Reversion Mosaicism in Primary Immunodeficiency Diseases

Reversion mosaicism has been reported in an increasing number of genetic disorders including primary immunodeficiency diseases. Several mechanisms can mediate somatic reversion of inherited mutations. Back mutations restore wild-type sequences, whereas second-site mutations result in compensatory changes. In addition, intragenic recombination, chromosomal deletions, and copy-neutral loss of heterozygosity have been demonstrated in mosaic individuals. Revertant cells that have regained wild-type function may be associated with milder disease phenotypes in some immunodeficient patients with reversion mosaicism. Revertant cells can also be responsible for immune dysregulation. Studies identifying a large variety of genetic changes in the same individual further support a frequent occurrence of reversion mosaicism in primary immunodeficiency diseases. This phenomenon also provides unique opportunities to evaluate the biological effects of restored gene expression in different cell lineages. In this paper, we review the recent findings of reversion mosaicism in primary immunodeficiency diseases and discuss its clinical implications.

Facilitated subcutaneous immunoglobulin use in pediatric patients with primary or secondary immunodeficiency diseases

Aim: While facilitated subcutaneous immunoglobulin (fSCIG) has been evaluated in pediatric patients with primary immunodeficiency diseases in clinical trials, real-world data are lacking. Materials & methods: This multicenter, retrospective, chart review study assessed fSCIG utilization in 30 patients less than 18 years old, with primary or secondary immunodeficiency diseases. Medical records were reviewed at fSCIG initiation and at 6 months. Results: Most (90%) patients received their first fSCIG infusion at a medical facility; by 6 months, all fSCIG infusions were administered at home by the patient/caregiver, the majority infusing every 3-4 weeks into a single site. No serious adverse drug reactions occurred. Conclusion: This study supports the feasibility and tolerability of administering fSCIG at home to pediatric patients with immunodeficiencies. Clinical Trial Registration: DRKS00015436 (German Clinical Trials Register).

As a Failure to Follow Basic Medical Rules for a Sample, Has a Costly Diagnosis of a Zoonosis

Cat-scratch disease can be transmitted from cats and dogs in winter. It is usually self-limited and caused by Bartonella henselae. It may cause serious symptoms, including neurological findings, especially in immune-deficient patients. A female patient was referred to our outpatient clinic at the age of 3 years and 10 months with a preliminary diagnosis of neurodegenerative metabolic disease. Her complaints began after a stray cat scratched her. We found out that the hospital to which she was admitted provided only local wound care due to her history of contact with a cat and that she was vaccinated against rabies. Her body temperature increased, her neck lymph nodes became swollen, and she developed otitis and mastoiditis after 1 month. Additionally, we discovered that she had deteriorated in her walking ability after 6 weeks and developed hand tremors after 10 weeks. It was discovered that previous centers to which the patient applied did not question cat contact. All metabolic tests performed for the differential diagnosis of last admission findings were considered nonspecific. Considering cat-scratch disease due to her clinical history, she was referred to the pediatric infection unit for a Bartonella henselae test, and the test result was 1/256 positive. Failure to follow basic medical rules might be costly in diagnosis and treatment. Cat scratch disease is a zoonosis and a major public health problem. In differential diagnosis, these medical procedures should always be considered before rare metabolic diseases.

Diverse clinical features and diagnostic delay in monogenic inborn errors of immunity: A call for access to genetic testing

BACKGROUND

Inborn errors of immunity (IEIs) are a group of conditions affecting immune system development and function. Due to their clinical heterogeneity and lack of provider awareness, patients suffer from long diagnostic delays that increase morbidity and mortality. Next-generation sequencing facilitates earlier diagnosis and treatment of IEIs, but too often patients are unable to see the benefit of this technology due to gaps in providers' knowledge regarding which patients to test and barriers to accessing sequencing.

METHODS

Here, we provide detailed clinical phenotyping and describe the impact of genetic sequencing on a cohort of 43 patients with monogenic IEIs seen in a tertiary care center from 2014 to 2019. Data were abstracted from a chart review, and a panel of clinical immunologists were consulted on the impact of genetic sequencing on their patients.

