Immunotherapy and immunopathologic studies in a patient with nucleoside phosphorylase deficiency

Point mutations at the purine nucleoside phosphorylase locus impair thymocyte differentiation in the mouse

Three point mutations on the Np(b) allele of the purine nucleoside phosphorylase locus in the mouse have been recovered by male germ cell mutagenesis. The mutants were backcrossed, 12-14 generations, and are designated in increasing order of severity of enzyme deficiency and phenotype: B6-NPE, Met-87 --> Lys; B6-NPF, Ala-228 --> Thr; and B6-NPG, Trp-16 --> Arg. A marked decline in total cell numbers per thymus occurs between 2 and 3 months for the more severe B6-NPF and B6-NPG mutants (35% and 52%, respectively) and by 8 months for the less severe B6-NPE mutation. The thymocyte population is thereafter characterized by a 3- or 8-fold expanded precursor, CD4-CD8- double-negative population and 15% or 55% reduced CD4+CD8+ double-positive cells for the B6-NPF and B6-NPG strains, respectively. Spleen lymphocyte Thy-1+ cells are reduced by 50% and spleen lymphocyte response to T cell mitogen and interleukin 2 is reduced by 80%. Increases of thymocyte dGTP pools of 5- and 2.5-fold for B6-NPF and B6-NPG mutants, respectively, are observed. The purine nucleoside phosphorylase-deficient mouse exhibits age-dependent progressive perturbations in thymocyte differentiation, reduced numbers of thymocytes, and reduced splenic T cell numbers and response. The progressive T cell deficit is similar to the human disorder.

Immunodeficiency in methylmalonic acidaemia

Three Chinese infants with methylmalonic acidaemia were described. They presented in the neonatal period with recurrent episodes of poor feeding, lethargy, apnoea and severe acidosis. The diagnosis was established by increased methylmalonic acid concentration in the plasma and/or urine. Pancytopenia was a prominent feature in all three patients. Only patient three had assessment of lymphocyte subsets and it showed diminished population of B-lymphocytes and a reversed CD4/CD8 ratio. All three patients were unresponsive to vitamin B12. They experienced severe infections including Gram-negative septicaemia, candidiasis and Pneumocystis carinii pneumonia which caused their deaths. Patients with this disease should be regarded as having severe immunodeficiency, and in addition to optimal metabolic control, they should be treated aggressively for any suspected infective episodes.

Adenosine deaminase and purine nucleoside phosphorylase deficiencies: evaluation of therapeutic interventions in eight patients

The courses of six patients with adenosine deaminase (ADA) and two with purine nucleoside phosphorylase (PNP) deficiencies were evaluated before and after therapy. The heterogeneity of immunologic and clinical parameters was striking in each enzyme deficiency. In both PNP and ADA deficiency, some patients had very low immunoglobulin levels, while others had normal levels. T-cell function was always low in patients with ADA deficiency. In the two patients with PNP deficiency, contrary to the classical descriptions of this disorder, T-cell function fluctuated with time. Five ADA-deficient patients were treated with irradiated normal red-cell transfusions as a form of enzyme replacement and showed no lasting benefit. Three of the ADA-deficient patients and one of the PNP-deficient patients were given transplants of haploidentical parental bone marrow stem cells without pretransplant immunosuppression. In the PNP-deficient patient, chimerism has not been documented on enzymatic testing. One ADA-deficient patient has demonstrated long-term engraftment with good B- and T-cell function. Haploidentical bone marrow transplantation is currently the preferred therapy for enzyme-deficient patients with absent T-cell function who do not have an HLA-identical donor, as it may result in a lasting reconstitution of immune function. In those patients with unsatisfactory responses to transplantation, however, specific enzyme replacement or gene therapy may be considered in the future.

