T-cell receptor excision circles in primary immunodeficiencies and other T-cell immune disorders

Immunophenotypes in psychosis: is it a premature inflamm-aging disorder?

Immunopsychiatric field has rapidly accumulated evidence demonstrating the involvement of both innate and adaptive immune components in psychotic disorders such as schizophrenia. Nevertheless, researchers are facing dilemmas of discrepant findings of immunophenotypes both outside and inside the brains of psychotic patients, as discovered by recent meta-analyses. These discrepancies make interpretations and interrogations on their roles in psychosis remain vague and even controversial, regarding whether certain immune cells are more activated or less so, and whether they are causal or consequential, or beneficial or harmful for psychosis. Addressing these issues for psychosis is not at all trivial, as immune cells either outside or inside the brain are an enormously heterogeneous and plastic cell population, falling into a vast range of lineages and subgroups, and functioning differently and malleably in context-dependent manners. This review aims to overview the currently known immunophenotypes of patients with psychosis, and provocatively suggest the premature immune "burnout" or inflamm-aging initiated since organ development as a potential primary mechanism behind these immunophenotypes and the pathogenesis of psychotic disorders.

Newborn screening for severe combined immunodeficiency and inborn errors of immunity

PURPOSE OF REVIEW

Severe combined immune deficiency (SCID) is the most devastating genetic disease of the immune system with an unfavorable outcome unless diagnosed early in life. Newborn screening (NBS) programs play a crucial role in facilitating early diagnoses and timely interventions for affected infants.

RECENT FINDINGS

SCID marked the pioneering inborn error of immunity (IEI) to undergo NBS, a milestone achieved 15 years ago through the enumeration of T-cell receptor excision circles (TRECs) extracted from Guthrie cards. This breakthrough has revolutionized our approach to SCID, enabling not only presymptomatic identification and prompt treatments (including hematopoietic stem cell transplantation), but also enhancing our comprehension of the global epidemiology of SCID.

SUMMARY

NBS is continuing to evolve with the advent of novel diagnostic technologies and treatments. Following the successful implementation of SCID-NBS programs, a call for the early identification of additional IEIs is the next step, encompassing a broader spectrum of IEIs, facilitating early diagnoses, and preventing morbidity and mortality.

Can T-cell and B-cell excision circles predict development of inhibitors in pediatric hemophilia A?

BACKGROUND

Hemophilia A (HA) therapy requires intravenous replacement infusions of factor (F) VIII concentrate. Inhibitors are high-affinity immunoglobulin G that are directed against FVIII and thereby render replacement therapy ineffective. This complication has significant prognostic implications. We aimed to examine the immune system involvement in inhibitor formation specifically T-cell excision circles (TRECs) and B-cell excision circles (KRECs), markers of new T and B cells, respectively, and examine them as surrogate markers for inhibitor formation.

METHODS

Blood samples were collected from 35 children with severe HA. Children were divided into two groups: with FVIII inhibitors and without FVIII inhibitors. TRECs and KRECs were measured in peripheral blood.

RESULTS

A total of 11 patients with inhibitors and 24 without were evaluated. Children with inhibitors had higher levels of TRECs however not statistically significant (p = 0.085). CjKREC levels were higher in the inhibitor patients (p = 0.003). Moreover, the sj/cjKREC ratio was lower in the inhibitor patients (p = 0.015).

CONCLUSIONS

Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and loss of peripheral tolerance. Improved knowledge regarding the involvement of the immune system in the formation of FVIII inhibitors will enable better therapy tailoring in the era of non-replacement therapies.

IMPACT

The etiology of FVIII inhibitor formation is multifactorial, in which the immune system plays a pivotal role. Our findings may add to the notion that inhibitor formation is attributed to humoral immunity due to peripheral B-cell expansion and production of antibodies against FVIII. Improved knowledge regarding the involvement of the immune system in the development of FVIII inhibitors will enable the identification of patients prone to inhibitor development and better therapy tailoring in the new era of non-replacement therapies.

Epigenetic liquid biopsies: a novel putative biomarker in immunology and inflammation

Immune and inflammatory processes occurring within tissues are often undetectable by blood cell counts, standard circulating biomarkers, or imaging, representing an unmet biomedical need. Here, we outline recent advances indicating that liquid biopsies can broadly inform human immune system dynamics. Nucleosome-size fragments of cell-free DNA (cfDNA) released from dying cells into blood contain rich epigenetic information such as methylation, fragmentation, and histone mark patterns. This information allows to infer the cfDNA cell of origin, as well as pre-cell death gene expression patterns. We propose that the analysis of epigenetic features of immune cell-derived cfDNA can shed light on immune cell turnover dynamics in healthy people, and inform the study and diagnosis of cancer, local inflammation, infectious or autoimmune diseases, as well as responses to vaccination.