RESULTS

We found that our patients had significant diagnostic delays, averaging 3.3 years; had diverse manifestations of immune system dysfunction; and had demonstrated highly complex medical needs, with on average 7.9 subspecialties involved in their care and 4.9 hospitalizations prior to definitive treatment. Our results also demonstrate the benefits of genetic testing, as it provided the majority of our patients with a diagnosis, and positively impacted their treatment, follow-up, and prognosis.

CONCLUSION

This paper expands the paucity of literature on genetically confirmed IEIs in North America and supports the expansion of access to genetic testing for patients with clinical features suggesting IEI, such as those presented in our cohort.

Recent advances in lentiviral vectors for gene therapy

Lentiviral vectors (LVs), derived from human immunodeficiency virus, are powerful tools for modifying the genes of eukaryotic cells such as hematopoietic stem cells and neural cells. With the extensive and in-depth studies on this gene therapy vehicle over the past two decades, LVs have been widely used in both research and clinical trials. For instance, third-generation and self-inactive LVs have been used to introduce a gene with therapeutic potential into the host genome and achieve targeted delivery into specific tissue. When LVs are employed in leukemia, the transduced T cells recognize and kill the tumor B cells; in β-thalassemia, the transduced CD34⁺ cells express normal β-globin; in adenosine deaminase-deficient severe combined immunodeficiency, the autologous CD34⁺ cells express adenosine deaminase and realize immune reconstitution. Overall, LVs can perform significant roles in the treatment of primary immunodeficiency diseases, hemoglobinopathies, B cell leukemia, and neurodegenerative diseases. In this review, we discuss the recent developments and therapeutic applications of LVs. The safe and efficient LVs show great promise as a tool for human gene therapy.

[Hyper IgE syndrome: atopic dermatitis as first manifestation. Case report]

Atopic dermatitis is the most common form of eczema often developed before the first year of life. Nevertheless, when the presentation is atypical or related to infections the diagnostic represents a challenge for the pediatricians. It is important to maintain a high index of suspicion for the detection of primary immunodeficiency associated to severe eczema. One of them is the autosomal dominant hyper-IgE syndrome characterized by recurrent skin and respiratory infections, atopic dermatitis, eosinophilia, and high serum IgE concentrations. In this paper, we report a 1 months and 29 days old baby girl diagnosed with hyper-IgE and a skin involvement since birth.

Steady-State Serum IgG Trough Levels Are Adequate for Pharmacokinetic Assessment in Patients with Immunodeficiencies Receiving Subcutaneous Immune Globulin

Patients with primary immunodeficiency diseases often require lifelong immunoglobulin (IG) therapy. Most clinical trials investigating IG therapies characterize serum immunoglobulin G (IgG) pharmacokinetic (PK) profiles by serially assessing serum IgG levels. This retrospective analysis evaluated whether steady-state serum IgG trough level measurement alone is adequate for PK assessment. Based on individual patient serum IgG trough levels from two pivotal trials (phase 2/3 European [NCT01412385] and North American [NCT01218438]) of weekly 20% subcutaneous IG (SCIG; Cuvitru, Ig20Gly), trough level-predicted IgG AUC (AUC_τ,tp) were calculated and compared with the reported AUC calculated from serum IgG concentration-time profiles (AUC_τ). In both studies, mean AUC_τ,tp values for Ig20Gly were essentially equivalent to AUC_τ with point estimates of geometric mean ratio (GMR) of AUC_τ,tp/AUC_τ near 1.0 and 90% CIs within 0.80-1.25. In contrast, for IVIG, 10%, mean AUC_τ,tp values were lower than AUC_τ by >20%, (GMR [90% CI]: 0.74 [0.70-0.78] and 0.77 [0.73-0.81] for the two studies, respectively). Mean AUC_τ,tp values calculated for 4 other SCIG products (based on mean IgG trough levels reported in the literature/labels) were also essentially equivalent to the reported AUC_τ (differences <10% for all except HyQvia, a facilitated SCIG product), while differences for IVIG products were >20%. In conclusion, steady-state serum IgG levels following weekly SCIG remain stable, allowing for reliable prediction of AUC over the dosing interval using trough IgG levels. These findings indicate that measuring steady-state serum IgG trough levels alone may be adequate for PK assessment of weekly SCIG.

