Modelling the impact of treatment adherence on the transmission of HIV drug resistance

INTRODUCTION

A lower adherence rate (percentage of individuals taking drugs as prescribed) to ART may increase the risk of emergence and transmission of HIV drug resistance, decrease treatment efficacy, and increase mortality rate. Exploring the impact of ART adherence on the transmission of drug resistance could provide insights in controlling the HIV epidemic.

METHODS

We proposed a dynamic transmission model incorporating the CD4 cell count-dependent rates of diagnosis, treatment and adherence with transmitted drug resistance (TDR) and acquired drug resistance. This model was calibrated and validated by 2008-2018 HIV/AIDS surveillance data and prevalence of TDR among newly diagnosed treatment-naive individuals from Guangxi, China, respectively. We aimed to identify the impact of adherence on drug resistance and deaths during expanding ART.

RESULTS

In the base case (ART at 90% adherence and 79% coverage), we projected the cumulative total new infections, new drug-resistant infections, and HIV-related deaths between 2022 and 2050 would be 420 539, 34 751 and 321 671. Increasing coverage to 95% would reduce the above total new infections (deaths) by 18.85% (15.75%). Reducing adherence to below 57.08% (40.84%) would offset these benefits of increasing coverage to 95% in reducing infections (deaths). Every 10% decrease in adherence would need 5.07% (3.62%) increase in coverage to avoid an increase in infections (deaths). Increasing coverage to 95% with 90% (80%) adherence would increase the above drug-resistant infections by 11.66% (32.98%).

CONCLUSIONS

A decrease in adherence might offset the benefits of ART expansion and exacerbate the transmission of drug resistance. Ensuring treated patients' adherence might be as important as expanding ART to untreated individuals.

Prediction of HIV-1 protease resistance using genotypic, phenotypic, and molecular information with artificial neural networks

Drug resistance is a primary barrier to effective treatments of HIV/AIDS. Calculating quantitative relations between genotype and phenotype observations for each inhibitor with cell-based assays requires time and money-consuming experiments. Machine learning models are good options for tackling these problems by generalizing the available data with suitable linear or nonlinear mappings. The main aim of this study is to construct drug isolate fold (DIF) change-based artificial neural network (ANN) models for estimating the resistance potential of molecules inhibiting the HIV-1 protease (PR) enzyme. Throughout the study, seven of eight protease inhibitors (PIs) have been included in the training set and the remaining ones in the test set. We have obtained 11,803 genotype-phenotype data points for eight PIs from Stanford HIV drug resistance database. Using the leave-one-out (LVO) procedure, eight ANN models have been produced to measure the learning capacity of models from the descriptors of the inhibitors. Mean R² value of eight ANN models for unseen inhibitors is 0.716, and the 95% confidence interval (CI) is [0.592-0.840]. Predicting the fold change resistance for hundreds of isolates allowed a robust comparison of drug pairs. These eight models have predicted the drug resistance tendencies of each inhibitor pair with the mean 2D correlation coefficient of 0.933 and 95% CI [0.930-0.938]. A classification problem has been created to predict the ordered relationship of the PIs, and the mean accuracy, sensitivity, specificity, and Matthews correlation coefficient (MCC) values are calculated as 0.954, 0.791, 0.791, and 0.688, respectively. Furthermore, we have created an external test dataset consisting of 51 unique known HIV-1 PR inhibitors and 87 genotype-phenotype relations. Our developed ANN model has accuracy and area under the curve (AUC) values of 0.749 and 0.818 to predict the ordered relationships of molecules on the same strain for the external dataset. The currently derived ANN models can accurately predict the drug resistance tendencies of PI pairs. This observation could help test new inhibitors with various isolates.

The QSAR Paradigm in Fragment-Based Drug Discovery: From the Virtual Generation of Target Inhibitors to Multi-Scale Modeling

Fragment-Based Drug Design (FBDD) has established itself as a promising approach in modern drug discovery, accelerating and improving lead optimization, while playing a crucial role in diminishing the high attrition rates at all stages in the drug development process. On the other hand, FBDD has benefited from the application of computational methodologies, where the models derived from the Quantitative Structure-Activity Relationships (QSAR) have become consolidated tools. This mini-review focuses on the evolution and main applications of the QSAR paradigm in the context of FBDD in the last five years. This report places particular emphasis on the QSAR models derived from fragment-based topological approaches to extract physicochemical and/or structural information, allowing to design potentially novel mono- or multi-target inhibitors from relatively large and heterogeneous databases. Here, we also discuss the need to apply multi-scale modeling, to exemplify how different datasets based on target inhibition can be simultaneously integrated and predicted together with other relevant endpoints such as the biological activity against non-biomolecular targets, as well as in vitro and in vivo toxicity and pharmacokinetic properties. In this context, seminal papers are briefly analyzed. As huge amounts of data continue to accumulate in the domains of the chemical, biological and biomedical sciences, it has become clear that drug discovery must be viewed as a multi-scale optimization process. An ideal multi-scale approach should integrate diverse chemical and biological data and also serve as a knowledge generator, enabling the design of potentially optimal chemicals that may become therapeutic agents.

Retention in care and mortality trends among patients receiving comprehensive care for HIV infection: a retrospective cohort study

BACKGROUND

Studies examining the relation between comprehensive care and health outcomes associated with comorbidities unrelated to HIV infection have focused mainly on the health outcomes of HIV-infected people and comorbid substance use disorders. We aimed to assess the impact of retention in comprehensive HIV infection care on overall, AIDS-related and non-AIDS-related mortality.

METHODS

Using a retrospective cohort design, we collected data for HIV-infected patients aged 19 years or more who first visited a comprehensive HIV infection clinic in Vancouver between Jan. 1, 2004, and Dec. 31, 2014. We defined retention in care as visit constancy (whether the patient attended the clinic at least once per given period) of 75% or greater. We used Poisson regression modelling to examine mortality trends. We performed Cox proportional hazards modelling to assess survival by retention during the first year of follow-up and identify factors associated with death.

RESULTS

A total of 2101 patients were included in the study. Of the 2101, 1340 (63.8%) were retained in the first year of care, and 271 (12.9%) died during the study period. Among the 264 cases in which the cause of death was known, although the primary underlying cause of death (74 [28.0%]) was AIDS-related, half of all AIDS-related deaths (37/74 [50%]) occurred early in the study (2004-2007). In later years, most deaths (147/184 [79.9%]) were non-AIDS-related. Overall mortality was significantly reduced among patients with higher retention in care during the first year of follow-up (per 20% increase in visit constancy; adjusted hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.79-0.96). Higher retention was also associated with reduced risk of AIDS-related death (adjusted HR 0.79, 95% CI 0.64-0.97).

INTERPRETATION

Although there was an overall trend toward decreased AIDS-related mortality over time, retention in care markedly decreased the likelihood of death. Maintaining patient engagement in comprehensive ancillary care is a patient-centred way of decreasing mortality rates among HIV-infected people.

Impact of lopinavir-ritonavir exposure in HIV-1 infected children and adolescents in Madrid, Spain during 2000-2014

Background

The most-used protease-inhibitor in children is Lopinavir-ritonavir (LPV/r), which provides durable suppression of viral load and increases CD4+T-counts. This study describes the virological outcome of the HIV-1-infected paediatric population exposed to LPV/r during 15 years in Spain.

