Perspective: diagnostic laboratories should urgently develop T cell assays for SARS-CoV-2 infection

Introduction: Diagnostic tests play a critical role in the management of Sars-CoV-2, the virus responsible for COVID-19. There are two groups of tests, which are in widespread use to identify patients who have contracted the virus. The commonly used reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) test becomes negative once viral shedding ceases by approximately 2-3weeks. Antibody tests directed to viral antigens become positive after the second week of infection. IgG antibody responses to the virus are muted in children, pregnant females, and those with mild symptoms. IgA and IgM antibodies rapidly wane, although IgG antibodies directed to the receptor-binding domain (RBD) of the spike (S) glycoprotein are more durable. Current data show variability in the sensitivity of commercial and in-house antibody tests to SARS-CoV-2.Areas covered: The role of T cells in acute illness is uncertain, but long-term protection against the virus may rely on memory T cell responses. Measuring memory T cell responses is important for retrospective confirmation of cases, who may have been infected early in the pandemic before reliable RT-qPCR tests were available and whose SARS-CoV-2 antibodies may have become undetectable. Relevant peer-reviewed published references from PubMed are included up to 15 March 2021.Expert opinion: After surveying the literature, the authors present the case for urgent development of diagnostic T cell assays for SARS-CoV-2 by accredited laboratories.

Bronchiectasis is associated with delayed diagnosis and adverse outcomes in the New Zealand Common Variable Immunodeficiency Disorders cohort study

Common variable immunodeficiency disorders (CVID) are multi-system disorders where target organ damage is mediated by infective, autoimmune and inflammatory processes. Bronchiectasis is probably the most common disabling complication of CVID. The risk factors for bronchiectasis in CVID patients are incompletely understood. The New Zealand CVID study (NZCS) is a nationwide longitudinal observational study of adults, which commenced in 2006. In this analysis, the prevalence and risk factors for bronchiectasis were examined in the NZCS. After informed consent, clinical and demographic data were obtained with an interviewer-assisted questionnaire. Linked electronic clinical records and laboratory results were also reviewed. Statistical methods were applied to determine if variables such as early-onset disease, delay in diagnosis and increased numbers of infections were associated with greater risk of bronchiectasis. One hundred and seven adult patients with a diagnosis of CVID are currently enrolled in the NZCS, comprising approximately 70% of patients known to have CVID in New Zealand. Fifty patients (46·7%) had radiologically proven bronchiectasis. This study has shown that patients with compared to those without bronchiectasis have an increased mortality at a younger age. CVID patients with bronchiectasis had a greater number of severe infections consequent to early-onset disease and delayed diagnosis. Indigenous Māori have a high prevalence of CVID and a much greater burden of bronchiectasis compared to New Zealand Europeans. Diagnostic latency has not improved during the study period. Exposure to large numbers of infections because of early-onset disease and delayed diagnosis was associated with an increased risk of bronchiectasis. Earlier diagnosis and treatment of CVID may reduce the risk of bronchiectasis and premature death in some patients.

Perspective: Application of the American College of Medical Genetics Variant Interpretation Criteria to Common Variable Immunodeficiency Disorders

Common variable immunodeficiency disorders (CVIDs) are rare primary immunodeficiency diseases (PIDs) mostly associated with late onset antibody failure leading to immune system failure. Patients with CVID are predisposed to disabling complications such as bronchiectasis and systemic autoimmunity. In recent years a large number of genetic defects have become associated with these disorders. Patients with a causative mutation are deemed to have CVID-like disorders, while those with mutations predisposing to or modifying disease severity remain within the spectrum of CVID as defined by current diagnostic criteria. Next-generation sequencing (NGS) allows simultaneous analysis of multiple genes. Potential mutations identified from NGS are commonly evaluated with the American College of Medical Genetics (ACMG) variant interpretation criteria to determine their pathogenicity (causality). Patients with CVID and CVID-like disorders have marked genetic, allelic, and phenotypic heterogeneity. Although all patients with a CVID phenotype should undergo genetic testing, the complexity of the genetics associated with these disorders is challenging. Variants of unknown significance (VUS) remain a significant barrier to realising the full potential of NGS in CVID and CVID-like disorders. Here we explore the nuances of applying the ACMG criteria to patients with CVID and CVID-like disorders. Close collaboration between the clinician, bioinformatics, and genetics professionals will improve the diagnostic yield from genetic testing and reduce the frequency of VUS.

