Delayed Diagnosis and Complications of Predominantly Antibody Deficiencies in a Cohort of Australian Adults

Cancer Trends in Inborn Errors of Immunity: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with inborn errors of immunity (IEI) are susceptible to developing cancer due to defects in the immune system. The prevalence of cancer is higher in IEI patients compared to the immunocompetent population and cancers are considered as an important and common cause of death in IEI patients.

OBJECTIVES

To systematically review demographic, genetic and cancer-related data of IEI patients with a history of malignancy. Moreover, we performed a meta-analysis aiming to determine the frequency of cancer in patients with different types of IEI.

METHODS

We conducted electronic searches on Embase, Web of Science, PubMed, and Scopus (until September 2023) introducing terms related to IEI and cancer. Studies with human subjects with confirmed IEI who had developed at least one malignancy during their lifetime were included.

RESULTS

A total number of 4607 IEI patients with a cancer history were included in the present study. Common variable immunodeficiency (CVID) had the highest number of reported cases (1284 cases), mainly due to a higher relative proportion of patients with predominantly antibody deficiencies (PAD) and their increased life expectancy contributing to the higher detection and reporting of cancers among these patients. The most common malignancy was hematologic/blood cancers (3026 cases, mainly diffuse large B cell lymphoma). A total number of 1173 cases (55.6%) succumbed to cancer, with the highest rate of bone marrow failure (64.9%). Among the patients with monogenic defects in IEI-associated genes, the majority of cases had ATM deficiency (926 cases), but the highest cancer frequency rate belonged to NBS1 deficiency (50.5%). 1928 cases out of total 4607 eligible cases had detailed data to allow further statistical analysis that revealed BRCA2 deficiency had the earliest cancer development (~ 38 months), lowest cure frequency, and highest fatality rate (85%), while ATM deficiency had the lowest cure frequency and highest fatality rate (72%) among total cases reviewed with exclusion of Fanconi anemia.

CONCLUSION

The overall reported cancer frequency in the cases reviewed with and without exclusion of Fanconi anemia was 11.1% (95% confidence interval: 9.8-12.5%) and 12.0% (95% confidence interval: 10.6-13.5%), respectively. Our study revealed that the incidence of cancer is significantly dependent on the molecular and pathway defects in IEI patients, and individualized early screening and appropriate treatment, might improve the prognosis of these patients.

Calculated globulin can be used as a screening test for antibody deficiency in children and adolescents

Purpose

Calculated globulin (CG, total protein minus albumin levels) correlate well with IgG levels and has been proposed as a suitable screening method for individuals with primary antibody deficiencies (PADs). We aimed to show the correlation of CG with IgG levels in children and adolescents, utilizing a common method for albumin measurement, bromocresol green.

Methods

Individuals from two Allergy and Immunology clinics were invited to participate. Inclusion criteria were age < 18, stable conditions, and signed informed consent. We included 1084 individuals. Immunoglobulin G values were determined by immunoturbidimetry; the colorimetric bromocresol green method and the Architect Biuret method were utilized for the albumin and total protein (TP) measurements, respectively.

Results

A total of 1084 individuals were included in the analysis and divided into 4 age groups (0 to <1 year, 1 to <4 years, 4 to <10 years, and 10 to <18 years). For all patients, the mean age was 6.1 (± 5) years old, the mean IgG was 9.4 (± 4.7) g/L, and CG was 23.7 (± 5.9) g/L. The most frequent diagnosis were respiratory allergies, followed by inborn errors of immunity. IgG and CG varied according to age group. Cutoff values for hypogammaglobulinemia varied from 13.8 g/L in children < 1 year to 23.1 g/L in children and adolescents aged 10 to <18 years. CG sensitivity varied from 70.9% in children aged 1 to <4 years old to 95.8% in children 4 to <10. Specificity ranged from 87.5% in children 4 to <10 years old to 100% in children and adolescents aged 10 to <18 years.

Conclusion

CG is a suitable screening test for hypogammaglobulinemia in children less than 18 years of age.

Epidemiology of bronchiectasis

Bronchiectasis is a chronic respiratory disease characterised by permanent enlargement of the airways associated with cough, sputum production and a history of pulmonary exacerbations. In the past few years, incidence and prevalence of bronchiectasis have increased worldwide, possibly due to advances in imaging techniques and disease awareness, leading to increased socioeconomic burden and healthcare costs. Consistently, a mortality increase in bronchiectasis patient cohorts has been demonstrated in certain areas of the globe, with mortality rates of 16-24.8% over 4-5 years of follow-up. However, heterogeneity in epidemiological data is consistent, as reported prevalence in the general population ranges from 52.3 to more than 1000 per 100 000. Methodological flaws in the designs of available studies are likely to underestimate the proportion of people suffering from this condition worldwide and comparisons between different areas of the globe might be unreliable due to different assessment methods or local implementation of the same method in different contexts. Differences in disease severity associated with diverse geographical distribution of aetiologies, comorbidities and microbiology might explain an additional quota of heterogeneity. Finally, limited access to care in certain geographical areas is associated with both underestimation of the disease and increased severity and mortality. The aim of this review is to provide a snapshot of available real-world epidemiological data describing incidence and prevalence of bronchiectasis in the general population. Furthermore, data on mortality, healthcare burden and high-risk populations are provided. Finally, an analysis of the geographical distribution of determinants contributing to differences in bronchiectasis epidemiology is offered.

Limitations in the clinical utility of vaccine challenge responses in the evaluation of primary antibody deficiency including Common Variable Immunodeficiency Disorders

Vaccine challenge responses are an integral component in the diagnostic evaluation of patients with primary antibody deficiency, including Common Variable Immunodeficiency Disorders (CVID). There are no studies of vaccine challenge responses in primary hypogammaglobulinemia patients not accepted for subcutaneous/intravenous immunoglobulin (SCIG/IVIG) replacement compared to those accepted for such treatment. Vaccine challenge responses in patients enrolled in two long-term prospective cohorts, the New Zealand Hypogammaglobulinemia Study (NZHS) and the New Zealand CVID study (NZCS), were compared in this analysis. Almost all patients in the more severely affected SCIG/IVIG treatment group achieved protective antibody levels to tetanus toxoid and H. influenzae type B (HIB). Although there was a highly significant statistical difference in vaccine responses to HIB, tetanus and diphtheria toxoids, there was substantial overlap in both groups. In contrast, there was no significant difference in Pneumococcal Polysaccharide antibody responses to Pneumovax® (PPV23). This analysis illustrates the limitations of evaluating vaccine challenge responses in patients with primary hypogammaglobulinemia to establish the diagnosis of CVID and in making decisions to treat with SCIG/IVIG. The conclusion from this study is that patients with symptoms attributable to primary hypogammaglobulinemia with reduced IgG should not be denied SCIG/IVIG if they have normal vaccine responses.

Time to diagnosis for a rare disease: managing medical uncertainty. A qualitative study

BACKGROUND

People with a rare disease commonly experience long delays from the onset of symptoms to diagnosis. Rare diseases are challenging to diagnose because they are clinically heterogeneous, and many present with non-specific symptoms common to many diseases. We aimed to explore the experiences of people with myositis, primary immunodeficiency (PID), and sarcoidosis from symptom onset to diagnosis to identify factors that might impact receipt of a timely diagnosis.

METHODS

This was a qualitative study using semi-structured interviews. Our approach was informed by Interpretive Phenomenological Analysis (IPA). We applied the lens of uncertainty management theory to tease out how patients experience, assess, manage and cope with puzzling and complex health-related issues while seeking a diagnosis in the cases of rare diseases.

RESULTS

We conducted interviews with 26 people with a rare disease. Ten participants had been diagnosed with a form of myositis, 8 with a primary immunodeficiency, and 8 with sarcoidosis. Time to diagnosis ranged from 6 months to 12 years (myositis), immediate to over 20 years (PID), and 6 months to 15 years (sarcoidosis). We identified four themes that described the experiences of participants with a rare disease as they sought a diagnosis for their condition: (1) normalising and/or misattributing symptoms; (2) particularising by clinicians; (3) asserting patients' self-knowledge; and (4) working together through the diagnosable moment.

