Transmission of HIV-1 drug resistance.

BACKGROUND: The use of highly-active anti-retroviral therapy (HAART) for treating HIV infections is increasing. Recent studies have demonstrated that HAART is improving both the length and quality of life in HIV-infected patients. Resistant strains of HIV arise when drug adherence is poor. This can lead to the transmission of drug-resistant strains of HIV to susceptible individuals. This can lead to suboptimal first-line therapy, if the resistance profile of the transmitted virus is unknown. OBJECTIVES: To review the mechanisms of how drug resistance arises; the methods used to characterise drug resistance; the problems arising with compliance leading to the development of drug-resistant HIV strains; the evidence for the incidence, prevalence and trends in the transmission of resistant HIV strains in different risk groups; and the evidence of suboptimal response to first-line therapy where transmission of a resistant HIV strain has occurred. On the basis of this, a case is presented for the routine resistance testing of all newly diagnosed HIV-infected individuals. STUDY DESIGN: Literature review. RESULTS AND CONCLUSIONS: There is evidence, though limited at present, that transmission of drug-resistant HIV strains can lead to suboptimal response to first-line therapy in newly diagnosed HIV-infected individuals. As the use of HAART can only increase in the future, and compliance will always be a problem in such HAART-treated patients, baseline resistance testing should become a routine part of their management.     

Different outcomes in patients achieving complete or partial viral load suppression on antiretroviral therapy

BACKGROUND: Potent combination antiretroviral therapy can reduce HIV plasma viral load (VL) to levels below the detection limit for as long as 2 years or more. A VL <500 HIV RNA copies/mL was until recently considered a reasonable therapeutic goal. However, lower levels seem necessary if VL rebounds and development of drug resistance are to be avoided. PATIENTS AND METHODS: The clinical and virologic outcome at 1 year were prospectively examined in a group of 100 patients who began a triple combination antiretroviral therapy regimen consisting of stavudine (d4T), lamivudine (3TC), and indinavir (IDV). A modified ultrasensitive VL test with a detection limit of 40 copies/mL and a point mutation nested polymerase chain reaction (PCR) assay for detecting the codon 184 mutation conferring 3TC resistance were used for testing samples collected longitudinally from these individuals. RESULTS: Overall, VL values <40 copies/mL were reached in 45% and 32% of patients at nadir and at 12 months, respectively. More than half (24 of 45 persons) who achieved a level <40 copies/mL at nadir remained with undetectable VL at 1 year, whereas this occurred in only one fourth (7 of 28 persons) of those having levels of 40 to 500 copies/mL (P < .05). However, rebounds in VL to >500 copies/mL at 1 year were seen at similar rates (26.6% and 25%, respectively) in persons achieving either complete (<40 copies/mL) or partial (40-500 copies/mL) VL suppression at nadir. In contrast, the codon 184 mutation emerged more frequently at 1 year in patients whose VL remained between 40 and 500 copies/mL at nadir than in those who reached a level <40 copies/mL (30.7% versus 0%; P < .05). CONCLUSION: Plasma VL at nadir after beginning highly active antiretroviral therapy (HAART) predicts the 1-year outcome. The achievement of levels of viremia <40 copies/mL are desirable during antiretroviral therapy if prolonged benefit is to be obtained. Because more than two thirds of persons with residual viremia do not show drug resistance, intensification strategies should be investigated for those patients with a good virologic response but without complete suppression during the first 6 months on HAART.     

Real versus virtual phenotype to guide treatment in heavily pretreated patients: 48-week follow-up of the Genotipo-Fenotipo di Resistenza (GenPheRex) trial

