The dual role of pharmacogenetics in HIV treatment: mutations and polymorphisms regulating antiretroviral drug resistance and disposition.

Significant intra- and interindividual variability has been observed in response to use of pharmacological agents in treatment of HIV infection. Treatment of HIV infection is limited by high rates of adverse drug reactions and development of resistance in a significant proportion of patients as a result of suboptimal drug concentrations. The efficacy of antiretroviral therapy is challenged by the emergence of resistant HIV-1 mutants with reduced susceptibility to antiretroviral drugs.

Antiviral effect of raltegravir on HTLV-1 carriers.

Background: In vitro studies support that integrase inhibitors, such as raltegravir, may inhibit human T cell lymphotropic virus type 1 (HTLV-1) replication. However, this hypothesis has not been tested in vivo.

Methods: HTLV-1-infected individuals were invited to participate in a pilot, open study that examined whether 400 mg of raltegravir twice daily could exhibit any recognizable virological effect over 12 months.

Transcription of preintegrated HIV-1 cDNA modulates cell surface expression of major histocompatibility complex class I via Nef.

Although transcription from unintegrated human immunodeficiency virus type 1 (HIV-1) DNA can occur inside infected cells, yielding all classes of viral mRNA transcripts, the translation of viral proteins is very limited. One of the proteins made is Nef, but it is unclear whether Nef produced in this way is able to play a role in immune evasion as occurs with integrated virus. We therefore asked whether transcription from preintegrated HIV-1 cDNAs could result in Nef-mediated modulation of cell surface major histocompatibility complex class I (MHC-I) expression.

Tetherin restricts direct cell-to-cell infection of HIV-1.

Background: Tetherin (BST-2/CD317/HM1.24) is an interferon (IFN)-inducible factor of the innate immune system, recently shown to exert antiviral activity against HIV-1 and other enveloped viruses by tethering nascent viral particles to the cell surface, thereby inhibiting viral release. In HIV-1 infection, the viral protein U (Vpu) counteracts this antiviral action by down-modulating tetherin from the cell surface.

Differential impact of the HIV-1 non-nucleoside reverse transcriptase inhibitor mutations K103N and M230L on viral replication and enzyme function.

Objectives: We wished to study the resistance profile of etravirine, a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) active against common human immunodeficiency virus type-1 (HIV-1) drug-resistant strains.

Methods: We compared the effects of K103N, the most prevalent NNRTI resistance mutation, and M230L on enzyme function, virus replication and extent of biochemical inhibition by etravirine, efavirenz and nevirapine.

Results: Growth kinetics analyses in cord blood mononuclear cells (CBMCs) demonstrated that K103N-containing virus replicated as well as wild-type (WT) virus and that the M230L-containing virus was severely impaired in replication ability in the absence of NNRTIs.

HIV-1 subtype B and C integrase enzymes exhibit differential patterns of resistance to integrase inhibitors in biochemical assays.

Background: Because of high intersubtype HIV-1 genetic variability, it has been shown that subtype-specific patterns of resistance to antiretroviral drugs exist. We wished to ascertain whether this might be true for integrase inhibitors.

Methods: We compared the susceptibility of subtype B and C HIV-1 integrase enzymes, harboring the previously reported resistance mutations E92Q, N155H, and E92Q/N155H, to clinically relevant integrase inhibitors.

Identification of novel mutations responsible for resistance to MK-2048, a second-generation HIV-1 integrase inhibitor.

MK-2048 represents a prototype second-generation integrase strand transfer inhibitor (INSTI) developed with the goal of retaining activity against viruses containing mutations associated with resistance to first-generation INSTIs, raltegravir (RAL) and elvitegravir (EVG). Here, we report the identification of mutations (G118R and E138K) which confer resistance to MK-2048 and not to RAL or EVG. These mutations were selected in vitro and confirmed by site-specific mutagenesis.

Expression of Nef from unintegrated HIV-1 DNA downregulates cell surface CXCR4 and CCR5 on T-lymphocytes.

Background: Transcription of HIV-1 cDNA prior to, or in the absence of, integration leads to synthesis of all classes of viral RNA transcripts. Yet only a limited range of viral proteins, including Nef, are translated in this context. Nef expression from unintegrated HIV-1 DNA has been shown to reduce cell surface CD4 levels in T-cells.

The M230L nonnucleoside reverse transcriptase inhibitor resistance mutation in HIV-1 reverse transcriptase impairs enzymatic function and viral replicative capacity.

The M230L mutation in HIV-1 reverse transcriptase (RT) is associated with resistance to first-generation nonnucleoside reverse transcriptase inhibitors (NNRTIs). The present study was designed to determine the effects of M230L on enzyme function, viral replication capacity (RC), and the extent to which M230L might confer resistance to the second-generation NNRTI etravirine (ETR) as well as to the first-generation NNRTIs efavirenz (EFV) and nevirapine (NVP). Phenotyping assays with TZM-bl cells confirmed that M230L conferred various degrees of resistance to each of the NNRTIs tested.

Stage-dependent inhibition of HIV-1 replication by antiretroviral drugs in cell culture.

Recent clinical trials have shown that the use of the HIV-1 integrase (IN) inhibitor raltegravir (RAL) results in drops in the viral load that are more rapid than those achieved by use of the reverse transcriptase (RT) inhibitor efavirenz. Previously, mathematical modeling of viral load decay that takes into account the stage of viral replication targeted by a drug has yielded data that closely approximate the clinical trial results. This model predicts greater inhibition of viral replication by drugs that act later in the viral replication cycle.

Comparative biochemical analysis of HIV-1 subtype B and C integrase enzymes.

Background: Integrase inhibitors are currently being incorporated into highly active antiretroviral therapy (HAART). Due to high HIV variability, integrase inhibitor efficacy must be evaluated against a range of integrase enzymes from different subtypes.

Methods: This study compares the enzymatic activities of HIV-1 integrase from subtypes B and C as well as susceptibility to various integrase inhibitors in vitro.

Human immunodeficiency virus type 1 recombinant reverse transcriptase enzymes containing the G190A and Y181C resistance mutations remain sensitive to etravirine.

Etravirine (ETR) is a second-generation nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI) active against common human immunodeficiency virus type 1 (HIV-1) drug-resistant strains. This study was designed to determine the extent to which each of the Y181C or G190A mutations in RT might confer resistance to ETR and other members of the NNRTI family of drugs. Recombinant HIV-1 RT enzymes containing either the Y181C or the G190A mutation, or both mutations in tandem, were purified.

Group A human rotavirus genomics: evidence that gene constellations are influenced by viral protein interactions.

Group A human rotaviruses (HRVs) are the major cause of severe viral gastroenteritis in infants and young children. To gain insight into the level of genetic variation among HRVs, we determined the genome sequences for 10 strains belonging to different VP7 serotypes (G types). The HRVs chosen for this study, D, DS-1, P, ST3, IAL28, Se584, 69M, WI61, A64, and L26, were isolated from infected persons and adapted to cell culture to use as serotype references.

An ATPase activity associated with the rotavirus phosphoprotein NSP5.

Interactions between NSP5 and NSP2 drive the formation of viroplasms, sites of genome replication and packaging in rotavirus-infected cells. The serine-threonine-rich NSP5 transitions between hypo- and hyper-phosphorylated isomers during the replication cycle. In this study, we determined that purified recombinant NSP5 has a Mg2+-dependent ATP-specific triphosphatase activity that generates free ADP and Pi (Vmax of 19.