Detection of newly produced T and B lymphocytes by digital PCR in blood stored dry on nylon flocked swabs

The Impact of Immune System Aging on Infectious Diseases

Immune system aging is becoming a field of increasing public health interest because of prolonged life expectancy, which is not paralleled by an increase in health expectancy. As age progresses, innate and adaptive immune systems undergo changes, which are defined, respectively, as inflammaging and immune senescence. A wealth of available data demonstrates that these two conditions are closely linked, leading to a greater vulnerability of elderly subjects to viral, bacterial, and opportunistic infections as well as lower post-vaccination protection. To face this novel scenario, an in-depth assessment of the immune players involved in this changing epidemiology is demanded regarding the individual and concerted involvement of immune cells and mediators within endogenous and exogenous factors and co-morbidities. This review provides an overall updated description of the changes affecting the aging immune system, which may be of help in understanding the underlying mechanisms associated with the main age-associated infectious diseases.

Clinical relevance of thymic and bone marrow outputs in multiple sclerosis patients treated with alemtuzumab

Thymic and bone marrow outputs were evaluated in 13 sequential samples of 68 multiple sclerosis patients who initiated alemtuzumab and were clinically followed for 48 months. Three months after alemtuzumab infusions, the levels of new T lymphocytes were significantly reduced, but progressively increased reaching the highest values at 36 months, indicating the remarkable capacity of thymic function recovery. Newly produced B cells exceeded baseline levels as early as 3 months after alemtuzumab initiation. Heterogeneous patterns of new T- and B-cell recovery were identified, but without associations with age, sex, previous therapies, development of secondary autoimmunity or infections, and disease re-emergence. Trial registration version 2.0-27/01/2016.

Modified quantitative approach for assessing peripheral blood TREC and KREC levels in immunodeficient patients

Introduction. The immune status is a multifaceted parameter quantitatively and qualitatively analyzing functional activity immune system state in immune organs as well as some non-specific mechanisms of antimicrobial protection. Peripheral blood level of T-receptor excision rings (TREC) and B-cell excision rings (KREC), respectively, can serve as surrogate markers of T- and B-cell maturation. Currently, the diagnostic kits available on the market have two significant disadvantages: i) the kits are aimed at diagnosing immunodeficiency conditions only in newborns and children, while keeping adult patients uncovered; ii) essentially, use solely single reference normalization gene for data normalization resulting in increased variability and decreased sensitivity of the assay data. The aim: to develop a highly sensitive method for laboratory assessment of the state of immunity in immunodeficient patients by using real-time PCR for assessing TREC and KREC level in children and adults. Materials and methods. There were used whole blood and dry blood spot samples obtained from newborns and adults, apparently healthy individuals as well as patients with verified PID and HIV-infection. A total of 2577 samples were examined. Commercial kits were used as comparison methods. Results. Multiplex PCR was carried out, analyzing the number of target molecules TREC and KREC, as well as fragments of the HPRT and RPP30 normalization genes analyzed with the developed series of plasmid calibrators. The established analytical range of TREC/KREC DNA measurements comprised 103 to 109 copies/mL. The accuracy of measurements on a tablet-type instrument (CFX) was 95.84%, on a rotary-type instrument (Rotor-Gene 3000) 95.11%, which corresponds to the standard indicator. The equivalence between the data obtained after assessing whole blood samples and dry blood drops was shown. The data analysis allowed to find out 100%-diagnostic specificity and sensitivity of the method proposed. Conclusion. The method developed by us allows to diagnose decline in T- and/or B-cell immunity in children and adults and can be used to detect TREC and KREC molecules both in peripheral whole blood samples and dry blood spots using Guthrie cards. Moreover, the uniform values of reference norms can be used regardless of the type of analyzed clinical material. The study data evidence about potential for effective use of multiplex PCR diagnostics both for complex primary testing/screening of newborns and assessing state of immunity to identify adult patients with PID and as a part of the diagnostic monitoring of patients with secondary immunodeficiencies, e.g., HIV infection.

Case Report: Late Onset of Myelodysplastic Syndrome From Donor Progenitor Cells After Allogeneic Stem Cell Transplantation. Which Lessons Can We Draw From the Reported Case?

