Clive Loveday

Antiretroviral Drug Resistance Testing in Adults Infected with Human Immunodeficiency Virus Type 1: 2003 Recommendations of an International AIDS Society-USA Panel

New information about the benefits and limitations of testing for resistance to human immunodeficiency virus (HIV) type 1 (HIV-1) drugs has emerged. The International AIDS Society-USA convened a panel of physicians and scientists with expertise in antiretroviral drug management, HIV-1 drug resistance, and patient care to provide updated recommendations for HIV-1 resistance testing. Published data and presentations at scientific conferences, as well as strength of the evidence, were considered. Properly used resistance testing can improve virological outcome among HIV-infected individuals. Resistance testing is recommended in cases of acute or recent HIV infection, for certain patients who have been infected as long as 2 years or more prior to initiating therapy, in cases of antiretroviral failure, and during pregnancy. Limitations of resistance testing remain, and more study is needed to refine optimal use and interpretation.

Prevalence of Drug-Resistant HIV-1 Variants in Untreated Individuals in Europe: Implications for Clinical Management

BACKGROUND Infection with drug-resistant human immunodeficiency virus type 1 (HIV-1) can impair the response to combination therapy. Widespread transmission of drug-resistant variants has the disturbing potential of limiting future therapy options and affecting the efficacy of postexposure prophylaxis. METHODS We determined the baseline rate of drug resistance in 2208 therapy-naive patients recently and chronically infected with HIV-1 from 19 European countries during 1996-2002. RESULTS In Europe, 1 of 10 antiretroviral-naive patients carried viruses with > or = 1 drug-resistance mutation. Recently infected patients harbored resistant variants more often than did chronically infected patients (13.5% vs. 8.7%; P=.006). Non-B viruses (30%) less frequently carried resistance mutations than did subtype B viruses (4.8% vs. 12.9%; P<.01). Baseline resistance increased over time in newly diagnosed cases of non-B infection: from 2.0% (1/49) in 1996-1998 to 8.2% (16/194) in 2000-2001. CONCLUSIONS Drug-resistant variants are frequently present in both recently and chronically infected therapy-naive patients. Drug-resistant variants are most commonly seen in patients infected with subtype B virus, probably because of longer exposure of these viruses to drugs. However, an increase in baseline resistance in non-B viruses is observed. These data argue for testing all drug-naive patients and are of relevance when guidelines for management of postexposure prophylaxis and first-line therapy are updated.

Reasons for modification and discontinuation of antiretrovirals: results from a single treatment centre.

ObjectiveTo describe the reasons for, and factors associated with, modification and discontinuation of highly active antiretroviral therapy (HAART) regimens at a single clinic. SubjectsA total of 556 patients who started HAART at the Royal Free Hospital were included in analyses. Modification was defined as stopping or switching any antiretrovirals in the regimen, whereas discontinuation was defined as the simultaneous stopping of all antiretrovirals included in the initial regimen. Reasons were classified as immunological/virological failure (IVF) and toxicities and patient choice/poor compliance (TPC). ResultsThe median CD4 count at starting HAART was 171 × 106 cells/l and viral load 5.07 log copies/ml. During a median follow-up of 14.2 months, 247 patients (44.4%) modified their HAART regimen, 72 due to IVF (29.1%) and 159 due to TPC (64.4%) and a total of 148 patients (26.6%) discontinued HAART. Older patients were less likely to modify HAART [relative hazard (RH), 0.73 per 10 years;P = 0.0008], as were previously treatment-naive patients (RH, 0.65;P = 0.0050), those in a clinical trial (RH, 0.64;P = 0.027) and those who started nelfinavir (RH, 0.57;P = 0.035). Patients who started with four or more drugs (RH, 2.21, P < 0.0001), who included ritonavir in the initial regimen (RH, 1.41;P = 0.035) or who had higher viral loads during follow-up (RH per log increase, 1.51;P < 0.0001) were more likely to modify HAART. ConclusionsThere was a high rate of modification and discontinuation of HAART regimens in the first 12 months, particularly due to toxicities, patient choice or poor compliance.

Tracing the HIV-1 subtype B mobility in Europe: a phylogeographic approach

BackgroundThe prevalence and the origin of HIV-1 subtype B, the most prevalent circulating clade among the long-term residents in Europe, have been studied extensively. However the spatial diffusion of the epidemic from the perspective of the virus has not previously been traced.ResultsIn the current study we inferred the migration history of HIV-1 subtype B by way of a phylogeography of viral sequences sampled from 16 European countries and Israel. Migration events were inferred from viral phylogenies by character reconstruction using parsimony. With regard to the spatial dispersal of the HIV subtype B sequences across viral phylogenies, in most of the countries in Europe the epidemic was introduced by multiple sources and subsequently spread within local networks. Poland provides an exception where most of the infections were the result of a single point introduction. According to the significant migratory pathways, we show that there are considerable differences across Europe. Specifically, Greece, Portugal, Serbia and Spain, provide sources shedding HIV-1; Austria, Belgium and Luxembourg, on the other hand, are migratory targets, while for Denmark, Germany, Italy, Israel, Norway, the Netherlands, Sweden, Switzerland and the UK we inferred significant bidirectional migration. For Poland no significant migratory pathways were inferred.ConclusionSubtype B phylogeographies provide a new insight about the geographical distribution of viral lineages, as well as the significant pathways of virus dispersal across Europe, suggesting that intervention strategies should also address tourists, travellers and migrants.