Methodology

Patients from the Madrid Cohort of HIV-1-infected-children and adolescents exposed to LPV/r as different line therapy during 2000–2014 were selected. The baseline epidemiological-clinical features, viral suppression, changes in CD4+T-CD8+T cell counts and drug susceptibility were recorded before and during LPV/r exposure. Drug resistance mutations (DRM) were identified in viruses from samples collected until 2011. We predicted drug susceptibility to 19 antiretrovirals among those carrying DRM using the Stanford′s HIVdb Algorithm.

Results

A total of 199 (37.3%) of the 534 patients from the cohort were exposed to LPV/r during 2000–2014 in first (group 1), second (group 2) or more line-therapies (group 3). Patients were mainly Spaniards (81.9%), perinatally infected (96.5%) with subtype-B (65.3%) and HIV-diagnosed before year 2000 (67.8%). The mean age at first LPV/r exposure was 9.7 years. After protease-inhibitor exposure, viral suppression was higher in groups 1 and 2 than in group 3. Viral suppression occurred in 87.5%, 68.6% and 64.8% patients from groups 1, 2 and 3, respectively. Among the 64 patients with available resistance data during LPV/r treatment, 27(42.3%) carried DRM to protease-inhibitor, 28 (58.3%) to reverse-transcriptase-inhibitors and 21 (43.7%) to non-reverse-transcriptase-inhibitors. Darunavir/ritonavir, atazanavir-ritonavir and tipranavir/ritonavir presented the highest susceptibility and nelfinavir the lowest.

Conclusions

A better lymphocyte recovering occurred when protease-inhibitor was taken as part of a first-line regimen and a higher number of patients reached viral suppression. The least compromised antiretrovirals for rescue antiretroviral regimens, according to DRM in the LPV/r-exposed-paediatric cohort, were mainly the new protease inhibitors.

Comparative analysis of drug resistance mutations in the human immunodeficiency virus reverse transcriptase gene in patients who are non-responsive, responsive and naive to antiretroviral therapy

Drug resistance mutations in the Pol gene of human immunodeficiency virus 1 (HIV-1) are one of the critical factors associated with antiretroviral therapy (ART) failure in HIV-1 patients. The issue of resistance to reverse transcriptase inhibitors (RTIs) in HIV infection has not been adequately addressed in the Indian subcontinent. We compared HIV-1 reverse transcriptase (RT) gene sequences to identify mutations present in HIV-1 patients who were ART non-responders, ART responders and drug naive. Genotypic drug resistance testing was performed by sequencing a 655-bp region of the RT gene from 102 HIV-1 patients, consisting of 30 ART-non-responding, 35 ART-responding and 37 drug-naive patients. The Stanford HIV Resistance Database (HIVDBv 6.2), IAS-USA mutation list, ANRS_09/2012 algorithm, and Rega v8.02 algorithm were used to interpret the pattern of drug resistance. The majority of the sequences (96 %) belonged to subtype C, and a few of them (3.9 %) to subtype A1. The frequency of drug resistance mutations observed in ART-non-responding, ART-responding and drug-naive patients was 40.1 %, 10.7 % and 20.58 %, respectively. It was observed that in non-responders, multiple mutations were present in the same patient, while in responders, a single mutation was found. Some of the drug-naive patients had more than one mutation. Thymidine analogue mutations (TAMs), however, were found in non-responders and naive patients but not in responders. Although drug resistance mutations were widely distributed among ART non-responders, the presence of resistance mutations in the viruses of drug-naive patients poses a big concern in the absence of a genotyping resistance test.

Antiretroviral therapy: Shifting sands

HIV/AIDS has been an extremely difficult pandemic to control. However, with the advent of antiretroviral therapy (ART), HIV has now been transformed into a chronic illness in patients who have continued treatment access and excellent long-term adherence. Existing indications for ART initiation in asymptomatic patients were based on CD4 levels; however, recent evidence has broken the shackles of CD4 levels. Early initiation of ART in HIV patients irrespective of CD4 counts can have profound positive impact on morbidity and mortality. Early initiation of ART has been found not only beneficial for patients but also to community as it reduces the risk of transmission. There have been few financial concerns about providing ART to all HIV-positive people but various studies have proven that early initiation of ART not only proves to be cost-effective but also contributes to economic and social growth of community. A novel multidisciplinary approach with early initiation and availability of ART at its heart can turn the tide in our favor in future. Effective preexposure prophylaxis and postexposure prophylaxis can also lower transmission risk of HIV in community. New understanding of HIV pathogenesis is opening new vistas to cure and prevention. Various promising candidate vaccines and drugs are undergoing aggressive clinical trials, raising optimism for an ever-elusive cure for HIV. This review describes various facets of tectonic shift in management of HIV.

Trends in drug resistance-associated mutations in a real-life cohort of Italian patients infected with HIV-1

Recent studies support the idea that human immunodeficiency virus type 1 (HIV-1) drug resistance is declining in developed countries. To help assess the current situation in Italy, the dynamics of drug resistance mutations in pol and integrase genes in plasma samples from HIV-1-positive patients attending Sapienza University Hospital, Rome, from 2003 to 2014 were analysed. In total, 1730 genotype resistance tests (GRTs) were retrospectively analysed. The prevalence of major drug resistance mutations (DRMs) was evaluated over time in the global population and in patients with antiretroviral therapy (ART) failure. Population dynamics, changes in ART administration, and HIV-1 RNA levels were analysed in combination with DRM trends. The global population showed a strong reduction in major DRMs to all drug classes. Over the 2003-2014 decade, resistance to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) declined from 80.0% to 18.7%, from 42.8% to 20.1% and from 74.2% to 8.3%, respectively (P<0.005 for all comparisons). However, only PI-associated mutations showed a significant decrease in patients experiencing ART failure. Interestingly, analysis of the integrase gene disclosed an increased resistance to integrase inhibitors, mainly regarding N155H, detected in 32.6% of raltegravir-treated patients in 2012-2014. In conclusion, in line with previous findings, this study shows that drug resistance is declining in Italy. However, the persistence of DRMs to NRTIs and NNRTIs suggests that despite adherence and treatment optimisation, some patients still experience therapy failure, emphasising the need for GRTs both in naïve and ART-failed patients.

Cohort Profile: HAART Observational Medical Evaluation and Research (HOMER) cohort

Since 1986, antiretroviral therapy (ART) has been available free of charge to individuals living with HIV in British Columbia (BC), Canada, through the BC Centre of Excellence in HIV/AIDS (BC-CfE) Drug Treatment Program (DTP). The Highly Active Antiretroviral Therapy (HAART) Observational Medical Evaluation and Research (HOMER) cohort was established in 1996 to maintain a prospective record of clinical measurements and medication profiles of a subset of DTP participants initiating HAART in BC. This unique cohort provides a comprehensive data source to investigate mortality, prognostic factors and treatment response among people living with HIV in BC from the inception of HAART. Currently over 5000 individuals are enrolled in the HOMER cohort. Data captured include socio-demographic characteristics (e.g. sex, age, ethnicity, health authority), clinical variables (e.g. CD4 cell count, plasma HIV viral load, AIDS-defining illness, hepatitis C co-infection, mortality) and treatment variables (e.g. HAART regimens, date of treatment initiation, treatment interruptions, adherence data, resistance testing). Research findings from the HOMER cohort have featured in numerous high-impact peer-reviewed journals. The HOMER cohort collaborates with other HIV cohorts on both national and international scales to answer complex HIV-specific research questions, and welcomes input from external investigators regarding potential research proposals or future collaborations. For further information please contact the principal investigator, Dr Robert Hogg (robert_hogg@sfu.ca).

