Antiretroviral Drug Resistance in HIV-1

Fluorometric assay for phenotypic differentiation of drug-resistant HIV mutants

Convenient drug-resistance testing of viral mutants is indispensable to effective treatment of viral infection. We developed a novel fluorometric assay for phenotypic differentiation of drug-resistant mutants of human immunodeficiency virus-I protease (HIV-PR) which uses enzymatic and peptide-specific fluorescence (FL) reactions and high-performance liquid chromatography (HPLC) of three HIV-PR substrates. This assay protocol enables use of non-purified enzyme sources and multiple substrates for the enzymatic reaction. In this study, susceptibility of HIV mutations to drugs was evaluated by selective formation of three FL products after the enzymatic HIV-PR reaction. This proof-of-concept study indicates that the present HPLC-FL method could be an alternative to current phenotypic assays for the evaluation of HIV drug resistance.

Primary resistance of human immunodeficiency virus type 1 in a reference center in Recife, Pernambuco, Brazil

To assess the prevalence of primary resistance of human immunodeficiency virus type 1 (HIV-1) to antiretrovirals, 84 patients chronically infected with HIV without prior antiretroviral treatment from Northeast Brazil were studied. Genotyping was performed using the ViroSeq Genotyping System. Thimidine analog mutations occurred in 3 (3.6%) patients. Accessory mutations related to NRTI occurred in 6 (7.1%) and related to PI in 67 (79.8%). Subtypes B (72.6%), F (22.6%), B/F 3 (3.6%), and C (1.2%) were detected. A low prevalence of major mutations related to NRTI in patients chronically infected by HIV was observed.

Therapeutic responses to AZT + 3TC + EFV in advanced antiretroviral naive HIV type 1-infected Ugandan patients

Convenient, non-food-dependent dosing, low tablet volume, and relatively low cost have made nonnucleoside reverse transcriptase inhibitors a first choice for both clinicians and patients in Uganda. Concerns exist as to their efficacy in patients with viral loads (VL) above 100,000 copies/ml, a feature common to about 75% of HIV-1-infected patients presenting at the Joint Clinical Research Center (JCRC) in Uganda. Furthermore, there are few data on the response to such therapy of non-B subtypes, A and D, predominant in Uganda. Presented here is a retrospective analysis of therapeutic responses in 11 antiretroviral (ARV) naïve HIV-1-infected Ugandan patients who had been initiated on zidovudine (AZT), lamivudine (3TC), and efavirenz (EFV). Laboratory assessments subsequent to initiation of ARV therapy, done at 11.6 +/- 3.9 weeks and 30.6 +/- 5.9 weeks, showed 88.9 and 71.4% patients achieved undetectable viral load, respectively. Virological suppression to below detection occurred in 85.7% of patients at 11.6 weeks despite baseline VL >or= 100,000 copies/ml. At 31 weeks there was a median increment of +183 cells/mm(3) in CD4(+) T lymphocytes. These findings reflect significant efficacy in the use of AZT + 3TC + EFV in advanced ARV naive non-B subtype HIV-1-infected patients. The therapeutic responses were comparable to those previously described in the western world.

Antiretroviral drug resistance mutations in antiretroviral-naive prisoners

We assessed the incidence of antiretroviral drug resistance in a cohort of 25 antiretroviral-naive, human immunodeficiency virus-positive inmates in Massachusetts. Silent mutations, unexpected mutations at resistant sites, and resistance mutations were recorded. Among these inmates, we found a prevalence of drug resistance mutations that was equivalent to the prevalence previously found in nonprison populations in the same state.

HIV-1 genotypic and phenotypic resistance

Antiretroviral failure caused by the development of drug resistance in HIV-1 is an increasingly common clinical problem. Two types of resistance assays are available to clinicians. Genotypic assays determine the presence of mutations associated with drug resistance. The interpretation of mutations is often complicated, however, and may require expert opinion. Phenotypic assays provide a direct measure of the drug susceptibility of the virus. The magnitude of increase, however, in viral drug inhibitory concentration that is predictive of clinical drug failure remains unknown for several antiretroviral drugs. The mutational patterns underlying resistance to each antiretroviral drug are often diverse, and cross-resistance patterns within each of the currently available classes are complex. Currently, resistance testing is recommended for patients who have virologic failure on an antiretroviral regimen. Furthermore, testing should also be considered in treatment-native patients when the prevalence of transmitted drug-resistant virus is expected to be high.

Extent of cross-resistance between agents used to treat human immunodeficiency virus type 1 infection in clinically derived isolates

The phenomenon of cross-resistance to antiretroviral agents used to treat human immunodeficiency virus type 1 infection is well known but so far has been only qualitatively described. Here, we quantitate the degree of cross-resistance among all commonly prescribed antiretroviral agents in almost 5,000 clinically derived recombinant isolates collected in the United States since January 2000.