Immunodeficiencies associated with errors in purine metabolism

The genetic deficiencies of adenosine deaminase and purine nucleoside phosphorylase lead to blocks in the purine pathway. The intracellular accumulation of deoxynucleosides and deoxynucleotides is toxic to both dividing and nondividing lymphocytes via multiple mechanisms. T-lymphocytes are uniquely sensitive to purine-mediated cytotoxicity because of a functional imbalance of phosphorylating and dephosphorylating enzymatic activities. These inborn errors or purine metabolism are rare disorders. The study of these conditions, however, has uncovered unique enzymatic properties of lymphocytes and lymphocyte subclasses. A better understanding of the mechanisms of lymphocytotoxicity in these two purine enzyme defects may lead to better modes of therapeutic manipulation of the immune system.

Thymic peptide hormones: basic properties and clinical applications in cancer

The manuscript will provide an in-depth and critical review of the nomenclature, biochemistry, biological properties, and a summary of published and on-going clinical trials with all reported thymic preparations, including both partially purified thymic factors (e.g., thymosin fraction 5, thymostimulin) as well as purified and synthesized thymic peptides (e.g., thymosin alpha 1, thymulin). Particular emphasis will be placed on which thymic peptides should be categorized as true hormones. In addition, the comparative biochemistry and biological activity in animals will be summarized and contrasted for all the currently available thymic factors. The effects, in vitro of thymic factors, on peripheral blood lymphocytes isolated from normal donors and patients with primary immunodeficiency disorders, autoimmune disorders, and neoplastic disorders will also be reviewed. Finally, a detailed critical summary of the clinical trials performed with each of the thymic preparations will be presented with an emphasis on treatment of patients with cancer.

Effect of thymosin alpha one on specific antibody response and susceptibility to infection in young and aged mice

The antibody response to a variety of antigens has been shown to diminish with age. We investigated the capacity for Thymosin Alpha One (T alpha 1) treatment to augment antibody production in tetanus toxoid (TT) and pneumococcal capsular polysaccharide (PN) inoculated young and old mice. We also measured survival of these immunized mice after aerosol exposure to Streptococcus pneumoniae. As predicted antibody response to TT, but not PN, was significantly reduced in the old animals and T alpha 1 augmented antitetanus antibody in both young and old mice. T alpha 1 did not have an effect on anti pneumococcal antibody production. All mice that had received PN did have an antibody response, yet survival after exposure to the organism was strikingly less in the old animals. Our data support the contention that antibody response to T-dependent antigens (such as tetanus toxoid) falls with aging but can be reconstituted somewhat by thymic factors. Furthermore, for T-independent antigen (such as pneumococcal capsular antigens) the age-related changes are less evident. In the latter situation, the presence of a brisk antibody response after vaccination was not sufficient to prevent pneumonia and death in old animals.

Adenosine deaminase and purine nucleoside phosphorylase activity in spleen cells of aged mice

The activities of two enzymes of purine metabolism, adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP), were determined in spleen lymphocytes from mice of various ages. We found that in the older animals, which have depressed responses to concanavalin A and phytohemagglutinin, there is a decrease in the activity of PNP but normal activity of ADA. The decline of PNP activity was seen at 7.5 months of age and appears to be concurrent with a decline in T-cell function. These results suggest that a decrease in PNP activity may be a contributing factor in the immunodeficient state of the aged.

Cellular immune deficiency with autoimmune hemolytic anemia in purine nucleoside phosphorylase deficiency

Immunologic and metabolic abnormalities were studied in a five year old boy with 0.07 per cent of normal erythrocyte purine nucleoside phosphorylase activity. The clinical course is characterized by severe autoimmune hemolytic anemia, a transient neurologic disorder with tremor and ataxia, and minor infectious illnesses. There is severe lymphopenia with decreased absolute numbers of T and B lymphocytes. Mitogen-stimulated blastogenesis is reduced, but response to allogeneic lymphocytes is normal. A monoclonal IgG protein is present. There is hypouricemia, elevated plasma inosine level, hypouricosuria and an increase in the urinary concentration of inosine and guanosine. The pattern of heterozygote distribution in the patient's family is compatible with an autosomal recessive trait in which heterozygotes are identifiable. In addition, the unusual laboratory and clinical manifestations of this patient illustrate the heterogeneity of the clinical syndrome associated with purine nucleoside phosphorylase deficiency.