Successes and gaps in uptake of regular, voluntary HIV testing for hidden street- and off-street sex workers in Vancouver, Canada

Despite evidence globally of the heavy HIV burden among sex workers (SWs) as well as other poor health outcomes, including violence, SWs are often excluded from accessing voluntary, confidential and non-coercive health services, including HIV prevention, treatment, care and support. This study therefore assessed the prevalence and association with regular HIV testing among street- and off-street SWs in Vancouver, Canada. Cross-sectional baseline data were used from a longitudinal cohort known as "An Evaluation of Sex Worker's Health Access" (AESHA; January 2010-July 2012). This cohort included youth and adult SWs (aged 14+ years). We used multivariable logistic regression to assess the relationship between explanatory variables and having a recent HIV test (in the last year). Of the 435 seronegative SWs included, 67.1% reported having a recent HIV test. In multivariable logistic regression analysis, having a recent HIV test remained significantly independently associated with elevated odds of inconsistent condom use with clients [adjusted (multivariable) odds ratios, AOR: 2.59, 95% confidence intervals [95% CIs]: 1.17-5.78], injecting drugs (AOR: 2.33, 95% CIs: 1.17-4.18) and contact with a mobile HIV prevention programme (AOR: 1.76, 95% CIs: 1.09-2.84) within the last six months. Reduced odds of having a recent HIV test was also significantly associated with being a migrant/new immigrant to Canada (AOR: 0.33, 95% CIs: 0.19-0.56) and having a language barrier to health care access (AOR: 0.26, 95% CIs: 0.09-0.73). Our results highlight successes of reaching SWs at high risk of HIV through drug and sexual pathways. To maximize the effectiveness of including HIV testing as part of comprehensive HIV prevention and care to SWs, increased mobile outreach and safer-environment interventions that facilitate access to voluntary, confidential and non-coercive HIV testing remain a critical priority, in addition to culturally safe services with language support.

Increase in transmitted resistance to non-nucleoside reverse transcriptase inhibitors among newly diagnosed HIV-1 infections in Europe

Background

One out of ten newly diagnosed patients in Europe was infected with a virus carrying a drug resistant mutation. We analysed the patterns over time for transmitted drug resistance mutations (TDRM) using data from the European Spread program.

Methods

Clinical, epidemiological and virological data from 4317 patients newly diagnosed with HIV-1 infection between 2002 and 2007 were analysed. Patients were enrolled using a pre-defined sampling strategy.

Results

The overall prevalence of TDRM in this period was 8.9% (95% CI: 8.1-9.8). Interestingly, significant changes over time in TDRM caused by the different drug classes were found. Whereas nucleoside resistance mutations remained constant at 5%, a significant decline in protease inhibitors resistance mutations was observed, from 3.9% in 2002 to 1.6% in 2007 (p = 0.001). In contrast, resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs) doubled from 2.0% in 2002 to 4.1% in 2007 (p = 0.004) with 58% of viral strains carrying a K103N mutation. Phylogenetic analysis showed that these temporal changes could not be explained by large clusters of TDRM.

Conclusion

During the years 2002 to 2007 transmitted resistance to NNRTI has doubled to 4% in Europe. The frequent use of NNRTI in first-line regimens and the clinical impact of NNRTI mutations warrants continued monitoring.

HIV drug resistance detected during low-level viraemia is associated with subsequent virologic failure

BACKGROUND

The clinical implications of emergent HIV drug resistance on samples with low-level viraemia (LLV <1000 copies/ml) remain unclear. We undertook the present analysis to evaluate the impact of emergent HIV drug resistance at LLV on the risk of subsequent virologic failure.

METHODS

One thousand, nine hundred and sixty-five patients had genotype results at LLV. Risk of virologic failure (≥1000 copies/ml) after LLV was evaluated by Kaplan-Meier analysis and Cox proportional hazards regression. Resistance was assessed using the Stanford algorithm or virtual phenotypes. Patients were grouped into four susceptibility categories ('GSS' or 'vPSS') during LLV, corresponding to the number of 'active' drugs prescribed: <1; 1-1.5; 2-2.5; and ≥3.

RESULTS

A total of 1702 patients with follow-up on constant therapy were eligible for analysis. Participants excluded due to changing therapy or loss to follow-up before their next observation had mostly similar characteristics to included participants. There was a 'dose-dependent' increase in the hazard ratio for virologic failure with susceptibility categories at LLV. Compared with a GSS of at least 3, hazard ratios for virologic failure were 1.4 for GSS 2-2.5; 2.0 for GSS 1-1.5; and 3.0 for GSS less than 1 (P < 0.001). Numerous sensitivity analyses confirmed these findings.

CONCLUSION

Our results demonstrate that emergent HIV drug resistance at LLV is strongly associated with subsequent virologic failure. Furthermore, we uncovered a 'dose-dependent' increase in the hazard ratio for virologic failure with decreasing GSS estimated at the time of LLV. On the basis of these findings, we propose that resistance genotyping be encouraged for HIV-infected individuals on antiretroviral therapy experiencing low-level viraemia.

First-line antiretroviral therapy with nevirapine versus lopinavir-ritonavir based regimens in a resource-limited setting

Objective:

To compare WHO first-line antiretroviral therapy (ART) with nonnucleoside reverse transcriptase inhibitors (NNRTI)-based regimen with a boosted protease inhibitor (bPI) regimen in a resource-limited setting regarding treatment outcome and emergence of drug resistance mutations (DRMs).

Methods:

Treatment-naive adults were randomized to nevirapine (NVP) or ritonavir-boosted lopinavir (LPV/r) regimens each in combination with tenofovir (TDF)/emtricitabine (FTC) or zidovudine (ZDV)/lamivudine (3TC). Primary endpoint was the incidence of therapeutical (clinical and/or virologic) failure at week 48 with follow-up till week 96.

Results:

Four hundred and twenty-five patients (120 men; 305 women) received at least one dose of the study drug. mITT analysis showed no difference in proportion of therapeutical failure between treatment arms [67/209 (32%) in NVP vs. 63/216 (29%) LPV/r at week 48 (P = 0.53); 88/209 (42%) in NVP vs. 83/216 (38%) in LPV/r at week 96 (P = 0.49)]. Per-protocol analysis demonstrated significantly more virologic failure with NVP than with LPV/r regimens [at week 48: 19/167 (11%) vs. 7/166 (4%), P = 0.014; at week 96: 27/158 (17%) vs. 13/159 (8%), P =  0.019)]. Drug resistance mutations to NNRTI were detected in 19 out of 22 (86.3%) and dual-class resistance to nucleoside reverse transcriptase inhibitor (NRTI) and NNRTI in 15 out of 27 (68.2%) of NVP failing patients. K65R mutation was present in seven out of 14 patients failing NVP-TDF/FTC regimen. No major protease inhibitor-DRM was detected among LPV/r failing patients. Discontinuation for adverse events was similar between treatment groups.

