Background The real-world effectiveness of pre-exposure prophylaxis (PrEP) may be influenced by circulating HIV strains resistant to either tenofovir or emtricitabine. Yet, few studies have examined rates of resistance to these drugs in clinical settings. Methods We conducted a retrospective cohort study of antiretroviral-naive participants in the Canadian Observational Cohort collaboration who initiated antiretroviral therapy between 2006 and 2014. In separate analyses, we determined the prevalence of pretherapy resistance and cumulative incidence of follow-up resistance to tenofovir and emtricitabine. We used multivariable proportional hazards models to examine associations between baseline variables and the development of resistance. Results We studied 6,622 antiretroviral-naive participants initiating therapy, of whom 5,428 (82.0%) had a baseline resistance test. Baseline resistance to tenofovir and emtricitabine was observed in 83 (1.5%) and 21 (0.4%) patients, respectively. Among patients without baseline resistance, the cumulative incidence of resistance to tenofovir and emtricitabine 5 years following treatment initiation was 0.0070 (95% CI 0.0046, 0.0095) and 0.033 (95% CI 0.028, 0.038), respectively. Following multivariable analysis, a baseline viral load ≥100,000 copies/ml was associated with emergence of tenofovir (hazard ratio [HR] 2.88; 95% CI 1.35, 6.15) and emtricitabine (HR 2.27; 95% CI 1.64, 3.15) resistance. Initiating an integrase inhibitor-based regimen and CD4 + T-cell count below 200 cells/mm 3 were also associated with resistance to each drug. Conclusions We observed a low prevalence of baseline resistance and a low incidence of emergence of resistance to tenofovir and emtricitabine among antiretroviral-naive patients in routine clinical care.

BACKGROUND:This study compared time to virological suppression and rebound between Indigenous and non-Indigenous individuals living with HIV in Canada initiating combination antiretroviral therapy (cART). METHODS:Data were from the Canadian Observational Cohort collaboration; eight studies of treatment-naive persons with HIV initiating cART after 1/1/2000. Fine and Gray models were used to estimate the effect of ethnicity on time to virological suppression (two consecutive viral loads [VLs] <50 copies/ml at least 3 months apart) after adjusting for the competing risk of death and time until virological rebound (two consecutive VLs >200 copies/ml at least 3 months apart) following suppression. RESULTS:Among 7,080 participants were 497 Indigenous persons of whom 413 (83%) were from British Columbia. The cumulative incidence of suppression 1 year after cART initiation was 54% for Indigenous persons, 77% for Caucasian and 80% for African, Caribbean or Black (ACB) persons. The cumulative incidence of rebound 1 year after suppression was 13% for Indigenous persons, 6% for Caucasian and 7% for ACB persons. Indigenous persons were less likely to achieve suppression than Caucasian participants (aHR=0.58, 95% CI 0.50, 0.68), but not more likely to experience rebound (aHR=1.03, 95% CI 0.84, 1.27) after adjusting for age, gender, injection drug use, men having sex with men status, province of residence, baseline VL and CD4+ T-cell count, antiretroviral class and year of cART initiation. CONCLUSIONS:Lower suppression rates among Indigenous persons suggest a need for targeted interventions to improve HIV health outcomes during the first year of treatment when suppression is usually achieved.

OBJECTIVE: Compare all-cause mortality between Indigenous participants and participants of other ethnicities living with HIV initiating combination antiretroviral therapy (cART) in an interprovincial multi-site cohort. METHODS: The Canadian Observational Cohort is a collaboration of 8 cohorts of treatment-naïve persons with HIV initiating cART after January 1, 2000. Participants were followed from the cART initiation date until death or last viral load (VL) test date on or before December 31, 2012. Cox proportional hazard models were used to estimate the effect of ethnicity on time until death after adjusting for age, gender, injection drug use, being a man who has sex with men, hepatitis C, province of origin, baseline VL and CD4 count, year of cART initiation and class of antiretroviral medication. RESULTS: The study sample consisted of 7080 participants (497 Indigenous, 2471 Caucasian, 787 African/Caribbean/Black (ACB), 629 other, and 2696 unknown ethnicity). Most Indigenous persons were from British Columbia (BC) (83%), with smaller numbers from Ontario (13%) and Québec (4%). During the study period, 714 (10%) participants died. The five-year survival probability was lower for Indigenous persons (0.77) than for Caucasian (0.94), ACB (0.98), other ethnicities (0.96) and unknown ethnicities (0.85) (p < 0.0001). In an adjusted proportional hazard model for which missing data were imputed, Indigenous persons were more likely to die than Caucasian participants (hazard ratio = 2.69, p < 0.0001). CONCLUSION: The mortality rate for Indigenous persons was higher than for other ethnicities and is largely reflective of the BC population. Addressing treatment challenges and identifying HIV- and non-HIV-related causes for mortality among Indigenous persons is required to optimize their clinical management.