HIV-1 viral load, phenotype, and resistance in a subset of drug-naive participants from the Delta trial

BACKGROUND The Delta trial showed that combination therapy (zidovudine plus didanosine and zidovudine plus zalcitabine) substantially lengthened life and reduced disease progression compared with zidovudine monotherapy. We did a nested virological study in three countries (France, the Netherlands, and the UK) to investigate changes in markers for viral load and antiretroviral-drug resistance during therapy. METHODS 240 zidovudine-naive HIV-1-infected patients were randomly assigned zidovudine only (n = 87), zidovudine plus didanosine (n = 80), or zidovudine plus zalcitabine (n = 73). Viral load in peripheral-blood mononuclear cells and plasma was measured by quantitative culture. Plasma HIV-1 RNA was measured by reverse-transcriptase PCR amplification, and serum p24 antigen by ELISA. Resistance to antiretroviral drugs was measured phenotypically by culture and genotypically by detection and quantification of drug-related point mutations in the pol gene. Analyses were done by intention to treat. FINDINGS The reduction in viral load was greatest 4-12 weeks after the start of therapy and was most pronounced in the combination-therapy study groups (median reductions of RNA at 4 weeks 1.58, 1.28, and 0.49 log10 copies/mL for zidovudine plus didanosine, zidovudine plus zalcitabine, and zidovudine only, respectively). RNA levels at 8 weeks were predictive of disease progression and death after allowance for baseline values. At 48 weeks, the proportion of participants with phenotypic zidovudine resistance was similar in all three groups: didanosine and zalcitabine resistance were rare; zidovudine genomic resistance correlated with phenotypic resistance (r = 0.54, p < 0.0001) and developed earlier in the combined-therapy groups. However, participants in the zidovudine monotherapy group had higher circulating loads of resistant virus than those in the combined-therapy groups. INTERPRETATION Combined antiretroviral therapy was more efficient at lowering virus load than monotherapy. Although zidovudine resistance was common in monotherapy and combined-therapy groups, circulating concentrations of resistant virus were substantially lower in the combination groups, which is likely to be a result of the continued antiviral activity of didanosine or zalcitabine.

Immunological, virological and clinical response to highly active antiretroviral therapy treatment regimens in a complete clinic population

BackgroundHighly active antiretroviral therapy (HAART) is now widely used in clinical practice and gives rise to a range of immunological, virological and clinical responses. ObjectivesTo describe the immunological, virological and clinical response to HAART and to examine the frequency of modification of the HAART regimen among patients from a single treatment centre. MethodsKaplan–Meier estimation and incidence rates were used to describe responses to HAART (a protease inhibitor or non-nucleoside drug in addition to at least two nucleoside analogues) among 421 patients from the Royal Free Hospital in London. ResultsThe median CD4 cell count at starting HAART was 186 × 106 cells/l [interquartile range (IQR) 76–310] and viral load was 5.13 log10 copies/ml (IQR 4.66–5.56). At 6 months after starting HAART, 51.1% of patients were estimated to have experienced a 100 × 106 cells/l increase in CD4 cell count; the median time for viral load to fall below 400 copies/ml was 3.7 months (95% confidence interval 3.2–4.4). At 6 months after the first viral load was < 400 copies/ml, 16.4% of patients were estimated to have failed on the basis of a single viral load > 400 copies/ml and 12.4% were estimated to have failed if the more stringent definition of two viral loads above the limit of detection was used. Compared with the pre-HAART era, the incidence of death among patients on HAART was one sixth of that level; new AIDS-defining illnesses was one seventh; and hospital admissions was one fifth. In total, 141 patients (33.5%) stopped at least one of the antiretroviral agents included as part of their HAART regimen; the occurrence of side effects was the most common reason (n = 63; 44.7%). ConclusionA good response occurred to an initial HAART regimen. There was a high rate of virological relapse, which varied considerably according to the definition of failure used. Even so, the rates of clinical progression and hospital admissions observed to date were low. Further follow-up of these patients is required to determine their long-term immunological, virological and clinical outcome.

Evolution of drug resistance in HIV-infected patients remaining on a virologically failing combination antiretroviral therapy regimen.