CONCLUSIONS

Managing medical uncertainty in the time before diagnosis of a rare disease can be complicated by patients discounting their own symptoms and/or clinicians discounting the scale and impact of those symptoms. Persistence on the part of both clinician and patient is necessary to reach a diagnosis of a rare disease. Strategies such as recognising pattern failure and accommodating self-labelling are key to diagnosis.

IPINeT Ped-unPAD Study: Goals, Design, and Preliminary Results

Background: An unclassified primary antibody deficiency (unPAD) is a widely heterogeneous clinical entity, recently identified within the spectrum of Inborn Errors of Immunity (IEIs). Since unPAD has been traditionally considered as a mild condition, it has incorrectly received little attention, resulting in the paucity of extensive and comparable studies describing its natural history. To address the gaps in characterizing, understanding, and managing pediatric unPAD patients, the Italian Primary Immunodeficiency Network (IPINet) Ped-unPAD study has recently been launched. Methods: Seventeen IPINeT Centers have expressed interest to participate, and data collection is still on-going. Hereby, we anticipate preliminary key issues emerging from the first 110 enrolled patients, attending three IPINet Centers. Results: A proportion of unPAD patients have experienced a severe infectious phenotype, which required hospitalization in a quarter of patients and antibiotic prophylaxis or Immunoglobulin Replacement Therapy in approximately 10% of patients. In this partial cohort, a mean follow-up (FU) of 5 years confirmed unPAD diagnosis in fifty percent of cases, with the remaining being reclassified as the Transient Hypogammaglobulinemia of Infancy (25%) and other IEIs (25%), such as a Common Variable Immunodeficiency, Selective IgA deficiency, Selective IgM deficiency, and IgG3 subclass deficiency. Conclusions: Despite a phenotype overlap at diagnosis, clinicians should be aware that unPAD is a mutable condition that deserves comprehensive evaluation and long-term monitoring to dissect the final diagnosis for optimal treatment.

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.

Cytomegalovirus drives Vδ1+ γδ T cell expansion and clonality in common variable immunodeficiency

The function and phenotype of γδ T cells in the context of common variable immunodeficiency (CVID) has not been explored. CVID is a primary immunodeficiency disorder characterized by impaired antibody responses resulting in increased susceptibility to infections. γδ T cells are a subset of unconventional T cells that play crucial roles in host defence against infections. In this study, we aim to determine the roles and functions of γδ T cells in CVID. We observe a higher frequency of Vδ1+ γδ T cells compared to healthy controls, particularly in older patients. We also find a higher proportion of effector-memory Vδ1+ γδ T cells and a more clonal T cell receptor (TCR) repertoire in CVID. The most significant driver of the Vδ1+ γδ T cell expansion and phenotype in CVID patients is persistent cytomegalovirus (CMV) viremia. These findings provide valuable insights into γδ T cell biology and their contribution to immune defence in CVID.

Electronic health record signatures identify undiagnosed patients with common variable immunodeficiency disease

Human inborn errors of immunity include rare disorders entailing functional and quantitative antibody deficiencies due to impaired B cells called the common variable immunodeficiency (CVID) phenotype. Patients with CVID face delayed diagnoses and treatments for 5 to 15 years after symptom onset because the disorders are rare (prevalence of ~1/25,000), and there is extensive heterogeneity in CVID phenotypes, ranging from infections to autoimmunity to inflammatory conditions, overlapping with other more common disorders. The prolonged diagnostic odyssey drives excessive system-wide costs before diagnosis. Because there is no single causal mechanism, there are no genetic tests to definitively diagnose CVID. Here, we present PheNet, a machine learning algorithm that identifies patients with CVID from their electronic health records (EHRs). PheNet learns phenotypic patterns from verified CVID cases and uses this knowledge to rank patients by likelihood of having CVID. PheNet could have diagnosed more than half of our patients with CVID 1 or more years earlier than they had been diagnosed. When applied to a large EHR dataset, followed by blinded chart review of the top 100 patients ranked by PheNet, we found that 74% were highly probable to have CVID. We externally validated PheNet using >6 million records from disparate medical systems in California and Tennessee. As artificial intelligence and machine learning make their way into health care, we show that algorithms such as PheNet can offer clinical benefits by expediting the diagnosis of rare diseases.

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.

Missed Opportunities to Diagnose Common Variable Immunodeficiency: a Population-Based Case-Control Study Identifying Indicator Diseases for Common Variable Immunodeficiency

PURPOSE

Delayed diagnosis of common variable immunodeficiency (CVID) remains a serious problem. We investigated whether some diseases diagnosed during out-patient visits or admission to hospitals could act as indicator conditions for CVID diagnosis.

METHODS

In this nested case-control study, we identified 128 cases diagnosed with CVID in Denmark (1999-2013) and 640 age-, gender-, and region-matched controls. We obtained data on diseases diagnosed at hospitals in the five years before CVID diagnosis from The National Hospital Registry. We grouped hospital diagnoses in 33 major disease categories and 210 subcategories. We used conditional logistic regression to calculate the odds ratios (OR) and 95% confidence intervals (CI) to estimate associations between disease exposure and subsequent CVID.

RESULTS

During the five years preceding a CVID diagnosis, cases had four times as many hospital contacts as the controls (p < 0.001). A diagnosis in 18 major disease categories showed a significant OR for subsequent diagnosis of CVID. The most substantial association with a subsequent CVID diagnosis was a diagnosis of lower respiratory tract infections (OR: 29.9; 95% CI: 14.2-63.2) and lung diseases (35.1; 15.0-82.5). We observed a similar association when we removed the last year before diagnosis from analysis and overall, in the years < 1, ≥ 1-3, and ≥ 3-5 before diagnosis, although the absolute number of exposures was small. Twenty-eight specific diseases displayed an at least 3-fold risk of subsequent CVID diagnosis.

CONCLUSION

Targeted screening for antibody deficiency in patients diagnosed with specific diseases associated with CVID may lead to earlier CVID diagnosis and treatment and thereby potentially reduced morbidity and mortality.

Screening for Antibody Deficiencies in Adults by Serum Electrophoresis and Calculated Globin

PURPOSE

This study aimed to investigate the correlation between calculated globulin (CG, total protein level minus albumin level) and the gamma globulin fraction (Gamma), obtained from serum protein electrophoresis with serum IgG levels in adults (≥ 18 years).

METHODS

Using linear regression models, analyses of CG and Gamma levels correlation with IgG levels in adults were performed. Receiver-operator curves were created to determine cutoff values and the respective sensitivity and specificity measures.

RESULTS

A total of 886 samples were analyzed. CG and Gamma were positively and statistically correlated with IgG levels (r2 = 0.4628 for CG, and = 0.7941 for Gamma, p < 0.0001 for both analyses). For the detection of hypogammaglobulinemia, i.e., IgG level below the reference value (6 g/L), a CG cutoff value of 24 g/L showed a sensitivity of 86.2% (95% CI 69.4-94.5) and a specificity of 92% (90.0-93.6). A Gamma cutoff value of 7.15 g/L yielded a sensitivity of 100% (88.3-100) and a specificity of 96.8 (95.3-97.8).

CONCLUSION

Both CG and Gamma levels determined by protein electrophoresis analysis may be used to screen for antibody deficiencies in adults, enabling earlier diagnosis of antibody deficiencies in a routine clinical setting.

Clinical Validation of a Primary Antibody Deficiency Screening Algorithm for Primary Care

PURPOSE

The diagnostic delay of primary antibody deficiencies (PADs) is associated with increased morbidity, mortality, and healthcare costs. Therefore, a screening algorithm was previously developed for the early detection of patients at risk of PAD in primary care. We aimed to clinically validate and optimize the PAD screening algorithm by applying it to a primary care database in the Netherlands.