233 1Clinique médicale du Quartier Latin; 2Unité hospitalière de recherche, d’enseignement et de soin sur le sida (UHRESS), Centre hospitalier de l’Université de Montréal (CHUM), Hôpital Saint-Luc; 3Service de lutte contre les infections transmissibles sexuellement par le sang, ministère de la Santé et des Services sociaux; 4Clinique Golberg, LeBlanc et Rosengren; 5UHRESS, McGill University Health Centre, Royal Victoria Hospital; 6Clinique médicale L’Actuel; 7UHRESS, CHUM, Hôpital-Dieu de Montréal; 8UHRESS, McGill University Health Centre, Montreal General Hospital; 9UHRESS, Hôpital Sainte-Justine, Centre maternel et infantile sur le sida; 10Comité des personnes atteintes du VIH du Québec; 11Coalition des organismes communautaires québécois de lutte contre le sida; 12UHRESS, CHUM, Hôpital Saint-Luc and Hôpital Notre-Dame; 13UHRESS, Centre hospitalier universitaire de Québec; 14Association des médecins microbiologistes infectiologues du Québec, Hôpital Maisonneuve-Rosemont, Montréal, Québec *Members of Le Comité consultatif sur la prise en charge Clinique des personnes vivant avec le VIH/Sida Ministère de la Santé et des services sociaux du Québec Correspondence and reprints: Dr Jean-Guy Baril, Clinique médicale du Quartier Latin, 905 boulevard René-Lévesque Est, Montréal, Québec H2L 5B1. Telephone 514-285-5500, fax 514-285-2226, e-mail jgbaril@vdn.ca Received for publication October 25, 2004. Accepted March 4, 2005 J-G Baril, P Junod, R LeBlanc, et al. HIV-associated lipodystrophy syndrome: A review of clinical aspects. Can J Infect Dis Med Microbiol 2005;16(4):233-243.

HIV therapeutic vaccination represents a potential alternative to chronic antiretroviral administration. Despite highly effective HIV antiretroviral therapy (HAART), residual immune deficiency may limit therapeutic vaccine effectiveness. We therefore vaccinated HIV patients with Streptococcus Pneumoniae (recall-antigen) and bacteriophage phiX174 (neo-antigen) as a first step in determining vaccine competency. Twenty-three adult males with undetectable viral loads for an average 8.2 +/- 4.3 years were administered Pneumovax 23 (PPV23) once and bacteriophage phiX174 antigen on three occasions. PPV23 antibody titers were measured at baseline and 4 weeks post-vaccination and phiX174 antibody levels at 4, 12, and 26 weeks. Responses to PPV23 were defined using AAAAI recommendations on diagnostic vaccination in primary immune deficiency. A protective serotype cutoff level was 1.3 ug/ml. Responses were considered normal if 70% of the serotypes were above the protective cutoff and had a 2-fold increase in the titers. Neutralizing antibody levels and rate of bacteriophage phiX174 inactivation (Kv) determined neo-antigen responses. Abnormal responses were defined as Kv values falling 2 standard deviations from the geometric mean of healthy controls. 16/23 (70%) subjects administered PPV23 had poor post-vaccine responses. In contrast, only 4/23 (17%) patients had inadequate responses to bacteriophage phiX174 vaccination. Despite well-controlled HIV disease, responses to PPV23 were poor. Unexpectedly, most patients responded normally to the neo-antigen phiX174. Studies prior to HAART demonstrated very low titers to phiX174. Further characterization of neo-antigen responses in larger HIV treated cohorts is required to better define vaccine competence and establish the effectiveness of HAART in immune functional recovery.

We sought to evaluate life expectancy and mortality of HIV-positive individuals initiating combination antiretroviral therapy (ART) across Canada, and to consider the potential error introduced by participant loss to follow-up (LTFU).

