Redefining Precision Medicine in Disorders of Immune Dysregulation

Impact of SARS-CoV-2 infection and COVID-19 on patients with inborn errors of immunity

Since the arrival of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in December 2019, its characterization as a novel human pathogen, and the resulting coronavirus disease 2019 (COVID-19) pandemic, over 6.5 million people have died worldwide-a stark and sobering reminder of the fundamental and nonredundant roles of the innate and adaptive immune systems in host defense against emerging pathogens. Inborn errors of immunity (IEI) are caused by germline variants, typically in single genes. IEI are characterized by defects in development and/or function of cells involved in immunity and host defense, rendering individuals highly susceptible to severe, recurrent, and sometimes fatal infections, as well as immune dysregulatory conditions such as autoinflammation, autoimmunity, and allergy. The study of IEI has revealed key insights into the molecular and cellular requirements for immune-mediated protection against infectious diseases. Indeed, this has been exemplified by assessing the impact of SARS-CoV-2 infection in individuals with previously diagnosed IEI, as well as analyzing rare cases of severe COVID-19 in otherwise healthy individuals. This approach has defined fundamental aspects of mechanisms of disease pathogenesis, immunopathology in the context of infection with a novel pathogen, and therapeutic options to mitigate severe disease. This review summarizes these findings and illustrates how the study of these rare experiments of nature can inform key features of human immunology, which can then be leveraged to improve therapies for treating emerging and established infectious diseases.

Human JAK1 gain of function causes dysregulated myelopoeisis and severe allergic inflammation

Primary atopic disorders are a group of inborn errors of immunity that skew the immune system toward severe allergic disease. Defining the biology underlying these extreme monogenic phenotypes reveals shared mechanisms underlying common polygenic allergic disease and identifies potential drug targets. Germline gain-of-function (GOF) variants in JAK1 are a cause of severe atopy and eosinophilia. Modeling the JAK1GOF (p.A634D) variant in both zebrafish and human induced pluripotent stem cells (iPSCs) revealed enhanced myelopoiesis. RNA-Seq of JAK1GOF human whole blood, iPSCs, and transgenic zebrafish revealed a shared core set of dysregulated genes involved in IL-4, IL-13, and IFN signaling. Immunophenotypic and transcriptomic analysis of patients carrying a JAK1GOF variant revealed marked Th cell skewing. Moreover, long-term ruxolitinib treatment of 2 children carrying the JAK1GOF (p.A634D) variant remarkably improved their growth, eosinophilia, and clinical features of allergic inflammation. This work highlights the role of JAK1 signaling in atopic immune dysregulation and the clinical impact of JAK1/2 inhibition in treating eosinophilic and allergic disease.

Future of Therapy for Inborn Errors of Immunity

Over the past 20 years, the rapid evolution in the diagnosis and treatment of primary immunodeficiencies (PI) and the recognition of immune dysregulation as a feature in some have prompted the use of "inborn errors of immunity" (IEI) as a more encompassing term used to describe these disorders [1, 2] . This article aims to review the future of therapy of PI/IEI (referred to IEI throughout this paper). Historically, immune deficiencies have been characterized as monogenic disorders resulting in immune deficiencies affecting T cells, B cells, combination of T and B cells, or innate immune disorders. More recently, immunologists are also recognizing a variety of phenotypes associated with one genotype or similar phenotypes across genotypes and a role for incomplete penetrance or variable expressivity of some genes causing inborn errors of immunity [3]. The IUIS classification of immune deficiencies (IEIs) has evolved over time to include 10 categories, with disorders of immune dysregulation accounting for a new subset, some treatable with small molecule inhibitors or biologics. [1] Until recently, management options were limited to prompt treatment of infections, gammaglobulin replacement, and possibly bone marrow transplant depending on the defect. Available therapies have expanded to include small molecule inhibitors, biologics, gene therapy, and the use of adoptive transfer of virus-specific T cells to fight viral infections in immunocompromised patients. Several significant contributions to the field of clinical immunology have fueled the rapid advancement of therapies over the past two decades. Among these are educational efforts to recruit young immunologists to the field resulting in the growth of a world-wide community of clinicians and investigators interested in rare diseases, efforts to increase awareness of IEI globally contributing to international collaborations, along with advancements in diagnostic genetic testing, newborn screening, molecular biology techniques, gene correction, use of immune modulators, and ex vivo expansion of engineered T cells for therapeutic use. The development and widespread use of newborn screening have helped to identify severe combined immune deficiency (SCID) earlier resulting in better outcomes [4]. Continual improvements and accessibility of genetic sequencing have helped to identify new IEI diseases at an accelerated pace [5]. Advances in gene therapy and bone marrow transplant have made treatments possible in otherwise fatal diseases. Furthermore, the increased awareness of IEI across the world has driven networks of immunologists working together to improve the diagnosis and treatment of these rare diseases. These improvements in the diagnosis and treatment of IEI noted over the past 20 years bring hope for a better future for the IEI community. This paper will review future directions in a few of the newer therapies emerging for IEI. For easy reference, most of the diseases discussed in this paper are briefly described in a summary table, in the order mentioned within the paper (Appendix).