We compared viroimmunologic response after real phenotype (r-PHT) versus virtual phenotype (v-PHT) in patients failing highly active antiretroviral therapy (HAART). A total of 201 patients with >2 years of exposure, more than six experienced drugs, >1000 HIV RNA copies/mL, and on stable HAART for >6 months were randomized to the r-PHT or v-PHT arm. The primary end point was the proportion of HIV plasma viral load (pVL) <400 copies/mL. Secondary end points were absolute pVL change, proportion of pVL reduction >0.5 log(10) copies/mL, and absolute CD4 cell change. In the intention-to-treat-last observation carried forward analysis, study outcomes were not significantly different between arms over 48 weeks of follow-up: 20% and 24% pVL <400 copies/mL; 58% and 61% pVL reduction >0.5 log(10) copies/mL; -0.92 and -0.94(10) log copies/mL mean pVL decrease; and +41.6 and +94.4 cells/mm(3) mean absolute CD4 increase in the r-PHT and v-PHT arms, respectively. On-treatment analyses gave similar results. In the multivariate analysis of pVL <400 copies/mL, the following covariates were independent predictors at week 48: adherence (OR p= 0.25; p=.002), baseline CD4 (OR = 4.39; p=.007), intravenous drug use as risk factor for HIV acquisition (OR = 0.33; p=.024), and sensitivity score of the new regimens by biologic cut-offs (OR = 1.84; p=.029). Prescribed drugs for which patients were naive resulted in marginal prediction (OR = 1.93; p=.054). In conclusion, virologic and immunologic outcomes did not differ when r-PHT or v-PHT was used in this cohort of heavily pretreated patients. Several factors should be considered to take better advantage of resistance testing, including treatment history, clinical status, and patients' ability to adhere to treatment.     

Mortality in patients with successful initial response to highly active antiretroviral therapy is still higher than in non-HIV-infected individuals

Mortality in HIV-infected patients has decreased dramatically since the introduction of highly active antiretroviral therapy (HAART). We analyzed progression to death in a population of 3678 antiretroviral treatment-naive patients from the ATHENA national observational cohort from 24 weeks after the start of HAART. Mortality was compared with that in the general population in the Netherlands matched by age and gender. Only log-transformed CD4 cell count (hazard ratio [HR] = 0.50, 95% confidence interval [CI]: 0.40 to 0.61 per unit increase) and plasma viral load (HR = 0.30, 95% CI: 0.15 to 0.60, HIV RNA level <100,000 vs. > or = 100,000 copies/mL) measured at 24 weeks and infection via intravenous drug use (IDU) (HR = 0.16, 95% CI: 0.10 to 0.26, non-IDU vs. IDU) were significantly associated with progression to death. For non-IDU patients with 600 x 10 CD4 cells/L and an HIV RNA level <100,000 copies/mL at 24 weeks, mortality was predicted to be 5.3 (95% CI: 3.5 to 8.4) and 10.4 (95% CI: 6.4 to 17.4) times higher than in the general population for 25-year-old men and women, respectively, and 1.15 (95% CI: 1.08 to 1.25) and 1.29 (95% CI: 1.16 to 1.50) times higher for 65-year-old men and women, respectively. Hence, mortality in HIV-infected patients with a good initial response to HAART is still higher than in the general population.     

A randomized controlled trial of the value of phenotypic testing in addition to genotypic testing for HIV drug resistance: evaluation of resistance assays (ERA) trial investigators

OBJECTIVES: To assess the clinical utility of phenotypic resistance testing in addition to genotypic resistance testing among HIV-1-infected patients experiencing virologic failure and with limited therapeutic options. DESIGN: Multicenter randomized trial. METHODS: Patients were eligible if a decision had been made to switch antiretroviral therapy, the most recent HIV-1 RNA plasma viral load (VL) exceeded 2000 copies/mL, and the clinician was unable to select a potent regimen of 3 or more drugs without access to a resistance test. Subjects were randomized to genotypic resistance testing alone (G arm) or to genotypic plus phenotypic testing (G + P arm). Patients had access to resistance testing at any time during follow-up (minimum of 1 year) according to the original allocation. The primary end point was change in plasma VL from baseline at 12 months. RESULTS: Three hundred eleven patients were recruited between February 2000 and July 2001. At baseline, mean VL and CD4 count were 4.23 log10 copies/mL and 275 cells/mm, respectively, and subjects had previous exposure to a mean of 7.7 antiretroviral drugs. There was no appreciable difference between the study arms in the drug regimens prescribed after randomization. Mean reduction in VL load at 12 months was similar in the 2 arms (G: 1.37 log10 reduction, G + P: 1.28 log10 reduction; P = 0.77), as was the proportion of subjects with VL <50 copies/mL (G: 35%, G + P: 27%). CONCLUSION: The study did not demonstrate added value of phenotypic resistance testing in conjunction with genotypic resistance testing in patients with limited therapeutic options.     