METHODS

The algorithm was applied to a data set of 61,172 electronic health records (EHRs). Four hundred high-scoring EHRs were screened for exclusion criteria, and remaining patients were invited for serum immunoglobulin analysis and referred if clinically necessary.

RESULTS

Of the 104 patients eligible for inclusion, 16 were referred by their general practitioner for suspected PAD, of whom 10 had a PAD diagnosis. In patients selected by the screening algorithm and included for laboratory analysis, prevalence of PAD was ~ 1:10 versus 1:1700-1:25,000 in the general population. To optimize efficiency of the screening process, we refitted the algorithm with the subset of high-risk patients, which improved the area under the curve-receiver operating characteristics curve value to 0.80 (95% confidence interval 0.63-0.97). We propose a two-step screening process, first applying the original algorithm to distinguish high-risk from low-risk patients, then applying the optimized algorithm to select high-risk patients for serum immunoglobulin analysis.

CONCLUSION

Using the screening algorithm, we were able to identify 10 new PAD patients from a primary care population, thus reducing diagnostic delay. Future studies should address further validation in other populations and full cost-effectiveness analyses.

REGISTRATION

Clinicaltrials.gov record number NCT05310604, first submitted 25 March 2022.

Patient-reported outcomes in patients with primary immunodeficiency diseases in Japan: baseline results from a prospective observational study

Introduction

Primary immunodeficiency diseases (PIDs) are rare inherited diseases resulting in impaired immunity. People with PID experience lower health-related quality of life (HR-QOL) and disease-related burdens in daily activities. This ongoing, prospective observational study aims to evaluate disease activity, treatment status, treatment-related burden, daily activities, and HR-QOL in patients with PID in Japan over a 1-year period. In this interim report (database lock: July 29, 2022), we present baseline results.

Methods

Participants were enrolled between November 2021 and May 2022; data were collected four times/year per participant until May 2023 using an online electronic patient-reported outcomes system. Patients with PID and healthy volunteers aged ≥12 years, residing in Japan, and with access to a smartphone were eligible. HR-QOL (primary endpoint) was assessed by the EuroQol-5 Dimensions-5 Levels (EQ-5D-5L) and the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36). Work productivity was assessed by the Work Productivity and Activity Impairment (WPAI) Questionnaire. Other aspects of PID and burden were assessed with a new questionnaire developed in-house. The study is registered at the University hospital Medical Information Network clinical trials registry (UMIN000045622).

Results

The full interim analysis set comprised 71 patients with PID and 47 healthy volunteers. The most common International Union of Immunological Societies PID category was primary antibody deficiency (56.3% of patients). Complications were common, especially recurrent respiratory tract infections (63.4%). Most patients with PID were treated with immunoglobulin replacement therapy (73.2%); 22.4% of these patients had serum immunoglobulin levels <700 mg/dL. Among patients who did not undergo hematopoietic cell transplantation, EQ-5D-5L (n=67) and SF-36 (n=59) Physical and Mental Component Summary scores were significantly lower than in healthy volunteers (p < 0.001). WPAI absenteeism, work productivity loss, and activity impairment scores were significantly lower in 42 working patients with PID than in 37 working healthy volunteers (p < 0.05). Other results indicated that patients with PID experience substantial burdens related to medical visits, expenses, work, and daily activities.

Discussion

This interim analysis confirms that patients with PID in Japan have lower HR-QOL and work productivity compared with healthy individuals and experience substantial limitations and burdens in their daily lives.

Combined immunodeficiency and impaired PI3K signaling in a patient with biallelic LCP2 variants

BACKGROUND

Inborn errors affecting components of the T-cell receptor signaling cascade cause combined immunodeficiency with various degrees of severity. Recently, homozygous variants in LCP2 were reported to cause pediatric onset of severe combined immunodeficiency with neutrophil, platelet, and T- and B-cell defects.

OBJECTIVE

We sought to unravel the genetic cause of combined immunodeficiency and early-onset immune dysregulation in a 26-year-old man who presented with specific antibody deficiency, autoimmunity, and inflammatory bowel disease since early childhood.

METHODS

The patient was subjected to whole-exome sequencing of genomic DNA and examination of blood neutrophils, platelets, and T and B cells. Expression levels of the Src homology domain 2-containing leukocyte protein of 76 kDa (SLP76) and tonic and ligand-induced PI3K signaling were evaluated by flow-cytometric detection of phosphorylated ribosomal protein S6 in B and T cells.

RESULTS

Compound heterozygous missense variants were identified in LCP2, affecting the proline-rich repeat domain of SLP76 (p.P190R and p.R204W). The patient's total B- and T-cell numbers were within the normal range, as was platelet function. However, neutrophil function, numbers of unswitched and class-switched memory B cells, and serum IgA were decreased. Moreover, intracellular SLP76 protein levels were reduced in the patient's B cells, CD4+ and CD8+ T cells, and natural killer cells. Tonic and ligand-induced levels of phosphorylated ribosomal protein S6 and ligand-induced phosphorylated PLCγ1 were decreased in the patient's B cells and CD4+ and CD8+ T cells.

CONCLUSIONS

Biallelic variants in LCP2 impair neutrophil function and T-cell and B-cell antigen-receptor signaling and can cause combined immunodeficiency with early-onset immune dysregulation, even in the absence of platelet defects.

Activated PI3Kδ syndrome - reviewing challenges in diagnosis and treatment

Activated PI3Kδ syndrome (APDS) is a rare inborn error of immunity (IEI) characterized primarily by frequent infections, lymphoproliferation and autoimmunity. Since its initial description in 2013, APDS has become part of the growing group of nearly 500 IEIs affecting various components of the immune system. The two subtypes of APDS - APDS1 and APDS2 - are caused by variants in the PIK3CD and PIK3R1 genes, respectively. Due to the rarity of the disease and the heterogeneous clinical picture, many patients are not diagnosed until years after symptom onset. Another challenge is the large number of PIK3CD and PIK3R1 variants whose functional significance for developing APDS is inconclusive. Treatment of APDS has so far been mostly symptom-oriented with immunoglobulin replacement therapy, immunosuppressive therapies and antibiotic or antiviral prophylaxes. Additionally, allogeneic stem cell transplantation as well as new targeted therapies are options targeting the root cause that may improve patients' quality of life and life expectancy. However, the clinical course of the disease is difficult to predict which complicates the choice of appropriate therapies. This review article discusses diagnostic procedures and current and future treatment options, and highlights the difficulties that physicians, patients and their caretakers face in managing this complex disease. This article is based on cohort studies, the German and US guidelines on the management of primary immunodeficiencies as well as on published experience with diagnosis and compiled treatment experience for APDS.

Immunoglobulin repertoire restriction characterizes the serological responses of patients with predominantly antibody deficiency

BACKGROUND

Predominantly antibody deficiency (PAD) is the most common category of inborn errors of immunity and is underpinned by impaired generation of appropriate antibody diversity and quantity. In the clinic, responses are interrogated by assessment of vaccination responses, which is central to many PAD diagnoses. However, the composition of the generated antibody repertoire is concealed from traditional quantitative measures of serological responses. Leveraging modern mass spectrometry-based proteomics (MS-proteomics), it is possible to elaborate the molecular features of specific antibody repertoires, which may address current limitations of diagnostic vaccinology.

OBJECTIVES

We sought to evaluate serum antibody responses in patients with PAD following vaccination with a neo-antigen (severe acute respiratory syndrome coronavirus-2 vaccination) using MS-proteomics.

METHODS

Following severe acute respiratory syndrome coronavirus-2 vaccination, serological responses in individuals with PAD and healthy controls (HCs) were assessed by anti-S1 subunit ELISA and neutralization assays. Purified anti-S1 subunit IgG and IgM was profiled by MS-proteomics for IGHV subfamily usage and somatic hypermutation analysis.