Purpose of the reviewDuring this era of unprecedented antiretroviral therapeutic efficacy, there is hope for successfully treated individuals to achieve a longevity approaching that of the general population. However, the recent identification of a higher incidence of cardiovascular, bone, metabolic, neurocognitive and other aging comorbidities is of major concern and may compromise that ability. The purpose of this review is to focus on the dynamic process of immune remodelling, known as immune senescence, which occurs during HIV infection, and how it impacts on long-term comorbidities.Recent findingsEarly aging in those with HIV appears to stem from persistent chronic inflammation and residual immune activation despite successful antiretroviral therapy. Multiple similarities exist between the T-cell-senescent phenotypes found in many chronic autoimmune and inflammatory conditions, including HIV disease, and the elderly. The immune risk phenotype is linked to poor clinical outcomes in the elderly and may also have clinical consequences in those with HIV.SummaryImmune senescence results in functional impairments of immunity and a reduced ability to adapt to metabolic stress. Understanding the factors driving the development of immune senescence is critical for the development of strategies to prevent early aging.

Objective(s):We investigated the probability of transitioning in or out of the CD3(+) T-cell homeostatic range during antiretroviral therapy, and we assessed the clinical impact of lost T-cell homeostasis (TCH) on AIDS-defining illnesses (ADIs) or death.Design:Within the Canadian Observational Cohort (CANOC), we studied 4463 antiretroviral therapy (ART)-naive HIV-positive patients initiating combination ART (cART) between 2000 and 2010.Methods:CD3(+) trajectories were estimated using a four state Markov model. CD3(+) T-cel percentage states were classified as follows: very low (<50%), low (50-64%), normal (65-85%), and high (>85%). Covariates associated with transitioning between states were examined. The association between CD3(+) T-cell percentage states and time to ADI/death from cART initiation was determined using Cox proportional hazards models.Results:A total of 4463 patients were followed for a median of 3 years. Two thousand, five hundred and eight (56%) patients never transitioned from their baseline CD3(+) T-cell percentage state; 85% of these had normal TCH. In multivariable analysis, individuals with time-updated low CD4(+) cell count, time-updated detectable viral load, older age, and hepatitis C virus (HCV) coinfection were less likely to maintain TCH. In the multivariable proportional hazards model, both very low and high CD3(+) T-cell percentages were associated with increased risk of ADI/death [adjusted hazard ratio=1.91 (95% confidence interval, CI: 1.27-2.89) and hazard ratio=1.49 (95% CI: 1.13-1.96), respectively].Conclusion:Patients with very low or high CD3(+) T-cell percentages are at risk for ADIs/death. To our knowledge, this is the first study linking altered TCH and morbidity/mortality in cART-treated HIV-positive patients.

Background HIV leads to CD4:CD8 ratio inversion as immune dysregulation progresses. We examined the predictors of CD4:CD8 normalization after combination antiretroviral therapy (cART) and determined whether normalization is associated with reduced progression to AIDS-defining illnesses (ADI) and death. Methods A Canadian cohort of HIV-positive adults with CD4:CD8<1.2 prior to starting cART from 2000–2010 were analyzed. Predictors of (1) reaching a CD4:CD8 ≥1.2 on two separate follow-up visits >30 days apart, and (2) ADI and death from all causes were assessed using adjusted proportional hazards models. Results 4206 patients were studied for a median of 2.77 years and 306 (7.2%) normalized their CD4:CD8 ratio. Factors associated with achieving a normal CD4:CD8 ratio were: baseline CD4+ T-cells >350 cells/mm3, baseline CD8+ T-cells <500 cells/mm3, time-updated HIV RNA suppression, and not reporting sex with other men as a risk factor. There were 213 ADIs and 214 deaths in 13476 person-years of follow-up. Achieving a normal CD4:CD8 ratio was not associated with time to ADI/death. Conclusions In our study, few individuals normalized their CD4:CD8 ratios within the first few years of initiating modern cART. This large study showed no additional short-term predictive value of the CD4:CD8 ratio for clinical outcomes after accounting for other risk factors including age and HIV RNA.

