Do dual nucleoside regimens have a role in an era of plasma viral load-driven antiretroviral therapy?

HIV viral load: a concept analysis and critique

In this article, we examine the concept of HIV viral load and how it has evolved over time (1995-2013) in the field of HIV/AIDS. Although the term viral load is used extensively in this field, few efforts have been directed toward the conceptualization of HIV viral load, which is often left unquestioned, undertheorized, and portrayed as a neutral and objective laboratory value that has remained relatively stable over time--with the exception of progressive advancements in technology, techniques, and sensitivity. The purpose of this article is to apply the evolutionary concept analysis method developed by Rodgers (1989, 2000a) to the concept of HIV viral load. To set the stage, we establish the need for a concept analysis of HIV viral load and provide an overview of the evolutionary view. Then, drawing on the steps proposed by Rodgers (2000a), we outline the process of data collection, management, and analysis. We then offer an in-depth discussion of the findings (attributes, antecedents, and consequences) informed by Wuest's (2000) critical approach to concept analysis. We conclude by highlighting the implications of this analysis for clinical practice, research, and theory.

Inadequacies in antiretroviral therapy use among Aboriginal and other Canadian populations

We undertook this study to provide a profile of Aboriginal people initiating antiretroviral therapy and their response to treatment. Aboriginal peoples were identified through self-report. Baseline socio-demographics and risk factors were compared between Aboriginal and non-Aboriginal participants as were baseline factors associated with two consecutive plasma viral load measures below 500 copies/ml using contingency table analysis. Multivariate survival analysis of the prognostic factors associated with time to two consecutive plasma viral load measures below 500 copies/ml among eligible participants was undertaken to characterize response to antiretroviral therapy. There were 892 participants with available data for this analysis, of those 146 (16%) self-identified as Aboriginal. Aboriginal participants were more likely to be female (p < or = 0.001), have lower baseline plasma viral loads (p = 0.010), be co-infected with HCV (p < 0.001), live in unstable housing (p < or = 0.001), and report an income of >10K CDN (p < or = 0.001) per annum. Aboriginal people were less likely to report men who have sex with men (p < or = 0.001) and more likely to report injection drug use (p < or = 0.001) as a risk factor for HIV infection. Aboriginal participants were more likely to receive double versus triple combination antiretroviral therapy (p = 0.002), be less adherent in the first year on therapy (p = 0.001) and to have a physician less experienced with treating HIV (p < or = 0.001). When these factors were controlled for, Aboriginal people treated with triple combination therapy were as likely to respond and suppress their viral load below 500 copies. In the era of HAART, our results indicate that Aboriginal people living with HIV/AIDS were less likely to receive optimal therapy. However, when Aboriginals did receive triple drug therapy they suppressed just as well as non-Aboriginals.

Outcome of critically ill human immunodeficiency virus-infected patients in the era of highly active antiretroviral therapy

The purpose of this study was to determine the effect of prior use of highly active antiretroviral therapy (HAART) on outcome of human immunodeficiency virus (HIV)- patients admitted to intensive care units (ICUs). This study was a retrospective chart review of 242 HIV-infected patients who required 259 consecutive admissions to a university-affiliated hospital ICU during a 3-year period. Patient demographics, CD4 count, admission diagnosis, prior HAART, Pneumocystis jiroveci prophylaxis, length of stay, and ICU and hospital mortality were determined. Overall hospital mortality was 39%. Comparing patients who had received HAART before an ICU admission to those who had not, we found no difference between ICU or hospital mortality, need of mechanical ventilation, ICU and hospital length of stay, and incidence of P jiroveci. Pulmonary diagnosis was the most frequent ICU admission diagnosis (30%). Logistic regression analysis showed HIV-related illness and mechanical ventilation were significant independent predictors of increased hospital mortality.

