Adenosine deaminase deficiency and purine nucleoside phosphorylase deficiency in common variable immunodeficiency

CTP synthetase activity assay by liquid chromatography tandem mass spectrometry in the multiple reaction monitoring mode

Cytidine 5'-triphosphate synthetase (CTPS) is known to be a central enzyme in the de novo synthesis of CTP. We have recently demonstrated that a deficiency in CTPS1 is associated with an impaired capacity of activated lymphocytes to proliferate leading to a combined immunodeficiency disease. In order to better document its role in immunomodulation, we developed a method for measuring CTPS activity in human lymphocytes. Using liquid chromatography-mass spectrometry, we quantified CTPS activity by measuring CTP in cell lysates. A stable isotope analog of CTP served as internal standard. We characterized the kinetic parameters V_max and K_m of CTPS and verified that an inhibition of the enzyme activity was induced after 3-deazauridine (3DAU) treatment, a known inhibitor of CTPS. We then determined CTPS activity in healthy volunteers, in a family whose child displayed a homozygous mutation in CTPS1 gene and in patients who had developed or not a chronic lung allograft dysfunction (CLAD) after lung transplantation. Linearity of the CTP determination was observed up to 451 μmol/L, with accuracy in the 15% tolerance range. Michaelis-Menten kinetics for lysates of resting cells were K_m =280±310 μmol/L for UTP, V_max =83±20 pmol/min and, for lysates of activated PBMCs, K_m =230±280 μmol/L for UTP, V_max =379±90 pmol/min. Treatment by 3DAU and homozygous mutation in CTPS1 gene abolished the induction of CTPS activity associated with cell stimulation, and CTPS activity was significantly reduced in the patients who developed CLAD. We conclude that this test is suitable to reveal the involvement of CTPS alteration in immunodeficiency.

The First Purine Nucleoside Phosphorylase Deficiency Patient Resembling IgA Deficiency and a Review of the Literature

Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive primary immunodeficiency disorder characterized by decreased numbers of T-cells, variable B-cell abnormalities, decreased amount of serum uric acid and PNP enzyme activity. The affected patients usually present with recurrent infections, neurological dysfunction and autoimmune phenomena. In this study, whole-exome sequencing was used to detect mutation in the case suspected of having primary immunodeficiency. We found a homozygous mutation in PNP gene in a girl who is the third case from the national Iranian registry. She had combined immunodeficiency, autoimmune hemolytic anemia and a history of recurrent infections. She developed no neurological dysfunction. She died at the age of 11 after a severe chicken pox infection. PNP deficiency should be considered in late-onset children with recurrent infections, autoimmune disorders without typical neurologic impairment.

Split aptamer based sensing platform for adenosine deaminase detection by fluorescence resonance energy transfer

In this paper, a split aptamer based fluorescence resonance energy transfer (FRET) platform was constructed for the determination of adenosine deaminase (ADA) activity by using gold nanoclusters (AuNCs) and gold nanoparticles (AuNPs). A single adenosine triphosphate (ATP) aptamer was split into two fragments (referred to as P1 and P2). P1 was covalently attached to the AuNCs at the 5' end (P1-AuNCs), and P2 was labeled with AuNPs at the 3' end (P2-AuNPs). In the presence of ATP, ATP bound with the two fragments with high affinity to link P1-AuNCs and P2-AuNPs together, thus the fluorescence of P1-AuNCs was quenched via FRET from P1-AuNCs to P2-AuNPs. With the addition of ADA, ATP was transformed into inosine triphosphate (ITP), and then P1 and P2 were released to cause the fluorescence recovery of the system. So a split aptamer based FRET platform for ADA detection can be established via the fluorescence intensity change of the system. This platform showed a good linear relationship between the fluorescence intensity and ADA concentration in the range of 2-120 U L^-1, and the limit of detection (LOD) was 0.72 U L^-1. Moreover, the detection of ATP in human serum sample demonstrated the accuracy and applicability of the method for ADA detection in real sample.

Infusion of Sibling Marrow in a Patient with Purine Nucleoside Phosphorylase Deficiency Leads to Split Mixed Donor Chimerism and Normal Immunity

