Are All Primary Immunodeficiency Disorders Inborn Errors of Immunity?

Renal complications in patients with predominantly antibody deficiency in the United States Immune Deficiency Network (USIDNET)

BACKGROUND

Prior studies have reported that renal insufficiency occurs in a small percentage of patients with predominantly antibody deficiency (PAD) and in about 2% of patients with common variable immunodeficiency.

OBJECTIVE

The goal of our study was to understand and evaluate the prevalence and type of renal complications in patients with PAD in the United States Immunodeficiency Network (USIDNET) cohort. We hypothesized that there is an association between certain renal complications and severity of immunophenotype in patients with PAD.

METHODS

We performed a query of patients with PAD from the USIDNET cohort with renal complications. Patients with documented renal disease such as chronic kidney disease (CKD), nephrolithiasis, nephritis, and renal failure syndrome were included. We compared immunophenotype, flow cytometry findings, and immunoglobulin levels of patients with PAD accompanied by renal complications with those of the total USIDNET cohort of patients with PAD.

RESULTS

We determined that 140 of 2071 patients with PAD (6.8%) had renal complications. Of these 140 patients, 50 (35.7%) had CKD, 46 (32.9%) had nephrolithiasis, 18 (12.9 %) had nephritis, and 50 (35.7%) had other renal complications. Compared with the total USIDNET cohort of patients with PAD, patients with CKD had lower absolute lymphocyte counts, CD3+ T-cell counts, CD4+ T-cell counts, CD19+ B-cell counts, CD20+ B-cell counts, and CD27+IgD- B-cell counts (P < .05 for all). Patients with nephritis had lower absolute lymphocyte counts, CD19+ B-cell counts, CD27+ B-cell counts, and IgE levels (P < .05 for all) than patients with PAD without renal disease.

CONCLUSIONS

We determined that 6.8% of the USIDNET cohort of patients with PAD had a documented renal complication. Compared with the overall cohort of patients with PAD, those patients with nephritis and CKD had a more severe immunophenotype.

Challenges for gene editing in common variable immunodeficiency disorders: Current and future prospects

The original CRISPR Cas9 gene editing system and subsequent innovations offers unprecedented opportunities to correct severe genetic defects including those causing Primary Immunodeficiencies (PIDs). Common Variable Immunodeficiency Disorders (CVID) are the most frequent symptomatic PID in adults and children. Unlike many other PIDs, patients meeting CVID criteria do not have a definable genetic defect and cannot be considered to have an inborn error of immunity (IEI). Patients with a CVID phenotype carrying a causative mutation are deemed to have a CVID-like disorder consequent to an IEI. Patients from consanguineous families often have highly penetrant early-onset autosomal recessive forms of CVID-like disorders. Individuals from non-consanguineous families may have autosomal dominant CVID-like disorders with variable penetrance and expressivity. This essay explores the potential clinical utility as well as the current limitations and risks of gene editing including collateral genotoxicity. In the immediate future the main application of this technology is likely to be the in vitro investigation of epigenetic and polygenic mechanisms, which are likely to underlie many cases of CVID and CVID-like disorders. In the longer-term, the CRISPR Cas9 system and other gene-based therapies could be utilized to treat CVID-like disorders, where the underlying IEI is known.

The Rapidly Expanding Genetic Spectrum of Common Variable Immunodeficiency-Like Disorders

The understanding of common variable immunodeficiency disorders (CVID) is in evolution. CVID was previously a diagnosis of exclusion. New diagnostic criteria have allowed the disorder to be identified with greater precision. With the advent of next-generation sequencing (NGS), it has become apparent that an increasing number of patients with a CVID phenotype have a causative genetic variant. If a pathogenic variant is identified, these patients are removed from the overarching diagnosis of CVID and are deemed to have a CVID-like disorder. In populations where consanguinity is more prevalent, the majority of patients with severe primary hypogammaglobulinemia will have an underlying inborn error of immunity, usually an early-onset autosomal recessive disorder. In nonconsanguineous societies, pathogenic variants are identified in approximately 20% to 30% of patients. These are often autosomal dominant mutations with variable penetrance and expressivity. To add to the complexity of CVID and CVID-like disorders, some genetic variants such as those in TNFSF13B (transmembrane activator calcium modulator cyclophilin ligand interactor) predispose to, or enhance, disease severity. These variants are not causative but can have epistatic (synergistic) interactions with more deleterious mutations to worsen disease severity. This review is a description of the current understanding of genes associated with CVID and CVID-like disorders. This information will assist clinicians in interpreting NGS reports when investigating the genetic basis of disease in patients with a CVID phenotype.