Blood levels of T-Cell Receptor Excision Circles (TRECs) provide an index of exposure to traumatic stress in mice and humans

Exposure to stress triggers biological changes throughout the body. Accumulating evidence indicates that alterations in immune system function are associated with the development of stress-associated illnesses such as major depressive disorder and post-traumatic stress disorder, increasing interest in identifying immune markers that provide insight into mental health. Recombination events during T-cell receptor rearrangement and T-cell maturation in the thymus produce circular DNA fragments called T-cell receptor excision circles (TRECs) that can be utilized as indicators of thymic function and numbers of newly emigrating T-cells. Given data suggesting that stress affects thymus function, we examined whether blood levels of TRECs might serve as a quantitative peripheral index of cumulative stress exposure and its physiological correlates. We hypothesized that chronic stress exposure would compromise thymus function and produce corresponding decreases in levels of TRECs. In male mice, exposure to chronic social defeat stress (CSDS) produced thymic involution, adrenal hypertrophy, and decreased levels of TRECs in blood. Extending these studies to humans revealed robust inverse correlations between levels of circulating TRECs and childhood emotional and physical abuse. Cell-type specific analyses also revealed associations between TREC levels and blood cell composition, as well as cell-type specific methylation changes in CD4T + and CD8T + cells. Additionally, TREC levels correlated with epigenetic age acceleration, a common biomarker of stress exposure. Our findings demonstrate alignment between findings in mice and humans and suggest that blood-borne TRECs are a translationally-relevant biomarker that correlates with, and provides insight into, the cumulative physiological and immune-related impacts of stress exposure in mammals.

Lessons Learned From Five Years of Newborn Screening for Severe Combined Immunodeficiency in Israel

BACKGROUND

Implementation of newborn screening (NBS) programs for severe combined immunodeficiency (SCID) have advanced the diagnosis and management of affected infants and undoubtedly improved their outcomes. Reporting long-term follow-up of such programs is of great importance.

OBJECTIVE

We report a 5-year summary of the NBS program for SCID in Israel.

METHODS

Immunologic and genetic assessments, clinical analyses, and outcome data from all infants who screened positive were evaluated and summarized.

RESULTS

A total of 937,953 Guthrie cards were screened for SCID. A second Guthrie card was requested on 1,169 occasions (0.12%), which resulted in 142 referrals (0.015%) for further validation tests. Flow cytometry immune-phenotyping, T cell receptor excision circle measurement in peripheral blood, and expression of TCRVβ repertoire for the validation of positive cases revealed a specificity and sensitivity of 93.7% and 75.9%, respectively, in detecting true cases of SCID. Altogether, 32 SCID and 110 non-SCID newborns were diagnosed, making the incidence of SCID in Israel as high as 1:29,000 births. The most common genetic defects in this group were associated with mutations in DNA cross-link repair protein 1C and IL-7 receptor α (IL-7Rα) genes. No infant with SCID was missed during the study time. Twenty-two SCID patients underwent hematopoietic stem cell transplantation, which resulted in a 91% survival rate.

CONCLUSIONS

Newborn screening for SCID should ultimately be applied globally, specifically to areas with high rates of consanguineous marriages. Accumulating data from follow-up studies on NBS for SCID will improve diagnosis and treatment and enrich our understanding of immune development in health and disease.

Pneumonia and Related Conditions in Critically Ill Patients—Insights from Basic and Experimental Studies

Pneumonia is an acute infectious disease with high morbidity and mortality rates. Pneumonia’s development, severity and outcome depend on age, comorbidities and the host immune response. In this study, we combined theoretical and experimental investigations to characterize pneumonia and its comorbidities as well as to assess the host immune response measured by TREC/KREC levels in patients with pneumonia. The theoretical study was carried out using the Columbia Open Health Data (COHD) resource, which provides access to clinical concept prevalence and co-occurrence from electronic health records. The experimental study included TREC/KREC assays in young adults (18–40 years) with community-acquired (CAP) (n = 164) or nosocomial (NP) (n = 99) pneumonia and healthy controls (n = 170). Co-occurring rates between pneumonia, sepsis, acute respiratory distress syndrome (ARDS) and some other related conditions common in intensive care units were the top among 4170, 3382 and 963 comorbidities in pneumonia, sepsis and ARDS, respectively. CAP patients had higher TREC levels, while NP patients had lower TREC/KREC levels compared to controls. Low TREC and KREC levels were predictive for the development of NP, ARDS, sepsis and lethal outcome (AUC_TREC in the range 0.71–0.82, AUC_KREC in the range 0.67–0.74). TREC/KREC analysis can be considered as a potential prognostic test in patients with pneumonia.

Digital Droplet PCR in Hematologic Malignancies: A New Useful Molecular Tool

Digital droplet PCR (ddPCR) is a recent version of quantitative PCR (QT-PCR), useful for measuring gene expression, doing clonality assays and detecting hot spot mutations. In respect of QT-PCR, ddPCR is more sensitive, does not need any reference curve and can quantify one quarter of samples already defined as "positive but not quantifiable". In the IgH and TCR clonality assessment, ddPCR recapitulates the allele-specific oligonucleotide PCR (ASO-PCR), being not adapt for detecting clonal evolution, that, on the contrary, does not represent a pitfall for the next generation sequencing (NGS) technique. Differently from NGS, ddPCR is not able to sequence the whole gene, but it is useful, cheaper, and less time-consuming when hot spot mutations are the targets, such as occurs with IDH1, IDH2, NPM1 in acute leukemias or T315I mutation in Philadelphia-positive leukemias or JAK2 in chronic myeloproliferative neoplasms. Further versions of ddPCR, that combine different primers/probes fluorescences and concentrations, allow measuring up to four targets in the same PCR reaction, sparing material, time, and money. ddPCR is also useful for quantitating BCR-ABL1 fusion gene, WT1 expression, donor chimerism, and minimal residual disease, so helping physicians to realize that "patient-tailored therapy" that is the aim of the modern hematology.