Characterization of the clinical and immunologic phenotype and management of 157 individuals with 56 distinct heterozygous NFKB1 mutations

BACKGROUND

An increasing number of NFKB1 variants are being identified in patients with heterogeneous immunologic phenotypes.

OBJECTIVE

To characterize the clinical and cellular phenotype as well as the management of patients with heterozygous NFKB1 mutations.

METHODS

In a worldwide collaborative effort, we evaluated 231 individuals harboring 105 distinct heterozygous NFKB1 variants. To provide evidence for pathogenicity, each variant was assessed in silico; in addition, 32 variants were assessed by functional in vitro testing of nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) signaling.

RESULTS

We classified 56 of the 105 distinct NFKB1 variants in 157 individuals from 68 unrelated families as pathogenic. Incomplete clinical penetrance (70%) and age-dependent severity of NFKB1-related phenotypes were observed. The phenotype included hypogammaglobulinemia (88.9%), reduced switched memory B cells (60.3%), and respiratory (83%) and gastrointestinal (28.6%) infections, thus characterizing the disorder as primary immunodeficiency. However, the high frequency of autoimmunity (57.4%), lymphoproliferation (52.4%), noninfectious enteropathy (23.1%), opportunistic infections (15.7%), autoinflammation (29.6%), and malignancy (16.8%) identified NF-κB1-related disease as an inborn error of immunity with immune dysregulation, rather than a mere primary immunodeficiency. Current treatment includes immunoglobulin replacement and immunosuppressive agents.

CONCLUSIONS

We present a comprehensive clinical overview of the NF-κB1-related phenotype, which includes immunodeficiency, autoimmunity, autoinflammation, and cancer. Because of its multisystem involvement, clinicians from each and every medical discipline need to be made aware of this autosomal-dominant disease. Hematopoietic stem cell transplantation and NF-κB1 pathway-targeted therapeutic strategies should be considered in the future.

Defining Common Variable Immunodeficiency Disorders in 2020

Common variable immunodeficiency disorders (CVID) are the most frequent symptomatic primary immune deficiency in adults. Because there is no known cause for these conditions, there is no single clinical feature or laboratory test that can confirm the diagnosis with certainty. If a causative mutation is identified, patients are deemed to have a CVID-like disorder caused by a specific primary immunodeficiency/inborn error of immunity. In the remaining patients, the explanation for these disorders remains unclear. The understanding of CVID continues to evolve and the authors review recent studies, which have addressed some of these uncertainties.

Inhaled modified angiotensin converting enzyme 2 (ACE2) as a decoy to mitigate SARS-CoV-2 infection

COVID-19 is a new zoonotic disease caused by the SARS-CoV-2 virus. Since its emergence in Wuhan City, China, the virus has rapidly spread across the globe causing calamitous health, economic and societal consequences. It causes disproportionately severe disease in the elderly and those with co-morbidities, such as hypertension and diabetes. There is currently no proven treatment for COVID-19 and a safe and effective vaccine is at least a year away. The virus gains access to the respiratory epithelium through cell surface angiotensin converting enzyme 2 (ACE2). The receptor binding domain (RBD) of the virus is unlikely to mutate without loss of pathogenicity and thus represents an attractive target for antiviral treatment. Inhaled modified recombinant human ACE2, may bind SARS-CoV-2 and mitigate lung damage. This decoy strategy is unlikely to provoke an adverse immune response and may reduce morbidity and mortality in high-risk groups.

TREATMENT OF IDIOPATHIC RETINAL VASCULITIS, ANEURYSMS, AND NEURORETINITIS (IRVAN) WITH PHOTOCOAGULATION IN COMBINATION WITH SYSTEMIC IMMUNOSUPPRESSION

BACKGROUND

Idiopathic retinal vasculitis, aneurysms, and neuroretinitis syndrome is a very rare primary retinal vasculitis. It seems to evolve in stages, where there is initially a florid vasculitis associated with aneurysm formation. Neuroretinitis and macula edema are common features. Subsequently, retinal ischemia ensues, leading to neovascularization. If untreated, further sight-threatening complications occur, including traction retinal detachment and secondary glaucoma.

METHODS AND RESULTS

Here, we describe a patient with early idiopathic retinal vasculitis, aneurysms, and neuroretinitis syndrome, who was treated with a combination of systemic immunosuppression and localized photocoagulation. There was substantial regression of the aneurysms and improvement of the macular edema. Treatment of the disorder should be based on the clinical stage and complications of the disorder.