RESULTS

Twelve patients with PAD who were vaccine-responsive were recruited with 11 matched vaccinated HCs. Neutralization and end point anti-S1 titers were lower in PAD. All subjects with PAD demonstrated restricted anti-S1 IgG antibody repertoires, with usage of <5 IGHV subfamilies (median: 3; range 2-4), compared to ≥5 for the 11 HC subjects (P < .001). IGHV3-7 utilization was far less common in patients with PAD than in HCs (2 of 12 vs 10 of 11; P = .001). Amino acid substitutions due to somatic hypermutation per subfamily did not differ between groups. Anti-S1 IgM was present in 64% and 50% of HC and PAD cohorts, respectively, and did not differ significantly between HCs and patients with PAD.

CONCLUSIONS

This study demonstrates the breadth of anti-S1 antibodies elicited by vaccination at the proteome level and identifies stereotypical restriction of IGHV utilization in the IgG repertoire in patients with PAD compared with HC subjects. Despite uniformly pauci-clonal antibody repertoires some patients with PAD generated potent serological responses, highlighting a possible limitation of traditional serological techniques. These findings suggest that IgG repertoire restriction is a key feature of antibody repertoires in PAD.

The Evolutionary Scenario of Pediatric Unclassified Primary Antibody Deficiency to Adulthood

BACKGROUND

Unclassified primary antibody deficiency (unPAD) is a relatively novel inborn error of immunity (IEI) condition that can vary with time to more defined entities. Since long-term follow-up (FU) studies are scarce, we aimed to provide insight into the evolutionary clinical and immunological scenario of unPAD children to adulthood and identification of biomarkers of primary immune deficiency (PID) persistence.

METHODS

A total of 23 pediatric unPAD patients underwent clinical and immunological FU for a mean time of 14 years (range 3-32 years, median 16 years).

RESULTS

UnPAD diagnosis may change over time. At the last FU, 10/23 (44%) children matched the diagnosis of transient hypogammaglobulinemia of infancy and 13/23 (56%) suffered from a persistent PID. In detail, an unPAD condition was confirmed in 7/23 (30%) patients, whereas 3/23 (13%), 2/23 (9%), and 1/23 (4%) were reclassified as common variable immunodeficiency, selective IgA deficiency, and isolated IgM deficiency, respectively. Low IgA, low specific antibody response to pneumococcus, and lower respiratory tract infections at diagnosis were independently associated with IEI persistence.

CONCLUSIONS

Long-term monitoring of unPAD patients is required to define their outcome and possible evolution towards a definitive IEI diagnosis.

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.

Development of a primary care screening algorithm for the early detection of patients at risk of primary antibody deficiency

BACKGROUND

Primary antibody deficiencies (PAD) are characterized by a heterogeneous clinical presentation and low prevalence, contributing to a median diagnostic delay of 3-10 years. This increases the risk of morbidity and mortality from undiagnosed PAD, which may be prevented with adequate therapy. To reduce the diagnostic delay of PAD, we developed a screening algorithm using primary care electronic health record (EHR) data to identify patients at risk of PAD. This screening algorithm can be used as an aid to notify general practitioners when further laboratory evaluation of immunoglobulins should be considered, thereby facilitating a timely diagnosis of PAD.

METHODS

Candidate components for the algorithm were based on a broad range of presenting signs and symptoms of PAD that are available in primary care EHRs. The decision on inclusion and weight of the components in the algorithm was based on the prevalence of these components among PAD patients and control groups, as well as clinical rationale.

RESULTS

We analyzed the primary care EHRs of 30 PAD patients, 26 primary care immunodeficiency patients and 58,223 control patients. The median diagnostic delay of PAD patients was 9.5 years. Several candidate components showed a clear difference in prevalence between PAD patients and controls, most notably the mean number of antibiotic prescriptions in the 4 years prior to diagnosis (5.14 vs. 0.48). The final algorithm included antibiotic prescriptions, diagnostic codes for respiratory tract and other infections, gastro-intestinal complaints, auto-immune symptoms, malignancies and lymphoproliferative symptoms, as well as laboratory values and visits to the general practitioner.

CONCLUSIONS

In this study, we developed a screening algorithm based on a broad range of presenting signs and symptoms of PAD, which is suitable to implement in primary care. It has the potential to considerably reduce diagnostic delay in PAD, and will be validated in a prospective study. Trial registration The consecutive prospective study is registered at clinicaltrials.gov under NCT05310604.

Value of diagnostic vaccination in diagnosis of humoral inborn errors of immunity

Inborn errors of immunity (IEIs) or primary immunodeficiency diseases, are disorders caused by genetic defects affecting immune function. Clinically, IEI presents mainly as recurrent or severe infections, immune dysregulation (autoimmunity or autoinflammatory disorders), and lymphoproliferation with or without dysmorphic features. Humoral IEIs are the largest subgroup of IEI, with a wide spectrum of quantitative and qualitative antibody defects. These disorders are normally diagnosed based on immunological evaluation; diagnostic vaccination is part of this evaluation. This review examines the importance and relevance of diagnostic vaccination in the diagnosis of humoral IEIs and different technologies which can be utilised in diagnosis.

The Autoimmune Manifestations in Patients with Genetic Defects in the B Cell Development and Differentiation Stages

PURPOSE

Primary B cell defects manifesting as predominantly antibody deficiencies result from variable inborn errors of the B cell lineage and their development, including impairments in early bone marrow development, class switch recombination (CSR), or terminal B cell differentiation. In this study, we aimed to investigate autoimmunity in monogenic patients with B cell development and differentiation defects.

METHODS

Patients with known genetic defects in the B cell development and differentiation were recruited from the Iranian inborn errors of immunity registry.

RESULTS

A total of 393 patients with a known genetic defect in the B cell development and differentiation (257 males; 65.4%) with a median age of 12 (6-20) years were enrolled in this study. After categorizing patients, 109 patients had intrinsic B cell defects. More than half of the patients had defects in one of the ATM (85 patients), BTK (76 patients), LRBA (34 patients), and DOCK8 (33 patients) genes. Fifteen patients (3.8%) showed autoimmune complications as their first manifestation. During the course of the disease, autoimmunity was reported in 81 (20.6%) patients at a median age of 4 (2-7) years, among which 65 patients had mixed intrinsic and extrinsic and 16 had intrinsic B cell defects. The comparison between patients with the mentioned four main gene defects showed that the patient group with LRBA defect had a significantly higher frequency of autoimmunity compared to those with other gene defects. Based on the B cell defect stage, 13% of patients with early B cell defect, 17% of patients with CSR defect, and 40% of patients who had terminal B cell defect presented at least one type of autoimmunity.

CONCLUSION

Our results demonstrated that gene mutations involved in human B cell terminal stage development mainly LRBA gene defect have the highest association with autoimmunity.

Early Diagnosis of Primary Immunodeficiency Disease Using Clinical Data and Machine Learning

BACKGROUND

Primary immunodeficiency diseases (PIDD) are a group of immune-related disorders that have a current median delay of diagnosis between 6 and 9 years. Early diagnosis and treatment of PIDD has been associated with improved patient outcomes.

OBJECTIVE

To develop a machine learning model using elements within the electronic health record data that are related to prior symptomatic treatment to predict PIDD.

METHODS

We conducted a retrospective study of patients with PIDD identified using inclusion criteria of PIDD-related diagnoses, immunodeficiency-specific medications, and low immunoglobulin levels. We constructed a control group of age-, sex-, and race-matched patients with asthma. The primary outcome was the diagnosis of PIDD. We considered comorbidities, laboratory tests, medications, and radiological orders as features, all before diagnosis and indicative of symptom-related treatment. Features were presented sequentially to logistic regression, elastic net, and random forest classifiers, which were trained using a nested cross-validation approach.

RESULTS

Our cohort consisted of 6422 patients, of whom 247 (4%) were diagnosed with PIDD. Our logistic regression model with comorbidities demonstrated good discrimination between patients with PIDD and those with asthma (c-statistic: 0.62 [0.58-0.65]). Adding laboratory results, medications, and radiological orders improved discrimination (c-statistic: 0.70 vs 0.62, P < .001), sensitivity, and specificity. Extending to the advanced machine learning models did not improve performance.

