research findings regarding immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome, focusing on clinical and immunological novelties, as well as emerging treatment strategies, based on the published literature of the last few years.

RECENT FINDINGS

While it is well known that IPEX can present with a wide range of atypical clinical manifestations, new and unique phenotypes continue to emerge, making it essential to maintain a high level of clinical suspicion both at the time of diagnosis and during follow-up. This unpredictability in clinical presentation is further compounded by the lack of a clear genotype-phenotype correlation. A valuable tool for monitoring comes from recent discoveries regarding the epigenetic signature of Tregs, which, by correlating with disease severity, could prove to be a useful biomarker for diagnosis and ongoing management. The use of biological agents is emerging as an alternative to traditional immunosuppression. Additionally, ongoing studies are exploring the feasibility of gene therapy through the introduction of the wild-type FOXP3 into peripheral CD4 + T cells.

SUMMARY

Further research is needed to fully understand the variable clinical presentations of IPEX and optimize tailored therapies, ensuring better management and outcomes for affected individuals.

Secondary Membranous Nephropathy and Immunodeficiency due to a Novel Biallelic Variant in CARMIL2

The cytosolic capping protein, Arp2/3 and myosin-I linker protein 2 or CARMIL2 plays an important role in T/B/NK cell function. Biallelic disease causing variants in CARMIL2 are known to cause immunodeficiency 58. We report a 13-year-old girl with recurrent infections, dermatitis and nephrotic syndrome since childhood. Her renal biopsy was suggestive of membranous nephropathy. Exome sequencing showed a homozygous novel stopgain variant, c.520C>T in CARMIL2 (NM_001013838.3). We expand the phenotypic spectrum of CARMIL2 related immunodeficiency to include membranous nephropathy secondary to probable immune dysregulation.

IL-7-dependent and -independent lineages of IL-7R-dependent human T cells

Infants with biallelic IL7R loss-of-function variants have severe combined immune deficiency (SCID) characterized by the absence of autologous T lymphocytes, but normal counts of circulating B and NK cells (T-B+NK+ SCID). We report 6 adults (aged 22 to 59 years) from 4 kindreds and 3 ancestries (Colombian, Israeli Arab, Japanese) carrying homozygous IL7 loss-of-function variants resulting in combined immunodeficiency (CID). Deep immunophenotyping revealed relatively normal counts and/or proportions of myeloid, B, NK, and innate lymphoid cells. By contrast, the patients had profound T cell lymphopenia, with low proportions of innate-like adaptive mucosal-associated invariant T and invariant NK T cells. They also had low blood counts of T cell receptor (TCR) excision circles, recent thymic emigrant T cells and naive CD4+ T cells, and low overall TCR repertoire diversity, collectively indicating impaired thymic output. The proportions of effector memory CD4+ and CD8+ T cells were high, indicating IL-7-independent homeostatic T cell proliferation in the periphery. Intriguingly, the proportions of other T cell subsets, including TCRγδ+ T cells and some TCRαβ+ T cell subsets (including Th1, Tfh, and Treg) were little affected. Peripheral CD4+ T cells displayed poor proliferation, but normal cytokine production upon stimulation with mitogens in vitro. Thus, inherited IL-7 deficiency impairs T cell development less severely and in a more subset-specific manner than IL-7R deficiency. These findings suggest that another IL-7R-binding cytokine, possibly thymic stromal lymphopoietin, governs an IL-7-independent pathway of human T cell development.

DIAPH1-Deficiency is Associated with Major T, NK and ILC Defects in Humans

Loss of function mutations in Diaphanous related formin 1 (DIAPH1) are associated with seizures, cortical blindness, and microcephaly syndrome (SCBMS) and are recently linked to combined immunodeficiency. However, the extent of defects in T and innate lymphoid cells (ILCs) remain unexplored. Herein, we characterized the primary T, natural killer (NK) and helper ILCs of six patients carrying two novel loss of function mutation in DIAPH1 and Jurkat cells after DIAPH1 knockdown. Mutations were identified by whole exome sequencing. T-cell immunophenotyping, proliferation, migration, cytokine signaling, survival, and NK cell cytotoxicity were studied via flow cytometry-based assays, confocal microscopy, and real-time qPCR. CD4+ T cell proteome was analyzed by mass spectrometry. p.R351* and p.R322*variants led to a significant reduction in the DIAPH1 mRNA and protein levels. DIAPH1-deficient T cells showed proliferation, activation, as well as TCR-mediated signaling defects. DIAPH1-deficient PBMCs also displayed impaired transwell migration, defective STAT5 phosphorylation in response to IL-2, IL-7 and IL-15. In vitro generation/expansion of Treg cells from naïve T cells was significantly reduced. shRNA-mediated silencing of DIAPH1 in Jurkat cells reduced DIAPH1 protein level and inhibited T cell proliferation and IL-2/STAT5 axis. Additionally, NK cells from patients had diminished cytotoxic activity, function and IL-2/STAT5 axis. Lastly, DIAPH1-deficient patients' peripheral blood contained dramatically reduced numbers of all helper ILC subsets. DIAPH1 deficiency results in major functional defects in T, NK cells and helper ILCs underlining the critical role of formin DIAPH1 in the biology of those cell subsets.