CONCLUSIONS

As shown here, a multidisciplinary approach can be very helpful in managing patients with this severe sight-threatening disorder.

The critical role of histology in distinguishing sarcoidosis from common variable immunodeficiency disorder (CVID) in a patient with hypogammaglobulinemia

Background

Common variable immunodeficiency disorders (CVID) are a rare group of primary immune defects, where the underlying cause is unknown. Approximately 10–20% of patients with typical CVID have a granulomatous variant, which has closely overlapping features with sarcoidosis.

Case presentation

Here we describe a young man who sequentially developed refractory Evans syndrome, cauda equina syndrome and most recently renal impairment. Following immunosuppression, he has made a recovery from all three life-threatening autoimmune disorders. As the patient was hypogammaglobulinemic for most of the time while on immunosuppression, vaccine challenges and other tests were not possible. Histological features were in keeping with sarcoidosis rather than the granulomatous variant of CVID. In the brief period when immunosuppression was lifted between the cauda equina syndrome and renal impairment, he normalised his immunoglobulins, confirming sarcoidosis rather than CVID was the underlying cause.

Conclusion

We discuss diagnostic difficulties distinguishing the two conditions, and the value of histological features in our diagnostic criteria for CVID in identifying sarcoidosis, while the patient was hypogammaglobulinemic. The key message from this case report is that the characteristic histological features of CVID can be very helpful in making (or excluding) the diagnosis, particularly when other tests are not possible.

Transient hypogammaglobulinaemia of infancy: many patients recover in adolescence and adulthood

Transient hypogammaglobulinaemia of infancy (THI) is a relatively rare disorder where there is an exaggeration of the physiological nadir of immunoglobulin (Ig)G between loss of transplacentally acquired maternal IgG and production by the infant. Patients may be vulnerable to infections during the period of hypogammaglobulinaemia. The precise time to recovery in all infants is currently unknown. We sought to determine the clinical features and time-course of recovery for patients with THI. We reviewed our experience with THI over the last three decades in order to describe clinical and laboratory features, as well as the time-course of recovery. Forty-seven patients were identified with THI. Only thirty-seven per cent remitted by 4 years of age, while some patients did not recover until the third or fourth decade. In keeping with previous studies, the majority (25 of 47) presented with recurrent infections, nine had a family history of immunodeficiency and 13 had adverse reactions to food as their dominant clinical manifestation. Chronic tonsillitis developed in 10 patients and symptoms improved following surgery. The group with food allergies recovered sooner than those presenting with infections or with a family history immunodeficiency. Eight patients failed to respond to at least one routine childhood vaccine. Two have IgA deficiency and four individuals recovering in adolescence and adulthood continue to have borderline/low IgG levels. None have progressed to common variable immunodeficiency disorders (CVID). THI is a misnomer, as the majority do not recover in infancy. Recovery from THI can extend into adulthood. THI must be considered in the differential diagnosis of adolescents or young adults presenting with primary hypogammaglobulinemia.

The Natural History of Untreated Primary Hypogammaglobulinemia in Adults: Implications for the Diagnosis and Treatment of Common Variable Immunodeficiency Disorders (CVID)

Background: Adults with primary hypogammaglobulinemia are frequently encountered by clinicians. Where IgG levels are markedly decreased, most patients are treated with subcutaneous or intravenous immunoglobulin (SCIG/IVIG), because of the presumed risk of severe infections. The natural history of untreated severe asymptomatic hypogammaglobulinemia is thus unknown. Similarly, there are no long-term prospective studies examining the natural history of patients with moderate reductions in IgG.

Methods: In 2006, we began a prospective cohort study of patients with symptomatic and asymptomatic reductions in IgG who were not immediately commenced on SCIG/IVIG. Over the course of 12 years, 120 patients were enrolled in the NZ hypogammaglobulinemia study (NZHS) including 59 who were asymptomatic.

Results: Five patients with profound primary hypogammaglobulinemia (IgG < 3 g/l), who were not on regular SCIG/IVIG have remained well for a mean duration of 139 months. This study has also shown most asymptomatic patients with moderate hypogammaglobulinemia (IgG 3.0–6.9 g/l) have been in good health for a mean observation period of 96 months. We have only identified one asymptomatic patient with moderate hypogammaglobulinemia who experienced progressive decline in IgG levels to <3 g/l and was accepted for IVIG replacement. Prospective monitoring has shown that none have suffered catastrophic infections or any of the severe autoimmune or inflammatory sequelae associated with Common Variable Immunodeficiency Disorders (CVID). Unexpectedly, 18.1% of asymptomatic and 41.6% of symptomatic hypogammaglobulinemic patients spontaneously increased their IgG into the normal range (≥7.0 g/l) on at least one occasion, which we have termed transient hypogammaglobulinemia of adulthood (THA). In this study, vaccine challenge responses have correlated poorly with symptomatic state and long-term prognosis including subsequent SCIG/IVIG treatment.