The Role of Respiratory Viruses in Children with Ataxia-Telangiectasia

Background: The impact of respiratory virus infection in patients diagnosed with ataxia-telangiectasia (A-T) has not been well studied. Methods: A prospective case control study was performed at a National Reference Unit for Primary Immunodeficiency in Spain (from November 2018 to July 2019), including patients younger than 20 years. Symptom questionnaires and nasopharyngeal swabs from multiple respiratory viruses’ polymerase chain reaction were collected monthly, and between visits in case of symptoms. Results: Twenty-two individuals were included (11 patients; 11 controls); 164 samples were obtained (81 patients; 84 controls). Patients presented respiratory symptoms more frequently compared with controls (26.5% vs. 3.5%; p < 0.01). Viral detection was observed in 23 (27.3%) episodes in patients and in 15 (17.8%) episodes in controls (p = 0.1). Rhinovirus was the most frequent virus in patients and controls (60% and 53.3%, respectively). Episodes with positive viral detection had associated symptoms in 54% of patients and 18% of controls (p = 0.07). However, patients with A-T presented a similar rate of symptoms during episodes with positive and negative viral detection (26% vs. 27%). The median points given for each questionnaire during symptomatic episodes with negative viral detection were 13/23 points, and during symptomatic positive detection, 7.5/23 points (p = 0.1). In the control group, all but two were asymptomatic during positive viral episodes (score: 2/23 and 3/23 points). Symptomatic episodes, with either positive or negative viral detection, were associated with lower IgA and higher IgM titers and higher CD8+ counts (p < 0.05), particularly when these episodes were moderate/severe. Conclusions: Patients with A-T more frequently present symptomatic viral infections than controls, especially those with lower IgA and higher IgM titers and higher CD8+ counts.

Evaluation of miR-210 expression in common variable immunodeficiency: patients with unsolved genetic defect

BACKGROUND

Common variable immunodeficiency (CVID) is one of the most prevalent forms of primary immunodeficiency diseases (PID). CVID is characterized by failure in the final differentiation of B lymphocytes and impaired antibody production but the pathogenesis is not known in the majority of patients. We postulated that the expression pattern of miRNAs in unsolved CVID patients might be the underlying epigenetic cause of the disease. Therefore, we aimed to assess the expression of hsa-miR-210-5p and FOXP3 transcription factor in CVID cases in comparison with healthy individuals.

METHODS

Eleven CVID cases with no genetic defects (all PID known genes excluded) and 10 sex and age-matched healthy individuals were enrolled in the study. T lymphocytes were purified from PBMC, and expression levels of miR-210-5p and FOXP3 mRNA were evaluated by real-time PCR.

RESULTS

We demonstrated that miR-210 expression in patients was significantly higher than the control group (P = 0.03). FOXP3 expression was slightly lower in patients compared with healthy controls (P = 0.86). There was a negative correlation between miR and gene expression (r: -0.11, P = 0.73). Among various clinical complications, autoimmunity showed a considerable rate in high-miR patients (P = 0.12, 42.8%), while autoimmunity was not observed in normal miR-210 patients.

CONCLUSIONS

Our results suggest a role for miR-210 in the pathogenesis of autoimmunity in CVID patients. Further studies would better elucidate epigenetic roles in CVID patients with no genetic defects.

Pulmonary Infections and Surgical Complications in a Young Girl with Signal Transducer and Activator of Transcription 3 Loss-of-Function Mutation Hyperimmunoglobulin E Syndrome: A Case Report

Introduction: Hyperimmunoglobulin E syndromes (HIESs) are characterized by a high serum immunoglobulin E (IgE) level, eczematoid rashes, recurrent staphylococcal skin abscesses, and recurrent pneumonia and pneumatocele formation. Autosomal dominant HIES is the most common form of HIES and mainly occurs due to loss-of-function mutations in the Signal Transducer and Activator of Transcription 3 (STAT3) gene (STAT3 LOF). Case Presentation: We report the case of an 11-year-old Peruvian girl diagnosed with STAT3 LOF caused by p.R382W mutation. She presented with recurrent staphylococcal pneumonia and empyema caused by the rarely reported Achromobacter xylosoxidans, which led to severe destruction of the lung parenchyma, multiple lung surgeries, and the development of bronchopleural fistulas. A laparotomy was also performed, which showed evidence of sigmoid colon perforation. The patient received immunoglobulin replacement therapy (IRT) and antibiotic prophylaxis, and the frequency of her infections has decreased over the past 3 years. Conclusion: This is the first case of STAT3 LOF diagnosed by genomic sequencing in Peru. Patients with this mutation have recurrent pulmonary infections, and require multiple surgical procedures with frequent complications. A. xylosoxidans infection could be related to the prolonged stay in intensive care leading to high mortality; therefore, additional care must be taken when treating patients with this infection. In addition, colonic perforation is a rare complication in STAT3 LOF patients. IRT and antibiotic prophylaxis appear to decrease the frequency of infections and hospitalizations.

