Transient Relapses (“Blips”) of Plasma HIV RNA Levels During HAART Are Associated With Drug Resistance:

Integrated analysis of viral blips, residual viremia, and associated factors in people with HIV: Results from a retrospective cohort study

The etiology of viral blips is not yet fully elucidated. One of the hypotheses is that blips reflect variations in residual viremia (RV) near the detectability threshold. In this study, we evaluated whether RV is associated with viral blips and which factors are associated with RV. All treatment regimens in 2010-2020 consisting of two nucleos(-t)ide reverse transcriptase inhibitors and one anchor (integrase strand transfer inhibitor [INSTI], non-nucleoside reverse transcriptase inhibitor [NNRTI], or protease inhibitor [PI]) in people with HIV (PWH) were evaluated for RV (detectable viremia <50 cp/mL) and blips (isolated viral loads [VLs] 50-499 cp/mL between measurements <50 cp/mL). All medical records were reviewed and regimens in which a VL ≥ 50 cp/mL was deemed to result from non-adherence (based on the documented conclusion by the treating physician) were excluded. Factors associated with blips and RV were identified using generalized linear mixed models. In total, 24 518 VLs from 1658 PWH were analyzed. VLs were measured during INSTI- (n = 5119; 20.9%), PI- (n = 8935; 36.4%), and NNRTI-use (n = 10 464; 42.7%). VLs were categorized as blips in 1.4% (n = 332). The 24,186 non-blip VLs were RNAneg (no RV) (n = 15 326; 63.4%), 1-19 cp/mL (n = 6318; 26.1%), 20-49 cp/mL (n = 1620; 6.7%), or <50 cp/mL with an unknown RV level (n = 922; 3.8%). In 193/1658 PWH (11.6%), the RV level was RNAneg in all VLs assessed. RV 1-19 cp/mL and 20-49 cp/mL (vs. RNAneg ) were significantly associated with subsequent viral blips (respective odds ratio 2.66 and 4.90 [95% confidence intervals: 1.98-3.58 and 3.41-7.04]). Zenith VL and use of PIs (vs. INSTIs/NNRTIs) were associated with higher RV and blip odds. This large cohort study showed that blips were associated with higher preceding RV. Both the anchor type and factors previously linked to the latent viral reservoir were associated with RV, suggesting blips having a multifactorial origin.

Efficacy, durability, and tolerability of bictegravir/emtricitabine/tenofovir alafenamide for the treatment of HIV in a real-world setting in Belgium

OBJECTIVES

Our objective was to evaluate the efficacy, durability, and tolerability of bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) in a real-world setting in Belgium.

METHODS

This was a retrospective, multicentre cohort study involving adult treatment-naïve (TN) and treatment-experienced (TE) people living with HIV receiving BIC/FTC/TAF between 1 January 2019 and 30 September 2020. The primary outcome was rate of virological suppression (plasma HIV-1 viral load <50 copies/mL; on-treatment analysis) at weeks 24 and 48. The main secondary outcomes included loss of virological suppression (LVS; two consecutive viral loads of >200 copies/mL after being virologically suppressed) by week 48 and analysis of resistance-associated mutations at time of LVS; tolerability of BIC/FTC/TAF over the 48-week study period; and change in weight and proportion of participants reporting a >10% weight gain at week 48.

RESULTS

Overall, 2001 participants were included. Through 48 weeks, overall rate of virological suppression was 93.5%, with similar results observed in the following subgroups: age ≥50 years (92.7%), women (92.8%), Black sub-Saharan African (91%), TN (94%), TE (93.2%), and non-suppressed at baseline (86.6%). LVS was observed in 0.7% (n = 14) of participants, with one participant developing resistance-associated mutations to nucleoside reverse transcriptase inhibitors (184 V) and integrase strand transfer inhibitors (263KR). Of the 131 (6.5%) treatment discontinuations, the most common reason was an adverse event (2.4%), with the most frequent being central nervous system/psychiatric (0.4%) and gastrointestinal (0.4%) toxicity. Median weight gain at week 48 was 2 kg (interquartile range -1 to 5), and a >10% weight increase was observed in 11.6% of participants.

CONCLUSION

In this large real-world cohort, BIC/FTC/TAF showed excellent virological efficacy in a diverse population of patients with HIV. Rare occurrence of emergent drug resistance was observed, and treatment was well tolerated.

Efficacy, durability, and tolerability of dolutegravir/lamivudine and dolutegravir/rilpivirine for the treatment of HIV in a real-world setting in Belgium

OBJECTIVES

A paradigm shift from three-drug regimens to two-drug regimens (2DRs) is currently taking place in real-world clinical practice. This study aimed to describe the efficacy, durability, and tolerability of dolutegravir (DTG)/lamivudine (3TC) and DTG/rilpivirine (RPV) in a real-world setting.

METHODS

This was a retrospective, observational, multicentre (ten centres in Belgium) study involving adult treatment-naïve and treatment-experienced people living with HIV on DTG/3TC or DTG/RPV between 1 January 2019 and 30 September 2020. The primary endpoint was rate of virological suppression (VS; plasma HIV-1 viral load [VL] <50 copies/ml) using an on-treatment analysis. Main secondary endpoints included the proportion of people that experienced loss of VS (LVS; defined as two consecutive HIV-1 VLs of >200 copies/ml after initially achieving VS) and a resistance analysis at the time of LVS; rate, incidence, and reasons for discontinuation of treatment (stopping treatment or changing any component of the 2DR); and change in weight, along with the proportion of people reporting a >10% weight gain. Ordinal logistic regression analysis examined associations between baseline variables and >10% on-treatment weight gain.

RESULTS

Overall, 948 people were included, of whom 734 (77%) were on DTG/3TC and 214 (23%) were on DTG/RPV. Baseline characteristics included 54% aged ≥50 years, 31% female, 31% Black sub-Saharan African, 95% treatment-experienced, and 8% with HIV-1 VL ≥50 copies/ml. Through 48 weeks, the rate of VS for the overall cohort was 98.3% (99.1% with 3TC; 96.2% with RPV). LVS was observed in 0.5% (n = 5) of the overall population (n = 1 [3TC group], n = 4 [RPV group]). There were 40 treatment discontinuations (4.2%, n = 27 [3TC group]; n = 13 [RPV group]), corresponding to an incidence of 4.7 per 100 patient-years. The most common reason for discontinuation was an adverse event (1.4%), with neurotoxicity the most frequent (0.5%). Median on-treatment weight gain at week 48 was 1 kg (interquartile range [IQR] -1-3) overall, 1 kg (IQR -1-3) in the 3TC group, and 2 kg (IQR 0-4) in the RPV group. A >10% weight increase was observed in 6.3% of people. Regression analysis showed that being on a tenofovir disoproxil fumarate-based regimen prior to 2DR initiation was the only variable associated with a >10% increase in weight from baseline (odds ratio 3.48; 95% confidence interval 1.13-10.68; p = 0.038).

CONCLUSION

In this real-world analysis, the 2DRs analysed were effective, durable, and safe for those who were treatment-naive and treatment-experienced. A slight increase in weight was associated with these regimens.

HIV-1 Genotypic Resistance Testing Using Sanger and Next-Generation Sequencing in Adults with Low-Level Viremia in China

OBJECTIVE

In this study, we aimed to determine drug-resistance mutations (DRMs) in HIV-1 patients with low-level viremia (LLV) and explored the performance of next-generation sequencing (NGS) in detecting HIV DRMs by using LLV samples.

METHODS

Overall, 80 samples with LLV were amplified and sequenced using a commercial Sanger sequencing (SS) genotyping kit. Furthermore, 51 samples successfully sequenced using SS were simultaneously subjected to NGS. Genotyping success rates of various viremia categories by two sequencing methods were calculated. Stanford HIV-1 drug-resistance database (HIVdb version 8.9) was used to analyze the DRMs. In the NGS assay, a threshold of 5% was considered for reporting low-frequency variants, and the DRMs detected using SS and NGS were compared.

RESULTS

The overall success rate of PR/RT regions was 88.1% (67/80) using SS and 86.3% (44/51) using NGS. Furthermore, a significant linear trend was noted between viral load and the genotyping success rate. A total of 38.8% (26/67) participants harbored at least one mutation, as revealed through SS. Moreover, the prevalence of DRMs in persistent LLV was significantly higher than that in intermittent LLV (62.1% vs. 21.1%; P < 0.05). A total of 69 DRMs were detected using the two sequencing methods at the threshold of 5%. Moreover, 10 DRMs missed by SS were detected using NGS, whereas 8 DRMs missed by NGS were detected by SS.

