Activity of glucosidase inhibitors against HIV infections

Detection of novel secondary metabolites

The study of antibiotics and other fermentation products has shown that a seemingly unlimited number of compounds with diverse structures are produced by microorganisms. The continued high rate of discovery of new chemical entities, in the light of the abundance of microbial products already described, is due to creative screening procedures that incorporate such features as the emphasis on unusual microorgnaisms, their special propagation and fermentation requirements, supersensitive and highly selective assays, genetic engineering both for the biosynthesis of new compounds and in the development of screening systems, early in vivo evaluation, improved isolation techniques, modern procedures for structure determination, computer-assisted identification, and an efficient multidisciplinary approach. This review focuses on the genesis and development of the gamut of methodologies that have led to the successful detection of the wide variety of novel secondary metabolites that include antibacterial, antigungal, antiviral and antitumour antibiotics, enzyme inhibitors, pharmacologically and immunologically active agents, products useful in agriculture and animal husbandry, microbial regulators, and other compounds for which no bioactive role has yet been found.

Attenuation of HIV-1 infectivity by an inhibitor of oligosaccharide processing

A series of inhibitors of trimming glucosidases and mannosidases were examined for antiviral activity toward HIV-1. N-butyl deoxynojirimycin (N-buDNJ) was found to be the most potent agent studied. Treatment of acutely infected lymphoid cells with 2.0 mM N-buDNJ reduced virus yield more than 90%, without affecting cell growth. Though lower concentrations of N-buDNJ (0.002-0.2 mM) did not affect HIV-1 production, there was complete inhibition of syncytia formation. Treatment of chronically infected lymphoid cells with 0.1-1.0 mM N-buDNJ resulted in no significant change in virus production, but 80% reduction of infectivity. The attenuation in HIV-1 infectivity was due at least partially to diminished binding to CD4+ lymphoid cells. Chronically infected lymphoid cells treated with 0.02-1.0 mM N-buDNJ for at least 3 days were markedly impaired in their ability to form syncytia with uninfected lymphoid cells. N-buDNJ treatment of HIV-1 infected cells resulted in both a reduction in the cell surface envelope proteins, and an increase in their apparent molecular weight. These results show that N-buDNJ can be used to impair the infectivity of HIV-1 without significant toxicity.

Glycosylation of the envelope glycoprotein gp130 of simian immunodeficiency virus from sooty mangabey (Cercocebus atys)

The envelope glycoprotein 130 ('130' referring to an Mr of 130,000) of simian immunodeficiency virus from sooty mangabey (Cercocebus atys) (SIVSM) was isolated from the cell-free supernatant of the SIVSM-infected human T-cell line H9, metabolically labelled with D-[6-3H]glucosamine. After digestion with Staphylococcus aureus V8 proteinase, radiolabelled N-glycans were liberated from resulting glycopeptides by sequential treatment with endo-beta-N-acetylglucosaminidase H and peptide:N-glycosidase F and fractionated by h.p.l.c. and gel filtration. Individual oligosaccharide species were characterized by enzymic microsequencing, chromatographic analyses and, in part, by acetolysis. The oligosaccharide structures thus established include oligomannosidic glycans with five to nine mannose residues as well as fucosylated and partially sialylated bi-, tri- and tetra-antennary N-acetyl-lactosaminic oligosaccharide species, the latter of which carry, in part, additional galactose residues or N-acetyl-lactosamine repeats. In comparison with the corresponding envelope glycoprotein 120 from human immunodeficiency virus type 1 (HIV-1), propagated in the same cell line [Geyer, Holschbach, Hunsmann and Schneider (1988) J. Biol. Chem. 263, 11760-11767], carbohydrates of the simian glycoprotein were found to consist of decreased amounts of oligomannosidic glycans and increased quantities of higher-branched N-acetyl-lactosaminic species.

Antibody-independent, complement-mediated enhancement of HIV-1 infection by mannosidase I and II inhibitors

Human immunodeficiency virus type 1 (HIV-1) infectivity and cytopathic effect require proper maturation of the viral envelope glycoprotein carbohydrate moieties. We have found that fresh human serum enhances the infectivity of HIV-1 in MT-2 cell infection assays when virus is synthesized in the presence of the mannosidase I inhibitor, 1-deoxymannojirimycin, or the mannosidase II inhibitor, swainsonine, but has no enhancing effect on virus synthesized in the presence of the glucosidase I inhibitors, castanospermine and 1-deoxynojirimycin, or the glucosidase II inhibitor, bromoconduritol. Enhanced infections were characterized by cytopathic effect, antigen synthesis and reverse transcriptase release, all which occurred sooner than in control-infected cultures. This enhancement of infection was also observed in C1q-deficient serum but was not observed in serum that was heat-inactivated or depleted of complement components C3 or factor B, thus suggesting a requirement for the alternate pathway of complement.