CONCLUSIONS

We developed a prediction model for early diagnosis of PIDD using historical data that are related to symptomatic care, which has potential to fill an important need in reducing the time to diagnose PIDD, leading to better outcomes for immunodeficient patients.

Clinical Aspects of B Cell Immunodeficiencies: The Past, the Present and the Future

B cells and antibodies are indispensable for host immunity. Our understanding of the mechanistic processes that underpin how B cells operate has left an indelible mark on the field of clinical pathology, and recently has also dramatically reshaped the therapeutic landscape of diseases that were once considered incurable. Evaluating patients with primary immunodeficiency diseases (PID)/inborn errors of immunity (IEI) that primarily affect B cells, offers us an opportunity to further our understanding of how B cells develop, mature, function and, in certain instances, cause further disease. In this review we provide a brief compendium of IEI that principally affect B cells at defined stages of their developmental pathway, and also attempt to offer some educated viewpoints on how the management of these disorders could evolve over the years.

Common Variable Immunodeficiency Enteropathy and Its Unpredictable Biopsy Findings: Not Everything Is Black and White

Common variable immunodeficiency syndrome (CVID) is a diverse entity characterized by hypogammaglobinemia and a propensity for recurrent infections. Involvement of the gastrointestinal tract has a variable manifestation ranging from asymptomatic involvement to florid signs and symptoms. Due to these incongruous findings, multiple concurrent biopsies are to be done for tissue diagnosis. Here, we present two cases diagnosed with CVID on the basis of clinical findings, lab investigations, and morphological features on biopsy.

Missed Opportunities? A retrospective study into adults hospitalized with invasive infection from airway pathogens

Background

Invasive disease caused by airway pathogens, including Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, and Moraxella catarrhalis, has high morbidity and mortality worldwide, with immunodeficiency being a known association with recurrent disease. The study aimed to describe the frequency of known immunodeficiency and predisposing factors in adult patients presenting with invasive infections and determine the frequency of screening for and detection of immunodeficiency.

Methods

A retrospective analysis was conducted at a large tertiary Australian health service, comprising multiple centers. Patients aged 18 years or older, in whom the above pathogens were isolated from sterile sites, were included as identified through a microbiology database, between 2015 and 2020. Using electronic medical records, patient demographics, medical history, outcomes of admission, and pathology results were captured and reviewed to address the aims.

Results

In 252 patients, S pneumoniae was the most common culprit, isolated in 73% (185/252), compared to 14.3% (36/252) and 11.5% (29/252) of infections caused by H influenzae and N meningitidis, respectively. Known diagnoses of secondary immunodeficiency were common (31% of patients). Of those presenting with invasive pneumococcal disease, 78% had at least 1 predisposing condition, though only 9 patients (6%) had previously received pneumococcal vaccination. Despite poor screening for immunodeficiency, 12 new diagnoses were made. While the commonest immunodeficiency was secondary, due to hematological and solid organ malignancies, 3 new primary immunodeficiency diagnoses were made.

Conclusions

Immunodeficiency is common in this patient population. Screening should be undertaken to ensure timely diagnosis and treatment of the underlying condition to avoid future morbidity and mortality.

Case Report: Cytomegalovirus Disease Is an Under-Recognized Contributor to Morbidity and Mortality in Common Variable Immunodeficiency

Background

Common Variable Immunodeficiency (CVID) is classified as a ‘Predominantly Antibody Deficiency’ (PAD), but there is emerging evidence of cellular immunodeficiency in a subset of patients. This evidence includes CVID patients diagnosed with cytomegalovirus (CMV) infection, a hallmark of ‘combined immunodeficiency’. CMV infection also has the potential to drive immune dysregulation contributing to significant morbidity and mortality in CVID. We aim to determine the extent of cellular immune dysfunction in CVID patients, and whether this correlates with CMV infection status.

Methods

We conducted a single-center retrospective cohort study of individuals with CVID at the Royal Melbourne Hospital, and identified patients with and without CMV disease or viraemia. We then isolated T-cells from patient and healthy donor blood samples and examined T-cell proliferation and function.

Results

Six patients (7.6%, 6/79) had either CMV disease (pneumonitis or gastrointestinal disease), or symptomatic CMV viraemia. A high mortality rate in the cohort of patients with CVID and CMV disease was observed, with 4 deaths in the period of analysis (66.6%, 4/6). Individuals with CMV infection showed reduced T-cell division in response to T-cell receptor (TCR) stimulation when compared with CMV-negative patients.

Discussion

This study demonstrates the morbidity and mortality associated with CMV in CVID, and highlights the need for focused interventions for patients with CVID at risk of CMV disease.

Common Variable Immunodeficiency in Elderly Patients: A Long-Term Clinical Experience

Background: Common variable immunodeficiency (CVID) is a complex, predominantly antibody deficiency usually diagnosed between 20−40 years. Few data about elderly patients are reported in the literature. Our aim was to evaluate the clinical phenotypes of elderly patients with CVID. Method: A retrospective analysis of adult patients with CVID was performed in our Referral Centre, focusing on the main differences between “older” patients (≥65 years at the diagnosis) and “younger” patients (<65 years). Results: The data from 65 younger and 13 older patients followed up for a median period of 8.5 years were available. At diagnosis, recurrent infections represented the only clinical manifestation in 61% and 69% of younger and older patients, respectively. The incidence of autoimmune diseases was higher in elderly patients compared with younger ones (30 vs. 18%, respectively). During the follow-up, the incidence of autoimmune disorders and enteropathy increased in the younger patients whereas neoplasia became the most prevalent complication in the elderly (38%). All patients received a replacement therapy with immunoglobulin, with good compliance. Conclusion: CVID occurrence in elderly patients is rarely described; therefore, the clinical characteristics are not completely known. In our series, neoplasia became the most prevalent complication in the elderly during the follow-up. In elderly patients, 20% SCIg was as safe as in the younger ones, with good compliance. A genetic analysis is important to confirm the diagnosis, identify specific presentations in the different ages, clarify the prognosis and guide the treatment. Future clinical research in this field may potentially help to guide their care.

Gut inflammation in CVID: causes and consequences

INTRODUCTION

There is a wide spectrum of noninfectious gastrointestinal pathology, causing considerable morbidity and mortality in CVID, where both etiology and effective therapy are under debate.

AREAS COVERED

This review will focus on the noninfectious inflammation in the GI tract in CVID patients, covering the both the upper and lower GI tract inflammation, including the liver. The controversy of the CVID enteropathy definition and that of gluten-free diet for celiac-like disease in CVID will be discussed. Furthermore, the review will cover the link between GI inflammation and GI cancer. Finally, the role of gut microbiota, IgA, and genetics and its relationship with CVID enteropathy is scrutinized. The authors reviewed literature from PubMed.

EXPERT OPINION

The heterogeneity and the unknown mechanism behind CVID enteropathy, and thereby the lack of effective treatment, is one of the key challenges in the field of CVID. Celiac-like disease in CVID is due to immune dysregulation, and a gluten-free diet is therefore not indicated. Gut microbial dysbiosis and mucosal IgA can initiate systemic and local inflammation and is involved in the immune dysregulation in CVID. Considering the heterogeneity of CVID enteropathy, personalized medicine is probably the future for these patients.

Nodular regenerative hyperplasia in X-linked agammaglobulinemia: An underestimated and severe complication

BACKGROUND

Late-onset complications in X-linked agammaglobulinemia (XLA) are increasingly recognized. Nodular regenerative hyperplasia (NRH) has been reported in primary immunodeficiency but data in XLA are limited.

OBJECTIVES

This study sought to describe NRH prevalence, associated features, and impact in patients with XLA.