CONCLUSION

Our data suggested that the genotyping resistance testing is necessary to guide antiretroviral therapy optimization in LLV patients.

Factors associated with low-level viraemia in people with HIV starting antiretroviral therapy: A Swedish observational study

Objective

Low-level viraemia (LLV) occurs in some people with HIV (PWH) receiving antiretroviral therapy (ART) and has been linked to inferior treatment outcomes. We investigated factors associated with LLV in a nationwide cohort of Swedish PWH starting ART.

Methods

Participants were identified from the InfCareHIV register, with the following inclusion criteria: ART initiation 2006–2017, age >15 years, ≥4 viral load (VL) results available and no documented treatment interruptions or virologic failure (≥2 consecutive VL ≥200 copies/ml) during follow-up. Starting from 6 months after ART initiation, participants were followed for 24 months and categorised as viral suppression (VS; VL <50 copies/ml) or LLV (≥2 consecutive VL 50–199 copies/ml). We analysed the association between the following factors and LLV using multivariable logistic regression: sex, age, pre-ART VL and CD4 count, ART regimen, country of birth, HIV-1 subtype and transmission category.

Results

Among 3383 participants, 3132 (92.6%) had VS and 251 (7.4%) had LLV. In univariable analyses, factors associated with LLV were male sex, higher age, lower pre-ART CD4 count, higher pre-ART VL and ART regimen. After adjustment, the following factors were associated with LLV (adjusted odds ratio; 95% confidence interval): male sex (1.6; 1.1–2.3), higher pre-ART VL (2.7; 2.2–3.3), pre-ART CD4 count <200 cells/μl (1.6; 1.2–2.2), protease inhibitor (PI)-based regimen (1.5; 1.1–2.1), non-standard ART (2.4; 1.0–5.5) and injecting drug use (2.0; 1.1–3.7).

Conclusion

Among Swedish PWH, LLV during ART was associated with markers of HIV disease severity before starting ART, male sex, injecting drug use and use of PI-based or non-standard ART regimens.

Low-level viremia and virologic failure in persons with HIV infection treated with antiretroviral therapy

BACKGROUND

The clinical management of low-level viremia (LLV) remains unclear. The objective of this study was to investigate the association of blips and LLV with virologic failure.

METHODS

We enlisted patients who newly enrolled into the HIV Research Network between 2005 and 2015, had HIV-1 RNA more than 200 copies/ml, and were either antiretroviral therapy (ART)-naive or ART-experienced and not on ART. Patients were included who achieved virologic suppression (≤50 on two consecutive viral loads) and had at least two viral loads following suppression. Blips and LLV (≥2 consecutive >51 copies/ml) were categorized separately into three categories: no blips/LLV, 51-200, 201-500. Cox proportional hazards regression was used to assess association between rates of blips/LLV and virologic failure (two consecutive >500).

RESULTS

The 2795 patients were mostly male (75.4%), black (50.3%), and MSM (52.9%). Median age was 38 years old (interquartile range 29-48). Most patients (88.8%) were ART-naive at study entry. Overall, 283 (10.1%) patients experienced virologic failure. A total of 152 (5.4%) patients experienced LLV to 51-200 and 110 (3.9%) patients experienced LLV to 201-500. Both LLV 51-200 [adjusted hazard ratio (aHR) 1.83 (1.10,3.04)] and LLV 201-500 [aHR 4.26 (2.65,6.86)] were associated with virologic failure. In sensitivity analysis excluding ART-experienced patients, the association between LLV 51 and 200 and virologic failure was not statistically significant.

CONCLUSION

LLV between 201 and 500 was associated with virologic failure, as was LLV between 51 and 200, particularly among ART-experienced patients. Patients with LLV below the current Department of Health and Human Services threshold for virologic failure (persistent viremia ≥200) may require more intensive monitoring because of increased risk for virologic failure.

Factors associated with HIV viral load "blips" and the relationship between self-reported adherence and efavirenz blood levels on blip occurrence: a case-control study

Background

The uncertain etiology of HIV viral load (VL) blips may lead to increased use of clinical resources. We evaluated the association of self-reported adherence (SRA) and antiretroviral (ART) drug levels on blip occurrence in US Military HIV Natural History Study (NHS) participants who initiated the single-tablet regimen efavirenz/emtricitabine/tenofovir disoproxil fumarate (EFV/FTC/TDF).

Methods

ART-naïve NHS participants started on EFV/FTC/TDF between 2006 and 2013 who achieved VL suppression (<50 copies/mL) within 12 months and had available SRA and stored plasma samples were included. Participants with viral blips were compared with those who maintained VL suppression without blips. Untimed EFV plasma levels were evaluated on consecutive blip and non-blip dates by high performance liquid chromatography, with a level ≥1 mcg/mL considered therapeutic. SRA was categorized as ≥85 or <85 %. Descriptive statistics were performed for baseline characteristics and univariate and multivariate Cox proportional hazard models were used to assess the relationship between covariates and blip occurrence.

Results

A total of 772 individuals met inclusion criteria, including 99 (13 %) blip and 673 (87 %) control participants. African-American was the predominant ethnicity and the mean age was 29 years for both groups. SRA ≥ 85 % was associated with therapeutic EFV levels at both blip and non-blip time points (P = 0.0026); however no association was observed between blips and SRA or EFV levels among cases. On univariate analysis of cases versus controls, blips were associated with higher mean pre-treatment VL (HR 1.45, 95 % CI 1.11–1.89) and pre-treatment CD4 count <350 cells/µL (68.1 vs 49.7 %). Multivariate analysis also showed that blips were associated with a higher mean VL (HR 1.42, 95 % CI 1.08–1.88; P = 0.0123) and lower CD4 count at ART initiation, with CD4 ≥500 cells/µL having a protective effect (HR 0.45, 95 % CI 0.22–0.95; P = 0.0365). No association was observed for demographic characteristics or SRA.

Conclusion

Blips are commonly encountered in the clinical management of HIV-infected patients. Although blip occurrence was not associated with SRA or EFV blood levels in our study, blips were associated with HIV-related factors of pre-ART high VL and low CD4 count. Additional studies are needed to determine the etiology of blips in HIV-infected patients.

Viral load monitoring and antiretroviral treatment outcomes in a pediatric HIV cohort in Ghana

Background

HIV-infected children in sub-Saharan Africa may be at a high risk of staying on a failing first-line regimen and developing drug-resistance HIV variants due to lack of routine viral load monitoring. We investigated whether cumulative viral load, measured as viremia copy-years (VCY) could predict morbidity in a setting where viral load is not routinely monitored.

Methods

This was a single-center prospective observational longitudinal study of HIV-infected children initiating antiretroviral therapy (ART) at the Pediatric HIV/AIDS Care program at Korle-Bu Teaching Hospital in Accra, Ghana. The main outcome was morbidity measured as frequency of hospitalizations, opportunistic infections, and outpatient sick visits. The main explanatory variable was viral load measured as VCY.

Results

The study included 140 children who initiated ART between September 2009 and May 2013 and had at least 2 viral load measurements. There were 184 hospitalizations, with pneumonia being the most common cause (22.8 %). A total of 102 opportunistic infections was documented, with tuberculosis being the most common opportunistic infection (68 %). A total of 823 outpatient sick visits was documented, with upper respiratory infections (14.2 %) being the most common cause. Forty-four percent of our study participants had >4 log₁₀ VCY. Children in this sub-cohort had a higher frequency of sick visits compared with those with <4 log₁₀ VCY (p = 0.03). Only 6.5 % of children with >4 log₁₀ VCY had been identified as treatment failure using WHO clinical and immunological treatment failure criteria.

Conclusions

High level of cumulative viral load may translate to virological failure and subsequent increased all-cause morbidity. Our finding of potential utility of VCY in pediatrics warrants further investigations. VCY may be a good alternate to routine viral load measurement as its determination may be less frequent and could be personalized to save cost.

The significance of HIV 'blips' in resource-limited settings: is it the same? analysis of the treat Asia HIV Observational Database (TAHOD) and the Australian HIV Observational Database (AHOD)

Introduction

Magnitude and frequency of HIV viral load blips in resource-limited settings, has not previously been assessed. This study was undertaken in a cohort from a high income country (Australia) known as AHOD (Australian HIV Observational Database) and another cohort from a mixture of Asian countries of varying national income per capita, TAHOD (TREAT Asia HIV Observational Database).