Immune function in newborns with in-utero exposure to anti-TNFα therapy

BACKGROUND AND AIM

Anti-TNFα is measurable in infants exposed in utero up to 12 months of age. Data about the exposure effect on the infant's adaptive immunity are limited. We aimed to prospectively evaluate the distribution and function of T and B cells, in infants of females with inflammatory bowel disease, in utero exposed to anti-TNFα or azathioprine.

METHODS

A prospective multi-center study conducted 2014-2017. Anti-TNFα levels were measured in cord blood, and at 3 and 12 months. T-cell repertoire and function were analyzed at 3 and 12 months by flow-cytometry, expression of diverse T cell receptors (TCR) and T-cell receptor excision circles (TREC) quantification assay. Serum immunoglobulins and antibodies for inactivated vaccines were measured at 12 months. Baseline clinical data were retrieved, and 2-monthly telephonic interviews were performed regarding child infections and growth.

RESULTS

24 pregnant females, age 30.6 (IQR 26.5-34.5) years were recruited, 20 with anti-TNFα (infliximab 8, adalimumab 12), and 4 with azathioprine treatment. Cord blood anti-TNFα was higher than maternal blood levels [4.3 (IQR 2.3-9.2) vs. 2.5 (IQR 1.3-9.7) mcg/ml], declining at 3 and 12 months. All infants had normal number of B-cells (n = 17), adequate levels of immunoglobulins (n = 14), and protecting antibody levels to Tetanus, Diphtheria, Hemophilus influenza-B and hepatitis B (n = 17). All had normal CD4+, CD8+ T-cells, and TREC numbers. TCR repertoire was polyclonal in 18/20 and slightly skewed in 2/20 infants. No serious infections requiring hospitalization were recorded.

CONCLUSION

We found that T-cell and B-cell immunity is fully mature and immune function is normal in infants exposed in utero to anti-TNFα, as in those exposed to azathioprine. Untreated controls and large-scale studies are needed to confirm these results.

Modern diagnostic capabilities of neonatal screening for primary immunodeficiencies in newborns

Population screening of newborns is an extremely important and informative diagnostic approach that allows early identification of babies who are predisposed to the development of a number of serious diseases. Some of these diseases are known and have effective treatment methods. Neonatal screening enables the early diagnosis and subsequent timely initiation of therapy. This helps to prevent serious complications and reduce the percentage of disability and deaths among newborns and young children. Primary immunodeficiency diseases and primary immunodeficiency syndrome (PIDS) are a heterogeneous group of diseases and conditions based on impaired immune system function associated with developmental defects and characterized by various combinations of recurrent infections, development of autoimmune and lymphoproliferative syndromes (genetic defects in apoptosis, gene mutation Fas receptor or ligand), granulomatous process, and malignant neoplasms. Most of these diseases manifest in infancy and lead to serious illness, disability, and high mortality rates. Until recently, it was impossible to identify children with PIDS before the onset of the first clinical symptoms, which are usually accompanied by complications in the form of severe coinfections of a viral-bacterial-fungal etiology. Modern advances in medical laboratory technology have allowed the identification of children with severe PIDS, manifested by T- and/or B-cell lymphopenia and other disorders of the immune system. This review discusses the main existing strategies and directions used in PIDS screening programs for newborns, including approaches to screening based on excision of T-cell receptors and kappa-recombination excision circles, as well as the potential role and place of next-generation sequencing technology to increase the diagnostic accuracy of these diseases.

Exploring genetic defects in adults who were clinically diagnosed as severe combined immune deficiency during infancy

Genetic diagnostic tools including whole-exome sequencing (WES) have advanced our understanding in human diseases and become common practice in diagnosing patients with suspected primary immune deficiencies. Establishing a genetic diagnosis is of paramount importance for tailoring adequate therapeutic regimens, including identifying the need for hematopoietic stem cell transplantation (HSCT) and genetic-based therapies. Here, we genetically studied two adult patients who were clinically diagnosed during infancy with severe combined immune deficiency (SCID). Two unrelated patients, both of consanguineous kindred, underwent WES in adulthood, 2 decades after their initial clinical manifestations. Upon clinical presentation, immunological workup was performed, which led to a diagnosis of SCID. The patients presented during infancy with failure to thrive, generalized erythematous rash, and recurrent gastrointestinal and respiratory tract infections, including episodes of Pneumocystis pneumonia infection and Candida albicans fungemia. Hypogammaglobulinemia and T-cell lymphopenia were detected. Both patients were treated with a 10/10 HLA matched sibling donor unconditioned HSCT. Retrospective genetic workup revealed homozygous bi-allelic mutations in IL7RA in one patient and in RAG2 in the other. Our study exemplifies the impact of retrospectively establishing a genetic diagnosis. Pinpointing the genetic cause raises several issues including optimized surveillance and treatment, understanding disease mechanisms and outcomes, future family planning, and social and psychological considerations.