Effect of Persistent Moderate Viremia on Disease Progression During HIV Therapy

OBJECTIVE

Although highly active antiretroviral therapy has been shown to lower plasma HIV-1 RNA in HIV infection, many patients do not reach the target goal of undetectable viremia. We evaluated whether risk of clinical progression varies by level of viral suppression achieved.

DESIGN

Patients in the Collaborations in HIV Outcomes Research/United States cohort who maintained stable HIV-1 RNA levels of either <400, 400 to 20,000, or >20,000 copies/mL during a run-in period of at least 6 months were studied. Baseline was the first day after this period.

METHODS

Proportional hazards models were used to quantify the relation between baseline HIV-1 RNA levels and risk of a new AIDS-defining diagnosis or death after adjusting for CD4 count, age, gender, ethnicity, study site, prior AIDS-defining diagnosis, and antiretroviral therapy history.

RESULTS

Patients (N = 3010) were followed for up to 4.3 years after the 6-month run-in period, with 343 deaths or AIDS-defining diagnoses reported. The risk of a new AIDS-defining diagnosis or death was not significantly different in the 400 to 20,000- and <400-copies/mL groups (6% vs. 7%, hazard ratio [HR] = 1.0, 95% confidence interval [CI]: 0.7-1.4; P = 0.9) but was significantly higher in the >20,000-copies/mL group (26%, HR = 3.3, 95% CI: 2.5-4.4; P < 0.001 vs. the <400-copies/mL group). Median CD4 count changes during the first year of follow-up showed increases of 75 and 13 cells/mm for the <400- and 400 to 20,000-copies/mL groups, respectively, whereas the >20,000-copies/mL group had a decrease of 23 cells/mm.

CONCLUSIONS

Patients who maintained baseline HIV-1 RNA levels of 400 to 20,000 copies/mL for at least 6 months preserved immunologic status and were no more likely to die or develop a new AIDS-defining diagnosis in the time frame studied than those with baseline levels <400 copies/mL. Patients with HIV-1 RNA levels >20,000 copies/mL at baseline had greater clinical and immunologic deterioration. These data suggest that maintenance of moderate viremia may confer clinical benefit not seen when viremia exceeds 20,000 copies/mL, and this should be taken into account when considering the risks and benefits of continuing failing therapy.

In vitro-in vivo model for evaluating the antiviral activity of amprenavir in combination with ritonavir administered at 600 and 100 milligrams, respectively, every 12 hours

The study objective was to evaluate the pharmacodynamics of amprenavir in an in vitro system, develop an exposure target for maximal viral suppression, and determine the likelihood of target attainment based on the pharmacokinetics of amprenavir and ritonavir in human immunodeficiency virus (HIV)-infected patients. Population pharmacokinetic data were obtained from 13 HIV-infected patients receiving amprenavir and ritonavir in doses of 600 and 100 mg, respectively, every 12 h. A 2,500-subject Monte Carlo simulation was performed. Target attainment was also estimated for a target derived from clinical data. Maximal viral suppression (in vitro) was achieved when amprenavir free-drug concentrations remained greater than four times the 50% effective concentration (EC(50)) for 80% of the dosing interval. At an amprenavir EC(50) of 0.03 microM, the likelihood of target attainment is 97.4%. For reduced-susceptibility isolates for which the EC(50)s are 0.05 and 0.08 microM, target attainment is 91.0 and 75.8%, respectively. For the clinical target of a trough concentration/EC(50) ratio of 5, the target attainment rates were similar. Treatment with amprenavir and ritonavir at doses of 600 and 100 mg, respectively, twice a day provides excellent suppression of wild-type isolates and reduced-susceptibility isolates up to an EC(50) of 0.05 micro M. Even at 0.12 microM, target attainment likelihood exceeds 50%, making this an option for patients with extensive exposure to protease inhibitors when this treatment is used with additional active antiretroviral agents.