Purine nucleoside phosphorylase (PNP) deficiency, a rare autosomal recessive metabolic disease causes combined immunodeficiency and developmental delay, hypotonia, and spasticity. Patients present with recurrent infections associated with T-lymphocytopenia, characteristically presenting later than patients with classical severe combined immunodeficiency (SCID). PNP, with adenosine deaminase (ADA), is part of the purine salvage pathway. The only curative therapy is hematopoietic stem cell transplantation. Myeloablative conditioning is recommended to prevent rejection caused by residual immune function. However, HLA-identical sibling stem cell infusions in ADA-SCID result in some donor stem cell engraftment and long-term thymopoiesis. We report a patient with PNP deficiency, who received HLA-identical sibling marrow without chemotherapy because of disseminated cytomegalovirus (CMV) infection. The patient presented at 14 months of age following recurrent infections, from early infancy, with persistent irritability, developmental delay, and hypotonia. She had neutropenia, pan-lymphocytopenia, and hypogammaglobulinemia with low plasma urate and erythrocyte PNP activity. Diagnosis was confirmed with a homozygous mutation in PNP. The patient was viremic with CMV detected in blood and CSF by PCR. Dual antiviral therapy improved the clinical condition and reduced the viral load. In view of the disseminated CMV infection, the decision was made to infuse stem cells without any pre-conditioning chemotherapy. She received a matched sibling donor unconditioned stem cell infusion at 16 months of age. The post-transplant course was uneventful. Blood PCR became negative for CMV. Global hypotonia persisted, although with significant improvement in irritability. At 4 years of age and 29 months post-transplant, the patient demonstrated normal T-lymphocyte and natural killer cell numbers. Recent thymic emigrants represented 12% of the total T-lymphocyte population. Lymphocyte proliferative responses to phytohemagglutinin were normal. Memory and class-switched B-lymphocytes were present. Immunoglobulin replacement had been discontinued, and there were normal IgG responses to tetanus vaccine, Haemophilus influenzae type B and pneumococcal conjugate vaccine antigens. There was 93% donor T-lymphocytes, 20% donor B-lymphocytes, and 5% donor myeloid cells, indicative of some donor stem cell engraftment. There was no significant infection history despite regular nursery attendance. Height and weight were following the 50th centile. Split mixed donor chimerism has corrected the immunological defect.

The First Report of a Pregnancy in a Patient with Purine Nucleoside Phosphorylase Deficiency

BACKGROUND

The cause of primary immunodeficiency has expanded to nearly 200 distinct disorders. An improved understanding of these disorders has resulted in decreased morbidity and mortality with reciprocal improved life expectancy. Obstetricians should have knowledge of primary immunodeficiency, as more women with these disorders will reach reproductive age.

CASE

21-year-old G1P0 with purine nucleoside phosphorylase (PNP) deficiency delivered a viable infant vaginally at 37 weeks. Although the patient's diagnosis and pregnancy placed her at increased risk for infection, she remained asymptomatic and infection-free throughout pregnancy.

CONCLUSION

The management of pregnancy complicated by PNP deficiency requires strict immune surveillance and regimented immunoglobulin replacement.

Late Onset Combined Immunodeficiency Presenting with Recurrent Pneumocystis jiroveci Pneumonia

Late onset combined immunodeficiency (LOCID) is a recently described variant of common variable immunodeficiency (CVID), involving adult patients presenting with opportunistic infections and/or low CD4+ lymphocyte counts. A 36-year-old male with unremarkable past medical history presented with fever, respiratory failure, and lymphocytopenia. He was found to have Pneumocystis jiroveci pneumonia (PJP), subsequently complicated by recurrent hospital-acquired Pseudomonas aeruginosa pneumonia and immune reconstitution phenomena, attributed to restoration of immunoglobulin levels. Clinicians should be aware of LOCID, which could be confused with HIV infection/AIDS or idiopathic CD4 lymphocytopenia. In the English bibliography there is only one case report, where PJP was the initial presentation of CVID (that case would probably be classified as LOCID). Phenomena of immune reconstitution are described in various settings, including primary immunodeficiency, manifesting as temporary clinical and radiologic deterioration and leading to misperceptions of therapeutic failure and/or presence of alternative/additional diagnoses.

Late-onset adenosine deaminase deficiency presenting with Heck's disease

Focal epithelial hyperplasia, also known as Heck's disease, is a rare but distinctive entity of viral etiology with characteristic clinical and histopathological features. It is a benign, asymptomatic disease of the oral mucosa caused by human papilloma viruses (HPV). Previous studies postulated an association between these lesions and immunodeficiency. Genetic deficiency of adenosine deaminase (ADA) results in varying degrees of immunodeficiency, including neonatal onset severe combined immunodeficiency (ADA-SCID), and milder, later onset immunodeficiency. We report a 12-year-old girl with the late onset-ADA deficiency presenting with Heck's disease. Our case report should draw attention to the possibility of immunodeficiency in patients with HPV-induced focal epithelial hyperplasia.

Adenosine deaminase in patients with primary immunodeficiency syndromes: the analysis of serum ADA1 and ADA2 activities

OBJECTIVES

We aimed to investigate the activity of ADA and its isoenzymes in serum of patients with various primary immunodeficiency (PID) syndromes.

DESIGN AND METHODS

Total ADA (tADA) and its isoenzymes were measured in 76 children with PID syndromes and 30 healthy controls using the Ellis method.

RESULTS

Our results indicated that tADA and ADA2 levels were higher in patients with Chronic Granulomatous Disease (CGD), Leukocyte Adhesion Deficiency (LAD), hyper IgM (HIM) and Wiskott-Aldrich Syndrome (WAS) than those of corresponding controls (P<0.01). There was a significant elevation of tADA and ADA1 activities in IgA deficiency patients as compared to healthy individuals (P<0.01).

CONCLUSIONS

Our results hypothesized that altered ADA activity may be associated with altered immunity. Therefore, serum ADA level could be used as an indicator along with other parameters in follow up of patients with CGD, LAD, IgA deficiency, HIM and WAS.