CARMIL1 regulates liver cancer cell proliferation by activating the ERK/mTOR pathway through the TRIM27/p53 axis

Capping protein regulatory factor and myosin 1 linker 1 is termed CARMIL1. CARMIL1 is involved in several physiological processes; it forms an actin filament network and plasma membrane-bound cellular projection tissues and positively regulates the cellular components and tissues. CARMIL1 exhibits important biological functions in cancer; nonetheless, these functions have not been completely explored. We aimed to investigate the novel functions of CARMIL1 in liver cancer, particularly in cell proliferation. The cell counting kit-8, 5-ethynyl-2'-deoxyuridine, Component A experiments, and subcutaneous tumor formation model suggest that CARMIL1 is central to the proliferation of liver cancer cells both in vivo and in vitro. We extracted CARMIL1 samples from The Cancer Genome Atlas Program and analyzed its enrichment. CARMIL1 regulated the pathway activity by affecting the expression of star molecular proteins of the extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR). Moreover, it influenced the proliferation ability of liver cancer cells. Western blotting suggested that CARMIL1 downregulation could affect ERK and mTOR phosphorylation. Results of the co-immunoprecipitation demonstrated that CARMIL1 binds to tripartite motif (TRIM)27, which in turn binds to p53. Subsequently, CARMIL1 can regulate p53 stability and promote its degradation through TRIM27. Additionally, CARMIL1 inhibition enhanced the sensitivity of liver cancer cells to sorafenib. Tumor growth was significantly inhibited in the group treated with sorafenib and CARMIL1, compared with the group treated with CARMIL1 alone. Sorafenib is a first-line targeted chemotherapeutic drug for hepatocellular carcinoma treatment. It increases the long-term survival of hepatocellular carcinoma by 44%. In this study, downregulated CARMIL1 combined with sorafenib significantly reduced the tumor volume and weight of the mouse subcutaneous tumor model, indicating the potential possibility of combining CARMIL1 with sorafenib in hepatocellular carcinoma treatment. In summary, CARMIL1 promotes liver cancer cell proliferation by regulating the TRIM27/p53 axis and activating the ERK/mTOR pathway.

Tipping the balance in autoimmunity: are regulatory t cells the cause, the cure, or both?

Regulatory T cells (Tregs) are a specialized subgroup of T-cell lymphocytes that is crucial for maintaining immune homeostasis and preventing excessive immune responses. Depending on their differentiation route, Tregs can be subdivided into thymically derived Tregs (tTregs) and peripherally induced Tregs (pTregs), which originate from conventional T cells after extrathymic differentiation at peripheral sites. Although the regulatory attributes of tTregs and pTregs partially overlap, their modes of action, protein expression profiles, and functional stability exhibit specific characteristics unique to each subset. Over the last few years, our knowledge of Treg differentiation, maturation, plasticity, and correlations between their phenotypes and functions has increased. Genetic and functional studies in patients with numeric and functional Treg deficiencies have contributed to our mechanistic understanding of immune dysregulation and autoimmune pathologies. This review provides an overview of our current knowledge of Treg biology, discusses monogenetic Treg pathologies and explores the role of Tregs in various other autoimmune disorders. Additionally, we discuss novel approaches that explore Tregs as targets or agents of innovative treatment options.

Multilayer concept of autoimmune mechanisms and manifestations in inborn errors of immunity: Relevance for precision therapy

Autoimmunity in inborn errors of immunity (IEIs) has a multifactorial pathogenesis and develops subsequent to a genetic predisposition in conjunction with gene regulation, environmental modifiers, and infectious triggers. On the basis of incremental data availability owing to upfront application of omics technologies, a more granular and dynamic view of mechanisms and manifestations is warranted. Here, we present a comprehensive novel concept of autoimmunity in IEIs that considers multiple layers of interdependent elements and connects 101 causative genes or deletions according to the quality of the allelic variants with 47 molecular pathways and 22 immune effector mechanisms. Furthermore, we list 50 resulting manifestations together with the corresponding Human Phenotype Ontology terms and review the types and frequencies of the most relevant clinical presentations. When all of its elements are taken together, this concept (1) extends the historical anatomic view of central versus peripheral tolerance toward multiple interdependent mechanisms of immune tolerance, (2) delineates the mechanisms underlying the protean clinical manifestations, and thereby, (3) points toward the most suitable precision therapy for autoimmunity in IEIs. The multilayer concept of autoimmune mechanisms and manifestations in IEIs will facilitate research design and provide clinical guidance on the use of precision medicine irrespective of the data depth available in each health care scenario.

Inborn errors of immunity underlying defective T-cell memory

PURPOSE OF REVIEW

T-cell memory is a complex process not well understood involving specific steps, pathways and different T-cell subpopulations. Inborn errors of immunity (IEIs) represent unique models to decipher some of these requirements in humans. More than 500 different IEIs have been reported to date, and recently a subgroup of monogenic disorders characterized by memory T-cell defects has emerged, providing novel insights into the pathways of T-cell memory generation and maintenance, although this new knowledge is mostly restricted to peripheral blood T-cell memory populations.

RECENT FINDINGS

This review draws up an inventory of the main and recent IEIs associated with T-cell memory defects and their mice models, with a particular focus on the nuclear factor kappa B (NF-κB) signalling pathway, including the scaffold protein capping protein regulator and myosin 1 linker 2 (CARMIL2) and the T-cell co-stimulatory molecules CD28 and OX-40. Besides NF-κB, IKZF1 (IKAROS), a key transcription factor of haematopoiesis and STAT3-dependent interleukin-6 signals involving the transcription factor ZNF341 also appear to be important for the generation of T cell memory. Somatic reversion mosaicism in memory T cells is documented for several gene defects supporting the critical role of these factors in the development of memory T cells with a potential clinical benefit.

SUMMARY

Systematic examination of T-cell memory subsets could be helpful in the diagnosis of IEIs.

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.