Human immunodeficiency virus drug resistance testing: state of the art in genotypic and phenotypic testing of antiretrovirals

A Review of Pediatric Human Immunodeficiency Virus Infection

Human immunodeficiency virus (HIV) affects millions of children worldwide. New pediatric cases are continuing to be diagnosed. However, with the approval and use of various new protocols and antiretroviral agents, transmission rates in perinatally exposed infants have dramatically declined and survival of HIV-infected children has been prolonged. Prevention education is the starting point to try to reduce future transmission; however, increases in HIV cases continue to be seen in the adolescent population. Current pharmacological therapy of HIV includes a multidrug regimen with the potential for numerous drug-drug interactions, adverse effects, and development of resistance. Routine monitoring of adherence is required to try to attain and sustain viral suppression. This review will focus on current treatment recommendations for infants, children, and adolescents infected with HIV, including newly approved agents in 2003. Pediatric considerations, including differences in diagnosis and monitoring, will also be discussed.

Evaluation of the editing process in human immunodeficiency virus type 1 genotyping

Sequencing-based human immunodeficiency virus type 1 (HIV-1) genotyping assays require subjective interpretation (editing) of sequence data from multiple primers to form consensus sequences and identify antiretroviral drug resistance mutations. We assessed interlaboratory variations in editing and their impact on the recognition of resistance mutations. Six samples were analyzed in a central laboratory by using a research-use-only HIV-1 genotyping system previously produced by Applied Biosystems. The electronic files of individual primer sequences from the samples were sent to 10 laboratories to compare sequence editing strategies. Each sequence data set included sequences from seven primers spanning protease codons 1 to 99 and reverse transcriptase codons 1 to 320. Each laboratory generated a consensus sequence for each sample and completed a questionnaire about editing strategy. The amount of editing performed, the concordance of consensus sequences among the laboratories, and the identification of resistance mutations were evaluated. Sequence agreement was high among the laboratories despite wide variations in editing strategies. All laboratories identified 66 (88%) of 75 resistance mutations in the samples. Nonconcordant identifications were made for 9 (12%) of the 75 mutations, all of which required editing for identification. These results indicate a need for standardized editing guidelines in genotyping assays. Proficiency in editing should be assessed in training and included in quality control programs for HIV-1 genotyping.

Role of therapeutic drug monitoring for protease inhibitors

OBJECTIVE

To review the role of therapeutic drug monitoring (TDM) for protease inhibitors in the treatment of HIV infection.

DATA SOURCES

Primary articles were identified using MEDLINE (1966-October 2000), EMBASE (1987-October 2000), AIDSLINE (1980-October 2000), Current Contents, PubMed, and Medscape. Further articles were identified from bibliographic review of primary articles and review papers. Abstracts presented at the World AIDS Conference, Interscience Conference on Antimicrobial Agents and Chemotherapy, and Conference on Retroviruses and Opportunistic Infections were also identified from 1997 to 2000.

STUDY SELECTION AND DATA EXTRACTION

All English-language, prospective clinical trials, as well as selected retrospective studies and case series, pertaining to therapeutic drug monitoring of protease inhibitors were included.

DATA SYNTHESIS

A number of clinical studies have found a good relationship between concentration and pharmacologic response and/or toxicity as well as wide interpatient variability in the pharmacokinetics of protease inhibitors. There also is some preliminary evidence of the usefulness of plasma drug concentrations to guide dosage adjustments of protease inhibitors in patients with liver dysfunction. Furthermore, there is preliminary evidence of a relationship between drug concentrations and resistance.

CONCLUSIONS

A number of clinical studies support the usefulness of TDM of protease inhibitors. However, before TDM can be of the most value, further evaluation requires simplified and standardized assays to be performed routinely by clinical laboratories; determination of the appropriate target concentration and therapeutic range, as well as the best predictor of pharmacologic response; and refined interpretation of plasma drug concentrations. Randomized, controlled clinical trials of patient outcomes are needed to assess the clinical utility of TDM for protease inhibitors.

Mutation takes no vacation: can structured treatment interruptions increase the risk of drug-resistant HIV-1?

We use a mathematical model to study the dynamics of HIV-1 replication during structured treatment interruptions (STIs) in infected patients. The model predicts rapid viral rebound, restoration of a latently infected cell pool, and critically, partially resistant mutant rebound that may be missed because of high levels of wild type virus. Because partially resistant viruses are capable of mutating to full resistance, a substantial increase in their numbers represents a threat to therapeutic response durability. Compared with continued treatment, STIs may increase the chance of mutation to full resistance by several thousandfold.