Purine nucleoside phosphorylase deficiency: a new case report and identification of two novel mutations (Gly156A1a and Val217Ile), only one of which (Gly156A1a) is deleterious

Purine Nucleoside Phosphorylase Deficient Severe Combined Immunodeficiencies: A Case Report and Systematic Review (1975-2022)

Purine nucleoside phosphorylase deficient severe combined immunodeficiency (PNP SCID) is one of the rare autosomal recessive primary immunodeficiency disease, and the data on epidemiology and outcome are limited. We report the successful management of a child with PNP SCID and present a systematic literature review of published case reports, case series, and cohort studies on PNP SCID listed in PubMed, Web of Science, and Scopus from 1975 until March 2022. Forty-one articles were included from the 2432 articles retrieved and included 100 PNP SCID patients worldwide. Most patients presented with recurrent infections, hypogammaglobulinaemia, autoimmune manifestations, and neurological deficits. There were six reported cases of associated malignancies, mainly lymphomas. Twenty-two patients had undergone allogeneic hematopoietic stem cell transplantation with full donor chimerism seen mainly in those receiving matched sibling donors and/or conditioning chemotherapy before the transplant. This research provides a contemporary, comprehensive overview on clinical manifestations, epidemiology, genotype mutations, and transplant outcome of PNP SCID. These data highlight the importance of screening for PNP SCID in cases presented with recurrent infections, hypogammaglobulinaemia, and neurological deficits.

Performance of chitosan polymer as platform during sensors fabrication and sensing applications

Chitosan is an important polymer produced from deacetylation of several sea and insects crusts. Due to its environmental fate and biological biocompatibility, it can be used in several biological and environmental applications. Sensing of biological compounds in human bodies and also in serum, blood, and different body fluids has found an important application instead of direct determination of the body fluids using complicated tools. Sensing process of biological compounds during bio-analysis of the biological systems, especially human fluids lack of several parameters including: high sensitivity, repeatability, speed of analysis and biocompatibility of the used analytical methods, especially in-vivo analysis. That was due to the time between sample handling and sample determination can change various components and concentrations of the bio-compounds. The need for in-situ analysis was directed the researchers for biosensors to overcome the upgrading problems of bio-analysis. Biosensors were the future of this issue. Chitosan can reserve as great platform for fabrication of different sensors to determine the elements, compounds and body bioactive compounds. The presence of different terminal amino and hydroxyl groups within chitosan framework facilitates the immobilization of different biomarkers to be used as sensing elements for the determined compounds. The use of chitosan as sensors platform was enhanced by using chitosan in its nanoforms.

The Broad Clinical Spectrum and Transplant Results of PNP Deficiency

PURPOSE

Purine nucleoside phosphorylase (PNP) is a known yet rare cause of combined immunodeficiency with a heterogeneous clinical presentation. We aim to add to the expanding clinical spectrum of disease, and to summarize the available data on bone marrow transplant for this condition.

METHODS

Data was collected from patient files retrospectively. A review of the literature of hematopoietic stem cell transplantation (HSCT) for PNP deficiency was conducted.

RESULTS

Four patients were treated in two centers in Israel. One patient died of EBV-related lymphoma with CNS involvement prior to transplant. The other three patients underwent successful HSCT with good immune reconstitution post-transplant (follow-up 8-108 months) and excellent neurological outcomes.

CONCLUSION

PNP is a variable immunodeficiency and should be considered in various clinical contexts, with or without neurological manifestations. HSCT offers a good treatment option, with excellent clinical outcomes, when preformed in a timely manner.

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.

Release of soluble and vesicular purine nucleoside phosphorylase from rat astrocytes and microglia induced by pro-inflammatory stimulation with extracellular ATP via P2X7 receptors