Conclusions: In spite of our favorable experience, we recommend patients with severe asymptomatic hypogammaglobulinemia are treated with SCIG/IVIG because of the potential risk of severe infections. Patients with moderate asymptomatic hypogammaglobulinemia have a good prognosis. Patients with symptomatic hypogammaglobulinemia are a heterogeneous group where some progress to SCIG/IVIG replacement, while many others spontaneously recover. This study has implications for the diagnosis and treatment of CVID.

Autoimmune diseases after hepatitis B immunization in adults: Literature review and meta-analysis, with reference to 'autoimmune/autoinflammatory syndrome induced by adjuvants' (ASIA)

BACKGROUND

To assess if hepatitis B vaccination in adults is causally associated with autoimmune diseases. Such causation has been claimed based mainly on case reports and uncontrolled studies, and a syndrome 'Autoimmune/autoinflammatory Disorder Induced by Adjuvants' (ASIA) has been claimed to be linked to immunization, particularly hepatitis B vaccination.

METHODS

Review of peer-reviewed literature from January 1990 to March 2017 identifying controlled studies with documented incidence of autoimmune diseases occurring after hepatitis B vaccinations in adults. From 1297 studies identified, 259 were further assessed and 49 reviewed further; 19 relevant papers reporting 21 results are reviewed here, and 14 results included in a meta-analysis.

RESULTS

Overall no association between hepatitis B vaccination and the onset of autoimmune diseases was seen. The overall odds ratio was 1.06, with 95% confidence limits of 0.93-1.21, with non-significant heterogeneity. Only one study showed a significant excess risk between hepatitis B immunisation and autoimmune disease.

CONCLUSIONS

Despite multiple case reports, there is no reliable scientific evidence of autoimmune diseases being caused by hepatitis B vaccinations.

Keeping it in the family: the case for considering late-onset combined immunodeficiency a subset of common variable immunodeficiency disorders

INTRODUCTION

Common variable immunodeficiency disorders (CVID) are the most frequent symptomatic primary immune defect in adults. Within the broad spectrum of CVID, a proportion of patients present with a predominant T cell phenotype associated with increased mortality. These patients are termed late-onset combined immunodeficiency (LOCID) and are currently separated from patients suffering from CVID. Areas covered: We have recently codiscovered a new CVID-like disorder caused by mutations of the NFKB1 gene. Members of this non-consanguineous New Zealand kindred have a very diverse spectrum of phenotypes in spite of carrying the identical mutation. The proband appears to have the autoimmune variant. The proband's recently deceased sister best matched LOCID while other family members are less severely affected, including one asymptomatic adult brother, who has an affected daughter. Differences in genetics was one of the main arguments for separating these disorders in the past. Expert commentary: Given the recent advances in the understanding of the genetic basis of these conditions, we present the case that LOCID should now be considered a subset of CVID, rather than a separate disorder. At a clinical level, this distinction is less important but it is imperative these patients are carefully evaluated, the relevant complications are treated, and they are offered prognostic information.

Clinical Implications of Digenic Inheritance and Epistasis in Primary Immunodeficiency Disorders

The existence of epistasis in humans was first predicted by Bateson in 1909. Epistasis describes the non-linear, synergistic interaction of two or more genetic loci, which can substantially modify disease severity or result in entirely new phenotypes. The concept has remained controversial in human genetics because of the lack of well-characterized examples. In humans, it is only possible to demonstrate epistasis if two or more genes are mutated. In most cases of epistasis, the mutated gene products are likely to be constituents of the same physiological pathway leading to severe disruption of a cellular function such as antibody production. We have recently described a digenic family, who carry mutations of TNFRSF13B/TACI as well as TCF3 genes. Both genes lie in tandem along the immunoglobulin isotype switching and secretion pathway. We have shown they interact in an epistatic way causing severe immunodeficiency and autoimmunity in the digenic proband. With the advent of next generation sequencing, it is likely other families with digenic inheritance will be identified. Since digenic inheritance does not always cause epistasis, we propose an epistasis index which may help quantify the effects of the two mutations. We also discuss the clinical implications of digenic inheritance and epistasis in humans with primary immunodeficiency disorders.