Objective:Studies focusing on HIV-hepatitis C virus (HCV) coinfected individuals without a history of IDU are limited. It is plausible that poorer clinical outcomes in HIV-HCV coinfection are due to factors associated with IDU, not from HCV itself. This study compares HIV treatment outcomes and survival between HIV-HCV coinfected individuals with and without IDU history.Design:Observational cohort study.Methods:We analyzed data from a multisite Canadian cohort study of HIV-positive individuals initiating combination antiretroviral therapy (ART) after 1 January 2000. This analysis was restricted to 1254 participants with HCV coinfection and known IDU history. Cox proportional hazards regression was used to evaluate time from ART initiation to virologic suppression (two consecutive measures <250copies/ml) and CD4(+) cell count recovery (+100cells/l). In order to account for loss to follow-up (LTFU), competing risk analysis was used to evaluate time to death.Results:A total of 1254 participants (31% women) were included. During a median follow-up time of 3.8 years (interquartile range=2.1-6.2), 217 deaths were reported and 148 participants were LTFU. In adjusted multivariable analysis, individuals with IDU history were significantly less likely to achieve virologic suppression [adjusted hazard ratio (AHR)=0.78, 95% confidence interval (CI)=0.64-0.95]; marginally less likely to have CD4(+) cell count recovery (AHR=0.82, 95% CI=0.66-1.00); and had a significantly higher risk of death (AHR=2.15, 95% CI=1.25-3.70).Conclusion:IDU history independently elevates risk for poorer clinical outcomes, separate from HCV coinfection. HIV-HCV coinfected persons are not homogeneous in characteristics or outcomes, suggesting care should be taken during statistical analyses if attributing poorer HIV-specific outcomes solely to HCV coinfection.

Objective: To evaluate the trends in abacavir (ABC) prescription among antiretroviral (ARV) medication-naive individuals following the presentation of the Data Collection on Adverse Events of Anti-HIV Drugs (DAD) cohort study. Methods: We conducted a retrospective cohort study of ARV medication-naive individuals in the Canadian Observational Cohort (CANOC). Results: Between January 1, 2000, and February 28, 2010, a total of 7280 ARV medication-naive patients were included in CANOC. We observed a significant change in the proportion of new ABC prescriptions immediately following the release of DAD (−11%; 95% confidence interval [CI]: −20% to −2.4%) and in the months following the presentation of these data (−0.66% per month; 95% CI: −1.2% to −0.073%). A post-DAD presentation decrease in the odds of being prescribed ABC versus tenofovir (TDF) was observed (adjusted odds ratio, 0.72 per year, 95% CI: 0.54-0.97). Conclusions: Presentation of the DAD was associated with a significant decrease in ABC use among ARV medication-naive, HIV-positive patients initiating therapy.

Background Cohort data examining differences by gender in clinical responses to combination antiretroviral therapy (ART) remain inconsistent and have yet to be explored in a multi-province Canadian setting. This study investigates gender differences by injection drug use (IDU) history in virologic responses to ART and mortality. Methods Data from the Canadian Observational Cohort (CANOC) collaboration, a multisite cohort study of HIV-positive individuals initiating ART after January 1, 2000, were included. This analysis was restricted to participants with a follow-up HIV-RNA plasma viral load measure and known IDU history. Weibull hazard regression evaluated time to virologic suppression (2 consecutive measures <50 copies/mL), rebound (>1000 copies/mL after suppression), and all-cause mortality. Sensitivity analyses explored the impact of presumed ART use in pregnancy on virologic outcomes. Results At baseline, women (1120 of 5442 participants) were younger (median 36 vs. 41 years) and more frequently reported IDU history (43.5% vs. 28.8%) (both p<0.001). Irrespective of IDU history, in adjusted multivariable analyses women were significantly less likely to virologically suppress after ART initiation and were at increased risk of viral load rebound. In adjusted time to death analysis, no differences by gender were noted. After adjusting for presumed ART use in pregnancy, observed gender differences in time to virologic suppression for non-IDU, and time to virologic rebound for IDU, became insignificant. Conclusions HIV-positive women in CANOC are at heightened risk for poor clinical outcomes. Further understanding of the intersections between gender and other factors augmenting risk is needed to maximize the benefits of ART.