Methods

Blips were defined as detectable VL (≥ 50 copies/mL) preceded and followed by undetectable VL (<50 copies/mL). Virological failure (VF) was defined as two consecutive VL ≥50 copies/ml. Cox proportional hazard models of time to first VF after entry, were developed.

Results

5040 patients (AHOD n = 2597 and TAHOD n = 2521) were included; 910 (18%) of patients experienced blips. 744 (21%) and 166 (11%) of high- and middle/low-income participants, respectively, experienced blips ever. 711 (14%) experienced blips prior to virological failure. 559 (16%) and 152 (10%) of high- and middle/low-income participants, respectively, experienced blips prior to virological failure. VL testing occurred at a median frequency of 175 and 91 days in middle/low- and high-income sites, respectively. Longer time to VF occurred in middle/low income sites, compared with high-income sites (adjusted hazards ratio (AHR) 0.41; p<0.001), adjusted for year of first cART, Hepatitis C co-infection, cART regimen, and prior blips. Prior blips were not a significant predictor of VF in univariate analysis (AHR 0.97, p = 0.82). Differing magnitudes of blips were not significant in univariate analyses as predictors of virological failure (p = 0.360 for blip 50–≤1000, p = 0.309 for blip 50–≤400 and p = 0.300 for blip 50–≤200). 209 of 866 (24%) patients were switched to an alternate regimen in the setting of a blip.

Conclusion

Despite a lower proportion of blips occurring in low/middle-income settings, no significant difference was found between settings. Nonetheless, a substantial number of participants were switched to alternative regimens in the setting of blips.

Comparative performances of HIV-1 RNA load assays at low viral load levels: results of an international collaboration

Low-level viremia during antiretroviral therapy and its accurate measurement are increasingly relevant. Here, we present an international collaboration of 4,221 paired blood plasma viral load (pVL) results from four commercial assays, emphasizing the data with low pVL. The assays compared were the Abbott RealTime assay, the Roche Amplicor assay, and the Roche TaqMan version 1 and version 2 assays. The correlation between the assays was 0.90 to 0.97. However, at a low pVL, the correlation fell to 0.45 to 0.85. The observed interassay concordance was higher when detectability was defined as 200 copies/ml than when it was defined as 50 copies/ml. A pVL of ∼100 to 125 copies/ml by the TaqMan version 1 and version 2 assays corresponded best to a 50-copies/ml threshold with the Amplicor assay. Correlation and concordance between the viral load assays were lower at a low pVL. Clear guidelines are needed on the clinical significance of low-level viremia.

High levels of CD2 expression identify HIV-1 latently infected resting memory CD4+ T cells in virally suppressed subjects

Resting memory CD4(+) T cells are the largest reservoir of persistent infection in HIV-1-positive subjects. They harbor dormant, stably integrated virus despite suppressive antiretroviral therapy, posing an obstacle to a cure. Surface markers that identify latently infected cells remain unknown. Microarray analyses comparing resting latently infected and uninfected CD4(+) T cells generated in vitro showed profound differences in the expression of gene programs related to transcriptional and posttranscriptional regulation, cell proliferation, survival, cycle progression, and basic metabolism, suggesting that multiple biochemical and metabolic blocks contribute to preventing viral production in latently infected cells. We identified 33 transcripts encoding cell surface markers that are differentially expressed between latently infected and uninfected cells. Quantitative reverse transcriptase PCR (RT-QPCR) and flow cytometry analyses confirmed that the surface marker CD2 was expressed at higher levels on latently infected cells. To validate this result in vivo, we sorted resting memory CD4(+) T cells expressing high and low surface levels of CD2 from six HIV-1-infected subjects successfully treated with antiretroviral drugs for at least 3 years. Resting memory CD4(+) CD2(high) T cells from all subjects harbored higher HIV-1 DNA copy numbers than all other CD4(+) T cell subsets. Moreover, after ex vivo viral reactivation, robust viral RNA production was detected only from resting memory CD4(+) CD2(high) T cells but not from other cell subsets. Altogether, these results show that a high CD2 expression level is a hallmark of latently infected resting memory CD4(+) T cells in vivo.

Influence of episodes of intermittent viremia ("blips") on immune responses and viral load rebound in successfully treated HIV-infected patients

Presenting episodes of intermittent viremia (EIV) under combination antiretroviral therapy (cART) is frequent, but there exists some controversy about their consequences. They have been described as inducing changes in immune responses potentially associated with a better control of HIV infection. Conversely, it has been suggested that EIV increases the risk of virological failure. A retrospective analysis of a prospective, randomized double-blinded placebo-controlled study was performed. Twenty-six successfully treated HIV-infected adults were randomized to receive an immunization schedule or placebo, and after 1 year of follow-up cART was discontinued. The influence of EIV on T cell subsets, HIV-1-specific T cell immune responses, and viral load rebound, and the risk of developing genotypic mutations were evaluated, taking into account the immunization received. Patients with EIV above 200 copies/ml under cART had a lower proportion of CD4(+) and CD4(+)CD45RA(+)RO(-) T cells, a higher proportion of CD8(+) and CD4(+)CD38(+)HLADR(+) T cells, and higher HIV-specific CD8(+) T cell responses compared to persistently undetectable patients. After cART interruption, patients with EIV presented a significantly higher viral rebound (p=0.007), associated with greater increases in HIV-specific lymphoproliferative responses and T cell populations with activation markers. When patients with EIV between 20 and 200 copies/ml were included, most of the differences disappeared. Patients who present EIV above 200 copies/ml showed a lower CD4(+) T cell count and higher activation markers under cART. After treatment interruption, they showed greater specific immune responses against HIV, which did not prevent a higher virological rebound. EIV between 20 and 200 copies/ml did not have this deleterious effect.

The clinical interpretation of viral blips in HIV patients receiving antiviral treatment: are we ready to infer poor adherence?

OBJECTIVES

Viral blips may be an indication of poor adherence to antiretroviral treatment. This article studies how the variations of the definitions of viral blips and that of the choice of sampling frame in studies investigating viral blips may contribute to the uncertainty of the associations between viral blips and possible causes.

DESIGN

Mathematical modeling study allows us to study the impact of different sampling frames and different definitions of blips upon study results that are usually not feasible in clinical settings.

METHODS

Using a previously published mathematical model, scenarios of different drug adherence levels and viral blips, with different sampling frames, were modeled.

RESULTS

In the case of viral blips as a result of nonadherence to combinational antiretroviral therapy, rather than calculating the incidence of blips directly from the number of blips observed in a given period of time, it is better to report the proportion of observations in a given period of time that are ≥50 copies per milliliter. Therefore, as the denominator, the number of observations in a given period of time is important. However, the proportion of blips is not very informative on the drug adherence level.

CONCLUSIONS

We should standardize definitions of viral blips and the choice of sampling frame and to report the proportion of observations of a given sampling frame in a given period of time that are ≥50 copies per milliliter, so that comparable data can be generated across different populations.

Magnitude of virologic blips is associated with a higher risk for virologic rebound in HIV-infected individuals: a recurrent events analysis

BACKGROUND

The importance of human immunodeficiency virus (HIV) blip magnitude on virologic rebound has been raised in clinical guidelines relating to viral load assays.

METHODS

Antiretroviral-naive individuals initiating combination antiretroviral therapy (cART) after 1 January 2000 and achieving virologic suppression were studied. Negative binomial models were used to identify blip correlates. Recurrent event models were used to determine the association between blips and rebound by incorporating multiple periods of virologic suppression per individual.

RESULTS

3550 participants (82% male; median age, 40 years) were included. In a multivariable negative binomial regression model, the Amplicor assay was associated with a lower blip rate than branched DNA (rate ratio, 0.69; P < .01), controlling for age, sex, region, baseline HIV-1 RNA and CD4 count, AIDS-defining illnesses, year of cART initiation, cART type, and HIV-1 RNA testing frequency. In a multivariable recurrent event model controlling for age, sex, intravenous drug use, cART start year, cART type, assay type, and HIV-1 RNA testing frequency, blips of 500-999 copies/mL were associated with virologic rebound (hazard ratio, 2.70; P = .002), whereas blips of 50-499 were not.