METHODS

Medical records of all patients with XLA referred to the National Institutes of Health between October 1994 and June 2019 were reviewed. Liver biopsies were performed when clinically indicated. Patients were stratified into NRH+ or NRH- groups, according to their NRH biopsy status. Fisher exact test and Mann-Whitney test were used for statistical comparisons.

RESULTS

Records of 21 patients with XLA were reviewed, with a cumulative follow-up of 129 patient-years. Eight patients underwent ≥1 liver biopsy of whom 6 (29% of the National Institutes of Health XLA cohort) were NRH+. The median age at NRH diagnosis was 20 years (range, 17-31). Among patients who had liver biopsies, alkaline phosphatase levels were only increased in patients who were NRH+ (P = .04). Persistently low platelet count (<100,000 per μL for >6 months), mildly to highly elevated hepatic venous pressure gradient and either hepatomegaly and/or splenomegaly were present in all patients who were NRH+. In opposition, persistently low platelet counts were not seen in patients who were NRH-, and hepatosplenomegaly was observed in only 1 patient who was NRH-. Hepatic venous pressure gradient was normal in the only patient tested who was NRH-. All-cause mortality was higher among patients who were NRH+ (5 of 6, 83%) than in the rest of the cohort (1 of 15, 7% among patients who were NRH- and who were classified as unknown; P = .002).

CONCLUSIONS

NRH is an underreported, frequent, and severe complication in XLA, which is associated with increased morbidity and mortality.

Cytomegalovirus in primary immunodeficiency

PURPOSE OF REVIEW

Cytomegalovirus (CMV) infection and disease are well described in the setting of secondary immunodeficiency. Less is known about CMV in the context of primary immunodeficiencies (PIDs), where inborn errors in one or more arms of the immune system result in variable degrees of CMV susceptibility.

RECENT FINDINGS

PID presents unique challenges in the diagnosis and management of CMV disease. The clinical presentation of CMV in PID is often severe, accelerated by underlying immune dysregulation and iatrogenic immunosuppression. Here we describe the clinical significance of CMV infection in PID, the key components of immune defence against CMV and how these are affected in specific PIDs. CMV disease is under-recognized as a complication of common variable immunodeficiency (CVID). High rates of CMV end-organ disease, mortality, development of CMV resistance and prolonged antiviral use have been observed in individuals with CVID.

SUMMARY

We recommend that clinicians tailor their approach to the individual based on their underlying immune deficit and maintain a high index of suspicion and low threshold for treatment. More research is required to improve stratification of CMV risk in PID, develop new diagnostic tools and manage end-organ disease in this cohort.

Serum Protein Electrophoresis May Be Used as a Screening Tool for Antibody Deficiency in Children and Adolescents

Background

Patients with antibody deficiency may experience exceptionally long diagnostic delays, increasing the risk of life-threatening infections, end-organ damage, mortality, and health costs.

Objective

This study aimed to analyze serum protein electrophoresis and verify the correlation between calculated globulin (CG, total protein minus albumin levels) or electrophoretically determined serum gamma globulin fraction (Gamma) with IgG levels in children and adolescents under 18 years old (yo).

Methods

We analyzed serum protein electrophoresis (GC or Gamma) and IgG levels from 1215 children and adolescents under 18 yo, classified into 5 age groups. We verified the correlation between CG or Gamma with serum IgG levels.

Results

Serum IgG levels varied according to age groups (from 4.3 ± 2.3 g/l in children under 6 months old to 11.4 ± 3.2 g/l in adolescents in the 10-<18 yo group). CG sensitivity and specificity to detect IgG below the reference range for all patients were 93.1% and 81.8%, respectively, and varied according to age group. Gamma sensitivity and specificity for all patients were 100% and 87.8%, respectively, and varied according to age group as well. We found serum IgG levels below the age reference level in 29 patients (2.4% of the cases) using CG or Gamma levels.

Conclusion

Both CG and Gamma levels may be of utility as a screening tool for earlier diagnosis of antibody deficiency in children and adolescents under 18 yo.

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.

Beyond monogenetic rare variants: tackling the low rate of genetic diagnoses in predominantly antibody deficiency

Predominantly antibody deficiency (PAD) is the most prevalent form of primary immunodeficiency, and is characterized by broad clinical, immunological and genetic heterogeneity. Utilizing the current gold standard of whole exome sequencing for diagnosis, pathogenic gene variants are only identified in less than 20% of patients. While elucidation of the causal genes underlying PAD has provided many insights into the cellular and molecular mechanisms underpinning disease pathogenesis, many other genes may remain as yet undefined to enable definitive diagnosis, prognostic monitoring and targeted therapy of patients. Considering that many patients display a relatively late onset of disease presentation in their 2nd or 3rd decade of life, it is questionable whether a single genetic lesion underlies disease in all patients. Potentially, combined effects of other gene variants and/or non-genetic factors, including specific infections can drive disease presentation. In this review, we define (1) the clinical and immunological variability of PAD, (2) consider how genetic defects identified in PAD have given insight into B-cell immunobiology, (3) address recent technological advances in genomics and the challenges associated with identifying causal variants, and (4) discuss how functional validation of variants of unknown significance could potentially be translated into increased diagnostic rates, improved prognostic monitoring and personalized medicine for PAD patients. A multidisciplinary approach will be the key to curtailing the early mortality and high morbidity rates in this immune disorder.

Update on Infections in Primary Antibody Deficiencies

Bacterial respiratory tract infections are the hallmark of primary antibody deficiencies (PADs). Because they are also among the most common infections in healthy individuals, PADs are usually overlooked in these patients. Careful evaluation of the history, including frequency, chronicity, and presence of other infections, would help suspect PADs. This review will focus on infections in relatively common PADs, discussing diagnostic challenges, and some management strategies to prevent infections.

Calculated globulin as a screening tool for hypogammaglobulinaemia or paraproteins in hospitalized patients

BACKGROUND

Calculated globulin fraction is derived from the liver function tests by subtracting albumin from the total protein. Since immunoglobulins comprise the largest component of the serum globulin concentration, increased or decreased calculated globulins and may identify patients with hypogammaglobulinaemia or hypergammaglobulinaemia, respectively.

METHODS

A retrospective study of laboratory data over 2.5 years from inpatients at three tertiary hospitals was performed. Patients with paired calculated globulins and immunoglobulin results were identified and clinical details reviewed. The results of serum electrophoresis testing were also assessed where available.

RESULTS

A total of 4035 patients had paired laboratory data available. A calculated globulin ≤20 g/L (<2nd percentile) had a low sensitivity (5.8%) but good positive predictive value (82.5%) for hypogammaglobulinaemia (IgG ≤5.7 g/L), with a positive predictive value of 37.5% for severe hypogammaglobulinaemia (IgG ≤3 g/L). Paraproteins were identified in 123/291 (42.3%) of patients with increased calculated globulins (≥42 g/L) who also had a serum electrophoresis performed. Significantly elevated calculated globulin ≥50 g/L (>4th percentile) were seen in patients with either liver disease (37%), haematological malignancy (36%), autoimmune disease (13%) or infections (9%).

CONCLUSIONS

Calculated globulin is an inexpensive and easily available test that assists in the identification of hypogammaglobulinaemia or hypergammaglobulinaemia which may prompt further investigation and reduce diagnostic delays.

Population pharmacokinetic modelling of intravenous immunoglobulin in patients with predominantly antibody deficiencies

AIMS

There is considerable interpatient variability in the pharmacokinetics (PK) of intravenous immunoglobulin G (IVIG), causing difficulty in optimizing individual dosage regimen. This study aims to estimate the population PK parameters of IVIG and to investigate the impact of genetic polymorphism of the FcRn gene and clinical variability on the PK of IVIG in patients with predominantly antibody deficiencies.

METHODS

Patients were recruited from four hospitals. Clinical data were recorded and blood samples were taken for PK and genetic studies. Population PK parameters were estimated by nonlinear mixed-effects modelling in Monolix®. Models were evaluated using the difference in objective function value, goodness-of-fit plots, visual predictive check and bootstrap analysis. Monte Carlo simulation was conducted to evaluate different dosing regimens for IVIG.