Premature CD4+ T Cells Senescence Induced by Chronic Infection in Patients with Acute Coronary Syndrome

Acquired immune responses mediated by CD4⁺ T cells contribute to the initiation and progression of acute coronary syndrome (ACS). ACS patients show acquired immune system abnormalities that resemble the characteristics of autoimmune dysfunction described in the elderly. This study aimed to investigate the role of premature CD4⁺ T cells senescence in ACS and the underlying mechanism. We compared the immunological status of 25 ACS patients, 15 young healthy individuals (C1), and 20 elderly individuals with absence of ACS (C2). The percentages of CD4⁺ T lymphocyte subsets (including naïve, regulatory, memory and effector T cells) in peripheral blood were analyzed. In ACS patients, a significant expansion of CD4⁺CD28^null effector T cells and a decline of CD4⁺CD25⁺CD62L⁺Treg cells were observed. In addition, patients with ACS showed an accelerated loss of CD4⁺CD45RA⁺CD62L⁺ naïve T cells and a compensatory increase in the number of CD4⁺CD45RO⁺ memory T cells. ACS patients demonstrated no significant difference in frequency of T cell receptor excision circles (TRECs) compared to age-matched healthy volunteers. The expression of p16^Ink4a was increased while CD62L was decreased in CD4⁺CD28^null T cells of ACS patients. Compared to healthy donors, ACS patients demonstrated the lowest telomerase activity in both CD4⁺CD28⁺and CD4⁺CD28^null T cells. The serum levels of C-reactive protein, Cytomegalovirus IgG, Helicobactor pylori IgG and Chlamydia pneumonia IgG were significantly higher in ACS patients. The results suggested that the percentage of CD4⁺ T cell subpopulations correlated with chronic infection, which contributes to immunosenescence. In conclusion, chronic infection induced senescence of premature CD4⁺T cells, which may be responsible for the development of ACS.

Decrease in naïve T cell production due to HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) development

Human T-lymphocytic virus 1 (HTLV-1) is mainly associated with adult T-cell leukemia/lymphoma (ATLL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP exhibit significant changes in their immune response, and HTLV-1 infection can interfere in cytokine production and perhaps in T cell production. The aims of this study were to evaluate thymic function in HAM/TSP patients and HTLV-1 healthy carriers (HCs) and correlate it to age and interleukin 7 (IL-7) gene expression. Thymic function in 21 HAM/TSP patients and 12 HCs was evaluated by quantifying T cell receptor rearrangement excision circle (TREC) particles and IL-7 gene expression, both measured by quantitative polymerase chain reaction. HAM/TSP patients presented lower TREC particle counts (p = 0.0112) and lower IL-7 expression (p = 0.0102) than HCs. Both TREC particles and IL-7 gene expression were separately analyzed in two age groups: ≤ 59 years and ≥60 years, The ≤59-year-old HAM/TSP patients had a lower TREC count compared with the ≤59-year-old HCs (p = 0.0476). In conclusion, HAM/TSP development could interfere with thymic function because the results showed TREC particle reduction in HAM/TSP patients in relation to HCs, and it could be associated with a concomitant reduction in IL-7 expression.

Decreased Thymic Output Contributes to Immune Defects in Septic Patients

Background: Prolonged immunosuppression and hypoinflammation, termed compensatory anti-inflammatory response syndrome (CARS), contribute to high morbidity and mortality in the late phase of sepsis. Although apoptosis is a well-known cause of lymphopenia in sepsis, the contribution of thymic output to immune alterations in sepsis and potential compensatory mechanisms are largely unknown. Methods: We investigate the release of CD4+ T cells from the thymus and their peripheral proliferation by evaluating T-cell receptor excision circles (TREC) and the expression of CD31 as markers for recent thymic emigrants (RTE) and their proliferative offspring in septic patients with relevant lymphopenia in the CARS phase. Moreover, we determine the aging of T cells by measuring telomere characteristics. Results: In septic patients, we found decreased CD4+ T-helper cell numbers, while CD8+ T cell numbers were unchanged. As a possible cause, we detected increased apoptosis of CD4+ T-helper cells and decreased levels of IL-7, which promotes the maturation of T cells in the thymus. Accordingly, the relative number of mature CD4+ T cells, TREC-containing CD4+ T cells, and CD31+ RTEs (characteristic of thymic output) was decreased, while the relative number of CD31-T cells (peripherally expanded naïve T cells) was increased. Furthermore, the telomere length decreased, although telomerase activity and markers for the shelterin complex were increased specifically in CD4+ but not in CD8+ T cells. Conclusion: We thus conclude that, in addition to T-cell apoptosis, decreased thymic output and increased aging of CD4+ T cells may contribute to lymphopenia and immunosuppression in sepsis. Increased proliferation of peripheral T cells cannot compensate for these effects.