-Dual nucleoside therapy for HIV infection: analysis of results and factors influencing viral response and long term efficacy

We performed a retrospective analysis of our experience with dual nucleoside regimens to look for predictors of long term benefit. The study evaluated a cohort of 68 HIV-infected patients treated at 3 Italian hospital-based facilities. The results were evaluated using univariate and multivariate statistical analysis. Fourty-three males and 25 females were treated for 22 +/- 14 months. Sixty three patients (92.6%) suffered no or low-grade side-effects. Thirty-four patients (50%) reached a viral load <400 copies/ml (undetectable). Viremia remained persistently undetectable in 9 cases (13.2%). Variable relapses of viremia were seen in 13 patients (19.1%) even though their therapys were not modified. Eight patients (11.8%) showed relapsing viremias persistently around or below 10,000 copies/ml. All patients reaching undetectable viremia but one showed increasing or stable CD4+ cell counts. Factors predicting favourable response were: pre-treatment CD4+ T-cells >150/microl, pre-treatment viremia <50,000 copies/ml, pre-treatment lymphocytes >1,500/microl, and no previous exposure to NRTI. Total lymphocyte counts and CD4+ T-cells showed a significant correlation. Dual NRTI regimens may be still considered for patients unable to tolerate HAART regimens and presenting with favourable predictors of response.

Socioeconomic status, access to triple therapy, and survival from HIV-disease since 1996

BACKGROUND

In the era before highly active antiretroviral therapy (HAART), socioeconomic status was associated with survival from HIV disease. We have explored socioeconomic status, access to triple therapy (HAART), and mortality in the context of a universal healthcare system.

METHODS

We evaluated 1408 individuals who initiated double or triple therapy between 1 August 1996 and 31 December 1999, and were followed until 31 March 2000. Cumulative HIV-related mortality rates were estimated using Kaplan-Meier methods and Cox proportional hazards regression.

RESULTS

In the overall Cox model, we found that adherence [risk ratio (RR) 0.83; per 10% increase], CD4 cell count (RR 1.53; per 100 cell decrease), and lower socioeconomic status (RR 2.19; high versus low), were associated with HIV-related mortality. However, socioeconomic status was not significant among patients prescribed triple therapy in a stratified analysis, or in a sub-analysis restricted to patients prescribed HAART in the initial regimen. When we investigated if inequitable access to HAART by socio-economic status could explain the discrepancy, we found that persons in the lower socio-economic strata were less likely to be prescribed triple therapy even after adjustment for clinical characteristics.

CONCLUSION

In a universal healthcare system, socioeconomic status was strongly associated with HIV-related mortality. When we investigated possible explanations for this association, we found that individuals of lower socioeconomic status were less likely to receive triple therapy after adjustment for clinical characteristics. Our findings highlight the need for the monitoring of therapeutic guidelines to ensure equitable access, as treatment strategies are updated.

"Discordant" increases in CD4 cell count relative to plasma viral load in a closely followed cohort of patients initiating antiretroviral therapy

BACKGROUND

In HIV-positive persons receiving antiretroviral therapy, CD4 cell responses are associated with optimal suppression of viral replication. However, increases in CD4 cell counts in the absence of viral suppression have been reported. We characterized plasma viral load (pVL) and CD4 cell count increases in closely followed patients to evaluate determinants and the prevalence of CD4 cell responses at a populational level.

METHODS

All HIV-positive patients in the province of British Columbia, Canada, who were antiretroviral naive and initiated therapy between August 1996 and May 1998 were eligible for the study. The selection criteria were that patients had to have CD4 cell counts and pVLs measured at baseline and at least once during eight 16-week periods after the initiation of therapy. We characterized CD4 cell responses and sought patients who had a "discordant" increase at 1 year, which was defined as an increase in CD4 cell count of >or=50/mm3 with a <1 log10 decrease in pVL. We also evaluated adherence and antiretroviral use.

RESULTS

Overall, when baseline and 1-year pVLs and CD4 cell counts were compared, 6.2% of patients had CD4 cell count increases without pVL decreases of >or=1 log10. However, when all pVLs before 1 year were considered, 92% of the discordant increases could be attributed to prior transient or partial viral suppression. Furthermore, although substantial increases in CD4 cell counts were observed in transient virologic responders, the cumulative number of antiretroviral agents used by this group was significantly higher than that used by full virologic responders (p <.001).