Background

Myelodysplastic syndromes and acute leukemias after allogeneic stem cell transplantation (allo-SCT) are mainly caused by recurrence of the primitive leukemic clones. More rarely, they originate from donor hematopoietic stem cells, developing the so-called donor cell leukemia (DCL) or myelodysplastic syndromes (DC-MDSs). DCL and DC-MDS can be considered as an in vivo model of leukemogenesis, and even if the pathogenetic mechanisms remain speculative, a genetic predisposition of donor progenitor cells, an altered host microenvironment, and the impairment of immune surveillance are considered the main causes.

Case Presentation

We report a case of DC-MDS diagnosed 5 years after an allo-SCT from a matched related donor (patient’s sister) in a patient with Philadelphia chromosome-positive B-cell acute lymphoblastic leukemia (Ph+ B-ALL). The sex-mismatch allowed us to identify the donor cell origin. At the onset, the DC-MDS was characterized by chromosome seven monosomy and NRAS, RUNX1, and BCOR mutations. Because of a familiar history of colorectal neoplasia and the variant allele frequency (VAF) of NRAS mutation at the onset, this mutation was searched on germline DNA in both the donor and the recipient, but the result was negative. Moreover, after transplant (+4 months), the patient developed severe and long-lasting chronic graft-versus-host disease (cGVHD), requiring multiple lines of treatments. Because of the severe immunosuppression, recurrent infections occurred and, lately, the patient died due to septic shock.

Conclusion

This case report highlights the need, whenever possible, to evaluate the donor origin of the posttransplant myelodysplasia and acute leukemias. The potential key role of the impaired immune surveillance and of long-lasting immunosuppression appears to be emerging in the development of this case of DC-MDS. Finally, this case reminds the importance to investigate the familiar genetic predisposition in donors with a familiar history of neoplasia.

A Multiplex, Droplet Digital PCR Assay for the Detection of T-Cell Receptor Excision Circles and Kappa-Deleting Recombination Excision Circles

BACKGROUND

T-cell receptor excision circles (TREC) and κ-deleting recombination receptor excision circles (KREC) concentrations can be used to assess and diagnose immune deficiencies, monitor thymic and bone marrow immune reconstitution, or follow responses to drug therapy. We developed an assay to quantify TREC, KREC, and a reference gene in a single reaction using droplet digital PCR (ddPCR).

METHODS

PCR was optimized for 3 targets: TREC, KREC, and ribonuclease P/MRP subunit p30 (RPP30) as the reference gene. Multiplexing was accomplished by varying the target's fluorophore and concentration. Correlation with clinical results was evaluated using 47 samples from healthy donors, 59 samples with T-cell and B-cell markers within the reference interval from the flow cytometry laboratory, 20 cord blood samples, and 34 samples submitted for exome sequencing for severe combined immunodeficiency disease (SCID).

RESULTS

The limit of the blank was 4 positive droplets, limit of detection 9 positive droplets, and limit of quantification 25 positive droplets, or 2.0 copies/μL. TREC and KREC copies/μL were as expected in the healthy donors and cord blood samples and concordant with the healthy flow cytometry results. Of the samples from the SCID Panel, 56.5% had a TREC count <20 copies/μL and 17.7% had a KREC count <20 copies/μL, suggestive of low T- and B-cell numbers, respectively.

CONCLUSIONS

Our multiplex ddPCR assay is an analytically sensitive and specific method for the absolute quantification of TREC and KREC. To the best of our knowledge, this paper is the first to describe the simultaneous quantification of TREC, KREC, and a reference gene by use of ddPCR.