HIV-1蛋白酶和逆转录酶抗药基因变异检测方法的建立及临床应用

目的 应用现有ＤＮＡ序列分析技术对人类免疫缺陷病毒１型（ＨＩＶ－１）的蛋白酶（ＰＲ）和逆转录酶（ＲＴ）基因进行简便、快速、准确的序列分析,在临床上为ＨＩＶ－１患者治疗方案的确定提供可靠依据。方法 从ＨＩＶ－１感染者血清中提取ＲＮＡ,用套管式逆转录－聚合酶链反应（ＲＴ－ＰＣＲ）扩增ＨＩＶ－１的ＰＲ和ＲＴ基因片段,并对此片段进行核苷酸序列分析。结果 本方法对血清中ＨＩＶ－１ＲＮＡ含量约２０００拷贝／ｍｌ以上的样品都能有效扩增。在序列分析时背景干扰少,对２５％左右的混合序列均能准确反映。通过对临床治疗病人进行动态序列分析观察,发现在药物治疗过程中,病人血浆中ＨＩＶ－１ＲＮＡ含量变化与ＰＲ和ＲＴ基因抗药性变异具有很大相关性。结论 ＰＲ和ＲＴ基因序列分析方法能够及时、准确地反映ＨＩＶ－１患者在抗病毒药物治疗过程中病毒的变     

Causes and Consequences of Incomplete HIV RNA Suppression in Clinical Trials

Abstract

The current goal of antiretroviral treatment is suppression of HIV RNA below 50 copies/mL. However, there is evidence for residual low-level plasma viraemia below 50 copies/mL for people with HIV RNA suppression on antiretroviral treatment. It is not clear whether more profound suppression of HIV RNA would lead to a lower risk of virological failure on antiretroviral treatment or emergent drug resistance. There is high variability in the currently used HIV RNA PCR assays for samples with HIV RNA levels close to the detection lower limit of 40–50 copies/mL. For patients who have HIV RNA levels just above 50 copies/mL (often called “single blips”), a repeat sample should be taken to investigate the possibility of technical error. In a systematic review of 48-week effi cacy from randomized clinical trials (N = 8,083), patients were signifi cantly more likely to show HIV RNA levels between 50–400 copies/mL while taking fi rst-line boosted PI-based HAART (7.3%) compared with fi rst-line NNRTI-based HAART (4.5%) (p < 0.01). However in a systematic review of emergent drug resistance at failure in the same trials, there was also a signifi cantly lower risk of emerging drug resistance after virological failure of boosted PI-based HAART (p < 0.01). Therefore, HIV RNA blips between 50–400 copies/mL may have different consequences for different classes of antiretrovirals. The most widely used method to analyse HIV RNA in clinical trials — time to loss of virological response (TLOVR) — uses two consecutive HIV RNA measurements to define both virological success and failure. However, other methods may improve precision and increase statistical power.     

Intermittent viremia during first-line, protease inhibitors-containing therapy: significance and relationship with drug resistance.

BACKGROUND: In HIV-infected patients on first-line antiretroviral therapy, the significance of intermittent viremia and their relationship with drug resistance remain unclear. OBJECTIVE: To study the virological characteristics of intermittent viremia (IV) and the association between IV and later virological failure (VF) in patients on a first-line, PI-containing therapy. STUDY DESIGN: Antiretroviral-naive patients were enrolled in the APROVIR substudy of the prospective, multicenter APROCO cohort at the time they initiated a PI-containing therapy and were followed-up at month 1 and every 2 months. IV was defined as plasma HIV-1 RNA > 500 copies/ml on a single specimen. VF were defined as: (1) viral rebound on two consecutive plasma specimens with HIV-1 RNA > 500 copies/ml after an initial response below 500 copies/ml, or (2) persistence of plasma HIV-1 RNA> or =500 copies/ml during the first year of follow-up. Genotypic resistance analysis was performed at baseline and at the time of IV. PI plasma concentrations were determined at the time of IV. RESULTS: IV was found in 20/219 patients in a 2 years follow-up. The occurrence of IV in the first year of therapy was associated with a higher risk of virological failure during the second year (p = 0.03). Genotypic resistance at the time of IV was found in only 4/16 patients and was not predictive of a subsequent virological failure. PI plasma levels suggested lack of adherence in 50% of patients with IV. CONCLUSION: The occurrence of IV > 500 copies/ml among patients on first-line, PI-containing ART is suggestive of a lack of adherence rather than the selection of resistant variants and should lead to an intensification of adherence monitoring in order to reduce the risk of subsequent VF.     