RESULTS

A total of 30 blood samples were analysed from 10 patients. The immunoglobulin G concentration data were best described by a one-compartment model with linear elimination. The final model included both volume of distribution (Vd) and clearance (CL) based on patient's individual weight. Goodness-of-fit plots indicated that the model fit the data adequately, with minor model mis-specification. Genetic polymorphism of the FcRn gene and the presence of bronchiectasis did not affect the PK of IVIG. Simulation showed that 3-4-weekly dosing intervals were sufficient to maintain IgG levels of 5 g L^-1 , with more frequent intervals needed to achieve higher trough levels.

CONCLUSIONS

Body weight significantly affects the PK parameters of IVIG. Genetic and other clinical factors investigated did not affect the disposition of IVIG.

Influenza-specific IgG1+ memory B-cell numbers increase upon booster vaccination in healthy adults but not in patients with predominantly antibody deficiency

Background

Annual influenza vaccination is recommended to all individuals over 6 months of age, including predominantly antibody deficiency (PAD) patients. Vaccination responses are typically evaluated by serology, and because PAD patients are by definition impaired in generating IgG and receive immunoglobulin replacement therapy (IgRT), it remains unclear whether they can mount an antigen-specific response.

Objective

To quantify and characterise the antigen-specific memory B (Bmem) cell compartment in healthy controls and PAD patients following an influenza booster vaccination.

Methods

Recombinant hemagglutinin (HA) from the A/Michigan/2015 H1N1 (AM15) strain with an AviTag was generated in a mammalian cell line, and following targeted biotinylation, was tetramerised with BUV395 or BUV737 streptavidin conjugates. Multicolour flow cytometry was applied on blood samples before and 28 days after booster influenza vaccination in 16 healthy controls and five PAD patients with circulating Bmem cells.

Results

Recombinant HA tetramers were specifically recognised by 0.5-1% of B cells in previously vaccinated healthy adults. HA-specific Bmem cell numbers were significantly increased following booster vaccination and predominantly expressed IgG1. Similarly, PAD patients carried HA-specific Bmem cells, predominantly expressing IgG1. However, these numbers were lower than in controls and did not increase following booster vaccination.

Conclusion

We have successfully identified AM15-specific Bmem cells in healthy controls and PAD patients. The presence of antigen-specific Bmem cells could offer an additional diagnostic tool to aid in the clinical diagnosis of PAD. Furthermore, alterations in the number or immunophenotype of HA-specific Bmem cells post-booster vaccination could assist in the evaluation of immune responses in individuals receiving IgRT.

Characterization of adult patients with IgG subclass deficiency and subnormal IgG2

Background

Adults with IgG subclass deficiency (IgGSD) with subnormal IgG2 are inadequately characterized.

Methods

We retrospectively analyzed observations in unrelated adults with IgGSD evaluated in a single hematology clinic (1991–2019) and selected those with subnormal serum IgG2 (<117 mg/dL (<1.2 g/L)) without corticosteroid therapy to describe: age; prevalence of women; upper/lower respiratory infection; autoimmune condition(s); atopy; other allergy; frequent or severe respiratory tract infection in first-degree relatives; IgG, IgG subclasses, IgA, and IgM; blood lymphocyte subpopulations; human leukocyte antigen (HLA)-A and -B types and haplotypes; and 23-valent pneumococcal polysaccharide vaccination (PPSV23) responses. We determined the prevalence of subnormal IgG2 among unrelated adults with IgGSD without corticosteroid therapy and compared general characteristics of those with and without subnormal IgG2.

Results

There were 18 patients (94.4% women) with subnormal IgG2. Mean age was 52 ± 11 y. Upper/lower respiratory infection occurred in 94.4%/74.8%, respectively. Autoimmune condition(s), atopy, other allergy, and frequent or severe respiratory infection in first-degree relatives occurred in 44.4%, 44.4%, 61.1%, and 22.2%, respectively. Median IgG2 was 105 mg/dL (83, 116). Subnormal IgG, IgG1, IgG3, IgG4, IgA, and IgM was observed in 66.7%, 50.0%, 100.0%, 5.6%, 33.3%, and 0%, respectively. Lymphocyte subpopulations were normal in most patients. HLA frequencies were similar in patients and controls. Three of 4 patients had no protective S. pneumoniae serotype-specific IgG levels before or after PPSV23. These 18 patients represent 7.6% of 236 adults with IgGSD. Prevalence of subnormal IgG, subnormal IgG3, and subnormal IgA was significantly greater in 18 adults with subnormal IgG2 than 218 adults without subnormal IgG2. Prevalence of subnormal IgM was significantly lower in patients with subnormal IgG2.

Conclusions

Characteristics of adults with IgGSD with subnormal IgG2 include female predominance, other immunologic abnormalities, subnormal IgG3 and/or IgG1, lack of HLA-A and -B association, and suboptimal PPSV23 response.

Discontinuation of immunoglobulin replacement therapy in patients with secondary antibody deficiency

INTRODUCTION

Secondary immunodeficiency is becoming a greater medical concern as the usage of immunosuppressive and biological treatments has increased. Individuals with certain medical conditions, such as hematological malignancies, can also have secondary immunodeficiency. Immunoglobulin replacement therapy (IGRT), which has been used for decades in inherited or primary immunodeficiency, provides some protection to patients with acquired and predominant antibody deficiency, i.e. secondary antibody deficiency (SAD). However, IGRT is costly, and supplies are limited. Although there are clinical guidelines on when to initiate IGRT, there is no guideline on when to discontinue it.

AREAS COVERED

The authors reviewed existing literature and provided an overview of the current state of knowledge regarding IGRT discontinuation in SAD patients.

EXPERT OPINION

Long-term supplementary immunoglobulin may not be necessary. Although it is possible to successfully transition away from IGRT in individuals with SAD, evidence-based practices are limited. Without clear guidelines and reliable prognostic markers, IGRT discontinuation practices are restricted to clinical judgment. For this reason, additional research should be conducted to identify markers that indicate the recovery of humoral immunity. Furthermore, the derivation and validation of a set of combined clinical and laboratory criteria to allow safe and timely IGRT discontinuation is warranted.

Chronic Lung Disease in Primary Antibody Deficiency: Diagnosis and Management

Chronic lung disease is a complication of primary antibody deficiency (PAD) associated with significant morbidity and mortality. Manifestations of lung disease in PAD are numerous. Thoughtful application of diagnostic approaches is imperative to accurately identify the form of disease. Much of the treatment used is adapted from immunocompetent populations. Recent genomic and translational medicine advances have led to specific treatments. As chronic lung disease has continued to affect patients with PAD, we hope that continued advancements in our understanding of pulmonary pathology will ultimately lead to effective methods that alleviate impact on quality of life and survival.

Heterogeneity of Liver Disease in Common Variable Immunodeficiency Disorders

Common variable immunodeficiency (CVID) is the most frequent primary immunodeficiency (PID) in adulthood and is characterized by severe reduction of immunoglobulin serum levels and impaired antibody production in response to vaccines and pathogens. Beyond the susceptibility to infections, CVID encompasses a wide spectrum of clinical manifestations related to a complex immune dysregulation that also affects liver. Although about 50% CVID patients present persistently deranged liver function, burden, and nature of liver involvement have not been systematically investigated in most cohort studies published in the last decades. Therefore, the prevalence of liver disease in CVID widely varies depending on the study design and the sampling criteria. This review seeks to summarize the evidence about the most relevant causes of liver involvement in CVID, including nodular regenerative hyperplasia (NRH), infections and malignancies. We also describe the clinical features of liver disease in some monogenic forms of PID included in the clinical spectrum of CVID as ICOS, NFKB1, NFKB2, CTLA-4, PI3Kδ pathway, ADA2, and IL21-R genetic defects. Finally, we discuss the clinical applications of the various diagnostic tools and the possible therapeutic approaches for the management of liver involvement in the context of CVID.