CONCLUSIONS

HIV-1 RNA assay was an important determinant of blip rates and should be considered in clinical guidelines. Blips ≥500 copies/mL were associated with increased rebound risk.

Broadly cross-neutralizing antibodies in HIV-1 patients with undetectable viremia

Several recent studies have identified HIV-infected patients able to produce a broad neutralizing response, and the detailed analyses of their sera have provided valuable information to improve future vaccine design. All these studies have excluded patients on antiretroviral treatment and with undetectable viral loads, who have an improved B cell profile compared to untreated patients. To better understand the induction of neutralizing antibodies in patients on antiretroviral treatment with undetectable viremia, we have screened 508 serum samples from 364 patients (173 treated and 191 untreated) for a broadly neutralizing antibody (bNAb) response using a new strategy based on the use of recombinant viruses. Sera able to neutralize a minipanel of 6 recombinant viruses, including envelopes from 5 different subtypes, were found in both groups. After IgG purification, we were able to confirm the presence of IgG-associated broadly neutralizing activity in 3.7% (7 of 191) of untreated patients with detectable viremia and 1.7% (3 of 174) of aviremic patients receiving antiretroviral treatment. We thus confirm the possibility of induction of a broad IgG-associated neutralizing response in patients on antiretroviral treatment, despite having undetectable viremia. This observation is in stark contrast to the data obtained from long-term nonprogressors, whose little neutralizing activity has been attributed to the low levels of viral replication.

Modeling latently infected cell activation: viral and latent reservoir persistence, and viral blips in HIV-infected patients on potent therapy

Although potent combination therapy is usually able to suppress plasma viral loads in HIV-1 patients to below the detection limit of conventional clinical assays, a low level of viremia frequently can be detected in plasma by more sensitive assays. Additionally, many patients experience transient episodes of viremia above the detection limit, termed viral blips, even after being on highly suppressive therapy for many years. An obstacle to viral eradication is the persistence of a latent reservoir for HIV-1 in resting memory CD4(+) T cells. The mechanisms underlying low viral load persistence, slow decay of the latent reservoir, and intermittent viral blips are not fully characterized. The quantitative contributions of residual viral replication to viral and the latent reservoir persistence remain unclear. In this paper, we probe these issues by developing a mathematical model that considers latently infected cell activation in response to stochastic antigenic stimulation. We demonstrate that programmed expansion and contraction of latently infected cells upon immune activation can generate both low-level persistent viremia and intermittent viral blips. Also, a small fraction of activated T cells revert to latency, providing a potential to replenish the latent reservoir. By this means, occasional activation of latently infected cells can explain the variable decay characteristics of the latent reservoir observed in different clinical studies. Finally, we propose a phenomenological model that includes a logistic term representing homeostatic proliferation of latently infected cells. The model is simple but can robustly generate the multiphasic viral decline seen after initiation of therapy, as well as low-level persistent viremia and intermittent HIV-1 blips. Using these models, we provide a quantitative and integrated prospective into the long-term dynamics of HIV-1 and the latent reservoir in the setting of potent antiretroviral therapy.

Response to zidovudine/didanosine-containing combination antiretroviral therapy among HIV-1 subtype C-infected adults in Botswana: two-year outcomes from a randomized clinical trial

BACKGROUND

Numerous national antiretroviral (ARV) treatment initiatives offering protease inhibitor-sparing combination antiretroviral therapy (cART) have recently commenced in southern Africa, the first of which began in Botswana in January 2002. Evaluation of the efficacy and tolerability of various protease inhibitor-sparing cART regimens requires intensive study in the region, as does investigation of the development of drug resistance and the optimal means of sustaining adherence. The "Tshepo" Study is the first large-scale, randomized, clinical trial that addresses these important issues among HIV-1 subtype C-infected ARV treatment-naive adults in southern Africa.

METHODS

The Tshepo Study is a completed, open-labeled, randomized study that enrolled 650 ARV-naive adults between December 2002 and 2004. The study is a 3 x 2 x 2 factorial design comparing the efficacy and tolerability among factors: (1) 3 combinations of nucleoside reverse transcriptase inhibitors (NRTIs): zidovudine (ZDV) + lamivudine (3TC), ZDV + didanosine (ddI), and stavudine (d4T) + 3TC; (2) 2 different nonnucleoside reverse transcriptase inhibitors (NNRTIs): nevirapine and efavirenz; and (3) 2 different adherence strategies: the current national "standard of care" versus an "intensified adherence strategy" incorporating a "community-based directly observed therapy." Study patients were stratified into 2 balanced CD4 T-cell count groups: less than 201 versus 201-350 cells per cubic millimeter with viral load greater than 55,000 copies per milliliter. Following Data Safety Monitoring Board recommendations in April 2006, ZDV/ddI-containing arms were discontinued due to inferiority in primary end point, namely, virologic failure with resistance. We report both overall data and pooled data from patients receiving ZDV/ddI- versus ZDV/3TC- and d4T/3TC-containing cART through April 1, 2006.

RESULTS

Four hundred fifty-one females (69.4%) and 199 males with a median age of 33.3 years were enrolled into the study. The median follow-up as of April 1, 2006, was 104 weeks, and loss to follow-up rate at 2 years was 4.1%. The median baseline CD4 T-cell count was 199 cells per cubic millimeter [interquartile ratio (IQR) 136-252], and the median plasma HIV-1 RNA level was 193,500 copies per milliliter (IQR 69-250, 472-500). The proportion of participants with virologic failure and genotypic resistance mutations was 11% in those receiving ZDV/ddI-based cART versus 2% in those receiving either ZDV/3TC- or d4T/3TC-based cART (P = 0.002). The median CD4 T-cell count increase at 1 year was 137 cells per cubic millimeter (IQR 74-223) and 199 cells per cubic millimeter (IQR 112-322) at 2 years with significantly lower gain in the ZDV/ddI arm. At 1 and 2 years, respectively, 92.0% and 88.8% of patients had an undetectable plasma HIV-1 RNA level (< or = 400 copies/mL). Kaplan-Meier survival estimates at 1 and 2 years were 96.6% and 95.4%. One hundred twenty patients (18.2%) had treatment-modifying toxicities, of which the most common were lipodystrophy, anemia, neutropenia, and Stevens-Johnson syndrome. There was a trend toward difference in time to treatment-modifying toxicity by pooled dual-NRTI combination and no difference in death rates.

CONCLUSIONS

The preliminary study results show overall excellent efficacy and tolerability of NNRTI-based cART among HIV-1 subtype C-infected adults. ZDV/ddI-containing cART, however, is inferior to the dual NRTIs d4T/3TC or ZDV/3TC when used with an NNRTI for first-line cART.

Identification of ongoing human immunodeficiency virus type 1 (HIV-1) replication in residual viremia during recombinant HIV-1 poxvirus immunizations in patients with clinically undetectable viral loads on durable suppressive highly active antiretroviral therapy

In most human immunodeficiency virus type 1 (HIV-1)-infected individuals who achieve viral loads of <50 copies/ml during highly active antiretroviral therapy (HAART), low levels of plasma virus remain detectable for years by ultrasensitive methods. The relative contributions of ongoing virus replication and virus production from HIV-1 reservoirs to persistent low-level viremia during HAART remain controversial. HIV-1 vaccination of HAART-treated individuals provides a model for examining low-level viremia, as immunizations may facilitate virus replication and sequence evolution. In a phase 1 trial of modified vaccinia virus Ankara/fowlpox virus-based HIV-1 vaccines in 20 HIV-infected young adults receiving HAART, we assessed the prevalence of low-level viremia and sequence evolution, using ultrasensitive viral load (<6.5 copies/ml) and genotyping (five-copy sensitivity) assays. Viral evolution, consisting of new drug resistance mutations and novel amino acid changes within a relevant HLA-restricted allele (e.g., methionine, isoleucine, glutamine, or arginine for leucine at position 205 of RT), was found in 1 and 3 of 20 subjects, respectively. Sequence evolution was significantly correlated with levels of viremia of between 6.5 and <50 copies/ml (P = 0.03) and was more likely to occur within epitopes presented by relevant HLA alleles (P < 0.001). These findings suggest that ongoing virus replication contributes to low-level viremia in patients on HAART and that this ongoing replication is subject to CD8(+) T-cell selective pressures.