Purine nucleoside phosphorylase (PNP), a crucial enzyme in purine metabolism which converts ribonucleosides into purine bases, has mainly been found inside glial cells. Since we recently demonstrated that PNP is released from rat C6 glioma cells, we then wondered whether this occurs in normal brain cells. Using rat primary cultures of microglia, astrocytes and cerebellar granule neurons, we found that in basal condition all these cells constitutively released a metabolically active PNP with Km values very similar to those measured in C6 glioma cells. However, the enzyme expression/release was greater in microglia or astrocytes that in neurons. Moreover, we exposed primary brain cell cultures to pro-inflammatory agents such as lipopolysaccharide (LPS) or ATP alone or in combination. LPS alone caused an increased interleukin-1β (IL-1β) secretion mainly from microglia and no modification in the PNP release, even from neurons in which it enhanced cell death. In contrast, ATP administered alone to glial cells at high micromolar concentrations significantly stimulated the release of PNP within 1 h, an effect not modified by LPS presence, whereas IL-1β secretion was stimulated by ATP only in cells primed for 2 h with LPS. In both cases ATP effect was mediated by P2X₇ receptor (P2X₇R), since it was mimicked by cell exposure to Bz-ATP, an agonist of P2X₇R, and blocked by cell pre-treatment with the P2X₇R antagonist A438079. Interestingly, ATP-induced PNP release from glial cells partly occurred through the secretion of lysosomal vesicles in the extracellular medium. Thus, during inflammatory cerebral events PNP secretion promoted by extracellular ATP accumulation might concur to control extracellular purine signals. Further studies could elucidate whether, in these conditions, a consensual activity of enzymes downstream of PNP in the purine metabolic cascade avoids accumulation of extracellular purine bases that might concur to brain injury by unusual formation of reactive oxygen species.

Purine nucleoside phosphorylase deficiency: a mutation update

Purine nucleoside phosphorylase (PNPase) deficiency is an autosomal recessive disorder affecting purine degradation and salvage pathways. Clinically, patients typically present with severe immunodeficiency, neurological dysfunction, and autoimmunity. Biochemically, PNPase deficiency may be suspected in the presence of hypouricemia. We report biochemical and genetic data on a cohort of seven patients from six families identified as PNPase deficient. In all patients, inosine, deoxyinosine, guanosine, and deoxyguanosine were elevated in urine, and mutation analysis revealed seven different mutations of which three were novel. The mutation c.770A>G resulted in the substitution p.His257Arg. A second novel mutation c.257A>G (p.His86Arg) was identified in two siblings and a third novel mutation, c.199C>T (p.Arg67X), was found in a 2-year-old female with delayed motor milestones and recurrent respiratory infections. A review of the literature identified 67 cases of PNPase deficiency from 49 families, including the cases from our own laboratory. PNPase deficiency was confirmed in 30 patients by genotyping and 24 disease causing mutations, including the three novel mutations described in this paper, have been reported to date. In five of the seven patients, plasma uric acid was found to be within the pediatric normal range, suggesting that PNPase deficiency should not be ruled out in the absence of hypouricemia.

Construction of amperometric uric acid biosensor based on uricase immobilized on PBNPs/cMWCNT/PANI/Au composite

A chitosan-glutaraldehyde crosslinked uricase was immobilized onto Prussian blue nanoparticles (PBNPs) absorbed onto carboxylated multiwalled carbon nanotube (c-MWCNT) and polyaniline (PANI) layer, electrochemically deposited on the surface of Au electrode. The nanohybrid-uricase electrode was characterized by scanning electron microscopic (SEM), Fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry. An amperometric uric acid biosensor was fabricated using uricase/c-MWCNT/PBNPs/Au electrode as working electrode, Ag/AgCl as standard and Pt wire as auxiliary electrode connected through a potentiostat. The biosensor showed optimum response within 4s at pH 7.5 and 40°C, when operated at 0.4V vs. Ag/AgCl. The linear working range for uric acid was 0.005-0.8 mM, with a detection limit of 5 μM. The sensor was evaluated with 96% recovery of added uric acid in sera and 4.6 and 5.4% within and between batch of coefficient of variation respectively and a good correlation (r=0.99) with standard enzymic colorimetric method. This sensor measured uric acid in real serum samples. The sensor lost only 37% of its initial activity after its 400 uses over a period of 7 months, when stored at 4°C.

Closely spaced multiple mutations as potential signatures of transient hypermutability in human genes

Data from diverse organisms suggests that transient hypermutability is a general mutational mechanism with the potential to generate multiple synchronous mutations, a phenomenon probably best exemplified by closely spaced multiple mutations (CSMMs). Here we have attempted to extend the concept of transient hypermutability from somatic cells to the germline, using human inherited disease-causing multiple mutations as a model system. Employing stringent criteria for data inclusion, we have retrospectively identified numerous potential examples of pathogenic CSMMs that exhibit marked similarities to the CSMMs reported in other systems. These examples include (1) eight multiple mutations, each comprising three or more components within a sequence tract of <100 bp; (2) three possible instances of "mutation showers"; and (3) numerous highly informative "homocoordinate" mutations. Using the proportion of CpG substitution as a crude indicator of the relative likelihood of transient hypermutability, we present evidence to suggest that CSMMs comprising at least one pair of mutations separated by < or =100 bp may constitute signatures of transient hypermutability in human genes. Although this analysis extends the generality of the concept of transient hypermutability and provides new insights into what may be considered a novel mechanism of mutagenesis underlying human inherited disease, it has raised serious concerns regarding current practices in mutation screening.