Establishing Simultaneous T Cell Receptor Excision Circles (TREC) and K-Deleting Recombination Excision Circles (KREC) Quantification Assays and Laboratory Reference Intervals in Healthy Individuals of Different Age Groups in Hong Kong

The clinical experience gathered throughout the years has raised awareness of primary immunodeficiency diseases (PIDD). T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) assays for thymic and bone marrow outputs measurement have been widely implemented in newborn screening (NBS) programs for Severe Combined Immunodeficiency. The potential applications of combined TREC and KREC assay in PIDD diagnosis and immune reconstitution monitoring in non-neonatal patients have been suggested. Given that ethnicity, gender, and age can contribute to variations in immunity, defining the reference intervals of TREC and KREC levels in the local population is crucial for setting up cut-offs for PIDD diagnosis. In this retrospective study, 479 healthy Chinese sibling donors (240 males and 239 females; age range: 1 month-74 years) from Hong Kong were tested for TREC and KREC levels using a simultaneous quantitative real-time PCR assay. Age-specific 5th-95th percentile reference intervals of TREC and KREC levels (expressed in copies per μL blood and copies per 106 cells) were established in both pediatric and adult age groups. Significant inverse correlations between age and both TREC and KREC levels were observed in the pediatric age group. A significant higher KREC level was observed in females than males after 9-12 years of age but not for TREC. Low TREC or KREC levels were detected in patients diagnosed with mild or severe PIDD. This assay with the established local reference intervals would allow accurate diagnosis of PIDD, and potentially monitoring immune reconstitution following haematopoietic stem cell transplantation or highly active anti-retroviral therapy in the future.

Immunologic characterization of a immunosuppressed multiple sclerosis patient that recovered from SARS-CoV-2 infection

A multiple sclerosis patient infected by SARS-CoV-2 during fingolimod therapy was hospitalized with moderate clinical features, and recovered in 15 days. High levels of CCL5 and CCL10 chemokines and of antibody-secreting B cells were detected, while the levels other B- and T-cell subsets were comparable to that of appropriate controls. However, CD4+ and CD8+ cells were oligoclonally expanded and prone to apoptosis when stimulated in vitro. This study suggests that fingolimod-immunosuppressed patients, despite the low circulating lymphocytes, may rapidly expand antibody-secreting cells and mount an effective immune response that favors COVID-19 recovery after drug discontinuation.

Immune recovery after in vivo T-cell depletion myeloablative conditioning hematopoietic stem cell transplantation in severe beta-thalassemia children

BACKGROUND

The clinical outcome of hematopoietic stem cell transplantation (HSCT) in those with severe beta-thalassemia (β-TM) is closely related to post-transplantation immune reconstitution (IR). However, the data on the IR in these settings are scarce.

METHODS

A prospective analysis of the clinical outcome and IR in 47 children with severe β-TM who underwent in vivo T-cell depletion myeloablative conditioning and matched sibling donor HSCT was performed. Immune reconstitution, including immune cell subset counts, as well as the generation of new T and B cells assays after HSCT, was measured.

RESULTS

In the first year after HSCT, bacterial infections and cytomegalovirus (CMV) reactivation were observed in 70.2% and 36.2% of the patients, respectively. In the same period, poor CD4⁺ T-cell recovery was observed. The B cells recovered within 6 months. Natural killer (NK) cells recovered as early as 1 month, but their function was defective. Cord blood and bone marrow (CB + BM) group had slower T-cell recovery, and higher B cells and NK cells in comparison with peripheral blood and bone marrow (PB + BM) group.

CONCLUSIONS

The high incidence of infection within 1 year after in vivo T-cell depletion myeloablative conditioning HSCT in severe β-TM was consistent with poor IR.

Detection of a CDH1 Rare Transcript Variant in Fresh-frozen Gastric Cancer Tissues by Chip-based Digital PCR

CDH1a, a non-canonical transcript of the CDH1 gene, has been found to be expressed in some gastric cancer (GC) cell lines, whereas it is absent in normal gastric mucosa. Recently, we detected CDH1a transcript variant in fresh-frozen tumor tissues obtained from patients with GC. The expression of this variant in tissue samples was investigated by the chip-based digital PCR (dPCR) approach presented here. dPCR offers the potential for an accurate, robust, and highly sensitive measurement of nucleic acids and is increasingly utilized for many applications in different fields. dPCR is capable of detecting rare targets; in addition, dPCR offers the possibility for absolute and precise quantification of nucleic acids without the need for calibrators and standard curves. In fact, the reaction partitioning enriches the target from the background, which improves amplification efficiency and tolerance to inhibitors. Such characteristics make dPCR an optimal tool for the detection of the CDH1a rare transcript.