Selective IgA Deficiency May Be an Underrecognized Risk Factor for Severe COVID-19

SARS-CoV-2, the agent responsible for COVID-19, has wreaked havoc around the globe. Hundreds of millions of individuals have been infected and well over six million have died from COVID-19. Many COVID-19 survivors have ongoing physical and psychiatric morbidity, which will remain for the rest of their lives. Early in the pandemic, it became apparent that older individuals and those with comorbidities including obesity, diabetes mellitus, coronary artery disease, hypertension, and renal and pulmonary disease were at increased risk of adverse outcomes. It is also clear that some immunodeficient patients, such as those with innate or T cell-immune defects, are at greater risk from COVID-19. Selective IgA deficiency (sIgAD) is generally regarded as a mild disorder in which most patients are asymptomatic because of redundancy in protective immune mechanisms. Recent data indicate that patients with sIgAD may be at high risk of severe COVID-19. SARS-CoV-2 gains entry primarily through the upper respiratory tract mucosa, where IgA has a critical protective role. This may underlie the vulnerability of sIgAD patients to adverse outcomes from COVID-19. This perspective highlights the need for ongoing research into mucosal immunity to improve COVID-19 treatments for patients with sIgAD.

Critical role of diagnostic SARS-CoV-2 T cell assays for immunodeficient patients

After almost 3 years of intense study, the immunological basis of COVID-19 is better understood. Patients who suffer severe disease have a chaotic, destructive immune response. Many patients with severe COVID-19 produce high titres of non-neutralising antibodies, which are unable to sterilise the infection. In contrast, there is increasing evidence that a rapid, balanced cellular immune response is required to eliminate the virus and mitigate disease severity. In the longer term, memory T cell responses, following infection or vaccination, play a critical role in protection against SARS-CoV-2.Given the pivotal role of cellular immunity in the response to COVID-19, diagnostic T cell assays for SARS-CoV-2 may be of particular value for immunodeficient patients. A diagnostic SARS-CoV-2 T cell assay would be of utility for immunocompromised patients who are unable to produce antibodies or have passively acquired antibodies from subcutaneous or intravenous immunoglobulin (SCIG/IVIG) replacement. In many antibody-deficient patients, cellular responses are preserved. SARS-CoV-2 T cell assays may identify breakthrough infections if reverse transcriptase quantitative PCR (RT-qPCR) or rapid antigen tests (RATs) are not undertaken during the window of viral shedding. In addition to utility in patients with immunodeficiency, memory T cell responses could also identify chronically symptomatic patients with long COVID-19 who were infected early in the pandemic. These individuals may have been infected before the availability of reliable RT-qPCR and RAT tests and their antibodies may have waned. T cell responses to SARS-CoV-2 have greater durability than antibodies and can also distinguish patients with infection from vaccinated individuals.

SARS-CoV-2 Omicron: Light at the End of the Long Pandemic Tunnel or Another False Dawn for Immunodeficient Patients?

COVID-19 has had a disastrous impact on the world. Apart from at least 6 million deaths, countless COVID-19 survivors are suffering long-term physical and psychiatric morbidity. Hundreds of millions have been plunged into poverty caused by economic misery, particularly in developing nations. Early in the pandemic, it became apparent certain groups of individuals such as the elderly and those with comorbidities were more likely to suffer severe disease. In addition, patients with some forms of immunodeficiency, including those with T-cell and innate immune defects, were at risk of poor outcomes. Patients with immunodeficiencies are also disadvantaged as they may not respond optimally to COVID-19 vaccines and often have pre-existing lung damage. SARS-CoV-2 Omicron (B.1.529) and its subvariants (BA.1, BA.2, etc) have emerged recently and are dominating COVID-19 infections globally. Omicron is associated with a reduced risk of hospitalization and appears to have a lower case fatality rate compared with previous SARS-CoV-2 variants. Omicron has offered hope the pandemic may finally be coming to an end, particularly for vaccinated, healthy individuals. The situation is less clear for individuals with vulnerabilities, particularly immunodeficient patients. This perspective offers insight into potential implications of the SARS-CoV-2 Omicron variant for patients with immunodeficiencies.