We examined the efficacy of tenofovir disoproxil fumarate (TDF) in blocking simian human immunodeficiency virus (SHIV) infection in Chinese rhesus macaques. Once weekly for 14 weeks or until a macaque became infected, 12 male macaques were inoculated intrarectally with amounts of SHIV(SF162P3) (10 median tissue culture infective doses; 3.8 x 10(5) virus particles) that were approximately 5-fold higher than the human immunodeficiency virus type 1 RNA levels noted in human semen during an acute infection. Of the 12 macaques, 4 received oral TDF daily, 4 received oral TDF once weekly, and 4 (control animals) received no TDF. The control animals became infected after receiving a median of 1.5 virus inoculations; macaques receiving TDF daily (1 macaque remained uninfected after 14 inoculations) and those receiving TDF weekly became infected after a median duration of 6.0 and 7.0 weeks, respectively. Although infection was delayed in treated macaques, compared with control macaques, the differences were not statistically significant (P=.315); however, the study was limited by the small numbers of animals evaluated and the variability in blood levels of TDF that resulted from oral dosing. These data demonstrate that treatment with oral TDF provided partial protection against SHIV infection but ultimately did not protect all TDF treated animals against multiple virus challenges.
We examined 516G>T polymorphisms at the gene encoding the cytochrome P450 in 100 human immunodeficiency virus-positive subjects who were receiving efavirenz (EFV). Elevated plasma EFV concentrations were found in 40% of subjects with the polymorphic homozygous genotype and 19% of subjects with the heterozygous genotype. Conversely, 20% of subjects with the wild-type genotype had subtherapeutic concentrations of EFV. CYP2B6-516 genotyping may help to identify subjects who have plasma EFV concentrations that are outside of the therapeutic range.
Ribavirin (RBV) in combination with pegylated interferon alpha (pegIFN) is currently the standard treatment of hepatitis C virus (HCV) infection. The development of anemia requires a reduction in RBV doses in a substantial proportion of patients, limiting their chances of treatment response. The primary goal of this study was to assess if early monitoring of RBV plasma levels could help to predict anemia as well as early HCV RNA response in HIV/HCV-coinfected individuals. The secondary goal was to evaluate if antiretroviral drugs might influence RBV plasma levels. Plasma RBV concentrations were measured at weeks 4 and 12 in 98 HIV/HCV-coinfected individuals who initiated therapy with pegIFN-2a (180 microg/wk) plus RBV (800-1200 mg/d). RBV plasma levels correlated with RBV dose per kilogram of body weight (P = 0.02). Larger drops in hemoglobin levels were independently associated with higher RBV plasma levels and zidovudine (ZDV) use (P < 0.001). Likewise, higher RBV levels (P = 0.007) and HCV genotype 3 (P < 0.001) were found to be independent predictors of virologic response at week 4. Similar findings were obtained at week 12. Patients receiving ZDV concomitantly showed significantly higher RBV plasma concentrations compared with those who did not (3.28 mug/mL vs. 2.51 mug/mL; P = 0.002). RBV levels were not significantly altered by the coadministration of other nucleoside/nucleotide analogues. In summary, RBV plasma levels correlate with the development of anemia and with the achievement of an early virologic response. Therefore, early therapeutic drug monitoring might help to tailor RBV dosages, improving the efficacy and safety of anti-HCV treatment.
Patients receiving ddI + TDF-based combinations show CD4+ T-cell declines despite achieving complete virus suppression. This effect generally progresses with time. An imbalance in adenosine metabolites within CD4+ T lymphocytes may explain this phenomenon, which resembles the genetic purine nucleoside phosphorylase deficiency syndrome.
ATV is relatively safe and provides significant virological response in PI-experienced patients, mainly among those with a low number of protease resistance mutations. The GIQ predicts accurately the virological response in patients receiving ATV. Hyperbilirubinemia is associated with higher ATV plasma levels.
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