Conclusion:

In resource-limited settings, first-line NNRTI-NRTI regimen as compared with bPI-based regimen provides similar outcome but is associated with a significantly higher number of virologic failure and resistance mutations in both classes that jeopardize future options for second-line therapy.

Patterns of transmitted HIV drug resistance in Europe vary by risk group

Background

In Europe, a continuous programme (SPREAD) has been in place for ten years to study transmission of drug resistant HIV. We analysed time trends of transmitted drug resistance mutations (TDRM) in relation to the risk behaviour reported.

Methods

HIV-1 patients newly diagnosed in 27 countries from 2002 through 2007 were included. Inclusion was representative for risk group and geographical distribution in the participating countries in Europe. Trends over time were calculated by logistic regression.

Results

From the 4317 patients included, the majority was men-having-sex-with-men -MSM (2084, 48%), followed by heterosexuals (1501, 35%) and injection drug users (IDU) (355, 8%). MSM were more often from Western Europe origin, infected with subtype B virus, and recently infected (<1 year) (p<0.001). The prevalence of TDRM was highest in MSM (prevalence of 11.1%), followed by heterosexuals (6.6%) and IDU (5.1%, p<0.001). TDRM was predominantly ascribed to nucleoside reverse transcriptase inhibitors (NRTI) with a prevalence of 6.6% in MSM, 3.3% in heterosexuals and 2.0% in IDU (p = 0.001). A significant increase in resistance to non- nucleoside reverse transcriptase inhibitors (NNRTIs) and a decrease in resistance to protease inhibitors was observed in MSM (p = 0.008 and p = 0.006, respectively), but not in heterosexual patients (p = 0.68 and p = 0.14, respectively).

Conclusions

MSM showed to have significantly higher TDRM prevalence compared to heterosexuals and IDU. The increasing NNRTI resistance in MSM is likely to negatively influence the therapy response of first-line therapy, as most include NNRTI drugs.

Determinants of progression to AIDS and death following HIV diagnosis: a retrospective cohort study in Wuhan, China

OBJECTIVE

To identify determinants associated with disease progression and death following human immunodeficiency virus (HIV) diagnosis.

METHODS

Disease progression data from the diagnosis of HIV infection or acquiring immunodeficiency syndrome (AIDS) to February 29, 2012 were retrospectively collected from the national surveillance system databases and the national treatment database in Wuhan, China. Kaplan-Meier method, Logistic regression and Cox proportional hazards model were applied to identify the related factors of progression to AIDS or death following HIV diagnosis.

RESULTS

By the end of February 2012, 181 of 691 HIV infectors developed to AIDS, and 129 of 470 AIDS patients died among whom 289 cases received concurrent HIV/AIDS diagnosis. Compared with men infected through homosexual behavior, injection drug users possessed sharply decreased hazard ratio (HR) for progression to AIDS following HIV diagnosis [HR = 0.31, 95% confidence interval (CI), 0.18-0.54, P = 4.01×10(-5)]. HIV infectors at least 60 years presented 1.15-fold (HR = 2.15, 95% CI, 1.15-4.03, P = 0.017) increased risk to develop AIDS when compared with those aged 17-29 years. Similarly, AIDS patients with diagnosis ages between 50 and 59 years were at a 1.60-fold higher risk of death (HR = 2.60, 95% CI, 1.18-5.72, P = 0.017) compared to those aged 19-29 years. AIDS patients with more CD4(+) T-cells within 6 months at diagnosis (cell/µL) presented lower risk of death (HR = 0.29 for 50- vs <50, 95% CI, 0.15-0.59, P = 0.001). The highly active antiretroviral therapy (HAART) delayed progression to AIDS from HIV diagnosis (HR = 0.15, 95% CI, 0.07-0.34, P = 6.46×10(-6)) and reduced the risk of death after AIDS diagnosis (HR = 0.02, 95% CI, 0.01-0.04, P = 7.25×10(-25)).

CONCLUSIONS

Progression to AIDS and death following HIV diagnosis differed in age at diagnosis, transmission categories, CD4(+) T-cell counts and HAART. Effective interventions should target those at higher risk for morbidity or mortality, ensuring early diagnosis and timely treatment to slow down the disease progression.

Client demands for unsafe sex: the socioeconomic risk environment for HIV among street and off-street sex workers

OBJECTIVE

Among sex workers (SWs) in Vancouver, Canada, this study identified social, drug use, sex work, environmental-structural, and client-related factors associated with being offered and accepting more money after clients' demand for sex without a condom.

DESIGN

Cross-sectional study using baseline (February 2010 to October 2011) data from a longitudinal cohort of 510 SWs.

METHODS

A 2-part multivariable regression model was used to identify factors associated with 2 separate outcomes: (1) being offered more money for sex without a condom in the last 6 months; and (2) accepting more money, among those who had been offered more money.

RESULTS

The sample included 490 SWs. In multivariable analysis, being offered more money for sex without a condom was more likely for SWs who used speedballs, had higher average numbers of clients per week, had difficulty accessing condoms, and had clients who visited other SWs. Accepting more money for sex without a condom was more likely for SWs self-reporting as a sexual minority and who had experienced client violence and used crystal methamphetamine less than daily (versus none) and less likely for SWs who solicited mainly indoors for clients (versus outdoor/public places).

CONCLUSIONS

These results highlight the high demand for sex without a condom by clients of SWs. HIV prevention efforts should shift responsibility toward clients to reduce offers of more money for unsafe sex. Programs that mitigate the social and economic risk environments of SWs alongside the removal of criminal sanctions on sex work to enable condom use within safer indoor workspaces are urgently required.

HIV Drug Resistance: Problems and Perspectives

Access to combination antiretroviral treatment (ART) has improved greatly over recent years. At the end of 2011, more than eight million HIV-infected people were receiving ART in low-income and middle-income countries. ART generally works well in keeping the virus suppressed and the patient healthy. However, treatment only works as long as the virus is not resistant against the drugs used. In the last decades, HIV treatments have become better and better at slowing down the evolution of drug resistance, so that some patients are treated for many years without having any resistance problems. However, for some patients, especially in low-income countries, drug resistance is still a serious threat to their health. This essay will review what is known about transmitted and acquired drug resistance, multi-class drug resistance, resistance to newer drugs, resistance due to treatment for the prevention of mother-to-child transmission, the role of minority variants (low-frequency drug-resistance mutations), and resistance due to pre-exposure prophylaxis.

Neurotoxicity of antiretroviral therapy

The neurological outcome of HIV infection has changed dramatically in the era of HAART. Despite effective suppression of plasma viral load and a substantial decrease in the incidence of HIV-associated dementia, neurocognitive impairment and peripheral neuropathy remain widespread. The neurotoxic side effects of antiretroviral (ARV) agents are among several contributing factors to this continued prevalence. Effective penetration of the CNS by ARV agents is paramount to treating neurological symptoms as well as systemic infection, but may also exacerbate the severity of drug-related neurotoxicity. The neurotoxic side effects of ARV agents vary widely between and within drug classes. The risks and benefits of combination regimens continue to evolve as more effective treatment protocols are developed.

Virologic response to tipranavir-ritonavir or darunavir-ritonavir based regimens in antiretroviral therapy experienced HIV-1 patients: a meta-analysis and meta-regression of randomized controlled clinical trials

BACKGROUND

The development of tipranavir and darunavir, second generation non-peptidic HIV protease inhibitors, with marked improved resistance profiles, has opened a new perspective on the treatment of antiretroviral therapy (ART) experienced HIV patients with poor viral load control. The aim of this study was to determine the virologic response in ART experienced patients to tipranavir-ritonavir and darunavir-ritonavir based regimens.