Assessment of Thymic Output Dynamics After in utero Infection of Mice With Coxsackievirus B4

The thymus is the main organ of the lymphatic system, in which T cells undergo a rigorous selection to ensure that their receptors (TCRs) will be functional and will not react against the self. Genes encoding for TCR chains are fragmented and must be rearranged by a process of somatic recombination generating TCR rearrangement excision circles (TRECs). We recently documented coxsackievirus B4 (CV-B4) infection of Swiss albino mouse thymus in the course of in utero transmission. In the current study, we intended to evaluate thymic output in this experimental model. For this purpose, pregnant Swiss albino mice were inoculated with CV-B4 at day 10 or 17 of gestation, and thymus and spleen were sampled from offspring at different time points and then subjected to quantification of TREC molecules and Ptk7 gene expression. Results showed a pronounced effect of in utero CV-B4 infection on the thymus with an increase in the cellularity and, consequently, the weight of the organ. sj and DβTREC analysis, by real-time PCR, revealed a significant decrease following CV-B4 infection compared to controls, a decrease which gets worse as time goes by, both in the thymus and in the periphery. Those observations reflect a disturbance in the export of T cells to the periphery and their accumulation within the thymus. The evaluation of Ptk7 transcripts in the thymus, for its part, showed a decrease in expression, especially following an infection at day 10 of gestation, which supports the hypothesis of T cell accumulation in a mature stage in the thymus. The various effects observed correlate either negatively or positively with the viral load in the thymus and spleen. Disruption in thymic export may indeed interfere with T cell maturation. We speculate that this may lead to a premature release of T cells and the possibility of circulating autoreactive or proliferation-impaired T cell clones.

Immune reconstitution after HSCT in SCID-a cohort of conditioned and unconditioned patients

Allogeneic hematopoietic stem cell transplantation (HSCT) is the effective mean of immune restoration in severe combined immunodefiency (SCID). Usually, HSCT without cytoreductive conditioning is attempted. Nevertheless, conditioning procedures are still preferred in a subset of patients. Herein, we describe the immunological outcome in a cohort of conditioned and unconditioned patients, from diagnosis, through transplantation, to follow-up. This retrospective study was conducted on 17 patients with SCID (10 conditioned, 7 unconditioned) who later underwent HSCT. Immune reconstitution was assessed in the post-transplant year by quantification of T cell receptor excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs), among additional laboratory and clinical evaluations. Unconditioned patients were diagnosed and transplanted earlier. TREC and KREC quantification showed a gradual increase in both groups, with higher levels in the conditioned group. Engraftment percentages differed drastically between groups, favoring the conditioned group. Unconditioned patients were significantly more dependent on intravenous immunoglobulins (IVIGs). One patient from each group succumbed to disease complications. Conditioning demonstrated superior laboratorial outcomes. Patients with unique characteristics (i.e., consanguinity, Bacillus Calmette-Guérin vaccination, impaired access to IVIG) may require personalized considerations. The effort to implement secondary prevention of SCID with newborn screening should continue.

MHC II deficient infant identified by newborn screening program for SCID

Newborn screening (NBS) programs for severe combined immunodeficiency (SCID), using the TREC-based assay, have enabled early diagnosis, prompt treatment, and eventually changed the natural history of affected infants. Nevertheless, it was believed that some affected infants with residual T cell, such as patients with MHC II deficiency, will be misdiagnosed by this assay. A full immune workup and genetic analysis using direct Sanger sequencing and whole exome sequencing have been performed to a patient that was identified by the Israeli NBS program for SCID. The patient was found to have severe CD4 lymphopenia with an inverted CD4/CD8 ratio, low TREC levels in peripheral blood, abnormal response to mitogen stimulation, and a skewed T cell receptor repertoire. HLA-DR expression on peripheral blood lymphocytes was undetectable suggesting a diagnosis of MHC II deficiency. Direct sequencing of the RFX5 gene revealed a stop codon change (p. R239X, c. C715T), which could cause the patient's immune phenotype. His parents were found to be heterozygote carriers for the mutation. Whole exome sequencing could not identify other potential mutations to explain his immunodeficiency. The patient underwent successful conditioned hematopoietic stem cell transplantation from healthy matched unrelated donor and is currently well and alive with full chimerism. Infants with MHC class II deficiency can potentially be identified by the TREC-based assay NBS for SCID. Therefore, MHC II molecules (e.g., HLA-DR) measurement should be part of the confirmatory immune-phenotyping for patients with positive screening results. This will make the diagnosis of such patients straightforward.

Immune Cells and Immunosenescence

Aging is associated with progressive loss of physiological integrity, leading to impaired physical and mental functions as well as increased morbidity and mortality. With advancing age, the immune system is no longer able to adequately control autoimmunity, infections, or cancer. The abilities of the elderly to slow down undesirable effects of aging may depend on the genetic background, lifestyle, geographic region, and other presently unknown factors. Although most aspects of the immunity are constantly declining in relation to age, some features are retained, while e.g. the ability to produce high levels of cytokines, response to pathogens by increased inflammation, and imbalanced proteolytic activity are found in the elderly, and might eventually cause harm. In this context, it is important to differentiate between the effect of immunosenescence that is contributing to this decline and adaptations of the immune system that can be quickly reversed if necessary.

