Long-term follow-up of patients taking tenofovir DF with low-level HIV-1 viremia and the K65R substitution in HIV-1 RT

Patients with on-going HIV-1 replication and a K65R mutation in HIV-1 RT were assessed for further development of RT mutations while taking tenofovir disoproxil fumarate and other antiretroviral drugs. K65R was observed in 10 out of 536 treatment-experienced patients entering the study. K65R became undetectable in two patients, and the development of additional resistance mutations was minimal. Over 18 months, no patient developed multinucleoside resistance (Q151M or T69 insertions) and plasma viral loads were stable (median +0.04 log10 copies/ml).     

K65R and Y181C are less prevalent in HAART-experienced HIV-1 subtype A patients

The vast majority of HIV-1 infections globally are caused by subtype A or C, although little is known about their drug resistance profiles. We found that HAART-experienced patients infected with subtype A had a lower prevalence of K65R and Y181C than those with subtypes B or C, despite similar exposure to antiretroviral agents that select for these mutations. If confirmed, this information may be important in the planning of antiretroviral regimens in patients infected with HIV-1 subtype A.     

Human immunodeficiency virus 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors may suppress the replication of specific drug-resistant (E138K)RT HIV-1 mutants or select for highly resistant (Y181C-->C181I)RT HIV-1 mutants.

Mutant HIV-1 that expresses a Glu138-->Lys substitution in its RT [(E138K)RT] is resistant to the HIV-1-specific RT inhibitor 2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)pyrimidine (TSAO). However, cell cultures infected with this mutant were completely protected against virus-mediated destruction by micromolar concentrations of the HIV-1-specific RT inhibitors tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), nevirapine, and bis(heteroaryl)piperazine (BHAP). In contrast, cells infected with a virus mutant that expresses a Tyr181-->Cys substitution in its RT [(Y181C)RT] were not protected by nevirapine and TIBO and were only temporarily protected by BHAP. HIV-1 mutant that emerged under the latter conditions contained a Cys181-->Ile substitution in their RT [(LC181I)RT]. This mutant proved highly resistant to all HIV-1-specific RT inhibitors tested, except for several 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) derivatives. When recombinant (C181I)RT was evaluated for susceptibility to the HIV-1-specific RT inhibitors, it was resistant to all inhibitors except the HEPT compounds. Since a (Y181F)RT HIV mutant strain was isolated from cells infected with (Y181C)RT HIV-1 and treated with BHAP, we postulate that the Ile codon was derived from a Cys-->Phe transversion mutation (TGT-->TTT), followed by a Phe-->Ile transversion mutation (TTT-->ATT).     

Electron-Topological Method of the non-nucleoside HIV-1 RT inhibitors study: structure-activity relationships

Structure activity relationships for a series of TIBO (4,5,6,7-tetrahydro-5-methylimidazo[4,5,1-j,k][1,4] benzodiazepin-2(1H)-one) derivatives, which significantly inhibit HIV-1 replication are analyzed by the Electron-Topological Method (ETM) and Artificial Neural Networks (ANNs). Activities of the TIBO series including 91 compounds are given as IC(50). Conformational analysis and quantum-chemical calculations are carried out for each TIBO derivatives, and then molecular fragments being specific for active compounds and non-active compounds are revealed by using ETM. In this study, we used optimized geometry data and electronic characteristics to form Electron-Topological Matrices of Contiguity (ETMCs) for all compounds in the series of TIBO derivatives. Effective charges on atoms are taken as diagonal elements, bond characteristics and optimized distances represent non-diagonal elements. To obtain the algorithmic base for the activity prediction, ANNs were used after the ETM (the so-called combined ETM-ANN method). As the result, 6 pharmacophores and anti-pharmacophores were chosen as the most important ones. The statistical coefficients calculated by the proposed algorithm were q(2)=0.82, for training set and q(2)= 0.72, for external test set respectively Thus, the found results showed that ETM-ANNs approach is a good convenient tool for QSAR studies.     

HIV-1 subtype distribution and the problem of drug resistance

Genetic diversity is a hallmark of HIV-1 infection with regard to the expansion of distinct viral subtypes (clades A, B, C, D, E, F, G, K, and O) in different geographical regions. Here, we discuss the issues of HIV-1 sensitivity to antiretroviral drugs and drug resistance in the context of HIV-1 subtype diversity. Virtually all available evidence suggests that all subtypes of HIV display similar sensitivity to antiviral drugs, but viruses from some subtypes or geographical regions may occasionally have a greater propensity to develop resistance against certain drugs than other viral variants. In some situations, the types of mutations associated with resistance may vary, as a result of subtle differences among subtypes with regard to the genetic code. This consideration notwithstanding, drug resistance is unlikely to become a more serious issue in developing than developed countries, and there is an urgency to make anti-HIV drugs available to all who are in need.