METHODS AND FINDINGS

A computer based literature search was conducted in the databases of HINARI (Health InterNetwork Access to Research Initiative), Medline and Cochrane library. Meta-analysis was performed by including randomized controlled studies that were conducted in ART experienced patients with plasma viral load above 1,000 copies HIV RNA/ml. The odds ratios and 95% confidence intervals (CI) for viral loads of <50 copies and <400 copies HIV RNA/ml at the end of the intervention were determined by the random effects model. Meta-regression, sensitivity analysis and funnel plots were done. The number of HIV-1 patients who were on either a tipranavir-ritonavir or darunavir-ritonavir based regimen and achieved viral load less than 50 copies HIV RNA/ml was significantly higher (overall OR = 3.4; 95% CI, 2.61-4.52) than the number of HIV-1 patients who were on investigator selected boosted comparator HIV-1 protease inhibitors (CPIs-ritonavir). Similarly, the number of patients with viral load less than 400 copies HIV RNA/ml was significantly higher in either the tipranavir-ritonavir or darunavir-ritonavir based regimen treated group (overall OR = 3.0; 95% CI, 2.15-4.11). Meta-regression showed that the viral load reduction was independent of baseline viral load, baseline CD4 count and duration of tipranavir-ritonavir or darunavir-ritonavir based regimen.

CONCLUSIONS

Tipranavir and darunavir based regimens were more effective in patients who were ART experienced and had poor viral load control. Further studies are required to determine their consistent viral load suppression effect as the duration of treatment is more prolonged.

Rilpivirine vs. efavirenz in HIV-1 patients with baseline viral load 100,000 copies/ml or less: week 48 phase III analysis

OBJECTIVES

To compare efficacy, resistance development, and safety between rilpivirine and efavirenz in treatment-naive, HIV-1-infected adults with baseline viral load 100,000 copies/ml or less in the pooled 48-week dataset of the ECHO (Efficacy Comparison in treatment-naive HIV-infected subjects Of TMC278 and EFV) and THRIVE (TMC278 against HIV, in a once-daily RegImen Vs. Efavirenz) trials.

DESIGN

Phase III, double-blind, double-dummy, randomized trials.

METHODS

Patients received rilpivirine 25 mg once daily (q.d.) or efavirenz 600 mg q.d. with two nucleoside/tide reverse transcriptase inhibitors [N(t)RTIs]. This analysis considers the subpopulation of 368 rilpivirine and 330 efavirenz patients with baseline viral load 100,000 copies/ml or less.

RESULTS

Significantly higher 48-week response rates (viral load <50 copies/ml, intent-to-treat-time-to-loss-of-virological response) were observed with rilpivirine vs. efavirenz [90 vs. 84%, respectively; difference 6.6% (95% confidence interval 1.6-11.5%)]. The proportion of patients experiencing virological failure (VF(res)) was 5% in each treatment group. A comparable proportion of VF(res) patients in each group developed nonnucleoside reverse transcriptase inhibitor resistance-associated mutations (RAMs) [rilpivirine: 6/16 (38%) vs. efavirenz: 5/12 (42%)]. A numerically higher proportion of rilpivirine VF(res) patients developed N(t)RTI RAMs [7/16 (44%)] vs. efavirenz [2/12 (17%)]; P = 0.2232. A significantly lower incidence for rilpivirine vs. efavirenz was observed for the following events: treatment-related grade 2-4 overall adverse events (17 vs. 30%; P <0.0001), rash (any type; 2 vs. 12%; P <0.0001), and neurological adverse events (19 vs. 40%; P <0.0001), including dizziness (10 vs. 29%; P <0.0001). There was no significant difference between groups in the total cholesterol/high-density lipoprotein cholesterol ratio.

CONCLUSION

In treatment-naive patients with baseline viral load 100,000 copies/ml or less, rilpivirine along with two N(t)RTIs achieved a high response, with a comparable frequency of VF(res) and more favorable tolerability than efavirenz.

Trends in antiretroviral therapy and prevalence of HIV drug resistance mutations in Sweden 1997-2011

OBJECTIVE

Describe trends in antiretroviral treatments and drug resistance mutations among Swedish HIV-patients over time 1997-2011.

METHODS

Treatment histories, viral sequences, and demographic and clinical data were retrieved from the national database InfCareHIV. All ART-experienced patients were included (N = 6537), while resistance tests were restricted to those obtained ≥90 days after ART start. This cohort is fully representative for Sweden since the database covers virtually all diagnosed HIV-patients since the start of the epidemic. Patients were grouped according to the year of first ART, and treatments and mutations were analyzed by calendar year.

RESULTS

The prevalence of major drug resistance mutations decreased dramatically over time, most rapidly between 2003 and 2007. Since then there has been a continued slow decrease for NRTI- and PI-associated mutations with an overall prevalence among all ART-experienced patients at 1.1% (NRTI) and 0.3% (PI) in 2011. NNRTI resistance reached the lowest level in 2007-2009 (0.6%), but is now increasing (0.9% in 2011). Patients with first ART exposure before 2001 are still highly overrepresented among those with PI and, to a lesser extent, NRTI resistance. In contrast, almost half of the patients with NNRTI mutations in 2011 initiated their first ART after 2007.

CONCLUSIONS

Tremendous improvements in ART options and knowledge have resulted in rapidly declining levels of resistance, and most of the current NRTI and PI mutations are found among patients with a history of suboptimal treatments. However, NNRTI resistance is increasing and is primarily found in patients infected in low- and middle-income countries who initiated ART in recent years. It is plausible that these patients were infected with resistant strains and it is therefore suggested that resource-rich countries like Sweden should test for resistance in minor quasispecies or use PI-based first-line regimens in patients who are at increased risk of carrying resistant virus.

Trends in Decline of Antiretroviral Resistance among ARV-Experienced Patients in the HIV Outpatient Study: 1999-2008

Background. Little is known about temporal trends in frequencies of clinically relevant ARV resistance mutations in HIV strains from U.S. patients undergoing genotypic testing (GT) in routine HIV care. Methods. We analyzed cumulative frequency of HIV resistance among patients in the HIV Outpatient Study (HOPS) who, during 1999-2008 and while prescribed antiretrovirals, underwent GT with plasma HIV RNA >1,000 copies/mL. Exposure ≥4 months to each of three major antiretroviral classes (NRTI, NNRTI and PI) was defined as triple-class exposure (TCE). Results. 906 patients contributed 1,570 GT results. The annual frequency of any major resistance mutations decreased during 1999-2008 (88% to 79%, P = 0.05). Resistance to PIs decreased among PI-exposed patients (71% to 46%, P = 0.010) as exposure to ritonavir-boosted PIs increased (6% to 81%, P < 0.001). Non-significant declines were observed in resistance to NRTIs among NRTI-exposed (82% to 67%), and triple-class-resistance among TCE patients (66% to 41%), but not to NNRTIs among NNRTI-exposed. Conclusions. HIV resistance was common but declined in HIV isolates from subgroups of ARV-experienced HOPS patients during 1999-2008. Resistance to PIs among PI-exposed patients decreased, possibly due to increased representation of patients whose only PI exposures were to boosted PIs.