T-cell receptor excision circle levels and safety of paediatric immunization: A population-based self-controlled case series analysis

T-cell receptor excision circle levels are a surrogate marker of T-cell production and immune system function. We sought to determine whether non-pathological levels of infant T-cell receptor excision circles were associated with adverse events following immunization. A self-controlled case series design was applied on a sample of 231,693 children who completed newborn screening for severe combined immunodeficiency in Ontario, Canada between August 2013 and December 2015. Exposures included routinely administered pediatric vaccines up to 15 months of age. Main outcomes were combined health services utilization for recognized adverse events following immunization. 1,406,981 vaccination events were included in the final dataset. 103,007 children received the Pneu-C-13 or Men-C-C vaccine and 97,998 received the MMR vaccine at 12 months of age. 67,725 children received the varicella immunization at 15 months. Our analysis identified no association between newborn T-cell receptor excision circle levels and subsequent health services utilization events following DTa-IPV-Hib, Pneu-C-13, and Men-C-C vaccinations at 2-month (RI 0.94[95%CI 0.87-1.02]), 4-month (RI 0.82[95%CI 0.75-0.9]), 6-month (RI 0.63[95%CI 0.57-0.7]) and 12-month (RI 0.49[95%CI 0.44-0.55]). We also found no trends in health services utilization following MMR (RI 1.43[95%1.34-1.52]) or varicella (RI 1.14[95%CI 1.05-1.23]) vaccination. Our findings provide further support for the safety of pediatric vaccinations.

T-cell Dysfunction in Glioblastoma: Applying a New Framework

A functional, replete T-cell repertoire is an integral component to adequate immune surveillance and to the initiation and maintenance of productive antitumor immune responses. Glioblastoma (GBM), however, is particularly adept at sabotaging antitumor immunity, eliciting severe T-cell dysfunction that is both qualitative and quantitative. Understanding and countering such dysfunction are among the keys to harnessing the otherwise stark potential of anticancer immune-based therapies. Although T-cell dysfunction in GBM has been long described, newer immunologic frameworks now exist for reclassifying T-cell deficits in a manner that better permits their study and reversal. Herein, we divide and discuss the various T-cell deficits elicited by GBM within the context of the five relevant categories: senescence, tolerance, anergy, exhaustion, and ignorance. Categorization is appropriately made according to the molecular bases of dysfunction. Likewise, we review the mechanisms by which GBM elicits each mode of T-cell dysfunction and discuss the emerging immunotherapeutic strategies designed to overcome them. Clin Cancer Res; 24(16); 3792-802. ©2018 AACR.

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

Quantification of specific T and B cells immunological markers in children with chronic and transient ITP

BACKGROUND

Immune thrombocytopenic purpura (ITP) is characterized by a transient (nonchronic) or permanent (chronic) decline in the number of platelets. Predicting the course of ITP, at the time of diagnosis, is of importance. Here we studied at diagnosis, clinical and immunological parameters in order to distinguish between different courses. The latter included the measure of new B and T cells using quantification of kappa-deleting recombination excision circles (KRECs) and T-cell receptor excision circles (TRECs), respectively.

METHODS

Blood samples were collected from 44 children with a clinical diagnosis of ITP. Real-time PCR was performed in order to quantify the number of copies of TREC and KREC followed by collection of clinical data from medical files. The children were retrospectively divided into two groups: chronic and nonchronic.

RESULTS

Twenty-four patients (54%) were classified as nonchronic ITP and 20 patients (46%) were classified as chronic ITP. We confirmed some clinical parameters (e.g., gender, age) but not others (e.g., preceding infection, level of thrombocytopenia) that distinguish patients with chronic and nonchronic course. While KREC quantification was similar in patients regardless the outcome of their disease, it was significantly higher than the level of controls (P < 0.05). TREC quantification was not different between patients and controls.

CONCLUSIONS

KREC but not TREC levels are different in patients comparing to controls, pointing to an overreaction of B-cell development as a role in the pathogenesis of ITP. These results may shed more lights on the immune mechanism of ITP.

Thymosin alpha 1 and HIV-1: recent advances and future perspectives

In spite of the consistent benefits for HIV-1 infected patients undergoing antiretroviral therapy, a complete immune reconstitution is usually not achieved. Actually, antiretroviral therapy may be frequently accompanied by immunological unresponsiveness, persistent inflammatory conditions and inefficient cytotoxic T-cell response. Thymosin alpha 1 is a thymic peptide that demonstrates a peculiar ability to restore immune system homeostasis in different physiological and pathological conditions (i.e., infections, cancer, immunodeficiency, vaccination and aging) acting as multitasking protein depending on the host state of inflammation or immune dysfunction. This review reports the present knowledge on the in vitro and in vivo studies concerning the use of thymosin alpha 1 in HIV-1 infection. Recent findings and future perspectives of therapeutic intervention are discussed.

