The therapeutic utility of a human immunodeficiency virus type 1 (HIV-1) protease inhibitor may depend on its intracellular concentration, which is a property of its uptake, metabolism, and/or efflux. Previous studies in our laboratory indicated that the addition of alpha 1 acid glycoprotein (alpha 1 AGP) to the medium markedly increased the amount of the drug required to limit infection in vitro. In this study, physiologically relevant concentrations of alpha 1 AGP and a radiolabeled inhibitor, A-80987, were used to determine both the uptake and activity of the agent in HIV-1-infected human peripheral blood mononuclear cells and cell lines. Both the uptake and efflux of 14C-labeled A-80987 were rapid (t1/2, < 5 min). Uptake of the drug was linearly dependent on the concentration but insensitive to the metabolic inhibitors KF, sodium cyanide, or CCCP (carbonyl cyanide m-chlorophenyl hydrazone). The amount of A-80987 which entered the cells was inversely proportional to the concentration of alpha 1 AGP (r2, 0.99) and directly proportional to the amount of extracellular non-protein-bound drug (r2, 0.99). Most importantly, the antiviral activity of the drug in HIV-1-infected peripheral blood mononuclear cells and MT-2 cells was directly related to the amount of intracellular A-80987. This study demonstrates that A-80987 binds to alpha 1 AGP, resulting in a free fraction below 10%. Cellular uptake of A-80987 is proportionally decreased in the presence of alpha 1 AGP, which results in less-than-expected antiviral activity. Importantly, we demonstrate for the first time that the inhibition of HIV protease is highly correlated with the amount of intracellular inhibitor.

Abacavir is a potent new carbocyclic nucleoside analogue. We employed our hollow-fiber pharmacodynamic modeling system to examine the antiretroviral effects of different abacavir exposures, as well as the impact of the schedule of drug administration on efficacy. Dose ranging of abacavir revealed that a concentration of four times the 50% effective concentration ( Because of these promising initial results, we extended the experiment to 30 days and examined three different schedules of administration that generated the same AUC at 24 h (AUC 24 ): 300 mg q12h, 600 mg q24h, and 1,200 mg q48h. The aim of the last of these regimens was to definitively demonstrate schedule failure. There was little difference between the 1,200-mg q48h treatment group and the untreated control at 30 days. Likewise, there was little difference between the 600-mg q24h and 300-mg q12h treatment groups. However, at circa day 18 of the experiment, there was a small increase in viral output of p24 in the once-daily dosing unit. Examination of virus from all groups demonstrated no phenotypic or genotypic differences. The small difference in hollow-fiber unit p24 in the once-daily dosing group was not due to emergence of resistance over the 30-day single-drug exposure. We conclude that the dose of abacavir currently being studied in clinical trials (300 mg orally q12h) will be efficacious for the majority of sensitive clinical isolates of HIV-1. These in vitro data also suggest that this drug may be able to be administered to patients on a once-daily basis at a dose of 600 mg.Abacavir is a new carbocyclic nucleoside analogue with potent anti-human immunodeficiency virus type 1 (HIV-1) activity. In clinical trial work (

Since plasma protein binding of antiinfectives can adversely affect drug activity, the effect of serum proteins on the in vitro antiviral activity of A77003, a human immunodeficiency virus type 1 (HIV) protease inhibitor, was investigated. In vitro, A77003 is effective in both acute and chronic infection in 10% fetal bovine or human serum. As the concentration of human serum was increased to 50%, antiviral efficacy decreased 3- to 6-fold. Purified human alpha 1 acid glycoprotein (alpha 1-AGP) at physiologic concentrations (0.5-2 mg/mL) dose-dependently reduced the antiviral activity of A77003. alpha 1-AGP at 1 mg/mL also antagonized the anti-HIV activity of A77003-zidovudine combinations. Therefore, higher concentrations of HIV protease inhibitors than would be predicted, on the basis of in vitro activity in the absence of physiologic concentrations of binding protein, may be required to effectively limit viral replication in vivo.

No abstract

SUMMARYProperly purified preparations of poliovirus particles are practically free of o-galactose and N-acetyl-D-glucosamine. These sugars, however, are found in crude virus preparations, obtained by high and low speed sedimentation and by CsCl-gradient fractionation from infected HeLa cells. They are separated from the virus particle by extraction with chloroform and subsequent isopycnic sedimentation of the virus preparation. Since o-galactose and N-acetyl-o-glucosamine are regular constituents of glycoproteins, the absence of significant amounts of these sugars demonstrates the lack of glycoproteins in poliovirus particles.Radioactive monosaccharides are recommended for the detection of cellular impurities in carbohydrate-free viruses.A simple and rapid method for the purification of large quantities of poliovirus by 'precipitation' with polyethylene glycol, resuspension in CsC1 solutions, extraction with chloroform and isopycnic sedimentation is described.