Characterization of HIV-1 from patients with virological failure to a boosted protease inhibitor regimen

The use of highly active antiretroviral treatment (HAART) regimens with unboosted protease inhibitors (PIs) has resulted in a high level of virological failure primarily due to the development of resistant virus. Current boosted PI regimens combine successfully low-dose ritonavir (r) with a second PI. The aim of the study was to estimate the proportion of patients, in a population based setting, who develop virological failure on a PI/r regimen. Through The Danish HIV Cohort Study 1,007 patients who received PI/r based treatment between 1995 and 2008 were identified. Twenty-three (2.3%) experienced virological failure, of whom 19 (83%) started PI/r treatment before 2001. Patients from Copenhagen (n=19) were selected to study the development of protease (PR) and gag cleavage site (CS) mutations during PI/r treatment and PI plasma levels at the time of virological failure. Three patients (16%) developed major PI resistance mutations. Mutations in the p7/p1 and p1/p6 gag CS only developed in patients with major or minor mutations in PR. Drug concentrations were low or undetectable in 10 out of the 19 patients. In total PR resistance mutations and low drug levels could account for 12 (63%) of the failure cases. In conclusion, virological failure to PI/r is a low and decreasing problem primarily caused by low plasma drug levels and to a lesser extent major PR mutations. Gag CS mutations did not contribute significantly to resistance development and virological failure.

Treatment limitations imposed by antiretroviral drug resistance mutations: implication for choices of first line regimens in resource-limited settings

BACKGROUND

Recent studies have suggested that failing nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimens may have greater potential to induce the development of resistance mutations, which may limit options for second-line therapy.

METHODS

Antiretroviral therapy (ART)-naïve individuals aged ≥18 years who initiated triple combination ART between January 2000 and June 2006 in British Columbia, Canada were enrolled in the study. We compared genotypic sensitivity scores (GSSs) derived from the development of resistance mutations between participants who initiated ART with ritonavir-boosted protease inhibitors (PIs) with those who initiated ART with NNRTIs, and determined the effects of these mutations on remaining active drugs.

RESULTS

A total of 1666 participants initiated ART, 818 (49.1%) with NNRTI-based regimens and 848 (50.9%) with boosted PI-based regimens. Among participants who developed resistance mutations, those who initiated NNRTI-based regimens had a lower median GSS than those on boosted PI-based regimens (9.8 vs. 11.0, respectively; P<0.001). Participants on boosted PI-based regimens [adjusted odds ratio (AOR) 3.68; 95% confidence interval (CI) 2.25, 6.01], those with ≥95% adherence to highly active antiretroviral therapy (HAART) (AOR 1.84; 95% CI 1.16, 2.92) and those with baseline CD4 count >200 cells/μL (AOR 3.44; 95% CI 1.73, 6.84) were more likely to have the maximum number of drug options.

CONCLUSION

The use of NNRTI-based first-line ART regimens may limit the options for second-line treatment when the number of available drugs is limited.

Rapid development of antiretroviral drug resistance mutations in HIV-infected children less than two years of age initiating protease inhibitor-based therapy in South Africa

Data on the development of antiretroviral drug resistance in HIV-1-infected children receiving protease inhibitor (PI)-based antiretroviral therapy (ART) are limited. We examined antiretroviral resistance among a cohort of 323 South African HIV-infected children <2 years old exposed to nevirapine for prevention of mother-to-child transmission. Ritonavir (RTV) was used initially for 138 children who were <6 months old or receiving antimycobacterial therapy; otherwise children received lopinavir/ritonavir (LPV/r)-based ART. HIV-1 population sequencing of the pol gene was conducted on all pretreatment samples and on posttreatment samples for children who did not achieve HIV-1 plasma RNA <400 copies/ml by 52 weeks. Among children in the cohort, 38 died, 22 had <24 weeks follow-up, 209 achieved virologic suppression, and 54 did not. Of 41 children without virologic suppression with posttreatment HIV genotype data available, major resistance mutations were found in 32 (78%): 14 (36%) had PI mutations including V82A, M46I, and L90M; 29 (71%) had M184V/I; and three had NNRTI mutations (K103N, Y181C, and G190A). Among the children who did not achieve virologic suppression, none of the seven children treated exclusively with LPV/r developed PI-related mutations, compared with 14 of 32 (44%) who received RTV-based regimens (p=0.036); PI genotypes were unavailable for two children. Seventy-eight percent of children without virologic suppression developed resistance mutations that impact second-line ART options. Only children who received RTV-based ART developed major PI-related resistance mutations, and use of this regimen should be avoided.

Low rate of virological failure and maintenance of susceptibility to HIV-1 protease inhibitors with first-line lopinavir/ritonavir-based antiretroviral treatment in clinical practice

Protease inhibitor (PI)-resistant HIV-1 has hardly ever been detected at failed boosted PI-based first-line antiretroviral regimens in clinical trials. However, this phenomenon has not been investigated in clinical practice. To address this gap, data from patients starting a first-line lopinavir/ritonavir (LPV/rtv)-based therapy with available baseline HIV-1 RNA load, a viral genotype and follow-up viral load after 3 and 6 months of treatment were extracted from the Italian Antiretroviral Resistance Cohort Analysis (ARCA) observational database. Based on survival analysis, 39 (7.1%) and 43 (7.8%) of the 548 examined patient cases had an HIV-1 RNA >500 and >50 copies/ml, respectively, after 6 months of treatment. Cox proportional hazard models detected baseline HIV-1 RNA (RH 1.79, 95%CI 1.10-2.92 per 1-log(10) increase, P=0.02) and resistance to the nucleoside backbone (RH 1.04, 95%CI 1.02-1.06 per 10-point increase using the Stanford HIVdb algorithm, P<0.001) as independent predictors of HIV-1 RNA at >500 copies/ml, but not at the >50 copies/ml cutoff criteria. Higher baseline viral load, older patient age, heterosexual route of infection and use of tenofovir/emtricitabine were predictors of failure at month 3 using the 50-copy and/or 500-copy threshold. Resistance to LPV/rtv did not occur or increase in any of the available 36 follow-up HIV-1 genotypes. Resistance to the nucleoside backbone (M184V) developed in four cases. Despite the likely differences in patient population and adherence, both the low rate of virological failure and the lack of development of LPV/rtv resistance documented in clinical trials are thus confirmed in clinical practice.

Risk of viral failure declines with duration of suppression on highly active antiretroviral therapy irrespective of adherence level

OBJECTIVE

To model the effect of adherence and duration of viral suppression on the risk of viral rebound.

METHODS

Viral rebound was defined as the first of at least two consecutive viral loads greater than 400 copies/mL after initial viral suppression. The main exposures were adherence, presence of antiretroviral class resistance before rebound or censoring date, and the percentage of follow-up time with viral suppression.

RESULTS

A total of 274 (N = 1305 [21%]) individuals experienced viral rebound. Median time of suppression before rebound was 2 years. Viral rebound was less likely to occur among those with longer duration of continuous viral suppression (odds ratio, 0.37; 95% confidence interval, 0.32 to 0.42). Among individuals with moderate levels of adherence (80% to less than 95%), the probability of virologic failure was 0.85 after being suppressed for 12 months and it was 0.08 after 72 months being suppressed (P < 0.01). Individuals with drug resistance were at a higher risk of viral rebound.