Monogenic Immune Diseases Provide Insights Into the Mechanisms and Treatment of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (GvHD) has become a leading cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT) and can burden patients with devastating and lifelong health effects. Our understanding of the pathogenic mechanisms underlying chronic GvHD remains incomplete and this lack of understanding is reflected by lack of clear therapeutic approaches to steroid refractory disease. Observations predominantly from mouse models and human correlative studies currently support a three phase model for the initiation and development of chronic GvHD: 1) early inflammation and tissue damage triggers the innate immune system. This leads to inflammatory cytokine/chemokine patterns that recruit effector immune cell populations; 2) chronic inflammation causes the loss of central and peripheral tolerance mechanisms leading to emergence of pathogenic B and T cell populations that promote autoimmune and alloimmune reactions; 3) the dysregulated immunity causes altered macrophage polarization, aberrant tissue repair leading to scarring and end organ fibrosis. This model has led to the evaluation of many new therapies aimed at limiting inflammation, targeting dysregulated signaling pathways and restoring tolerance mechanisms. However, chronic GvHD is a multisystem disease with complex clinical phenotypes and it remains unclear as to which cluster of patients will respond best to specific therapeutic strategies. However, it is possible to gain novel insights from immune-related monogenic diseases. These diseases either share common clinical manifestations, replicate steps from the three phase chronic GvHD model or serve as surrogates for perfectly targeted drugs being investigated in chronic GvHD therapy. In this review, we will summarize the evidence from these monogenic immune related diseases that provide insight into pathogenic pathways in chronic GvHD, rationales for current therapies and novel directions for future drug discovery.

Failure of Viral-Specific T Cells Administered in Pre-transplant Settings in Children with Inborn Errors of Immunity

PURPOSE

Use of adoptive immunotherapy with virus-specific T cells (VST) in patients with inborn errors of immunity prior to hematopoietic stem cell transplantation (HSCT) has been reported in few patients. We report our experience, reviewing all the cases previously reported.

METHODS

We report four children with inborn errors of immunity who received VST infusion in a pre-HSCT setting in two reference centers in Spain and review all inborn errors of immunity cases previously reported.

RESULTS

Taking into account our four cases, nine children have been reported to receive VST prior to HSCT to date: 3 severe combined immunodeficiency, 2 CTPS1 deficiency, 1 dyskeratosis congenital, 1 ORAI1 deficiency, 1 Rothmund-Thomson syndrome, and 1 combined immunodeficiency without confirmed genetic defect. In four patients, immunotherapy resulted in clinical improvement, allowing to proceed to HSCT. In these cases, the infusion was started closely to viral diagnosis [mean time 28 days (IQR; 17-52 days)], and the VST was followed shortly thereafter by HSCT [mean time 28 days (IQR; 10-99 days)]. Viremia was controlled after HSCT in two cases (performed 7 and 36 days after the infusion). Multiple infusions were required in many cases. Five out of nine patients died before receiving HSCT. These patients presented with a prolonged and uncontrolled infection before VST administration [mean time from viral diagnosis to VST infusion was 176 days (IQR; 54-1687)].

CONCLUSIONS

In patients with inborn errors of immunity, the efficacy of VST for treating disseminated viral infections in pre-transplant settings seems to have a limited efficacy. However, this therapy could be used in a pre-emptive setting before severe viral disease occurs or closely to HSCT.

Novel mutations in hyper-IgM syndrome type 2 and X-linked agammaglobulinemia detected in three patients with primary immunodeficiency disease

Background

Ambiguous or atypical phenotypes can make a definite diagnosis of primary immunodeficiency diseases based on biochemical indices alone challenging. Further, mortality in early life because of infections in patients with these conditions supports the use of genetic tests to facilitate rapid and accurate diagnoses.