The significance of low-level plasma HIV viral load on COBAS TaqMan HIV-1 assays for patients with undetectable plasma viral load on COBAS Amplicor monitor version 1.5

BACKGROUND

COBAS TaqMan assay is a new HIV assay for measuring plasma viral load (VL). A significant number of patients with undetectable plasma VL on Amplicor assay were reported to have detectable VL with TaqMan in the study centre.

PURPOSE

The aim of the present study was to investigate the significance of detectable VL counts with TaqMan assay amongst patients who have had undetectable plasma VL with COBAS Amplicor assay.

METHOD

Observational study on patients who have had undetectable (<less than 50 copies/mL) plasma VL with COBAS Amplicor version 1.5 assay but detectable plasma VL with COBAS TaqMan assay between June 1, 2006 and April 30, 2007. All patients were on highly active antiretroviral therapy (HAART) for longer than 6 months before use of COBAS TaqMan assay. Patients with detectable VL were followed up on a monthly basis until their VL was <40 copes/mL or there was confirmed new resistance to HAART using genotypic and Virco resistance assay.

RESULTS

Plasma VL was detectable (>40 copies/mL) in 113 (14%) patients on 126 episodes using TaqMan assay. VL was less than 500 copies/mL in 90% of those episodes. All episodes ended with VL <40 copies/mL after a median of 117 (94-143) days without change in HAART regimes. The duration of those episodes was longer than 150 days in 75% of cases. No new mutation was detected amongst specimens with detectable VL.

CONCLUSION

Short-term detectable VL may be common with using TaqMan assay. This phenomenon did not result in new mutations or failure of HAART in study patients in the short term.

Determinants of Virological Failure after Successful Viral Load Suppression in First-Line Highly Active Antiretroviral Therapy

Background

We aimed to investigate the long-term virological outcomes of a cohort initially showing good responses to first-line highly active antiretroviral therapy (HAART) with no evidence of virological failure during the first year after achieving viral load (VL) undetectability (<50 copies/ml).

Methods

Virological failure was defined as a confirmed VL>400 copies/ml or a single VL>400 copies/ml followed by a treatment change or end of follow-up. Risk factors for low-level VL rebound (50–400 copies/ml) in the first year after achieving undetectability and for virological failure during subsequent follow-up were investigated by logistic and Poisson regression.

Results

In the first year after achieving VL undetectability, 354/1,386 (25.5%) patients experienced low-level VL rebound, the remaining patients maintained consistent undetectability. Low-level rebound occurred less commonly with non-nucleoside reverse transcriptase inhibitor (NNRTI)-based HAART than with other regimens ( P=0.01). Over median 2.2 (range 0.0–7.4) years of subsequent follow-up, 86 (6.2%) patients experienced virological failure, corresponding to 2.30 failures per 100 person-years (95% confidence interval [CI] 1.82–2.79). Independent predictors of virological failure included low-level rebound during the first year after achieving undetectability relative to consistent undetectability (rate ratio [RR] 2.18, 95% CI 1.15–4.10), female gender (RR 1.79, 95% CI 1.12–2.85) and receiving a ritonavir-boosted protease inhibitor (PI/r) relative to NNRTI-based HAART (RR 1.88, 95% CI 1.02–3.46).

Conclusions

Patients on first-line HAART who maintain consistent VL undetectability for 1 year have a low risk of subsequent virological failure. A subset might benefit from targeted interventions, including women and patients on PI/r-based HAART.

Immunologic, virologic, and clinical consequences of episodes of transient viremia during suppressive combination antiretroviral therapy

OBJECTIVE

To investigate immunologic, virologic, and clinical consequences of episodes of transient viremia in patients with sustained virologic suppression.

METHODS

From the AIDS Therapy Evaluation Project, Netherlands cohort, 4447 previously therapy-naive patients were selected who were on continuous combination antiretroviral therapy and had initial success (2 consecutive HIV RNA measurements <50 copies/mL). During episodes of viral suppression (RNA <50 copies/mL), low-level viremia (RNA 50 to 1000 copies/mL), or high-level viremia (RNA >1000 copies/mL) after initial success, the occurrence of therapy changes, drug resistance, and clinical events was assessed.

RESULTS

During 11,187 person-years of follow-up, 1281 (28.8%) patients had at least 1 RNA measurement >50 copies/mL. Among 8069 episodes, there were 5989 (74.2%) episodes of suppression, 1711 (21.2%) episodes of low-level viremia, and 369 (4.6%) episodes of high-level viremia. Most episodes of low-level viremia consisted of < or =2 RNA measurements (93.7%), were without clinical events or therapy changes (79.6%), and were without changes in CD4 cell counts. Therapy changes (52.3% of episodes) and resistance (23.3%) were frequently observed during high-level viremia.

CONCLUSIONS

Episodes of low-level viremia are frequent and short lasting, and the low proportion of episodes with clinical events suggests that leaving therapy unchanged is a clinically acceptable strategy. In contrast, high-level viremia is associated with resistance and is often followed by therapy changes.

A sudden rise in viral load is infrequently associated with HIV-1 superinfection

OBJECTIVE

To investigate the association between an unexpected increase in the blood plasma HIV-1 viral load in chronically untreated HIV-infected patients and the occurrence of an HIV superinfection, we analyzed the HIV-1 quasispecies in plasma samples before and at peak level in 14 patients.

RESULTS

Phylogenetic analysis of HIV-1 env-V3 fragments showed that in 2 patients a superinfection had occurred: their dominant V3 population at the peak level clustered separately from the V3 sequences in a sample predating the peak level. The rapid rise in viral load could be attributed to upper respiratory tract infections or a vaccination in 4 patients, suggesting that even minor health problems can result in significantly increased HIV-1 replication. In most other patients, no minor or major medical condition accompanied the rise in HIV-1 viral load, implying that in these patients the viral load increase was probably associated with disease progression.

CONCLUSION

This study suggests that an unexpected rapid rise in the plasma HIV-1 viral load of untreated patients can infrequently be ascribed to an HIV-1 superinfection.

Transient viremia, plasma viral load, and reservoir replenishment in HIV-infected patients on antiretroviral therapy

When antiretroviral therapy (ART) is administered for long periods to HIV-1-infected patients, most achieve viral loads that are "undetectable" by standard assay methods (ie, HIV-1 RNA <50 copies/mL). Despite sustaining viral loads lower than the level of detection, a number of patients experience unexplained episodes of transient viremia or viral "blips." We propose that transient activation of the immune system by infectious agents may explain these episodes of viremia. Using 2 different mathematical models, one in which blips arise because of target cell activation and subsequent infection and another in which latent cell activation generates blips, we establish a nonlinear (power law) relationship between blip amplitude and viral load (under ART) that suggest blips should be of lower amplitude, and thus harder to detect, as increasingly potent therapy is used. This effect can be more profound than is predicted by simply lowering the baseline viral load from which blips originate. Finally, we suggest that sporadic immune activation may elevate the level of chronically infected cells and replenish viral reservoirs, including the latent cell reservoir, providing a mechanism for recurrent viral blips and low levels of viremia under ART.

Plasma viral load threshold for sustaining intrahost HIV type 1 evolution

The objective of the present study was to determine if natural suppression of plasma viremia below the detection limit of commercial assays (50-80 copies HIV-1 RNA/ml) can contain the HIV-1 evolution. HIV-1 quasispecies complexity in PBMC DNA was assessed in the env gene at two time points in 14 long-term nonprogressors (LTNPs). Sequence changes consistent with viral evolution was found in all patients with a median plasma RNA viral load >100 copies/ml. Evidence of low-level viral evolution was detected in two of four patients with intermittent viremia and a median plasma HIV-1 RNA load of >80 copies/ml. No significant evolution was observed in the three LTNPs with persistent viral suppression below the detection limit. Overall, a significant positive correlation (p < 0.001) was observed between viral evolution and plasma RNA viral load in the LTNPs analyzed. These results suggest that the detection limit of ultrasensitive viremia assays could represent an important threshold below which intrahost HIV-1 evolution does not occur.

Transient Viral Load Increases in HIV-Infected Children in the UK and Ireland: What do They Mean?

Objectives

To investigate transient increases in viral load during sustained suppression in children in the UK and Ireland Collaborative HIV Paediatric Study (CHIPS).

Design

Cohort of HIV-infected children from 39 centres.