Fabrication of dissolved O2 metric uric acid biosensor using uricase epoxy resin biocomposite membrane

Uricase purified from 20-day-old leaves of cowpea was immobilized on to epoxy resin membrane with 80% retention of initial activity of free enzyme and a conjugation yield of 0.056 mg/cm(2). The uricase epoxy resin bioconjugate membrane was mounted over the sensing part of the combined electrode of 'Aqualytic' dissolved O(2) (DO) meter to construct a uric acid biosensor. The biosensor measures the depletion of dissolved O(2) during the oxidation of uric acid by immobilized uricase, which is directly proportional to uric acid concentration. The biosensor showed optimum response within 10-12s at a pH 8.5 and 35 degrees C. A linear relationship was found between uric acid concentration from 0.025 to 0.1 mM and O(2) (mg/l) consumed. The biosensor was employed for measurement of uric acid in serum. The mean value of uric acid in serum was 4.92 mg/dl in apparently healthy males and 3.11 mg/dl in apparently healthy females. The mean analytic recoveries of added uric acid in reaction mixture (8.9 and 9.8 mg/dl) were 93.6 +/- 2.34 and 87.18 +/- 3.17% respectively. The within and between batch CVs were < 6.5 and < 5.0%, respectively. The serum uric acid values obtained by present method and standard enzymic colorimetric method, showed a good correlation (r - 0.996) and regression equation being y - 0.984x + 0.0674. Among the various metabolites tested only, glucose (11%), urea (38%), NaCl (25%) and cholesterol (13%) and ascorbic acid (56%) caused decrease, while, MgSO(4) and CaCl(2) had no effect on immobilized enzyme. The enzyme electrode showed only 32% decrease during its use for 100 times over a period of 60 days at 4 degrees C.

An unconditioned bone marrow transplantation in a child with purine nucleoside phosphorylase deficiency and its unique complication

Purine nucleoside phosphorylase deficiency is a rare immunodeficiency syndrome characterized by recurrent infections, neurological dysfunction, and autoimmunity. Early diagnosis and hematopoietic stem cell transplantation may reverse the dismal prognosis in PNP deficiency. This report presents a new PNP deficiency case successfully transplanted without a conditioning regimen from an HLA-identical family donor, who developed a complication of disseminated BCG infection.

Purine nucleoside phosphorylase deficiency in a patient with spastic paraplegia and recurrent infections

Purine nucleoside phosphorylase deficiency is a rare autosomal recessive immunodeficiency disease. The characteristic features of the disease include severe T cell immune defects with recurrent infections, a failure to thrive, and progressive neurological findings. To date, 35 cases of purine nucleosidase phosphorylase deficiency have been reported worldwide. A 2-year-old female patient was hospitalized due to recurrent infections starting from 6 months and a fever that had continued for a month. The parents were first cousins. Physical examination showed a failure to thrive, herpetic lesions around the lips, painful lesions on the tongue and the buccal mucosa, lung infection, and spastic paraparesis in the lower extremities. She had motor and mental retardation. Laboratory tests revealed lymphopenia; low CD3, CD4, and CD8 counts; normal immunoglobulin levels; low uric acid; and very low purine nucleoside phosphorylase enzyme activity (1.4 nmol/h/mg; normal range, 490-1530). DNA sequencing of the purine nucleosidase phosphorylase gene revealed a missense homozygous mutation, a G to A transition at exon 4 position 64 (349G>A transition), which led to a substitution of alanine by threonine at codon 117 (Ala117Thr). Both parents were heterozygous for the mutation. This is the second purine nucleosidase phosphorylase deficient case to have been presented and carrying this mutation worldwide. Various antibiotics, antifungal drugs, and intravenous immunoglobulin were used to treat the infections during her 3 months. This form of treatment proved to be unresponsive, resulting in her subsequent death at 26 months of age.

Novel mutations and hot-spots in patients with purine nucleoside phosphorylase deficiency

Purine nucleoside phosphorylase (PNP) deficiency results in severe immune dysfunction and early death from infections. Lymphopenia, reduced serum uric acid, and abnormal PNP enzymatic activity assist in the diagnosis of PNP-deficient patients. Analysis of the gene encoding PNP in these patients reveals several recurring mutations. Identification of these hot-spots for mutation may allow faster confirmation of the diagnosis in suspected cases.