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Most of the compounds currently used for treatment of HIV-1 infection are reverse transcriptase inhibitors and protease inhibitors. Several early steps in the HIV-1 life cycle such as virus attachment to host cell and cell-virus fusion are potential targets for drugs. Since most of the target molecules involved in this infection step are cellular, it is expected that the drug resistant mutations occur less frequently than those against viral enzymes. In this review, new inhibitors of entry and fusion are summarized that are promising.

The virion surface of the human immunodeficiency virus (HIV-1) is covered with an envelope glycoprotein gp120. Study of the oligosaccharide structures of gp120 suggests that the high mannose type of oligosaccharides are essential for HIV-1 infection. Pradimicin A, an antifungal antibiotic isolated from Actinomadura hibisca, and the derivative BMY-28864 have the ability to inhibit HIV-1 infection in vitro. The inhibitory effect was suppressed by addition of high mannose type oligosaccharides of gp120. BMY-28864 bound directly to gp120, mannose-BSA, and neoglycolipids containing high mannose type oligosaccharides but not to natural mammalian glycoproteins. The binding was Ca2+ dependent and was inhibited by mannose. BMY-28864 is a unique carbohydrate-binding antibiotic which has never been reported. It is possible to block HIV-1 infection by targeting oligosaccharide chains of the envelope glycoprotein.

The surface of the human immunodeficiency virus (HIV-1), a causative agent for acquired immunodeficiency syndrome (AIDS), is covered with the major envelope glycoprotein gp120, of which the carbohydrate moiety accounted for 50% of the molecular mass. There is evidence that glycosylation of gp120 is prerequisite to the various stages of HIV infection. The oligosaccharide structures of gp120 have been determined using recombinant gp120 of HIV-1 (IIIB) produced in chinese hamster ovary cells and virus-derived gp120 isolated from H9 lymphocytes chronically infected with HIV-1 (IIIB). Three oligosaccharides have been suggested to be involved in the HIV-infection process. Occurrence of infection process which is independent of CD4 recognition and mediated by gp120 oligosaccharides, mannose-binding protein, and complement system has been suggested.