Structured treatment interruptions in primary HIV-1 infection: the ANRS 100 PRIMSTOP trial

BACKGROUND: Whether structured treatment interruptions (STIs) can induce anti-HIV immune response and control HIV replication following discontinuation of highly active antiretroviral therapy (HAART) in patients with primary HIV infection is controversial. METHODS: In this multicenter, prospective trial, patients with early symptomatic primary HIV infection were given HAART continuously for 34 weeks. Afterward, patients with plasma viral load (PVL) <50 copies/mL entered the STI phase, which consisted of 3 consecutive periods of 2, 4, and 8 weeks off HAART, each separated by 12 weeks on HAART. HAART was permanently stopped at week 84 and patients were followed up for 24 weeks. The primary endpoint for definition of virologic success was a PVL <50 copies/mL during the 6 months following HAART discontinuation. RESULTS: Of the 29 patients enrolled, 26 completed the trial. Six months after HAART discontinuation, only 1 patient (3.8%, 95% CI: 0.1% to 19.6%) had PVL <50 copies/mL, whereas 6 of 26 (23.1%, 95% CI: 9.0% to 43.7%) had PVL <1000 copies/mL. Female gender was the only parameter significantly associated with a PVL <1000 copies/mL. No other parameter, either at baseline or before HAART discontinuation, predicted virologic success at week 108. A major protease inhibitor resistance mutation (L90M) developed in 3 patients. CONCLUSIONS: This trial failed to confirm that a significant proportion of patients with primary HIV infection can maintain suppression of viremia after a sequence of HAART/STIs followed by HAART discontinuation.     

Initial response to highly active antiretroviral therapy in HIV-1C-infected adults in a public sector treatment program in Botswana

OBJECTIVE: To describe the response to highly active antiretroviral treatment (HAART) in a public sector pilot antiretroviral (ARV) treatment program in Botswana. METHODS: The response to HAART is described in adult HIV-infected ARV-naive patients initiating treatment from April 2001 to January 2002 at Princess Marina Hospital in Gaborone, Botswana. Patients had medical and laboratory evaluations before initiating ARV treatment and were followed longitudinally. For analysis, data were collected from charts and patient management records. RESULTS: One hundred fifty-three ARV-naive patients initiated HAART. Most received didanosine plus stavudine (ddI + d4T) with efavirenz or nevirapine. The mean CD4 cell count increase was 149 cells/mm at 24 weeks and 204 cells/mm at 48 weeks. The percentage of patients with an HIV-1 RNA level < or =400 copies/mL was 87.0% at 24 weeks and 78.8% at 48 weeks. The Kaplan-Meier 1-year survival estimate was 84.7% (79.0%, 90.8%), with a 3.2-fold increased risk (P = 0.004) of mortality among patients with a CD4 cell count <50 cells/mm. The 1-year Kaplan-Meier estimate of toxicity-related drug switches was 32.2% (20.3%, 40.4%). The most common toxicity was peripheral neuropathy, occurring more frequently in patients with a preexisting diagnosis of peripheral neuropathy and among those placed on ddI + d4T-containing regimens. CONCLUSIONS: An excellent response to HAART was observed among HIV-1C-infected patients, paralleling those seen elsewhere. Despite excellent responses, high rates of toxicity were observed for ddI + d4T-containing regimens.     

Why are baseline HIV RNA levels 100,000 copies/mL or greater associated with mortality after the initiation of antiretroviral therapy?