CONCLUSIONS

The risk of viral rebound decreased with longer duration of viral suppression within each of adherence strata studied. Although perfect adherence remains an important goal of therapy to prevent disease progression, individuals with long-term viral suppression may be able to miss more doses without experiencing viral rebound.

Epidemiology of antiretroviral multiclass resistance

Given the recent evolution of therapeutic trends, the frequency and determinants of multiclass-resistant HIV infection in the modern combination highly active antiretroviral therapy (HAART) era are less well understood. In this study, the authors characterize the epidemiology of antiretroviral multiclass resistance among HAART-naïve patients enrolled in a province-wide HAART distribution program in British Columbia, Canada. HAART and resistance testing are free to eligible individuals in British Columbia. This study was based on patients who initiated naïve on HAART and were followed during January 1, 2000-June 30, 2007. Explanatory logistic and survival models were built to identify those factors most influential in the emergence of multiclass resistance. Among the 1,820 individuals in our study, 833 (46%) were tested for antiretroviral resistance at least once during their follow-up. Multiclass resistance was observed in 142 individuals (n = 833; 17%) during a median follow-up of 14 months (interquartile range, 3-34 months) (incidence rate, 0.8 cases/1,000 person-months). The authors found that initial nonnucleoside reverse transcriptase inhibitor-based HAART was the main determinant of multiclass resistance. Given that these inhibitors are still widely used, priority should be given to make resistance testing and viral load monitoring a standard part of human immunodeficiency virus care to maximize the long-term efficacy and efficiency of HAART.

Epidemiology of treatment failure: a focus on recent trends

PURPOSE OF REVIEW

As antiretroviral therapy has been refined with the development of more potent agents and simpler regimens, fewer individuals experience treatment failure. This review will highlight recent trends in treatment failure and virologic resistance in the developed world and resource-limited settings.

RECENT FINDINGS

The goal of antiretroviral therapy in all individuals, regardless of prior treatment exposure or HIV drug resistance, is to achieve full suppression of viral replication with a viral load of less than 50 copies/ml. This goal has been made a reality by the development of newer agents and simpler, better tolerated regimens. Recent cohort studies have demonstrated improved virologic outcomes in the current antiretroviral era, with decreased rates of virologic failure and associated resistance. Improved tolerability has aided adherence, which remains a key determinant of treatment success. Cohorts in resource-limited settings report improved clinical and virologic outcomes as rollout of highly active antiretroviral therapy programs continues.

SUMMARY

There has been a reassuring decrease in the frequency of virological failure and drug resistance in the modern highly active antiretroviral therapy era. This observation provides an important incentive to strengthen support of antiretroviral therapy programs to optimize virological outcomes, particularly in resource-limited settings in which access to newer agents and laboratory monitoring may be needed to ensure sustainable success.

Differential survival benefit of universal HAART access in Brazil: a nation-wide comparison of injecting drug users versus men who have sex with men

OBJECTIVE

Brazil accounts for approximately 70% of injection drug users (IDUs) receiving highly active antiretroviral therapy (HAART) in low-income/middle-income countries. We evaluated the impact of HAART availability/access on AIDS-related mortality among IDUs versus men who have sex with men (MSM).

DESIGN

Nation-wide analysis on Brazilian IDU and MSM diagnosed with AIDS in 2000-2006.

METHODS

Four national information systems were linked, and Cox regression was used to assess impact of HAART availability/access on differential AIDS-related mortality.

RESULTS

Among 28,426 patients, 6777 died during 87,792 person-years of follow-up. Compared with MSM, IDU were significantly less likely to be receiving HAART, to have ever had determinations for CD4 or viral load. After controlling for confounders, IDU had a significantly higher risk of death (adjusted hazard ratio: 1.94; 95% confidence interval: 1.84 to 2.05). Among the subset that had at least 1 CD4 and viral load determination, higher risk of death among IDU persisted (hazard ratio: 1.82; 95% confidence interval: 1.58 to 2.11). Nonwhite ethnicity significantly increased this risk, whereas prompt HAART uptake after AIDS diagnosis reduced the risk of death. After controlling for spatially correlated survival data, AIDS-related mortality remained higher in IDU than in MSM.

CONCLUSIONS

Despite free/universal HAART access, differential AIDS-related mortality exists in Brazil. Efforts are needed to identify and eliminate these health disparities.

Successes, challenges, and limitations of current antiretroviral therapy in low-income and middle-income countries

As a result of the scale-up of antiretroviral treatment (ART) programmes and substantial financial support worldwide, an increasing number of HIV-infected individuals in low-income and middle-income countries (LIMCs) now have access to ART. Despite this progress, important questions remain on the best use of ART and how patients should be maintained on a successful regimen. This Review addresses some of the issues faced by those managing the epidemic in LMICs, including when to start treatment, choice of first-line ART, and when to switch regimens. Although the first priority must be continued expansion of access to ART, there should be a move towards starting ART earlier to treat individuals before they reach advanced stages of disease, to reduce early mortality, and to build support for improved monitoring of treatment failure. There is also a need for more randomised controlled studies to identify the long-term outcomes, cost-effectiveness of ART, and use of virological monitoring in LMICs.

Characterization of virologic failure patients on darunavir/ritonavir in treatment-experienced patients

OBJECTIVE

Characterization of resistance development in virologic failure patients on the protease inhibitor darunavir administered with low-dose ritonavir (DRV/r) in the 48-week analysis of TMC114/r In Treatment-experienced pAtients Naive to lopinavir (TITAN).

DESIGN

TITAN is a randomized, controlled, open-label, phase III, noninferiority trial comparing the efficacy and safety of DRV/r with that of lopinavir/ritonavir (LPV/r) in HIV-1-infected, treatment-experienced, LPV-naive patients. The primary endpoint was the proportion of patients with HIV-1 RNA less than 400 copies/ml at week 48.

METHODS

Patients received DRV/r 600/100 mg twice daily (n = 298) or LPV/r 400/100 mg twice daily (n = 297), and an optimized background regimen. Patients who lost or never achieved HIV-1 RNA less than 400 copies/ml after week 16 were considered virologic failure patients. Genotyping and phenotyping were performed.

RESULTS

The virologic failure rate in the DRV/r arm (10%, n = 31) was lower than in the LPV/r arm (22%, n = 65). Furthermore, fewer virologic failure patients in the DRV/r arm than in the LPV/r arm developed primary protease inhibitor mutations (6 vs. 20) or nucleoside reverse transcriptase inhibitor resistance-associated mutations (4 vs. 15). In addition, fewer virologic failure patients on DRV/r than on LPV/r lost susceptibility to the protease inhibitor (3 vs. 13) or nucleoside reverse transcriptase inhibitor(s) (3 vs. 14) used in the treatment regimen or to other protease inhibitors. Most DRV/r-treated virologic failure patients retained susceptibility to all protease inhibitors.

CONCLUSION

In treatment-experienced, LPV-naive patients, the overall virologic failure rate in the DRV/r arm was low and was associated with limited resistance development. These findings showed that the use of DRV/r in earlier lines of treatment was less likely to lead to cross-resistance to other protease inhibitors compared with LPV/r.