CONCLUSIONS

Our results demonstrate that virtually all CD4 cell count increases can be attributed to transient or partial pVL suppression. Unmeasured pVL suppression likely explains discordant responses that have been previously reported. Similarities between transient and full virologic responders also appear to be time limited and are often associated with greater cumulative use of antiretroviral therapy by transient virologic responders.

Impact of adherence on duration of virological suppression among patients receiving combination antiretroviral therapy

OBJECTIVE

To assess the effect of adherence to antiretroviral therapy on the duration of virological suppression after controlling for whether or not the patient ever attained a plasma viral load below the limit of detection of sensitive HIV-1 RNA assays.

METHODS

Data were combined from three randomized, blinded clinical trials (INCAS, AVANTI-2, and AVANTI-3) that compared the antiviral effects of two- and three-drug antiretroviral regimens. Virological suppression was defined as maintaining a plasma viral load below 1000 copies/mL. Adherence was defined prospectively and measured by patient self-report.

RESULTS

Adherence did not have a major impact on the probability of achieving virological suppression for patients receiving dual therapy. However, for patients receiving triple therapy, adherence increased the probability of virological suppression, whether the plasma viral load nadir was above or below the lower limit of quantification. Compared to adherent patients with a plasma viral load nadir below the lower limit of quantification, the relative risk of virological failure was 3.0 for non-adherent patients with a nadir below the limit, 18.1 for adherent patients with a nadir above the limit, and 32.1 for non-adherent patients with a nadir above the limit.

CONCLUSION

For patients receiving current three-drug antiretroviral regimens, adherence to therapy and plasma viral load nadir are important factors determining the duration of virological suppression.

The importance of bacterial sepsis in intensive care unit patients with acquired immunodeficiency syndrome: Implications for future care in the age of increasing antiretroviral resistance

OBJECTIVE

To describe the clinical characteristics and outcomes of patients with acquired immunodeficiency syndrome (AIDS) admitted to the intensive care unit (ICU).

DESIGN

An observational cohort study with retrospective chart review.

SETTING

ICU of an urban university medical center.

PATIENTS

Consecutive ICU admissions of patients with AIDS at an urban university medical center between December 1993 and June 1996.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For each patient, we recorded ICU admission diagnosis, clinical characteristics, and outcome. Among 129 ICU admissions of patients with AIDS, 102 (79%) were admitted for infections, of which (45%) had infections caused by bacteria. Pseudomonas aeruginosa, Staphylococcus aureus, and other enteric pathogens were the most frequent isolates. Pneumonia accounted for 65% of 102 admissions for infections. Overall hospital mortality was 54%, but mortality was higher (68%) for patients with bacterial sepsis. Neutropenia was associated with differences in unadjusted survival rates, whereas CD4 counts were not. Independent predictors of hospital mortality included increasing acute physiology scores and severity of sepsis.

CONCLUSIONS

In our ICU, among patients with AIDS, sepsis resulting from bacterial infection is now a more frequent cause of admission than Pneumocystis carinii pneumonia. Severity of illness and the presence of severe sepsis were the clinical predictors most associated with increased mortality. Patients who are not receiving or responding to highly active antiretroviral therapy may become as likely to be admitted to an ICU with a treatable bacterial infection as with classic opportunistic infections. Therefore, broad-spectrum empirical antibacterial therapy is particularly important when the etiology of infection is uncertain.

Prolonged suppression of human immunodeficiency virus type 1 RNA during dual nucleoside reverse-transcriptase-inhibitor therapy in clinical practice

Because there is limited information about suppression of virus loads (determined by current "ultrasensitive" assays) in patients receiving nucleoside reverse-transcriptase inhibitors (NRTIs) alone, we reviewed our experience in clinical practice with patients who had virus loads of <25 copies/mL after >1 year of treatment with dual NRTIs.