Common variable immune deficiency: reviews, continued puzzles, and a new registry

BACKGROUND

Common variable immune deficiency (CVID) is a clinically and immunologically heterogenous primary immune deficiency first described more than 50 years ago. The main features are hypogammaglobulinemia, recurrent infections, and other complications. While CVID is considered as a genetic immune defect, and several genes have been reported as leading to the CVID phenotype, one of the most puzzling features of CVID is the sporadic inheritance pattern and the relatively late onset. In most cases, no other family members have any immune defect. The mean age at diagnosis is between 25 and 45 years of age. These features suggest the interplay between either several or numerous genes with or without potential environmental factors.

Successful HLA-identical hematopoietic stem cell transplantation in a patient with purine nucleoside phosphorylase deficiency

PNP deficiency is an autosomal recessive metabolic disorder characterized by severe combined immunodeficiency, autoimmune hemolytic anemia, and by a complex of neurologic manifestations including ataxia, developmental delay, and spasticity. PNP protein catalyzes the phosphorolysis of deoxyinosine and deoxyguanosine. It is found in most tissues of the body but is expressed at the highest levels in lymphoid tissues. This tissue distribution explains why the lymphoid system is predominantly affected in PNP deficiency. We describe a five-yr-old boy with muscular hypertonia, impaired growth, autoimmune hemolytic anemia, and neutropenia who underwent HSCT from his HLA-identical sister. One yr post-HSCT, the boy developed normal immunological functions, and his neurological status improved.

Purine nucleoside phosphorylases: properties, functions, and clinical aspects

The ubiquitous purine nucleoside phosphorylases (PNPs) play a key role in the purine salvage pathway, and PNP deficiency in humans leads to an impairment of T-cell function, usually with no apparent effects on B-cell function. This review updates the properties of the enzymes from eukaryotes and a wide range of prokaryotes, including a tentative classification of the enzymes from various sources, based on three-dimensional structures in the solid state, subunit composition, amino acid sequences, and substrate specificities. Attention is drawn to the compelling need of quantitative experimental data on subunit composition in solution, binding constants, and stoichiometry of binding; order of ligand binding and release; and its possible relevance to the complex kinetics exhibited with some substrates. Mutations responsible for PNP deficiency are described, as well as clinical methods, including gene therapy, for corrections of this usually fatal disease. Substrate discrimination between enzymes from different sources is also being profited from for development of tumour-directed gene therapy. Detailed accounts are presented of design of potent inhibitors, largely nucleosides and acyclonucleosides, their phosphates and phosphonates, particularly of the human erythrocyte enzyme, some with Ki values in nanomolar and picomolar range, intended for induction of the immunodeficient state for clinical applications, such as prevention of host-versus-graft response in organ transplantations. Methods of assay of PNP activity are reviewed. Also described are applications of PNP from various sources as tools for the enzymatic synthesis of otherwise inaccessible therapeutic nucleoside analogues, as coupling enzymes for assays of orthophosphate in biological systems in the micromolar and submicromolar ranges, and for coupled assays of other enzyme systems.

Measurement of Plasma and Intracellular S-Adenosylmethionine and S-Adenosylhomocysteine Utilizing Coulometric Electrochemical Detection: Alterations with Plasma Homocysteine and Pyridoxal 5′-Phosphate Concentrations

Background: The relative changes in plasma and intracellular concentrations of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) may be important predictors of cellular methylation potential and metabolic alterations associated with specific genetic polymorphisms and/or nutritional deficiencies. Because these metabolites are present in nanomolar concentrations in plasma, methods of detection generally require time-consuming precolumn processing or metabolite derivatization.

Methods: We used HPLC with coulometric electrochemical detection for the simultaneous measurement of SAM and SAH in 200 μL of plasma, 106 lymphocytes, or 10 mg of tissue. Filtered trichloroacetic acid extracts were injected directly into the HPLC system without additional processing and were eluted isocratically.

Results: The limits of detection were 200 fmol/L for SAM and 40 fmol/L SAH. In plasma extracts, the interassay CV was 3.4–5.5% and the intraassay CV was 2.8–5.6%. The analytical recoveries were 96.8% and 97.3% for SAM and SAH, respectively. In a cohort of healthy adult women with mean total homocysteine concentrations of 7.3 μmol/L, the mean plasma value was 156 nmol/L for SAM and 20 nmol/L for SAH. In women with increased homocysteine concentrations (mean, 12.1 μmol/L), plasma SAH, but not SAM, was increased (P &lt;0.001), and plasma pyridoxal 5′-phosphate concentrations were reduced (P &lt;0.001). Plasma SAM/SAH ratios were inversely correlated with homocysteine concentrations (r = 0.73; P &lt;0.01), and the SAM/SAH ratio in plasma was directly correlated with the intracellular SAM/SAH ratio in lymphocytes (r = 0.70; P &lt;0.01).

Conclusions: Increased homocysteine in serum is associated with an increase in SAH and a decrease in the SAM/SAH ratio that could negatively affect cellular methylation potential. Accurate and sensitive detection of these essential metabolites in plasma and in specific tissues should provide new insights into the regulation of one-carbon metabolism under different nutritional and pathologic conditions.