Initial intravenous immunoglobulin doses should be based on adjusted body weight in obese patients with primary immunodeficiency disorders

Background

Immunoglobulin therapy plays a critical role in the treatment of immunodeficiency disorders as well as autoimmune and inflammatory conditions. In immunodeficient patients, there has been controversy whether initial loading doses of intravenous (IVIG) should be based on actual body weight or a calculated parameter such as adjusted body weight in obese patients.

Case presentation

I describe a patient with Common Variable Immunodeficiency disorder (CVID) who underwent bariatric surgery for morbid obesity. Her weight decreased by 50% to below her calculated ideal body weight (IBW) while her immunoglobulin requirement fell by approximately 20%. Her steady state serum IgG increased from approximately 7 g/l to 11.7 g/l concomitant with weight loss.

Conclusions

I present this observation as support for the recommendation that initial loading doses of SCIG/IVIG in immunodeficiency should be based on adjusted body weight (AjBW) and not actual body weight in obese patients. This has important fiscal implications for treating obese patients with immunodeficiency disorders.

Epistatic interactions between mutations of TACI (TNFRSF13B) and TCF3 result in a severe primary immunodeficiency disorder and systemic lupus erythematosus

Common variable immunodeficiency disorders (CVID) are a group of primary immunodeficiencies where monogenetic causes account for only a fraction of cases. On this evidence, CVID is potentially polygenic and epistatic although there are, as yet, no examples to support this hypothesis. We have identified a non-consanguineous family, who carry the C104R (c.310T>C) mutation of the Transmembrane Activator Calcium-modulator and cyclophilin ligand Interactor (TACI, TNFRSF13B) gene. Variants in TNFRSF13B/TACI are identified in up to 10% of CVID patients, and are associated with, but not solely causative of CVID. The proband is heterozygous for the TNFRSF13B/TACI C104R mutation and meets the Ameratunga et al. diagnostic criteria for CVID and the American College of Rheumatology criteria for systemic lupus erythematosus (SLE). Her son has type 1 diabetes, arthritis, reduced IgG levels and IgA deficiency, but has not inherited the TNFRSF13B/TACI mutation. Her brother, homozygous for the TNFRSF13B/TACI mutation, is in good health despite profound hypogammaglobulinemia and mild cytopenias. We hypothesised that a second unidentified mutation contributed to the symptomatic phenotype of the proband and her son. Whole-exome sequencing of the family revealed a de novo nonsense mutation (T168fsX191) in the Transcription Factor 3 (TCF3) gene encoding the E2A transcription factors, present only in the proband and her son. We demonstrate mutations of TNFRSF13B/TACI impair immunoglobulin isotype switching and antibody production predominantly via T-cell-independent signalling, while mutations of TCF3 impair both T-cell-dependent and -independent pathways of B-cell activation and differentiation. We conclude that epistatic interactions between mutations of the TNFRSF13B/TACI and TCF3 signalling networks lead to the severe CVID-like disorder and SLE in the proband.

Evidence Refuting the Existence of Autoimmune/Autoinflammatory Syndrome Induced by Adjuvants (ASIA)

Autoimmune/autoinflammatory syndrome induced by adjuvants (ASIA) was described in 2011. Over time the condition and its triggers have broadened to include several autoimmune disorders, the macrophagic myofasciitis syndrome, the Gulf war syndrome, the sick building syndrome, siliconosis, and the chronic fatigue syndrome. The aluminum-containing adjuvants in the hepatitis B vaccine and the human papillomavirus vaccine in particular have been stated to be the major causes of the disorder. Here, we review the specificity of the diagnostic criteria for ASIA. We also examine relevant human data, pertaining to causation, particularly from patients undergoing allergen-specific immunotherapy (IT). Patients undergoing allergen-specific IT receive 100 to 500 times more injected aluminum over 3 to 5 years, compared with hepatitis B and human papillomavirus vaccine recipients. In a large pharmacoepidemiological study, in contrast to case series of ASIA, patients receiving aluminum-containing allergen IT preparations were shown to have a lower incidence of autoimmune disease. In another clinical trial, there were no increases in exacerbations in a cohort of patients with systemic lupus erythematosus immunized with the hepatitis B vaccine. Current data do not support the causation of ASIA by vaccine adjuvants containing aluminum, which should be of reassurance to patients undergoing routine immunizations as well as to those undergoing allergen-specific IT.