Initiating highly active antiretroviral therapy (HAART) with low CD4 counts or AIDS-defining illnesses (ADIs) increases risk of treatment failure and death. We examined factors associated with late initiation among 18- to 29-year-olds within the Canadian Observational Cohort (CANOC) collaboration, a multi-site study of HIV-positive persons who initiated HAART after 2000. Late initiation was defined as beginning HAART with a CD4 count <200 cells/mm(3) and/or having a baseline ADI. Multivariable logistic regression was used to identify independent correlates of late initiation. In total, 1026 individuals (422 from British Columbia, 400 from Ontario, and 204 from Quebec) met our age criteria. At HAART initiation, median age was 27 years (interquartile range, 24, 28 years). A total of 412 individuals (40%) identified as late initiators. Late initiation was associated with female gender, age >25 years at initiation, initiating treatment in earlier years, and having higher baseline viral load. The high number of young adults in our cohort starting HAART late indicates important target populations for specialized services, increased testing, and linkages to care.

Background: Controversy about the relative performance of abacavir (ABC)/lamivudine (3TC) and tenofovir (TDF)/emtricitabine (FTC) in initial combination antiretroviral therapy (cART) exists. Methods: We compared the times to regimen failure (composite of virologic failure or switching/stopping nucleosides for any reason) according to nucleoside backbone in treatment-naive patients starting cART in a retrospective observational cohort study. Additional endpoints included virologic failure, switching/stopping nucleosides for nonvirologic reasons, and virologic suppression. Treatment-naive noninjection drug user individuals in the Canadian Observational Cohort initiating ABC/3TC-containing or TDF/FTC-containing cART with efavirenz, nevirapine, lopinavir/ritonavir, or atazanavir/ritonavir with ≥6 months follow-up were included. Multivariable proportional hazards regression models accounting for competing risks were used to model outcomes. Results: One thousand seven hundred sixty-four individuals (588 ABC/3TC, 1176 TDF/FTC) were included. Median (interquartile range) follow-up times were 34 (23-50) and 20 (13-30) months, respectively. Time to regimen failure was similar for ABC/3TC versus TDF/FTC [adjusted hazard ratio, (aHR) = 0.96, 95% CI = 0.80 to 1.17] after adjusting for baseline viral load (VL), sex, province, third antiretroviral agent, year of cART initiation, HLA-B*5701 test availability, and rate of VL testing. No differences were observed in time to virologic failure (aHR = 0.84, 95% CI = 0.58 to 1.20), switching/stopping nucleosides for nonvirologic reasons (aHR = 1.02, 95% CI = 0.81 to 1.28), or virologic suppression (aHR = 0.96, 95% CI = 0.83 to 1.10). There was no statistical interaction between backbone and baseline VL for any outcome. Results were similar when stratified by baseline VL ≤ 100,000 or > 100,000 copies per milliliter. Conclusions: In our naive noninjection drug user HIV-infected patients starting cART, there was no difference in time to regimen failure, virologic failure, switching/stopping nucleosides, or virologic suppression with ABC/3TC versus TDF/FTC.

Objective: To determine the long-term impact of immunologic discordance (viral load,50 copies/mL and CD4(+) count <200 cells/mm(3)) in antiretroviral-naive patients initiating combination antiretroviral therapy (cART).Methods: Our analysis included antiretroviral-naive individuals from a population-based Canadian Observational Cohort that initiated cART after January 1, 2000, and achieved virologic suppression. Multivariable Cox proportional hazards regression was used to examine the association between 1-year and 2-year immunologic discordance and time to death from all-causes. Correlates of immunologic discordance were assessed with logistic regression.Results: Immunologic discordance was observed in 19.9% (404 of 2028) and 10.2% (176 of 1721) of individuals at 1 and 2 years after cART initiation, respectively. Two-year immunologic discordance was associated with an increased risk of death [adjusted hazard ratio = 2.69; 95% confidence interval (CI): 1.26 to 5.78]. One-year immunologic discordance was not associated with death (adjusted hazard ratio = 1.12; 95% CI: 0.54 to 2.30). Two-year immunologic discordance was associated with older age (aOR per decade = 1.23; 95% CI: 1.03 to 1.48), male gender (aOR = 1.86; 95% CI: 1.09 to 3.16), injection drug use (aOR = 2.75; 95% CI: 1.81 to 4.17), and lower baseline CD4(+) count (aOR per 100 cells = 0.24; 95% CI: 0.19 to 0.31) and viral load (aOR per log(10) copies/mL = 0.46; 95% CI: 0.33 to 0.65).Conclusions: Immunologic discordance after 2 years of cART in antiretroviral-naive individuals was significantly associated with an increased risk of mortality.