A randomized, double-blind trial of half versus standard dose of zidovudine plus zalcitabine in Thai HIV-1-infected patients (study HIV-NAT 001). HIV Netherlands Australia Thailand Research Collaboration

BACKGROUND

Triple combination antiretroviral therapy, recommended as standard of care, is unaffordable for much of the developing world.

OBJECTIVES

To establish whether half doses of zidovudine (AZT) and zalcitabine (ddC) are as effective as standard doses in a Thai population with lower body weight than Western populations and predominantly infected with HIV-1 subtype E.

METHODS

A group of 116 antiretroviral naive patients, with CD4 cell counts 100-500 x 10(6) cells/l, were randomized to: AZT 200 mg three times daily plus ddC 0.75 mg three times daily versus AZT 100 mg three times daily plus ddC 0.375 mg three times daily and followed-up regularly for 48 weeks.

RESULTS

The study enrolled 111 patients: 59 men and 52 women, body weight (mean +/- standard deviation) 56.4 +/- 12.3 kg, mean CD4 cell count 324 x 10(6) cells/l, mean HIV RNA 4.7 log10 copies/ml. There were no significant differences between the two groups. Twelve patients discontinued, including two deaths that were unrelated to study medication. No significant differences in adverse events were seen. Week 48 data for the standard dose and half dose arms, respectively, were mean CD4 cell count increases of 52 and 78 x 10(6) cells/l (P = 0.34), mean plasma HIV-1 RNA reduction of 1.4 and 1.1 log10 copies/ml (P = 0.10), HIV RNA of < 400 copies/ml in 52 and 20%[ (P = 0.001). Participants with higher than mean baseline CD8 cell counts (mean 1062 x 10(6) cells/l) showed greater decline in CD8 cells on standard doses. Further analysis showed improved reduction in HIV RNA (P < 0.0001) and in the percentage with undetectable HIV RNA (P = 0.0137) in the standard dose arm, corrected for baseline HIV RNA, which if < 4.75 log10 copies/ml significantly correlated with HIV RNA < 400 copies/ml at week 48.

CONCLUSION

At week 48, the proportion with HIV RNA < 400 copies/ml was significantly higher in the standard dose arm; lower baseline HIV RNA correlated with better HIV RNA outcome at 48 weeks. The arms did not differ in CD4 cell response but standard doses correlated with greater CD8 cell decline.

A randomized, dose-finding study with didanosine plus stavudine versus didanosine alone in antiviral-naive, HIV-infected Thai patients

OBJECTIVES

To evaluate the safety and efficacy of four different regimens of didanosine (ddI) + stavudine (d4T) in HIV-infected Thais.

DESIGN

Prospective, open-label, randomized study.

METHODS

Patients were randomized to four regimens of high and low doses of ddI and d4T or to ddI alone. D4T was added to the ddI-alone arm after week 24. The duration of study was 48 weeks.

RESULTS

Seventy-eight patients were randomized (mean CD4 cell count, 255 x 10(6)/l; mean plasma HIV-1 RNA; 4.3 log10 copies/ml). In the intent-to-treat analysis, 78% of patients in the pooled combination arms and 20% of the patients in the ddI alone arm (to which d4T was added after 24 weeks) showed plasma HIV-1 RNA < 500 copies/ml at week 24 (P < 0.001), and 59% versus 53% at week 48, respectively. In addition, the proportion of patients with < 50 HIV-1 RNA copies/ml was 13% versus 7% at week 24 (P = 0.5) and 17% versus 20% at week 48 respectively. At week 24, median CD4 cell count increases from baseline were 101 x 10(6)/l in the pooled combination versus 76 x 10(6)/l in the ddI alone arm (P = 0.78). Logistic regression modeling suggested a correlation between receiving high dose ddI and achieving HIV-1 RNA < 500 copies/ml at week 48 (P = 0.07).