Predominantly Antibody-Deficient Patients With Non-infectious Complications Have Reduced Naive B, Treg, Th17, and Tfh17 Cells

Background: Patients with predominantly antibody deficiency (PAD) suffer from severe and recurrent infections that require lifelong immunoglobulin replacement and prophylactic antibiotic treatment. Disease incidence is estimated to be 1:25,000 worldwide, and up to 68% of patients develop non-infectious complications (NIC) including autoimmunity, which are difficult to treat, causing high morbidity, and early mortality. Currently, the etiology of NIC is unknown, and there are no diagnostic and prognostic markers to identify patients at risk.

Objectives: To identify immune cell markers that associate with NIC in PAD patients.

Methods: We developed a standardized 11-color flow cytometry panel that was utilized for in-depth analysis of B and T cells in 62 adult PAD patients and 59 age-matched controls.

Results: Nine males had mutations in Bruton's tyrosine kinase (BTK) and were defined as having X-linked agammaglobulinemia. The remaining 53 patients were not genetically defined and were clinically diagnosed with agammaglobulinemia (n = 1), common variable immunodeficiency (CVID) (n = 32), hypogammaglobulinemia (n = 13), IgG subclass deficiency (n = 1), and specific polysaccharide antibody deficiency (n = 6). Of the 53, 30 (57%) had one or more NICs, 24 patients had reduced B-cell numbers, and 17 had reduced T-cell numbers. Both PAD–NIC and PAD+NIC groups had significantly reduced Ig class-switched memory B cells and naive CD4 and CD8 T-cell numbers. Naive and IgM memory B cells, Treg, Th17, and Tfh17 cells were specifically reduced in the PAD+NIC group. CD21^lo B cells and Tfh cells were increased in frequencies, but not in absolute numbers in PAD+NIC.

Conclusion: The previously reported increased frequencies of CD21^lo B cells and Tfh cells are the indirect result of reduced naive B-cell and T-cell numbers. Hence, correct interpretation of immunophenotyping of immunodeficiencies is critically dependent on absolute cell counts. Finally, the defects in naive B- and T-cell numbers suggest a mild combined immunodeficiency in PAD patients with NIC. Together with the reductions in Th17, Treg, and Tfh17 numbers, these key differences could be utilized as biomarkers to support definitive diagnosis and to predict for disease progression.

Defining Polysaccharide Antibody Deficiency: Measurement of Anti-Pneumococcal Antibodies and Anti-Salmonella typhi Antibodies in a Cohort of Patients with Recurrent Infections

BACKGROUND

The correlation between different methods for the detection of pneumococcal polysaccharide vaccine (PPV) responses to diagnose specific polysaccharide antibody deficiency (SAD) is poor and the criteria for defining a normal response lack consensus. We previously proposed fifth percentile (p5) values of PPV responses as a new cutoff for SAD.

OBJECTIVE

To analyze the association of SAD (determined by either World Health Organization (WHO)-standardized ELISA or multiplex bead-based assay) with abnormal response to Salmonella (S.) typhi Vi vaccination in a cohort of patients with recurrent infections.

METHODS

Ninety-four patients with a clinical history suggestive of antibody deficiency received PPV and S. typhi Vi vaccines. Polysaccharide responses to either 3 or 18 pneumococcal serotypes were measured by either the WHO ELISA or a multiplex in-house bead-based assay. Anti-S. typhi Vi IgG were measured by a commercial ELISA kit. Allohemagglutinins (AHA) were measured by agglutination method.

RESULTS

Based on the American Academy of Allergy, Asthma and Immunology (AAAAI) criteria for WHO ELISA, 18/94 patients were diagnosed with SAD and 22/93 based on serotype-specific p5 cutoffs for bead-based assay. The association between the two methods was significant, with 10 subjects showing abnormal response according to both techniques. Abnormal response to S. typhi Vi vaccination was found in 7 patients, 6 of which had SAD. No correlation was found between polysaccharide response and AHA, age, or clinical phenotype.

CONCLUSION

The lack of evidence-based gold standards for the diagnosis of SAD represents a challenge in clinical practice. In our cohort, we confirmed the insufficient correlation between different methods of specific PPV response measurement, and showed that the S. typhi Vi response was not contributive. Caution in the interpretation of results is warranted until more reliable diagnostic methods can be validated.

Quantification of T-Cell and B-Cell Replication History in Aging, Immunodeficiency, and Newborn Screening

Quantification of T-cell receptor excision circles (TRECs) has impacted on human T-cell research, but interpretations on T-cell replication have been limited due to the lack of a genomic coding joint. We here overcome this limitation with multiplex TRG rearrangement quantification (detecting ~0.98 alleles per TCRαβ+ T cell) and the HSB-2 cell line with a retrovirally introduced TREC construct. We uncovered <5 cell divisions in naive and >10 cell divisions in effector memory T-cell subsets. Furthermore, we show that TREC dilution with age in healthy adults results mainly from increased T cell replication history. This proliferation was significantly increased in patients with predominantly antibody deficiency. Finally, Guthrie cards of neonates with Down syndrome have fewer T and B cells than controls, with similar T-cell and slightly higher B-cell replication. Thus, combined analysis of TRG coding joints and TREC signal joints can be utilized to quantify in vivo T-cell replication, and has direct applications for research into aging, immunodeficiency, and newborn screening.

How to Identify Common Variable Immunodeficiency Patients Earlier: General Practice Patterns

PURPOSE

Diagnostic delay is a major problem concerning common variable immunodeficiency (CVID). We aimed to determine the pattern of general practitioner (GP) consultations in individuals diagnosed with CVID within 3 years before the diagnosis and whether the risk of diagnosis was associated with the frequency of consultations or character of examinations.

METHODS

We conducted a nested case-control study, identifying 132 adult CVID patients and 5940 age- and gender-matched controls from national registers during 1997-2013. We used conditional logistic regression to calculate the odds ratios (OR) and 95% confidence intervals (95%CI).

RESULTS

The median number of consultations among individuals with CVID was more than twice that of the controls in all 3 years (3rd, 10; 2nd, 11.5; and 1st, 15.4 vs. 4). We found a statistically significant association between the number of consultations and the risk of a subsequent CVID diagnosis, independent of age and gender, but strongest in the individuals < 40 years. In the 3rd year before diagnosis, having 9-15 consultations compared with 1-4 was associated with an OR (95%CI) of 5.0 (2.3-10.9), 2.4 (1.1-5.4), and 1.3 (0.3-5.3) for those aged 18-40, 41-60, and > 60, respectively. Several examinations (i.e., blood tests for inflammation/infection and pulmonary function test) were associated with increased odds of a subsequent CVID diagnosis.

CONCLUSION

The risk of a CVID diagnosis was highly related to both the number of consultations and the character of examinations performed by the GP. CVID should be a differential diagnosis among patients with multiple consultations, especially in patients < 40 years old.

Pulmonary Manifestations of Predominantly Antibody Deficiencies

Predominantly antibody deficiencies (PADs) are the most frequent forms of primary immunodeficiency diseases (PIDs). Commonly accompanied with complications involving several body systems, immunoglobulin substitution therapy along with prophylactic antibiotics remained the cornerstone of treatment for PADs and related complications. Patients with respiratory complications should be prescribed an appropriate therapy as soon as possible and have to be adhering to more and longer medical therapies. Recent studies identified a gap for screening protocols to monitor respiratory manifestations in patients with PADs. In the present chapter, the pulmonary manifestations of different PADs for each have been discussed. The chapter is mainly focused on X-linked agammaglobulinemia, common variable immunodeficiency, activated PI3K-δ syndrome, LRBA deficiency, CD19 complex deficiencies, CD20 deficiency, other monogenic defects associated with hypogammaglobulinemia, immunoglobulin class switch recombination deficiencies affecting B-cells, transient hypogammaglobulinemia of infancy, and selective IgA deficiency.