Gene replacement therapy for inborn errors of purine metabolism

Effective retroviral vectors carrying the human HPRT and ADA genes have been described. Initial characterization of the retroviral gene transfer system using the HPRT vector allowed the delineation of several parameters important in viral titer, expression, and stability. Using the HPRT and ADA vectors, we have initiated experiments designed to insert these human genes into various tissues of the mouse and have demonstrated expression of both transduced genes in mouse bone marrow cells. Further work with these and other vector constructions is underway in the hope that this technique may allow safe and effective treatment of ADA and HPRT deficiencies, paving the way for treatments of other inborn errors of metabolism through somatic gene replacement therapy.

Isolation and characterization of a Chinese hamster lung cell tryptophanyl-tRNA synthetase mutant

A novel type of temperature-sensitive protein synthetic mutant was isolated from V-79 Chinese hamster lung cells using an amino acid analog suicide selection. The expression of the temperature sensitive phenotype of the mutant is greatly affected by the concentration of tryptophan in the culture medium. In addition, the activity of tryptophanyl-tRNA synthetase is undetectable in cell-free extracts prepared from the mutant cells. The results suggest that the mutant has an alteration in the structural gene encoding tryptophanyl-tRNA synthetase.

Mouse mononuclear phagocyte antigenic heterogeneity detected by monoclonal antibodies

Identification and characterization of the many cellular and subcellular changes that underlie various macrophage functions have been hampered by the problem of population heterogeneity. The problem has remained because, in the case of most functions, we have not had the means to examine cells at a level below that of whole populations. We report here the potential means to do so. Rat anti-mouse mononuclear phagocyte monoclonal antibodies were raised against adherent cells cultured from bone marrow. These antibodies were used to delineate and, in the presence of complement, eliminate subpopulations of macrophages. The extent to which antigenic heterogeneity occurs was shown in several mononuclear phagocyte populations that are commonly employed experimentally. Some antibodies reacted with most mononuclear phagocytes tested, whereas others showed marked selectivity of binding. As expected, resident populations were less heterogeneous antigenically than inflammatory populations were. The data both extend what is known about mononuclear phagocyte population heterogeneity and suggest means by way of which this heterogeneity can be overcome.

Antigenic analyses of two axenized strains of Entamoeba histolytica by two-dimensional immunoelectrophoresis

Antigens in extracts of two strains of Entamoeba histolytica (HT-31 and HK-9) were studied by two-dimensional immunoelectrophoresis (2D-IEP) and 32 and 20 different antigenic components were detected, respectively. Cross-reactions between heterologous systems showed a large number of shared antigens between the two strains. Extracts were fractionated by Sephadex G-200 chromatography. Of the fractions obtained, fraction II of both strains was found to have the most reactive antigenic components. Precipitin patterns of fraction II from HT-31 and HK-9 with sera from patients showed similar 2D-IEP profiles and suggested that in this fraction antigens common to both strains exist which elicit antibody in individuals with E. histolytica infections.

Structural relatedness of mouse lactate dehydrogenase isozymes, A4 (muscle), B4 (heart), and C4 (testis)

Three homotetrameric lactate dehydrogenase isozymes, LDH-M(A4), LDH-H(B4), and LDH-X(C4), from DBA/2J mice have been purified by affinity chromatography. The amino acid compositions of the subunits A,B, and C, based on a molecular weight of 36,000, have been determined. The compositional relatedness of these isozymes indicates that subunits A (muscle) and B (heart) are more closely related to each other than to subunit C (testis). Tryptic peptide maps and amino acid compositions of some active site peptides apear to confirm the compositional relatedness among these isozymes. The sequence of the loop region of mouse C subunit seems to be markedly different from all known A and B sequences, and the structural and functional implications are discussed.