Methods

Genetic and clinical analyses of three unrelated Chinese children with clinical manifestations of recurrent infections, who were considered to have primary immunodeficiency diseases, were conducted. Patient clinical features and serum immunological indices were recorded. Next‐generation sequencing was used to screen for suspected pathogenic variants. Family co‐segregation and in silico analysis were conducted to evaluate the pathogenicity of identified variants, following the American College of Medical Genetics and Genomics guidance.

Results

All three patients were found to have predominant antibody defects. Sequencing analysis revealed that one had two compound heterozygous variants, c.255C>A and c.295C>T, in the autosomal gene, activation‐induced cytidine deaminase (AICDA). The other two patients were each hemizygous for the variants c.1185G>A and c.82C>T in the Bruton's tyrosine kinase (BTK) gene on the X chromosome. In silico analysis revealed that identified substituted amino acids were highly conserved and predicted to cause structural and functional damage to the proteins.

Conclusion

Four pathogenic variants in AICDA and BTK were confirmed to cause different forms of hyper‐IgM syndrome type 2 (HIGM2) and X‐linked agammaglobulinemia (XLA); two were novel mutations that have never been reported previously. This is the first report of HIGM2 caused by AICDA deficiency in a patient from the Chinese mainland.

Gene Editing for the Treatment of Primary Immunodeficiency Diseases

With conventional treatments for primary immunodeficiency diseases (PIDs), such as allogeneic stem cell transplantation or autologous gene therapy, still facing important challenges, the rapid development of genome editing technologies to more accurately correct the mutations underlying the onset of genetic disorders has provided a new alternative, yet promising platform for the treatment of such diseases. The prospect of a more efficient and specific therapeutic tool has pushed many researchers to apply these editing tools to correct genetic, phenotypic, and functional defects of numerous devastating PIDs with extremely promising results to date. Despite these achievements, lingering concerns about the safety and efficacy of genome editing are currently being addressed in preclinical studies. This review summarizes the progress made toward the development of gene editing technologies to treat PIDs and the optimizations that still need to be implemented to turn genome editing into a next-generation treatment for rare monogenic life-threatening disorders.

Heterozygous TLR3 Mutation in Patients with Hantavirus Encephalitis

Puumala hantavirus (PUUV) hemorrhagic fever with renal syndrome (HFRS) is common in Northern Europe; this infection is usually self-limited and severe complications are uncommon. PUUV and other hantaviruses, however, can rarely cause encephalitis. The pathogenesis of these rare and severe events is unknown. In this study, we explored the possibility that genetic defects in innate anti-viral immunity, as analogous to Toll-like receptor 3 (TLR3) mutations seen in HSV-1 encephalitis, may explain PUUV encephalitis. We completed exome sequencing of seven adult patients with encephalitis or encephalomyelitis during acute PUUV infection. We found heterozygosity for the TLR3 p.L742F novel variant in two of the seven unrelated patients (29%, p = 0.0195). TLR3-deficient P2.1 fibrosarcoma cell line and SV40-immortalized fibroblasts (SV40-fibroblasts) from patient skin expressing mutant or wild-type TLR3 were tested functionally. The TLR3 p.L742F allele displayed low poly(I:C)-stimulated cytokine induction when expressed in P2.1 cells. SV40-fibroblasts from three healthy controls produced increasing levels of IFN-λ and IL-6 after 24 h of stimulation with increasing concentrations of poly(I:C), whereas the production of the cytokines was impaired in TLR3 L742F/WT patient SV40-fibroblasts. Heterozygous TLR3 mutation may underlie not only HSV-1 encephalitis but also PUUV hantavirus encephalitis. Such possibility should be further explored in encephalitis caused by these and other hantaviruses.

Nocardiosis Associated with Primary Immunodeficiencies (Nocar-DIP): an International Retrospective Study and Literature Review

PURPOSE

Nocardiosis is a life-threatening infectious disease. We aimed at describing nocardiosis in patients with primary immunodeficiency diseases (PID).

METHODS

This international retrospective cohort included patients with PID and nocardiosis diagnosed and/or published from Jan 1, 2000, to Dec 31, 2016. To identify nocardiosis cases, we analyzed PID databases from the French National Reference Center for PID (Paris, France) and the National Institute of Health (NIH, United States of America) and we performed a literature review on PubMed.