Resistance to available antiretroviral (ARV) agents is of increasing concern, and development of novel agents that address this problem has been identified as a major public health priority. As ARV resistance becomes more prevalent with extended use of existing agents, individuals with HIV infection resistant to all three traditional classes of ARVs, nucleoside reverse transcriptase inhibitors (NRTIs), non‐nucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs), find themselves increasingly limited with regard to effective treatment options. The need for tolerable new drug regimens that effectively suppress viral replication while being simple to adhere to is increasingly pressing. This article reviews the epidemiology of antiretroviral drug resistance, the factors that contribute to the emergence of resistance, and presents data that support the need for early detection of resistance and maximal virologic suppression in order to delay treatment failure and reduce mortality. Healthcare providers are encouraged to optimize therapy through the use of new agents from existing drug classes, which can minimize cross‐resistance, as well as agents with novel mechanisms of action, in order to realize the potential for greater viral containment and to forestall development of resistance mutations. This article evaluates several emerging therapies that are in late‐stage clinical development and promise to expand treatment options for highly treatment‐experienced patients with the goal of improving outcomes for HIV‐infected individuals whose options for sustained antiviral efficacy are increasingly limited. J. Med. Virol. 80:565–576, 2008. © 2008 Wiley‐Liss, Inc.

Concomitant HIV and hepatitis C virus (HCV) is a common yet complex coinfection. The present document is a practical guide for treating HCV infection in people coinfected with HIV. Effective antiretroviral therapies have prolonged survival rates for HIV-infected people over the past decade, which have made latent complications of HCV major causes of morbidity and mortality in these patients. Advances in the treatment of HCV (eg, combined pegylated interferon and ribavirin) offer the possibility of eradicating HCV infection in coinfected persons. The treatment of HCV must be considered in all cases. Intensive management of the adverse effects of HCV treatment is one of the factors for the success of these therapies. HCV eradication is predicted to decrease the mortality associated with coinfection and reduce the toxicity of HIV treatment.

Recent data from clinical trials investigating the efficacy of enfuvirtide, a fusion inhibitor, in treatment-experienced patients have revealed that the addition of enfuvirtide (ENF) to an active boosted protease inhibitor regimen doubles the rate of virological response. At week 48 of the TORO studies, 55% of patients previously naive to and receiving lopinavir/ritonavir (LPV/r) with ENF achieved a viral load of <400 copies/mL compared with 24% of patients treated with LPV/r alone. At week 24 of the RESIST studies, 70% of previously ENF-naive patients who took both ENF and tipranavir/ritonavir (TPV/r) achieved a >or=1 log10 reduction in viral load compared with 37% of such patients treated with TPV/r alone. Similarly, concomitant use of TMC114/ritonavir (TMC114/r) with ENF, compared with TMC114/r alone, increased the number of patients with <50 copies/mL from 46% to 64% in a combined 24-week analysis from the POWER trials. Data from these trials suggest that combining one agent from a new class with a new agent from a previously exposed class offers a greater chance of achieving full virological control than either type of agent alone. Undetectable viraemia should be the primary objective for treatment-experienced patients requiring a switch in therapy, and the present data support the combination of an active boosted protease inhibitor with an agent from a new class (e.g., ENF) for triple-class-experienced patients.

BACKGROUND AND OBJECTIVES: An eight-member group consisting of Canadian infectious disease and immunology specialists and a family physician with significant experience in HIV management was convened to update existing recommendations, specifically intended for use by Canadian HIV-treating physicians, on the appropriate use of enfuvirtide in HIV/AIDS patients with resistance to other antiretroviral drugs. METHODS: Evidence from the literature and expert opinions of the group members formed the basis of the guidelines. Comments on the draft guidelines were obtained from other physicians across Canada with HIV expertise. The final guidelines represent the group's consensus agreement. RESULTS AND CONCLUSIONS: The recommendations were developed to guide physicians in optimal practices in patient selection for enfuvirtide treatment and subsequent patient management. The issues considered include positive predictors of response to enfuvirtide, stage of disease, optimization of the background regimen, early indicators of enfuvirtide response, and patient education and support.