Objective: To estimate the extent of drug resistance accumulation in patients kept on a virologically failing regimen and its determinants in the clinical setting. Design: The study focused on 110 patients of EuroSIDA on an unchanged regimen who had two genotypic tests performed at two time points (t0 and t1) when viral load was > 400 copies/ml. Methods: Accumulation of resistance between t0 and t1 was measured using genotypic susceptibility scores (GSS) obtained by counting the total number of active drugs (according to the Rega system v6.4.1) among all licensed antiretrovirals as of 1 January 2006. Patients were grouped according to the number of active drugs in the failing regimen at t0 (GSS_f-t0). Results: At t0, patients had been on the failing combination antiretroviral therapy (cART) for a median of 11 months (range, 6–50 months). Even patients with extensive resistance to the failing regimen were still receiving benefit from treatment. An overall 6-monthly increase of 1.96 (SD, 2.23) International Aids Society-mutations and an average loss of 1.25 (SD, 1.81) active drugs were estimated. In comparison with patients with GSS_f-t0 = 0, the number of active drugs lost was –1.08 [95% confidence interval (CI), –2.13 to –0.03; P = 0.04] in those with GSS_f-t0 of 0.5–1.5 and –1.24 (95% CI, –2.44 to –0.04; P = 0.04) in those with GSS_f-t0 ≥ 2. Conclusions: In patients kept on the same virologically failing cART regimen for a median of 6 months, there was considerable accumulation of drug resistance mutations, particularly in patients with initial low level of resistance to the failing regimen. Randomized comparisons of maintenance treatment strategies while awaiting a new suppressive therapy to become available are warranted.

The Calculated Genetic Barrier for Antiretroviral Drug Resistance Substitutions Is Largely Similar for Different HIV-1 Subtypes

Background: The genetic barrier, defined as the number of mutations required to overcome drug-selective pressure, is an important factor for the development of HIV drug resistance. Because of high variability between subtypes, particular HIV-1 subtypes could have different genetic barriers for drug resistance substitutions. This study compared the genetic barrier between subtypes using some 2000 HIV-1 sequences (>600 of non-B subtype) isolated from anti-retroviral-naive patients in Europe. Methods: The genetic barrier was calculated as the sum of transitions (scored as 1) and/or transversions (2.5) required for evolution to any major drug resistance substitution. In addition, the number of minor protease substitutions was determined for every subtype. Results: Few dissimilarities were found. An increased genetic barrier was calculated for I82A (subtypes C and G), V108I (subtype G), V118I (subtype G), Q151M (subtypes D and F), L210W (subtypes C, F, G, and CRF02_AG), and P225H (subtype A) (P < 0.001 compared with subtype B). A decreased genetic barrier was found for I82T (subtypes C and G) and V106M (subtype C) (P < 0.001 vs subtype B). Conversely, minor protease substitutions differed extensively between subtypes. Conclusions: Based on the calculated genetic barrier, the rate of drug resistance development may be similar for different HIV-1 subtypes. Because of differences in minor protease substitutions, protease inhibitor resistance could be enhanced in particular subtypes once the relevant major substitutions are selected.

Course of viral load throughout HIV-1 infection

Summary: HIV‐1 RNA levels are routinely monitored as part of patient management. However, little is known about the course of HIV‐1 RNA levels over the entire period of infection. The aim of this study was to investigate the course of HIV‐1 RNA levels in a cohort of men with hemophilia who were observed for up to 17 years after HIV‐1 seroconversion, and to assess the risk of HIV disease progression at any HIV‐1 RNA level. Viral loads were measured on annual stored serum samples in 107 men with hemophilia A using the Roche Amplicor Monitor assay with non‐B primers. On average, HIV‐1 RNA levels increased significantly by 0.11 log10 per year over the course of HIV infection. This rate of increase was significantly faster in those who developed AIDS or died over the subsequent 12 to 17 year period, and in those who were older at HIV‐1 seroconversion. The risk of developing AIDS and death remained low when the HIV‐1 RNA level was below 4 log10 copies/ml, but increased rapidly thereafter, supporting current guidelines for the initiation of antiretroviral therapy after the viral load has exceeded this level.

HIV-1 RNA serum-load and resistant viral genotypes during early zidovudine therapy

The response of HIV-1 to initial zidovudine (ZDV) treatment was assessed in 11 patients with severe HIV disease. We quantified serum HIV-1 concentrations and mutations associated with ZDV resistance by culture-independent methods. There was a prompt fall in serum HIV-1 RNA within 1-2 days of treatment with maximum suppression by seven days, which was paralleled by changes in serum p24 antigen (p24 Ag). Serum RNA started to return to pretreatment levels within weeks. The HIV reverse transcriptase (RT) gene in most patients developed mutations associated with drug resistance within months and as early as 25 days on therapy in one patient. The codon changes were not sufficient to explain the early return of serum HIV-1 RNA levels and their patterns continued to evolve after patients stopped taking ZDV. The significance of these findings is discussed in relation to the limited long-term efficacy of ZDV. The dynamic time course of viral load and RT responses to ZDV is of particular importance in short-term interventions such as pregnancy.