Methods

Transient viraemia was defined as ≥1 detectable viral loads (≥50 copies/ml) between two undetectable values (<50 copies/ml) <280 days apart, during a period of sustained viral suppression (from a confirmed level of <50 copies/ml until the last undetectectable measurement before antiretroviral therapy change or until a confirmed level of >50 copies/ml).

Results

Of 595 children initiating HAART without previous treatment, 347 (58%) achieved sustained suppression. Of these, 78 (23%) experienced 109 episodes of transient viraemia (median 134 copies/ml); 92 (84%) had levels of <1,000 copies/ml (maximum 39,839). Transient viraemia was more common during second-line therapy (25/100 child-years [CY]) and following a previous episode (19/100 CY) compared with first-line therapy without a previous episode (11/100 CY). Rates decreased with age at HAART initiation (incidence rate ratio [IRR] 0.95 per year older; P=0.05), but were higher in those suppressed for longer (IRR 1.63 in those suppressed for ≥1 year versus <1 year; P=0.03). CD4+ and CD8+ T-cell counts were similar before and after transient viraemia. Of detectable viral loads during periods of suppression 44% were transient increases rather than virological failure: experiencing transient viraemia did not increase subsequent virological failure ( P=0.20).

Conclusions

Transient viraemia is relatively common among children on HAART, occurring more frequently in those starting HAART at younger ages, on second-line therapy and after longer suppression. It does not appear to affect CD4+ or CD8+ T-cell counts or the risk of subsequent virological failure. Natural variation, assay effects and adherence might all have a role.

Rapid selection of drug-resistant HIV-1 during the first months of suppressive ART in treatment-naive patients

OBJECTIVE

Efficient antiretroviral therapy (ART) of HIV-1 infection reduces the viral load to undetectable levels and restores the immune system. However, therapy failure appears in a substantial fraction of patients and is mostly associated with the appearance of drug-resistant viruses. It is still not clear when the drug pressure leads to the earliest selection and appearance of drug-resistant HIV-1 populations. In this study, we wanted to determine whether drug-resistant viruses are already selected during viral decline within the first months of ART.

DESIGN AND METHODS

Fifteen mostly chronically HIV-1 infected patients were included. None had received ART prior to this study. The selection of three key resistance mutations, L90M (protease), K103N and M184V (reverse transcriptase), were measured by allele-specific real-time PCR allowing us to track minority quasispecies with a discriminative power of 0.01-0.2%.

RESULTS

Drug-resistant HIV-1 variants were found in 7/15 patients (46.7%) prior to ART. Rapid selection of drug resistance was detected in six patients (40%) independent of the presence of drug-resistant HIV-1 prior to ART. The risk for the selection of drug resistant viruses was correlated with the time until viral load became undetectable (P = 0.02). Besides the proportional increment of drug-resistant viruses, we observed in two patients a quantitative increase of this virus population while the total viral load decreased.

CONCLUSIONS

Drug-resistant viruses can be selected and replicate even in the first weeks of suppressive ART, thus, intensification of ART during the initial treatment period should be considered and further evaluated in clinical studies.

Changing antiretroviral therapy in the setting of virologic relapse: review of the current literature

Virologic relapse after initial virologic suppression remains a concern for patients on antiretroviral therapy (ART). Multiple factors may contribute to virologic relapse, including suboptimal adherence, resistance, and pharmacokinetic issues. The major guidelines for HIV care are in agreement that ART regimen change is indicated in relapse because resistance is identified, but the guidelines are not completely clear on the timing of regimen change. When relapse occurs due to resistance, patients may continue with viremia well below their set points, stable or increasing CD4+ counts, and clinical health for several years. However, delaying a switch in the treatment regimen may lead to the accumulation of resistance which compromises future treatment response. In general, a lower switch threshold is recommended for patients during relapse on first or second line regimens.

Communication of HIV viral load to guide sexual risk decisions with serodiscordant partners among San Francisco men who have sex with men

The objective of this study was to estimate frequency and correlates of discussing HIV viral load (VL) with serodiscordant sex partners to guide decisions about sexual activities among men who have sex with men (MSM). We conducted a cross-sectional survey of 573 San Francisco MSM. Among 507 who knew their HIV status, 397 (78%) were familiar with the term 'viral load', and half (n=199) had a serodiscordant partner in the prior year. These 199 respondents (n=130 [65%] HIV-positive; n=69 [35%] HIV-negative) were the focus of this analysis. A majority (n=111, 56%) discussed VL in the prior year with serodiscordant partners specifically to guide decisions about sexual risk behaviour. Discussion was more common among HIV-positive than HIV-negative participants (adjusted odds ratio [AOR], 3.5; 95% confidence interval [CI], 1.6-7.6), and African Americans compared to whites (AOR, 3.7; 95% CI, 1.5-9.5). HIV-negative men who discussed VL were more concerned about becoming infected, but also more willing to engage in risky behaviour with a partner whose VL is undetectable, than men not discussing VL. Some HIV-negative men may be discussing VL to engage in higher risk behaviour upon learning of an HIV-positive partner's undetectable VL. Interventions targeting MSM should explain that while risk of transmission is likely reduced with a low blood plasma VL, it is not necessarily eliminated.

HIV-1-specific CD4+ T cell responses in chronically HIV-1 infected blippers on antiretroviral therapy in relation to viral replication following treatment interruption

The impact of transient viral load blips on anti-HIV-1 immune responses and on HIV-1 rebound following treatment interruption (TI) is not known. Clinical and immunological parameters were measured during 40 weeks of antiretroviral therapy (ART) and following TI in an observational cohort of 16 chronically HIV-1-infected subjects with or without observed viral load blips during ART. During therapy, blips in seven subjects were associated with higher anti-HIV-1 (p24) CD4+ T cell lymphoproliferative responses (p = 0.04), without a significant difference in T cell activation or total anti-HIV-1 CD8+ T cell interferon-gamma (IFN-gamma) responses when compared to nine matched non-blippers. Therapy interruption resulted in a significantly higher viral rebound in blippers by 8 week despite retention of higher lymphoproliferative p24 responses (p = 0.01) and a rise in CD3+ T cell activation (p = 0.04) and anti-HIV-1 CD8+ T cell responses in blippers by week 4 when compared to non-blippers. Past week 4 of interruption, therapy re-initiation criteria were also met by a higher frequency in blippers by week 14 (p < 0.04) with no difference between groups by week 24. These data support that blippers have higher anti-HIV lymphoproliferative responses while on ART but experience equal to higher viral rebound as compared to matched non-blippers upon TI.

Syphilis and human immunodeficiency virus (HIV)-1 coinfection: influence on CD4 T-cell count, HIV-1 viral load, and treatment response

OBJECTIVES

To assess the effect of human immunodeficiency virus (HIV)-1 and syphilis coinfection on HIV-ribonucleic acid (RNA) viral load, CD4 cell count, and the response in rapid plasmin reagin (RPR) to treatment of the syphilis infection.

STUDY DESIGN

Cases of syphilis diagnosed during 1 year in HIV-infected patients in Copenhagen were included. HIV-RNA, CD4 cell counts, and RPR-serology were measured before, during, and after syphilis.

RESULTS

Forty-one patients were included. CD4 cell count decreased significantly during infection in patients with primary and secondary stages of syphilis (mean 106 cells/mm, P = 0.03). Treatment of syphilis was associated with an increase in the CD4 cell count and a decrease in HIV-RNA in the overall group (mean 66 cells/mm and -0.261 RNA log10 copies/ml, P = 0.02 and 0.04). The serological response rates for 15 patients treated with penicillin and 25 treated with doxycycline were the same.

CONCLUSION

Syphilis was associated with a decrease in CD4 cell counts and an increase in HIV-RNA levels that both improved after treatment of syphilis.

Density-dependent decay in HIV-1 dynamics

The decay of HIV-1-infected cell populations after treatment with antiretroviral therapy has been measured using simple exponential decay models. These models are unlikely to be realistic over periods longer than a few months, however, because the population dynamics of HIV are complex. We considered an alternate model developed by Perelson and colleagues that extends the standard model for biphasic viral load decline and allows for nonlinear log decay of infected cell populations. Using data from 6 children on highly active antiretroviral therapy (HAART) and a single parameter in the new model, the assumption of log linear decay of infected cell populations is tested. Our analysis indicates that the short-lived and long-lived infected cell populations do not decay according to a simple exponential model. Furthermore, the resulting estimates of time to eradication of infected cell compartments are dramatically longer than those previously reported (eg, decades vs. years for long-lived infected cell populations and years vs. weeks for short-lived infected cell populations). Furthermore, estimates of the second-phase decay rates are significantly different than 0 for most children when obtained using the Perelson biphasic decay model. In contrast, this rate is not significantly different than 0 when the density-dependent decay model is used for parameter estimation and inference. Thus, the density-dependent decay model but not the simple exponential decay model is consistent with recent data showing that even under consistent HAART-mediated suppression of viral replication, decay rates of infected cell reservoirs decay little over several years. This suggests that conclusions about long-term viral dynamics of HIV infection based on simple exponential decay models should be carefully re-evaluated.