BACKGROUND: There is conflicting evidence regarding the impact of baseline plasma HIV RNA on virologic responses after the initiation of triple-drug antiretroviral therapy (highly active antiretroviral therapy [HAART]). This has made it difficult to interpret the recently reported association between baseline plasma HIV RNA and mortality. We evaluated whether baseline CD4 cell count and plasma HIV RNA predicted virologic suppression (<500 copies/mL) and rebound (> or =500 copies/mL) among adherent HIV-infected patients. METHODS: Antiretroviral-naive HIV-infected patients were stratified by baseline CD4 cell count, plasma HIV RNA, and adherence level. Cox and logistic regression were used to evaluate the time to suppression and rebound and the odds of ever achieving HIV RNA suppression. RESULTS: A total of 1422 individuals initiated HAART between August 1, 1996 and July 31, 2000 and were followed to March 31, 2002. Adherent patients with HIV RNA levels > or =100,000 copies/mL and 50 to 99,999 copies/mL were slower to suppress HIV RNA than patients with baseline HIV RNA <50,000 copies/mL in Kaplan-Meier analyses. Although the odds of RNA suppression among adherent patients with baseline RNA levels <50,000 copies/mL and 50 to 99,999 copies/mL were similar (P = 0.197), patients with baseline HIV RNA > or =100,000 copies/mL were markedly less likely ever to achieve suppression during follow-up (adjusted odds ratio: 0.27 [95% confidence interval: 0.13-0.54]; P < 0.001). No differences in the rate of virologic rebound were observed between adherent patients in the various baseline HIV RNA strata, and CD4 cell count was not associated with suppression or rebound. CONCLUSIONS: Baseline HIV RNA > or =100,000 copies/mL was associated with a significantly lower likelihood of ever achieving HIV RNA suppression during follow-up. These findings likely explain the association between baseline HIV RNA levels and mortality and have important implications for the development of therapeutic guidelines.     

Virologic rebound on HAART in the context of low treatment adherence is associated with a low prevalence of antiretroviral drug resistance

The contributions of viral drug resistance, drug pharmacokinetics, and treatment adherence to failure of protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) have been explored in isolation. We examined the interactions between these factors. Patients on their first PI-based HAART combination for >6 months with plasma HIV viral load (VL) >1000 copies/mL ("viremic" group) were compared with patients with a stable VL <50 copies/mL ("nonviremic" group). Data were collected on adherence (measured electronically), PI plasma levels (sampled randomly, at trough and twice after an observed dose), viral genotype, and phenotype. Mean adherence was significantly lower in the viremic group (84.3% versus 100.1%; p =.005). In the viremic group, substitutions in HIV protease were detected most frequently in the following positions in subjects on indinavir (IDV): L10I/V (35.7%), M46I/L (35.7%), A71T/V (35.7%), V82A (42.9%); and for subjects on nelfinavir (NFV): D30N (50.0%), V77I (56.3%), N88D (37.5%). Phenotypic resistance was detected in 20% of isolates from patients on IDV and 42% on NFV. Lower adherence was associated with detection of fewer resistance substitutions (r = 0.52; p =.005) and less phenotypic resistance (rho = 0.56, p =.005). There were no differences between the groups in pharmacokinetics. However, in viremic subjects, lower postdose NFV levels were associated with higher resistance (rho = -0.61, p =.02).     

HIV-infected patients receiving lopinavir/ritonavir-based antiretroviral therapy achieve high rates of virologic suppression despite adherence rates less than 95%

BACKGROUND: The observation that extremely high levels of medication adherence are required to achieve complete virologic suppression is based largely on studies of treatment-experienced patients receiving HIV protease inhibitor (PI)-based therapy without ritonavir boosting. This study aims to define the level of adherence needed to achieve virologic suppression in patients receiving boosted PI-based highly active antiretroviral therapy (HAART) with lopinavir/ritonavir. METHODS: HIV-infected adults receiving a regimen containing lopinavir/ritonavir were recruited into a prospective, observational study of the relation between adherence to lopinavir/ritonavir and virologic outcomes. Adherence was measured using the Medication Event Monitoring System (MEMS; Aardex, Union City, CA). HIV-1 viral load (VL) was measured at week 24. RESULTS: The final study population contained 64 subjects. Eighty percent had AIDS, 97% received lopinavir/ritonavir before enrollment, and most had more than 7 years of HAART experience. Mean adherence overall was 73%. Eighty percent and 59% achieved a VL <400 copies/mL and a VL <75 copies/mL, respectively. Mean adherence was 75% in those achieving a VL <75 copies/mL. High rates of virologic suppression were observed in all adherence quartiles, including the lowest quartile (range of adherence: 23.5%-53.3%). CONCLUSIONS: Moderate levels of adherence can lead to virologic suppression in most patients taking lopinavir/ritonavir-based HAART.     