RESULTS

Forty-nine cases of nocardiosis associated with PID were included: median age at diagnosis of nocardiosis was 19 (0-56) years and most cases were observed among chronic granulomatous disease (CGD) patients (87.8%). Median time from symptoms to diagnosis of Nocardia infection was 20 (2-257) days. Most frequent clinical nocardiosis presentation was pneumonia (86.7%). Twelve-month mortality rate was 4.2%, and 11.9% of patients experienced a possible recurrence of infection. Nocardiosis more frequently led to the diagnosis of PID among non-CGD patients than in CGD patients. Non-CGD patients experienced more cerebral nocardiosis and more disseminated infections, but mortality and recurrence rates were similar. Highest incidences of nocardiosis among PID cohorts were observed among CGD patients (0.0057 and 0.0044 cases/patient-year in the USA and in France, respectively), followed by IL-12p40 deficiency.

CONCLUSIONS

Among 49 cases of nocardiosis associated with PID, most patients had CGD and lung involvement. Both mortality and recurrence rates were low.

Hematopoietic Stem Cell Transplantation in Children with Inborn Errors of Immunity: a Multi-center Experience in Colombia

PURPOSE

To characterize the pediatric population with inborn errors of immunity (IEI) that was treated with hematopoietic stem cell transplantation (HSCT) in three reference centers in Colombia. What have been the characteristics and outcomes of hematopoietic stem cell transplantation in pediatric patients with inborn errors of immunity in three reference care centers in Colombia between 2007 and 2018?

METHODS

We conducted an observational, retrospective cohort study in children with a diagnosis of IEI who underwent HSCT between 2007 and 2018.

RESULTS

Forty-seven patients were identified, and 5 were re-transplanted. Sixty-eight percent were male. The median age at diagnosis was 0.6 years, and for HSCT was 1.4 years. The most common diseases were chronic granulomatous disease (38%) followed by severe combined immune deficiencies (19%) and hemophagocytic lymphohistiocytosis (15%). Cord blood donors were the most used source of HSCT (44%). T cell-replete grafts from haploidentical donors using post-transplantation cyclophosphamide represent 37% of the cohort. All patients received conditioning, 62% with a non-myeloablative regimen. Calcineurin inhibitors were the main graft-versus-host disease prophylaxis (63.8%). Acute graft-versus-host disease developed in 35% of the total patients. The most frequent post-transplant infections were viral and fungal infections. The 1-year overall survival rates for the patients who received HSCT from identical, haploidentical, and cord sources were 80%, 72%, and 63%, respectively. The 5-year overall survival was 63%.

CONCLUSIONS

HSCT is a curative treatment option for some IEI and can be performed with any donor type. Early and timely treatment in referral centers can improve survival.

Geographic Variability and Pathogen-Specific Considerations in the Diagnosis and Management of Chronic Granulomatous Disease

Chronic granulomatous disease (CGD) is a rare but serious primary immunodeficiency with varying prevalence and rates of X-linked and autosomal recessive disease worldwide. Functional defects in the phagocyte nicotinamide adenine dinucleotide phosphate oxidase complex predispose patients to a relatively narrow spectrum of bacterial and fungal infections that are sometimes fastidious and often difficult to identify. When evaluating and treating patients with CGD, it is important to consider their native country of birth, climate, and living situation, which may predispose them to types of infections that are atypical to your routine practice. In addition to recurrent and often severe infections, patients with CGD and X-linked female carriers are also susceptible to developing many non-infectious complications including tissue granuloma formation and autoimmunity. The DHR-123 oxidation assay is the gold standard for making the diagnosis and it along with genetic testing can help predict the severity and prognosis in patients with CGD. Disease management focuses on prophylaxis with antibacterial, antifungal, and immunomodulatory medications, prompt identification and treatment of acute infections, and prevention of secondary granulomatous complications. While hematopoietic stem-cell transplantation is the only widely available curative treatment for patients with CGD, recent advances in gene therapy may provide a safer, more direct alternative.

Screening for primary immunodeficiency diseases by next-generation sequencing in early life

Objective

We aimed to use next-generation sequencing (NGS) for the early diagnosis of primary immunodeficiency diseases (PIDs) and define its effects on medical management for an infant cohort in early life.

Methods

A single-centre study was conducted from November 2015 to April 2018. Infants less than 3 months old with infections or abnormal white blood cell counts were enrolled in the study. Gene variants were analysed by NGS, and once a mutation was found in a PID-associated gene, the immune functions associated with this mutation were detected. The diagnosis rate of PIDs in the cohort was the main outcome. The patients received corresponding management and follow-up treatments.