HIV-1 viral load blips are of limited clinical significance

Many patients on highly active antiretroviral therapy (HAART) who achieve undetectable HIV-1 RNA levels experience transient episodes of detectable viraemia or blips, suggesting there is incomplete suppression of viral replication. This raises concern that drug resistance mutations could develop and cause eventual treatment failure. However, data from recent studies indicate that most blips are actually random biological and statistical variations around a mean viral load below detectable levels (<50 copies/mL) or due to false elevations of viral load from laboratory processing artefacts. Blips are not typically associated with the development of resistance mutations and most importantly are not associated with virological or clinical failure of previously adequate HAART.

Is moderate HIV viremia associated with a higher risk of clinical progression in HIV-infected people treated with highly active antiretroviral therapy: evidence from the Italian cohort of antiretroviral-naive patients study

OBJECTIVE

To assess the risk of clinical progression (CP) according to the duration of time spent without complete viral load (VL) suppression compared with that associated with periods of stably suppressed viremia in HIV-infected people who started highly active antiretroviral therapy (HAART) when previously naïve to antiretrovirals.

DESIGN

A cohort study of patients having started HAART after enrollment in the Italian Cohort of Antiretroviral-Naive Patients (ICoNA) and being followed for at least 6 months.

METHODS

Person-years spent in different categories according to the VL level and the change in VL from the most recent value before the initiation of HAART were calculated. A multivariable Poisson regression model, including potential confounders, was constructed.

RESULTS

A total of 3023 patients were studied. The overall rate of CP was 13.4 per 1000 person-years. Evidence for a higher risk of CP was observed for people with a current VL >10,000 copies/mL. For each year longer spent on HAART with a VL >100,000 copies/mL, a 5-fold increased risk was observed (relative risk [RR] = 5.34, 95% confidence interval [CI]: 2.83 to 1.08; P = 0.0001). An increased risk of CP in patients with current suppression <1.5 log10 copies/mL (RR = 2.34, 95% CI: 1.16 to 4.74; P = 0.02) and in those with no suppression or a VL higher than their set point (RR = 2.39, 95% CI: 1.17 to 4.89; P = 0.02) was observed compared with those with suppression of >3 log10 copies/mL, although it was not significant. Longer duration on HAART with a VL suppressed below set point seemed to confer protection against CP.

CONCLUSIONS

Virologic failure to antiretroviral drugs is common. The risk of CP may remain low despite a low but detectable level of HIV viremia.

Virological control during the first 6-18 months after initiating highly active antiretroviral therapy as a predictor for outcome in HIV-infected patients: a Danish, population-based, 6-year follow-up study

BACKGROUND

Our objective was to examine whether virological control during the first 6-18 months after HAART initiation is a predictor for viral suppression, CD4+ cell count increase, and mortality in human immunodeficiency virus (HIV)-infected patients 18-90 months after initiation of highly active antiretroviral therapy (HAART).

METHODS

We conducted a population-based observational cohort study in Denmark. Patients were divided into 3 groups, according to the proportion of time each patient had a detectable HIV RNA load (i.e., > or = 400 copies/mL) during the 6-18 months after HAART initiation: 0% of the time interval (group 1), 1%-99% of the time interval (group 2), and 100% of the time interval (group 3). The proportion of patients with undetectable HIV RNA, CD4+ cell count changes, and mortality were examined by logistic, linear, and Cox regression analyses, respectively. We constructed cumulative mortality curves.

RESULTS

We observed 2046 patients, for a total of 8898 person-years of follow-up that started at 18 months after HAART initiation. Mean CD4+ cell count increase rates during 72 months of follow-up were as follows: group 1, 3.3 x 10(6) cells/L per month (95% confidence interval [CI], 2.9-3.7 x 10(6) cells/L); group 2, 2.9 x 10(6) (95% CI, 2.5-3.3 x 10(6) cells/L); and group 3, 2.6 x 10(6) (95% CI, 2.0-3.3 x 10(6) cells/L). Survival at 72 months were as follows: group 1, 92.7% (95% CI, 90.5%-94.4%); group 2, 85.6% (95% CI, 82.1%-88.5%); and group 3, 76.1% (95% CI, 70.6%-80.7%). At 72 months, 96% of group 1, 83% of group 2, and 57% of group 3 had an HIV RNA load of < 400 copies/mL (P < .01). Treatment interruption before baseline was a predictor of mortality in group 2 (adjusted rate ratio, 2.94; 95% CI, 1.75-4.92]).

CONCLUSIONS

Viral suppression during the first 6-18 months after HAART initiation predicts viral suppression, CD4+ cell count progression, and survival at 72 months.

Intermittent episodes of detectable HIV viremia in patients receiving nonnucleoside reverse-transcriptase inhibitor-based or protease inhibitor-based highly active antiretroviral therapy regimens are equivalent in incidence and prognosis

BACKGROUND

Intermittent episodes of detectable human immunodeficiency virus (HIV) viremia (hereafter referred to as "blips") are generally not predictive of subsequent virologic failure. Limited data are available for patients treated with nonnucleoside reverse-transcriptase inhibitor (NNRTI)-based regimens.

METHODS

A retrospective cohort study evaluated patients receiving highly active antiretroviral therapy who were followed for > or =12 months, achieved an HIV RNA load of <50 copies/mL, and underwent evaluation every 2-3 months. A blip was defined as 1 HIV RNA load measurement of 50-1000 copies/mL that was preceded and followed by another HIV RNA load measurement of <50 copies/mL. The frequency and predictors of blips and virologic failure were studied.

RESULTS

There were 244 patients in the NNRTI group and 136 patients in the protease inhibitor (PI) group. Baseline characteristics between the 2 groups were similar. A total of 34% of patients in the NNRTI group and 33% in the PI group experienced viral blips (P=.855), with corresponding incidences of 19.2 and 19.7 blips, respectively, per 100 person-years. Median time to blips was 50.0 months after initiation of therapy in the NNRTI group (95% confidence interval [CI], 44.8-55.3 months) and 43.6 months in the PI group (95% CI, 33.7-53.6 months; P=.632, by the log-rank test). By Cox proportional hazards model analysis, only a history of antiretroviral therapy use (hazard ratio [HR], 2.01; P<.001) and a CD4 cell count of <200 cells/ mu L (HR, 1.70; P=.021) increased the risk for having a blip. During a median follow-up period of 23.5 months, 7.8% of patients in the NNRTI group and 8.1% in the PI group experienced virologic failure (P=.917). Cox proportional hazards model analysis showed that only a baseline CD4 cell count of <200 cells/ mu L predicted virologic failure (HR, 2.74; P=.032).

CONCLUSIONS

There is no difference in the frequency or prognostic significance of viral blips between patients receiving NNRTI-based therapy and patients receiving PI-based therapy. Our results suggest that viral blips occur at a similar rate among patients receiving NNRTI-based regimens and patients receiving PI-based regimens and that they are not predictive of virologic failure.

Evidence that low-level viremias during effective highly active antiretroviral therapy result from two processes: expression of archival virus and replication of virus

Episodes of low-level viremia (LLV), with plasma human immunodeficiency virus type 1 (HIV-1) RNA levels ranging from 50 to 400 copies (c)/ml, occur commonly during highly active antiretroviral therapy (HAART). LLV has been associated with virologic failure of HAART in some studies, while in others LLV did not appear to affect the clinical outcome. To understand the processes leading to LLV, genetic analyses were used to determine whether plasma virions emanated from archived or from newly evolved viral genomes. Episodes of LLV (plasma HIV-1 RNA, 50 to 379 [median, 77] c/ml) were detected in 21/37 (57%) HIV-1-infected children with median plasma HIV-1 RNA levels of <50 c/ml during 79 patient years of HAART. Viral sequences were derived by direct sequencing of PCR products from 21 plasma specimens diluted to end point. In phylogenetic analysis, LLV viral sequences grouped with virus from early in the course of infection in 8/11 subjects. Six specimens had multiple identical viral sequences, suggesting origin from clonally expanded infected cells. LLV plasma virus evolved over time, indicating viral replication, in 3/11 subjects. Two of these had frequent LLV, including the selection of drug-resistant mutants. In summary, plasma virus from episodes of LLV during effective HAART appeared to originate from two distinct processes, (i) clonal outgrowth from long-lived HIV-1-infected cells, presumably following activation and proliferation of these cells, and (ii) ongoing viral replication that included the selection of new drug-resistant mutants. These observations provide a plausible explanation for the divergent clinical outcomes previously associated with LLV.