T Cell Receptor Excision Circle (TREC) Monitoring after Allogeneic Stem Cell Transplantation; a Predictive Marker for Complications and Clinical Outcome

Allogeneic hematopoietic stem cell transplantation (HSCT) is a well-established treatment modality for a variety of malignant diseases as well as for inborn errors of the metabolism or immune system. Regardless of disease origin, good clinical effects are dependent on proper immune reconstitution. T cells are responsible for both the beneficial graft-versus-leukemia (GVL) effect against malignant cells and protection against infections. The immune recovery of T cells relies initially on peripheral expansion of mature cells from the graft and later on the differentiation and maturation from donor-derived hematopoietic stem cells. The formation of new T cells occurs in the thymus and as a byproduct, T cell receptor excision circles (TRECs) are released upon rearrangement of the T cell receptor. Detection of TRECs by PCR is a reliable method for estimating the amount of newly formed T cells in the circulation and, indirectly, for estimating thymic function. Here, we discuss the role of TREC analysis in the prediction of clinical outcome after allogeneic HSCT. Due to the pivotal role of T cell reconstitution we propose that TREC analysis should be included as a key indicator in the post-HSCT follow-up.

Insight into normal thymic activity by assessment of peripheral blood samples

The thymus is a highly specialized organ for T cell receptor (TCR) rearrangement and selection mechanisms that ensure the formation of functional and self-tolerant cells. Little is known about how peripheral blood assessment of thymic function reflects thymus activity during infancy. We compared thymic function-related markers in the thymus with those in peripheral blood in order to check their correlations. We concomitantly blood samples from immunocompetent infants who underwent cardiac surgery that involved thymectomy. The studied thymic markers included TCR excision circles (TRECs), four different TCRD (TCR delta chain) gene rearrangements, the TCR repertoire, regulatory T cells (Tregs, defined as the CD4+CD25+FOXP3+ cell population) and real-time quantitative polymerase chain reaction (RQ-PCR) mRNA expression of forkhead box P3 (FOXP3). Twenty patients were enrolled in this study. Their mean age at the time of the surgery was 3 months/5 days ± 3 months/18 days. There was a significant correlation between thymic and peripheral blood levels of TREC, all four TCRD gene rearrangements and the amount of Tregs. The levels of these parameters were significantly higher in the thymus than those detected in the peripheral blood. The TCR repertoire distribution in both samples was similar. FOXP3 mRNA levels in the thymus and peripheral blood correlated well. Our findings demonstrated a strong and significant correlation between peripheral blood and intra-thymic activity parameters during infancy. Assessment of these parameters in peripheral blood can be used to accurately estimate different intra-thymic capacities for assessing T cell function in health and disease.

A call to include severe combined immunodeficiency in newborn screening program

Quantification of the T cell receptor excision circles (TRECs) has recently emerged as a useful non-invasive clinical and research tool to investigate thymic activity. It allows the identification of T cell production by the thymus. Quantification of TREC copies has recently been implemented as the preferred test to screen neonates with severe combined immunodeficiency (SCID) or significant lymphopenia. Neonatal genetic screening for SCID is highly important in countries with high rates of consanguinous marriages, such as Israel, and can be used for early diagnosis, enabling prompt therapeutic intervention that will save lives and improve the outcome of these patients. TREC measurement is also applicable in clinical settings where T cell immunity is involved, including any T cell immunodeficiencies, HIV infection, the aging process, autoimmune diseases, and immune reconstitution after bone marrow transplantation.

TAKE-HOME MESSAGES

Severe combined immunodeficiency, a life-threatening condition, can be detected by neonatal screening.The earlier the detection and the quicker the implementation of appropriate treatment, the greater the likelihood for improved outcome, even cure, for the affected children.TRECs and KRECs quantification are useful screening tests for severe T and B cell immunodeficiency and can be used also to evaluate every medical condition involving T and B cell immunity.

Cytokine production by bone marrow mononuclear cells in inherited bone marrow failure syndromes

Fanconi anaemia (FA), dyskeratosis congenita (DC), Diamond-Blackfan anaemia (DBA), and Shwachman-Diamond syndrome (SDS) are characterized by the progressive development of bone marrow failure. Overproduction of tumour necrosis factor-α (TNF-α) from activated bone marrow T-cells has been proposed as a mechanism of FA-related aplasia. Whether such overproduction occurs in the other syndromes is unknown. We conducted a comparative study on bone marrow mononuclear cells to examine the cellular subset composition and cytokine production. We found lower proportions of haematopoietic stem cells in FA, DC, and SDS, and a lower proportion of monocytes in FA, DC, and DBA compared with controls. The T- and B-lymphocyte proportions were similar to controls, except for low B-cells in DC. We did not observe overproduction of TNF-α or IFN-γ by T-cells in any patients. Induction levels of TNF-α, interleukin (IL)-6, IL-1β, IL-10, granulocyte colony-stimulating factor, and granulocyte-macrophage colony-stimulating factor in monocytes stimulated with high-dose lipopolysaccharide (LPS) were similar at 4 h but lower at 24 h when compared to controls. Unexpectedly, patient samples showed a trend toward higher cytokine level in response to low-dose (0·001 μg/ml) LPS. Increased sensitivity to LPS may have clinical implications and could contribute to the development of pancytopenia by creating a chronic subclinical inflammatory micro-environment in the bone marrow.