Adherence to antiretroviral therapy and its association with sexual behavior in a national sample of women with human immunodeficiency virus

To delineate the relationship between adherence to human immunodeficiency virus (HIV) therapy and sexual behavior among HIV type 1-infected women in the United States, data were collected from October 1998 through March 1999 from 766 HIV-positive women on adherence to therapy, risk behavior, and disease markers. Adherence rates of >/=95% were reported by 66% of the patients. In multivariate analyses, patients with lower rates of adherence tended to be younger (odds ratio [OR], 1.69), to be active drug users (OR, 2.27), to have detectable virus load levels (OR, 2.00), and to have a lower quality of life (OR, 1.20). Among sexually active women, lower adherence rates were associated with an increased risk for inconsistent condom use (adjusted OR, 2.17). Although counseling regarding sexual behavior and adherence to treatment regimens are often addressed separately, our data highlight the importance of discussing these factors in relation to one another, particularly with regard to patients experiencing virologic failure.

Smaller amounts of antiretroviral drugs are needed when combined with an active ribozyme against HIV-1

We have tested for combined anti-HIV-1 effects of a hammerhead ribozyme and antiretroviral drugs and the possibility of reducing the drug burden of patients on highly active antiretroviral therapy (HAART). The antiretroviral compounds used represent the three groups in HAART: nucleoside analogue reverse-transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, and protease inhibitors. A human T cell line (HUT78), stably expressing a hammerhead ribozyme targeted to nef (hhRz.nef(9016-9029)), was infected with HIV-1(SF2) in the presence of a single drug. The combined effects on HIV-1 replication were measured by p24 antigen determinations over a 2-week period. In the presence of the ribozyme, smaller amounts of antiretroviral drugs were required to reduce the HIV-1 p24 levels equally as much as when only drugs were present. The results support a strategy of combining ribozyme gene therapy with HAART to improve the long-term outcome of anti-HIV-1 therapy.

Clinical use of genotypic and phenotypic drug resistance testing to monitor antiretroviral chemotherapy

Assays that detect antiretroviral drug resistance in human immunodeficiency virus have recently become available to clinicians. Phenotypic assays measure the drug susceptibility of the virus by determining the concentration of drug that inhibits viral replication in tissue culture. Genotypic assays determine the presence of mutations that are known to confer decreased drug susceptibility. Although each type of assay has specific advantages, limitations associated with these tests often complicate the interpretation of results. Several retrospective clinical trials have suggested that resistance testing may be useful in the assessment of the success of salvage antiretroviral therapy. Prospective, controlled trials have demonstrated that resistance testing improves short-term virological response. Resistance testing is currently recommended to help guide the choice of new drugs for patients after treatment has failed and for pregnant women. Resistance testing should also be considered for treatment-naïve patients, to detect transmission of resistant virus.

Antiretroviral therapy 2000

As we enter the new millennium, there have been dramatic improvements in the care of patients with HIV infection. These have prolonged life and decreased morbidity and mortality. There are fourteen currently available antiretrovirals approved in the United States for the treatment of this infection. The medications, including their pharmacokinetic properties, side effects, and dosing are reviewed. In addition, the current approach to the use of these medicines is discussed.

Comparative analysis of HIV type 1 genotypic resistance across antiretroviral trial treatment regimens

From data on HIV-1 genotypes collected from antiretroviral trial participants who fail virologically, we describe methods for comparing distributions of acquired HIV-1 mutations across different treatment regimens. Given a definition of a "mutational distance" that summarizes the genetic change of a subject's virus in a way that captures the resistance cost of exposure to an antiretroviral regimen, these comparative analyses inform about the relative treatability of emergent virus by next-line therapy directed to the same viral target. The utility of the methods is illustrated by application to data from AIDS Clinical Trials Group (ACTG) Study 241. We find that patients failing zidovudine/didanosine/nevirapine accumulated a 2.41-fold greater nonnucleoside reverse transcriptase inhibitor (RTI) mutational distance than patients failing zidovudine/didanosine [95% confidence interval (1.55, 5.26), p < 0.000001], quantitating expectations that adding a nonnucleoside RTI to a double nucleoside regimen may attenuate future effectiveness of nonnucleoside RTI therapy for nucleoside-experienced patients if viremia is not suppressed. We also find that persons with extensive prior experience with suboptimal nucleoside therapy who were virologically failing zidovudine/didanosine/nevirapine or zidovudine/didanosine accumulated a similar nucleoside RTI mutational distance, implying that the addition of the nonnucleoside RTI did not preserve future nucleoside options.