Gender differences in HIV-1 RNA rebound attributed to incomplete antiretroviral adherence among HIV-Infected patients in a population-based cohort

BACKGROUND: There have been growing concerns about possible gender-related differences in rates of responses to highly active antiretroviral therapy (HAART). We therefore examined the association between gender and time to HIV-1 RNA rebound in antiretroviral-naive HIV-infected patients initiating HAART in a population-based setting. METHODS: We evaluated all antiretroviral-naive HIV-infected men and women who achieved HIV-1 RNA suppression at least once (HIV RNA <500 copies/mL) after initiating HAART between August 1, 1996 and July 31, 2000 and who were followed until March 31, 2002 in a province-wide HIV treatment program. We evaluated time to HIV-1 RNA rebound (> or =500 copies/mL) using Kaplan-Meier methods and Cox proportional hazards regression. RESULTS: In total, 844 (87.0%) men and 126 (13.0%) women initiated HAART during the study period and achieved HIV-1 RNA suppression at least once. Overall rates of rebound were 47.4% and 34.0% for women and men, respectively (log-rank, P < 0.021). Women were less likely to be > or =95% adherent (P = 0.001) and more likely to have a history of injection drug use (P = 0.001). In multivariate analysis, incomplete adherence was found to be highly predictive of HIV-1 RNA rebound (adjusted relative hazard [ARH] = 4.00, 95% confidence interval [CI]: 3.33-5.00). Although female patients had higher rates of HIV-1 RNA rebound in univariate analysis (relative hazard [RH] = 1.39, 95% CI: 1.05-1.82), this was no longer statistically significant once other known confounders such as adherence and injection drug use were adjusted for (RH = 0.95, 95% CI: 0.71-1.28). When the analyses were stratified based on history of injection drug use, we found that rates of rebound were higher among injection drug-using women than among injection drug-using men (P = 0.048), whereas there was no gender difference among non-injection drug users with respect to rebound (P = 0.345). CONCLUSIONS: We found that higher rates of HIV-1 RNA rebound among women were primarily explained by incomplete adherence, which was more prevalent among women in this cohort. Our findings suggest that psychosocial factors such as drug use and incomplete adherence predict HIV-1 RNA rebound and that gender differences in time to rebound can be largely attributed to a disproportionate prevalence of these factors among women in this population.     

In vivo emergence of drug-resistant mutations at less than 50 HIV-1 RNA copies/mL that are maintained at viral rebound in longitudinal plasma samples from human immunodeficiency virus type-1-infected patients on highly active antiretroviral therapy

OBJECTIVE: Emergence of human immunodeficiency virus type-1 (HIV-1) genotypic drug resistance is generally attributed to noncompliance, poorly absorbed drugs, or drug-to-drug interaction. Attempts to determine emerging genotypic drug resistance from study subjects on highly active antiretroviral therapy (HAART) relied on insensitive polymerase chain reaction (PCR) techniques, revealing wild type HIV-1 or precursor resistant genotypes from few plasma samples successfully amplified with <50 copies/mL. STUDY DESIGN/METHODS: In this analysis, using Applied Biosystems' ViroSeq HIV-1 Genotyping Systems, Version 2.0 (Applied Biosystems, Foster City, CA, USA) and the supplemental, for research use only, nested PCR primers, genotypic drug resistance was determined in longitudinal plasma samples from 11 study subjects on HAART. RESULTS: In 4 of 11 study subjects, newly emerging genotypic primary resistant mutations were detected in plasma samples with <50 copies/mL. Most of these primary drug-resistant mutations were detected in subsequent longitudinal samples with detectable viral load (viral breakthrough). CONCLUSIONS: This analysis suggests sufficient viral replication <50 copies/mL to generate genotypic drug resistance in study subjects on suppressive HAART.