Results

Among 2392 patients who were genetically tested with NGS, 51 infants were diagnosed with PIDs. Seven types of PIDs were detected, and the most common (25/51, 49%) were combined immunodeficiencies with associated or syndromic features. Thirty-five patients (68.6%) were cured or had improved outcomes after being diagnosed with PID. The NGS cost was US$280 per case.

Conclusions

This study not only highlighted the potential of NGS to rapidly deliver molecular diagnoses of PIDs but also indicated that the prevalence of PIDs is underestimated. With broader use, this approach has the potential to alter clinical strategies.

The Usefulness of Scintigraphic Studies in the Assessment of Asymptomatic Bowel Disease in Patients with Primary Antibody Diseases

Enteropathy may be the first presentation of immunodeficiency or it may occur during the course of the disease and in association with malabsorption in patients affected by primary antibody diseases. For these patients, immunoglobulin G (IgG) replacement therapy prevents infectious and non-infectious complications. Nonetheless some patients cannot achieve optimal IgG trough levels, even when treated with high Ig doses in absence of protein-losing syndromes. We investigated seven patients affected by common variable immunodeficiencies (CVIDs) and treated with high Ig doses (600–800 mg/kg/month) showing low IgG trough level. Patients underwent abdominal scintigraphy with human polyclonal immunoglobulin G labeled with 99mTc and with white blood cells labeled by 111 Indium-oxinate to investigate asymptomatic bowel inflammation. A concentration of labeled leukocytes in abdominal segments greater than that observed with human polyclonal immunoglobulin G was evident only in one patient. In five patients a slight concentration of both radiopharmaceuticals was reported, due to mild intestinal inflammatory response. These data might be related to mild increase of capillary permeability in the absence of inflammation leukocyte mediated. This study discloses a new cause of IgG-accelerated catabolism due to inflammatory bowel conditions without diarrhea in CVID patients.

Expanding TREC and KREC Utility in Primary Immunodeficiency Diseases Diagnosis

Primary immunodeficiency diseases (PID) area heterogeneous group of disorders caused by genetic defects of the immune system, which manifest clinically as recurrent infections, autoimmune diseases or malignancies. Early detection of PID remains a challenge, particularly in older children with milder and less specific symptoms. This study aimed to assess TREC and KREC diagnostic ability in PID. Data from children assessed by clinical immunologists at Speransky Children's Hospital, Moscow, Russia with suspected immunodeficiencies were analyzed between May 2013 and August 2016. Peripheral blood samples were sent for TREC/KREC, flow cytometry (CD3, CD4, CD8 and CD19), IgA and IgG analysis. A total of 434 children [189 healthy, 97 with group I and II PID (combined T and B cell immunodeficiencies & well-defined syndromes with immunodeficiency) and 148 group III PID (predominantly antibody deficiencies)] were included. Area under the curve (AUC) for TREC in PID groups I and II diagnosis reached 0.82 (CI = 0.75-0.90), with best model providing sensitivity of 65% and specificity of 92%. Neither TREC, nor KREC had added value in PID group III diagnosis. In this study, the predictive value of TREC and KREC in PID diagnosis was examined. We found that the TREC had some diagnostic utility for groups I and II PID. Possibly, addition of TREC measurements to existing clinical diagnostic algorithms may improve their predictive value. Further investigations on a larger cohort are needed to evaluate TREC/KREC abilities to be used as diagnostic tools on a wider scale.

Immunodeficiency and disorders of immune dysregulation

The spectrum of clinical features associated with primary immune deficiency disorders (PIDs) has broadened due to the recent identification of many novel causative genes. Patients present with increased susceptibility to infections in addition to significant immune dysregulation, often leading to multiple autoimmunity, lymphoproliferation, and malignancy. Immunosuppressive treatment is often required but has to be weighed against augmented infectious risk. Recently, the improved molecular understanding of the mechanisms underlying many loss-of-function (LOF) and gain-of-function (GOF) genetic defects leading to PIDs has set the ground for the development of mechanism-based therapeutic strategies that target a specific cell function. This article describes the clinical and laboratory features of selected recently described PIDs associated with immune dysregulation and novel precision medicine strategies aimed to control the disease burden in affected patients.