Reduced T cell receptor excision circle levels in the colonic mucosa of microscopic colitis patients indicate local proliferation rather than homing of peripheral lymphocytes to the inflamed mucosa

Dysregulated T cell responses in the intestine may lead to chronic bowel inflammation such as collagenous colitis (CC) and lymphocytic colitis (LC), together known as microscopic colitis (MC). Having demonstrated increased local T cell responses in the intestinal mucosa of MC patients, we investigated the recent thymic emigrants by measuring T cell receptor excision circle (TREC) levels in the colonic biopsies from CC (n = 8), LC (n = 5), and CC or LC patients in histopathological remission (CC-HR, n = 3) (LC-HR, n = 6), non-inflamed diarrhoea patients (n = 17), and controls (n = 10) by real-time PCR. We observed lower median TREC levels in both CC and LC patients as well as in LC-HR patients compared to controls. In contrast to MC patients, non-inflamed diarrhoea patients presented with enhanced TREC levels compared to controls. None of the recorded differences did, however, reach statistical significance. A trend towards increased relative expression of CD3 was noted in all MC subgroups examined and reached statistical significance in LC patients compared to controls. In conclusion, reduced TRECs level in the colonic mucosa, together with our previously demonstrated enhanced expression of Ki67⁺ T cells, suggests local expansion of resident T lymphocytes in the inflamed mucosa of MC patients.

The role of hematopoietic stem cell transplantation in SP110 associated veno-occlusive disease with immunodeficiency syndrome

BACKGROUND

Veno-occlusive disease with immunodeficiency (VODI) is an autosomal recessive disorder of combined immunodeficiency (CID) and hepatic injury. Hematopoietic stem cell transplantation (HSCT) - the only definitive treatment for CID - appeared to have a high rate of complications in a previous report. In this study, we describe a new group of patients with VODI highlighting further clinical and immunologic aspects of this disease and re-evaluating the effectiveness of HSCT for the treatment of this disorder.

PATIENTS AND METHODS

Review of clinical data, immunologic features, molecular studies, treatment, and final outcome of eight kindred members with VODI.

RESULTS

The patients described had clinical and immunologic findings consistent with VODI. The molecular studies revealed a new mutation in the SP110 gene. HSCT was carried out in five patients and was successful in three.

CONCLUSIONS

The diagnosis of VODI should be considered in all patients regardless of ethnicity with a severe combined immunodeficiency (SCID)-like presentation, especially with a normal mitogen response, or with signs of hepatic injury. VODI is a primary immune deficiency, which can be successfully corrected by bone marrow transplantation if applied early in the course of disease using appropriate conditioning.

HIV 2-long terminal repeat circular DNA is stable in primary CD4+T Cells

Treatment resistant latent reservoirs remain a barrier to cure HIV, but the maintenance and properties of these reservoirs are not completely understood. 2-LTR circular HIV DNA has been used to assess ongoing viral replication in HAART treated patients. However, the half-life of this DNA form is still debated with conflicting in vivo and in vitro data. Prior in vitro studies have focused on cell lines or short lived activated cells in cultures of brief duration, while in vivo studies have the added complications of cell migration, division, and death. Therefore, we monitored the stability of 2-LTR circles in primary CD4+T cells in a month long culture and compared it to the stability of integrated HIV DNA and T cell receptor excision circles (TRECs), another circular DNA form that is thought to be stable. We found that 2-LTRs, along with TRECs, were stable, suggesting 2-LTRs do not necessarily indicate ongoing replication.

Cellular calibrators to quantitate T-cell receptor excision circles (TRECs) in clinical samples

T-cell receptor excision circles (TRECs) are circular DNA molecules formed during rearrangement of the T-cell receptor (TCR) genes during lymphocyte development. Copy number of the junctional portion of the δRec-ψJα TREC, assessed by quantitative PCR (qPCR) using DNA from dried blood spots (DBS), is a biomarker for newly formed T cells and absent or low numbers of TRECs indicate SCID (severe combined immunodeficiency) or T lymphocytopenia. No quantitation standard for TRECs exists. To permit comparison of TREC qPCR results with a reliable method for counting TRECs across different laboratories, we sought to construct a stable cell line containing a normal human chromosomal constitution and a single copy of the TREC junction sequence. A human EBV (Epstein Barr virus)-transformed B-cell line was transduced with a lentivirus encoding mCherry fluorescence, puromycin resistance and the δRec-ψJα TREC sequence. A TREC-EBV cell line, with each cell carrying a single lentiviral insertion was established, expanded and shown to have one TREC copy per diploid genome. Graded numbers of TREC-EBV cells added to aliquots of T lymphocyte depleted blood showed TREC copy number proportional to TREC-EBV cell number. TREC-EBV cells, therefore, constitute a reproducible cellular calibrator for TREC assays, useful for both population-based screening for severe combined immunodeficiency and evaluation of naïve T-cell production in clinical settings.