CONCLUSIONS

The d4T/ddI combination was superior to ddI alone in producing HIV-1 viral suppression. At week 48, > 60% of patients treated with this combination reached HIV-1 RNA levels < 500 copies/ml. Receiving high dose ddI but not d4T may correlate with a better viral suppression.

The triple combination indinavir-zidovudine-lamivudine is highly synergistic

Administration of the combination of indinavir-zidovudine-lamivudine has been demonstrated to cause a large fraction of treated patients to have a decline in human immunodeficiency virus type 1 (HIV-1) copy number to below the detectability of sensitive assays. A recent investigation (G. L. Drusano, J. A. Bilello, D. S. Stein, M. Nessly, A. Meibohm, E. A. Emini, P. Deutsch, J. Condra, J. Chodakewitz, and D. J. Holder, J. Infect. Dis. 178:360-367, 1998) demonstrated that the durability of the antiviral effect was affected by combination chemotherapy. Zidovudine-lamivudine-indinavir differed significantly from the combination of zidovudine plus indinavir. We hypothesized that the addition of lamivudine might alter the regimen, producing a synergistic anti-HIV effect. In vitro analysis of drug interaction demonstrated that zidovudine-indinavir interacted additively. The addition of lamivudine in concentrations which suppressed viral replication by 20% or less by itself demonstrated marked increases in the synergy volume, increasing the synergy volume 20-fold with the addition of 320 nM lamivudine (which does not suppress HIV by itself) and 40-fold with the addition of 1,000 nM lamivudine (20% viral inhibition as a single agent). A fully parametric analysis with a newly developed model for three-drug interaction confirmed and extended these observations. The interaction term (alpha(IND,AZT, 3TC)) for all three drugs showed the greatest degree of synergy. This marked synergistic interaction among the three agents may explain some of the clinical results which differentiate this regimen from the double-drug regimen of zidovudine plus indinavir.

Dual nucleoside regimens in nonadvanced HIV infection: prospective follow-up of 130 patients, Aquitaine Cohort, 1996 to 1998. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine (GECSA)

OBJECTIVE

To describe the response to combinations of two nucleoside reverse transcriptase inhibitors (NRTIs) initiated early in the course of HIV infection under routine circumstances and to research prognostic factors indicating good virologic response.

SETTING

Patients of the Aquitaine Cohort, a hospital-based open cohort that had been recruiting since 1987 in five public hospitals of the Aquitaine region in southwestern France.

METHODS

Prospective cohort study of antiretroviral-naive patients with CD4+ cell counts >0.350 x 10(9)/L who started dual NRTI therapy between January 1996 and June 1997. Intent-to-treat analysis and multivariate logistic regression were used with data collected up to March 31, 1998.

RESULTS

In this study, 130 patients were enrolled with a median follow-up of 14 months. At the time of first prescription, 79% were in U. S. Centers for Disease Control and Prevention (CDC) group A, 16% in group B, and 5% in group C; median CD4+ cell count was 0.466 x 10(9)/L and median HIV RNA level was 4.52 log10 copies/ml. The two main combinations used were zidovudine (AZT) plus zalcitabine (ddC; 38%) and AZT plus didanosine (ddI; 37%). At week 52, median CD4+ and HIV RNA responses were, respectively, +80 cells and -1.6 log; the proportions of patients with HIV RNA level <5000 and <500 copies/ml were 70% and 45%, respectively, and 96% of the patients had a CD4+ cell count >0.350 x 10(9)/L at that time. At their last follow-up, 3 patients had reached been diagnosed with full-blown AIDS and the AIDS-free survival probability at 1 year was 98.2% (95% confidence interval [CI], 93.1-99.6); 1 death had occurred. The only significant variable associated with an undetectable HIV RNA level at 1 year was a lower HIV RNA level at the first prescription of dual therapy.

CONCLUSION

Our data indicate that dual nucleoside combinations could be a therapeutic option for patients diagnosed and observed during follow-up in the early course of HIV infection.