Newborn Screening for Primary Immunodeficiencies: The Gaps, Challenges, and Outlook for Developing Countries

Primary immunodeficiency diseases (PIDs) are genetically inherited diseases characterized by an increased susceptibility to infections, autoimmunity, lymphoproliferation, and malignancies. PIDs are under-diagnosed and the registered cases and reported prevalence are far below the estimated numbers especially in countries with large population and high consanguinity rates. Delays in diagnosis yield major morbidities and mortalities with resultant increased economic burden. Newborn screening using TRECs and KRECs, currently being implemented in some countries, is aimed through early diagnosis, to overcome the delays in the diagnosis and hence the poor outcome of some of the severe PIDs. However, the limited resources in developing countries challenges the implementation of newborn PID screening programs. There are considerable gaps in our knowledge that must be bridged. Setting the norms of TRECs and KRECs for each country is needed. Furthermore, some PIDs that might present in the neonatal period could not be detected by the current screening programs, and their diagnosis requires clinical expertise. Not to mention, local guidelines for the management of patients diagnosed by NBS should be set forth. Also, in the absence of NBS, clinicians should be aware of the early manifestations of PID. All these mandate conducting studies genuine to each country, developing programs for raising public awareness and clinical training of physicians to attain the required immunological skills.

Development of multiple gallstones in a child with lipopolysaccharide-responsive beige-like anchor protein mutation

A defect in the lipopolysaccharide-responsive beige-like anchor protein (LRBA) gene is a newly defined rare cause of primary immunodeficiency diseases, which manifests as immune dysregulation and humoral immune deficiency. LRBA deficiency is a combined immunodeficiency. A boy with LRBA deficiency is described in this report. He had been diagnosed with Evans syndrome in a haematology clinic. He was referred to an immunology and allergy clinic for frequent respiratory tract infections. He also had hepatosplenomegaly but no lymphadenopathy. Immunological evaluation revealed hypogammaglobulinaemia, increased double-negative T cells, decreased memory B cells and switched B cells, and an inverted CD4/CD8 ratio. LRBA deficiency was considered due to common variable immunodeficiency-autoimmune lymphoproliferative overlap syndrome. A homozygote mutation (c.1964C>T) in LRBA was found through exome sequencing. Gastrointestinal investigation was performed due to unexplained abdominal pain. It revealed atrophic gastritis, partial villous atrophy, and multiple gallstones. There was no chronic diarrhoea or failure to thrive. The abdominal pain disappeared after a cholecystectomy. Multiple gallstones have not been reported in other LRBA-deficient patients who also had autoimmune haemolytic anaemia. Multiple gallstones that require cholecystectomy can develop in LRBA-deficient patients during adolescence.

Flow Cytometry Contributions for the Diagnosis and Immunopathological Characterization of Primary Immunodeficiency Diseases With Immune Dysregulation

Almost 70 years after establishing the concept of primary immunodeficiency disorders (PIDs), more than 320 monogenic inborn errors of immunity have been identified thanks to the remarkable contribution of high-throughput genetic screening in the last decade. Approximately 40 of these PIDs present with autoimmune or auto-inflammatory symptoms as the primary clinical manifestation instead of infections. These PIDs are now recognized as diseases of immune dysregulation. Loss-of function mutations in genes such as FOXP3, CD25, LRBA, IL-10, IL10RA, and IL10RB, as well as heterozygous gain-of-function mutations in JAK1 and STAT3 have been reported as causative of these disorders. Identifying these syndromes has considerably contributed to expanding our knowledge on the mechanisms of immune regulation and tolerance. Although whole exome and whole genome sequencing have been extremely useful in identifying novel causative genes underlying new phenotypes, these approaches are time-consuming and expensive. Patients with monogenic syndromes associated with autoimmunity require faster diagnostic tools to delineate therapeutic strategies and avoid organ damage. Since these PIDs present with severe life-threatening phenotypes, the need for a precise diagnosis in order to initiate appropriate patient management is necessary. More traditional approaches such as flow cytometry are therefore a valid option. Here, we review the application of flow cytometry and discuss the relevance of this powerful technique in diagnosing patients with PIDs presenting with immune dysregulation. In addition, flow cytometry represents a fast, robust, and sensitive approach that efficiently uncovers new immunopathological mechanisms underlying monogenic PIDs.