Bevirimat Inhibits p24 Release from the Capsid p25 Precursor in Human Thymocytes.

<p>Thymocytes dispersed from NL4-3- and SP1/A1V-infected SCID-hu Thy/Liv implants were cultured in the presence of the indicated range of concentrations of bevirimat for 2 days. Purified virions was lysed and individual viral proteins were detected with HIV-1 Ig. Note the target-specific and dose-dependent reduction of CAp25 cleavage in the presence of bevirimat. The presence of the drug does not affect the stoichiometry of the precursor Pr55Gag polyprotein nor does it inhibit cleavage of the matrix protein, MAp17 (lower panel, longer exposure).</p

Postexposure Dosing of Bevirimat also Reduces Viral Load.

<p>Mice were treated by twice-daily oral gavage with bevirimat at 100 mg/kg per day beginning 1 day before (−1), 1 day after (+1), or 3 days after (+3) virus inoculation of Thy/Liv implants with HIV-1 NL4-3 and JD. Dosing was continued until implant collection 14 days (JD) and 21 days (NL4-3) after inoculation. Antiviral efficacy was assessed by determining cell-associated HIV-1 RNA and p24. There was no reduction in viral load in bevirimat-treated mice inoculated with bevirimat-resistant SP1/A1V, whereas 3TC treatment (30 mg/kg per day by twice-daily oral gavage) was highly effective. Data are expressed as means±SEM; *<i>p</i>≤0.05 for treated mice versus untreated mice by the Mann-Whitney U test for 6–8 mice per group.</p

Protease Inhibitor-Resistant HIV-1 has Impaired CA-SP1 Cleavage.

<p>Wild-type NL4-3 and protease mutant NL4-3 PR_I54V+V82A virions were collected from transfected 293T cells grown in the presence (20 µM) or absence of bevirimat and analyzed for particle maturation by Western blot using a p24 monoclonal antibody. The protease mutant is deficient in CA-SP1 cleavage and is comparable to bevirimat-treated wild-type virus, however, the drug has a more dramatic effect on CA-SP1 cleavage in HIV-1 PR_I54V+V82A.</p

In Vivo Competitions Reveal No Impairment of SP1/A1V Replication.

<p>Sequencing of CA-SP1 RNA from three SCID-hu Thy/Liv mice coinfected with equivalent infectious units of NL4-3 and SP1/A1V reveal no impairment of SP1/A1V replication 28 days after implant inoculation. The A-to-V substitution in SP1 is conferred by a C-to-T mutation at nucleotide 1880.</p

In Vivo Competition Results for NL4-3 and Bevirimat-Resistant SP1/A1V.

a<p>Viral species identified by sequencing amplicons generated after RT-PCR of CA RNA as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001251#pone-0001251-g006" target="_blank">Figure 6</a>.</p

The A1V Mutation in SP1 Does Not Affect Kinetics of Viral Replication or Thymocyte Depletion.

<p>Bevirimat-resistant SP1/A1V replicates and depletes thymocytes with kinetics comparable to wild-type NL4-3 in SCID-hu Thy/Liv mice. Viral replication was assessed by determining implant viral load (A), and thymocyte depletion was assessed by total implant cellularity, thymocyte viability, and CD4/CD8 ratio (B) for NL4-3-infected versus SP1/AIV-infected mice for 6 mice per group. Data are expressed as means±SEM; there were no statistically significant differences in viral load or thymocyte depletion at any of the three time points. The number in each graph is the proportion of SP1/A1V to NL4-3 in area under the curve.</p

Mice have High Concentrations of Bevirimat in Plasma 0.5–1 h after Oral Administration.

<p>Serial plasma samples were collected after the final dose from SCID-hu Thy/Liv mice that had been treated with 100 mg/kg per day for 21 days. Mean±SEM for four mice.</p

(–)-FTC is more potent than 3TC against HIV-1 NL4-3 in SCID-hu Thy/Liv mice.

<p>Mice were treated by twice-daily oral gavage with 3TC or (–)-FTC at 10, 30, and 100 mg/kg per day beginning on day –1. Antiviral efficacy was assessed by determining HIV-1 RNA (A) and p24 (B), and thymocyte protection was assessed by percentage of DP thymocytes (C) (means±SEM). *p≤0.05, compared with untreated mice for the number of mice indicated under each bar.</p

T-20 causes dose-dependent reductions in viral load in HIV-1 NL4-3 D36G-infected SCID-hu Thy/Liv mice.

<p>Mice were treated by twice-daily subcutaneous injection with T-20 at 10, 30, and 100 mg/kg per day beginning on day −1. Antiviral efficacy was assessed by determining cell-associated HIV-1 RNA and p24. Data are expressed as means±SEM; *p≤0.05 for treated mice versus untreated mice by the Mann-Whitney U test for the number of mice indicated under each bar.</p

Antiretroviral drug dosage levels adjusted for difference in surface area-to-body weight ratio between mice and humans

a<p>From ref. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone.0000655-DeClercq1" target="_blank">[56]</a>.</p>b<p>Based on 60 kg adult human weight and 20 g mouse weight.</p>c<p>Human dosage×12.3 (fold difference in surface area to body weight between mice and humans; from ref. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone.0000655-Freireich1" target="_blank">[45]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone.0000655-Bast1" target="_blank">[46]</a>.</p>d<p>Calculated by linear regression of the viral RNA data shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone-0000655-g003" target="_blank">Figures 3</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone-0000655-g004" target="_blank"></a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone-0000655-g005" target="_blank"></a><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000655#pone-0000655-g006" target="_blank">6</a> at the equivalent mouse dosage level.</p