Early antiretroviral therapy: the role of cohorts

PURPOSE OF REVIEW

To review the data that contribute to the debate on the optimal time to initiate highly active antiretroviral therapy in HIV-infected individuals, with a focus on the information that is available from cohort studies.

RECENT FINDINGS

The findings from cohort studies generally support initiation of highly active antiretroviral therapy at CD4 cell counts more than 350 cells/microl. In particular, the findings that death rates among treated HIV-infected individuals are higher than those in the general population, and that the risks of AIDS and serious non-AIDS events are higher in those with lower CD4 cell counts (even when the count remains >350 cells/microl), suggest that earlier initiation of highly active antiretroviral therapy may prevent some excess morbidity and mortality. However, given the lack of adjustment for lead-time bias in many analyses, the potential for residual confounding and the possible incomplete ascertainment of relevant outcomes in cohorts, it cannot be concluded that the benefits of highly active antiretroviral therapy when started at higher CD4 cell counts will outweigh the possible detrimental effects.

SUMMARY

Whereas the data from cohort studies currently support initiation of highly active antiretroviral therapy at CD4 cell counts more than 350 cells/microl, there is an urgent need for data from randomized trials to inform this decision.

Should HIV therapy be started at a CD4 cell count above 350 cells/microl in asymptomatic HIV-1-infected patients?

PURPOSE OF REVIEW

The aim is to review the available data that contribute to the debate on the optimal time to initiate highly active antiretroviral therapy (HAART) in HIV-infected individuals with a CD4 cell count more than 350 cells/microl.

RECENT FINDINGS

Although few randomized data exist that can contribute to this debate, a number of findings from observational studies generally support earlier initiation of HAART. In particular, the findings that death rates remain higher in HIV-infected individuals than in uninfected individuals, even when successfully treated, and that both AIDS and several serious non-AIDS events are more common in those with a lower CD4 cell count (even when this count is above 350 cells/microl), suggest that earlier initiation of HAART may prevent much of the excess morbidity and mortality that remains in this patient group.

SUMMARY

Currently, the data would generally support initiation of HAART in patients with CD4 cell counts more than 350 cells/microl. However, given the strong potential for confounding in observational studies and the lack of adjustment for lead-time bias in many analyses, it is not possible to rule out possible long-term detrimental effects of earlier use of HAART until the results from fully powered randomized trials that directly address this issue become available.

Evolution and predictors of HIV type-1 drug resistance in patients failing combination antiretroviral therapy in Italy

Background

This study aimed to examine the evolution of genotypic drug resistance prevalence in treatment-failing patients in the multicentre, Italian, Antiretroviral Resistance Cohort Analysis (ARCA).

Methods

Patients with a drug resistance genotype test performed between 1999 and 2006 at failure of a combination antiretroviral therapy and with complete treatment history were selected. The prevalence of resistance was measured overall, per calendar year, per drug class and per treatment line at failure.

Results

The overall resistance prevalence was 81%. Resistance to nucleoside reverse transcriptase inhibitors (NRTIs) declined after 2002 (68% in 2006; χ2 for trend P=0.004); resistance to non-NRTIs (NNRTIs) stabilized after 2004; and resistance to protease inhibitors (PIs) declined after 2001 (43% in 2006; P=0.004). In first-line failures, NRTI resistance decreased after 2002 ( P=0.006), NNRTI resistance decreased after 2003 ( P=0.001) and PI resistance decreased after 2001 ( P<0.001). Independent predictors of resistance to any class were HIV type-1 transmission by heterosexual contacts as compared with injecting drug use, a higher number of experienced regimens, prior history of suboptimal therapy, higher viral load and CD4+ T-cell counts, more recent calendar year and viral subtype B carriage, whereas the use of PI-based versus NNRTI-based regimens at failure was associated with a reduced risk of resistance. There was an increase of type-1 thymidine analogue and of protease mutations L33F, I47A/V, I50V and I54L/M, whereas L90M decreased over calendar years.

Conclusions

During more recent years, emerging drug resistance has decreased, particularly in first-line failures. The prevalence continues to be high in multiregimen-failing patients.

[Clinical utility of atazanavir]

Atazanavir (ATV) is a protease inhibitor (PI) in which its main qualities, compared to other PI are dosing convenience, good tolerability and excellent metabolic profile. These characteristics makes it more like a nonnucleoside than a PI, but with the increased genetic barrier common to PI. It is indicated in initial treatment, simplification treatment or a change due to toxicity and in first line rescue treatment. The administering of ATV boosted with ritonavir (300/100 mg/d) has been approved in Europe in all clinical situations. In naïve patients it has been combined with practically all the nucleoside analogue pairs and has shown to be as effective as lopinavir/ritonavir and even efavirenz. In the USA, this indication has been approved for almost 5 years and ATV has become the most prescribed PI, while the EMEA has approved it this year. ATV is an optimal drug to replace other antiretrovirals in simplification strategies or changes due to toxicity. In several studies it has been shown that, in patients with good virological control, it can LPV/r or another PI, the therapeutic efficacy being maintained, with excellent tolerance and an improved lipid profile, and decreasing the cardiovascular risk. This strategy is widely used in Spain. In this scenario some patients could benefit from non-boosted ATV treatment (400 mg/d). ATV is an effective and very attractive option in first line rescue treatments in which the virus shows little or no resistance to PI, as its simplicity and tolerability can improve problems with compliance, the main cause of therapeutic failure. In patients with moderate resistance to PI, ATV is as effective as LPV/r. The survival of patients with HIV infection is increasingly longer and factors such as tolerability, cardiovascular risk and the adaptability of the treatment to the lifestyle of the patient, become more important, therefore ATV must play an important role in the treatment of HIV-infection.

Differential impact of adherence on long-term treatment response among naive HIV-infected individuals

OBJECTIVES

To examine the long-term impact of adherence on virologic, immunologic, and dual response stratified by type of HAART regimen in treatment-naive patients starting HAART in British Columbia, Canada; and to assess the degree of virologic and immunologic response associated with emergence of drug resistance, progression to AIDS, and mortality.

METHODS

Eligible participants initiated HAART between 1 January 2000 and 30 November 2004, were followed until 30 November 2005, and had at least 2 years of follow-up. Virologic and immunologic responses were dichotomized at their median values. Virologic response was defined as at least 65% of follow-up time with plasma viral load (pVL) of less than 50 copies/ml. Immunologic response was defined as a CD4 cell count increase of at least 145 cells/microl. Adherence measures were based on prescription refill compliance. Proportional odds models and logistic regression were used to address our objectives.

RESULTS

The distribution of patient responses was 394 (44.9%) for CD4+/pVL+ (best), 350 (39.9%) for CD4-/pVL+ or CD4+/pVL- (incomplete), and 134 (15.3%) for CD4-/pVL- (worst). We found a positive correlation between adherence and virologic and immunologic responses (P < 0.01). Having worst compared with best response (reference group) was associated with higher odds of mortality (odds ratio: 6.09; 95% confidence interval: 2.57-14.42) and emergence of drug resistance (odds ratio: 10.56; 95% confidence interval: 5.93-18.81) even after adjusting for adherence and HAART regimen.

CONCLUSION

Patients not attaining the best virologic and immunologic responses are at a high risk for emergence of drug resistance and mortality, and these responses are highly dependent on the adherence level and initial HAART regimen. Patients on protease inhibitor-single did worse no matter the adherence level.