Approach to the Treatment-experienced patient

Failure of antiretroviral therapy can occur for a variety of reasons, but is often caused by or accompanied by drug resistance, which increases with continued time on nonsuppressive, failing regimens. Response to early virologic failure on an initial regimen may be associated with minimal or no resistance and can sometimes be managed simply by reinforcing adherence or by intensifying therapy. Resistance testing is an important tool for managing patients who are failing therapy; it should be used in most cases to guide selection of the next regimen. For patients with extensive treatment experience and drug resistance, there are a variety of approaches that have been suggested when fully suppressive options are not available. Clinicians caring for such patients must balance the benefit of slower progression associated with continued therapy against the risk of increasing drug resistance and loss of future treatment options.

The 48-week efficacy of once-daily saquinavir/ritonavir in patients with undetectable viral load after 3 years of antiretroviral therapy

OBJECTIVES

To evaluate the efficacy and safety of once-daily saquinavir-soft-gel-capsules/ritonavir (SQV-SGC/RTV) 1600 mg/100 mg plus dual nucleoside reverse transcriptase inhibitors (NRTIs) in HIV-infected patients with plasma viral load (pVL) <50 HIV-1 RNA copies/mL following 3 years of antiretroviral therapy.

METHODS

A total of 69 patients with pVL <50 copies/mL after 162 weeks of antiretroviral treatment started SQV-SGC/RTV 1600 mg/100 mg once-daily while continuing dual NRTIs. Previous treatment consisted of 66 weeks of treatment with a half/full dose of zidovudine (ZDV)/zalcitabine (ddC), followed by 2 years of SQV-SGC twice a day (bid) plus ZDV/lamivudine (3TC) or didanosine (ddI)/stavudine (d4T). Efficacy (pVL), safety and immunological changes (CD4 cell counts) were evaluated after 48 weeks in this open-label, single-arm prospective study.

RESULTS

SQV-SGC/RTV once-daily was well tolerated. No patient changed regimens or was lost to follow-up. After 48 weeks, 63 of 69 patients (91%) had pVL <50 copies/mL (five of the six remaining patients had pVL <400 copies/mL, and one patient had an unexplained rise to 39 500 copies/mL, which decreased to <50 copies/mL 12 weeks later). Median CD4 count increased from 534 cells/muL at the start of the SQV-SGC/RTV once-daily treatment to 664 cells/muL (P<0.001). Compared to the preceding 48 weeks on bid SQV-SGC, the CD4 cell count improved significantly on once-daily SQV-SGC/RTV (P<0.001).

CONCLUSIONS

These data support the use of SQV-SGC/RTV 1600 mg/100 mg once-daily with two NRTIs as a convenient, safe and cost-saving regimen to maintain viral suppression and CD4 counts for 48 weeks in this preselected cohort on highly active antiretroviral therapy (HAART) with pVL <50 copies/mL. The CD4 count rise may be a result of continued immune reconstitution in patients with well-controlled infection.

Control of viral rebound through therapeutic immunization with DermaVir

OBJECTIVE

To reconstitute immune responses capable of eliminating infected cells and suppressing viral load during chronic retroviral infection.

DESIGN

: A topical, DNA-based therapeutic immunization (DermaVir) was designed to express most of the regulatory and structural viral genes in dendritic cells.

METHODS

DermaVir alone and in combination with antiretroviral drugs was tested in chronically SIV-infected macaques.

RESULTS

DermaVir provided virological, immunological and clinical benefit for SIV-infected macaques during chronic infection and AIDS. In combination with antiretroviral drugs, DermaVir augmented SIV-specific T-cell responses and enhanced control of viral load rebound during treatment interruptions.

CONCLUSIONS

The results indicate the feasibility of therapeutic immunization even in immune compromised hosts, and suggest that DermaVir can complement antiretroviral drugs to sustain suppression of HIV-1 replication.

Evaluation of HIV-1 kinetic models using quantitative discrimination analysis

MOTIVATION

Since the identification of human immunodeficiency virus (HIV) over twenty years ago, many mathematical models of HIV dynamics have been proposed. The purpose of this study was to evaluate intracellular and intercellular scale HIV models that best described the dynamics of viral and cell titers of a person, where parameters were determined using typically available patient data. In this case, 'best' was defined as the model most capable of describing experimental patient data and was determined by Bayesian-based model discrimination analysis and the ability to provide realistic results.

RESULTS

Twenty models of HIV-1 viral dynamics were initially evaluated to determine whether parameters could be obtained from readily available clinical data from established HIV-1 patients with stable disease. Based on this analysis, three models were chosen for further examination and comparison. Parameters were estimated using experimental data from a cohort of 338 people monitored for up to 2484 days. The models were evaluated using a Bayesian technique to determine which model was most probable. The model ultimately selected as most probable was overwhelmingly favored relative to the remaining two models, and it accounted for uninfected cells, infected cells and cytotoxic T lymphocyte dynamics. The authors developed a fourth model for comparison purposes by combining the features of the original three models. Parameters were estimated for the new model and the statistical analysis was repeated for all four models. The model that was initially favored was selected again upon model discrimination analysis.

CONTACT

srivasta@engr.uconn.edu.

Dynamics of intermittent viremia during highly active antiretroviral therapy in patients who initiate therapy during chronic versus acute and early human immunodeficiency virus type 1 infection

The meaning of viral blips in human immunodeficiency virus type 1 (HIV-1)-infected patients treated with seemingly effective highly active antiretroviral therapy (HAART) is still controversial and under investigation. Blips might represent low-level ongoing viral replication in the presence of drug or simply release of virions from the latent reservoir. Patients treated early during HIV-1 infection are more likely to have a lower total body viral burden, a homogenous viral population, and preserved HIV-1-specific immune responses. Consequently, viral blips may be less frequent in them than in patients treated during chronic infection. To test this hypothesis, we compared the occurrence of viral blips in 76 acutely infected patients (primary HIV infection [PHI] group) who started therapy within 6 months of the onset of symptoms with that in 47 patients who started HAART therapy during chronic infection (chronic HIV infection [CHI] group). Viral blip frequency was approximately twofold higher in CHI patients (0.122 +/- 0.12/viral load [VL] sample, mean +/- standard deviation) than in PHI patients (0.066 +/- 0.09/VL sample). However, in both groups, viral blip frequency did not increase with longer periods of observation. Also, no difference in viral blip frequency was observed between treatment subgroups, and the occurrence of a blip was not associated with a recent change in CD4(+) T-cell count. Finally, in PHI patients the VL set point was a significant predictor of blip frequency during treatment.

Long-term suppression of plasma viremia with highly active antiretroviral therapy despite virus evolution and very limited selection of drug-resistant genotypes

HIV-1 evolution and the possible emergence of mutations associated with resistance to antiretroviral inhibitors have been evaluated in a cohort of sixty-three patients successfully treated with highly active antiretroviral therapy (HAART). The patients under effective HAART were recruited in three different hospitals in Spain, and none of them had been treated (naïve) before entering this study. HIV-1 RNA levels, CD4+, and CD8+ T-cell counts were determined, and nucleotide sequences of proviral regions encoding protease and reverse transcriptase (RT) were obtained for longitudinal blood samples spanning a mean follow-up period of 88 weeks. Phylogenetic reconstructions and calculations of genetic distances among the different sequences of each patient were performed. All except one of the patients under study showed an early and sustained decrease in plasma HIV-1 RNA to levels that were below 200 copies/ml. The plasma viral decline paralleled a significant increase in the CD4+ T-lymphocyte counts. Amino acid sequence analyses revealed the occurrence of mutations associated with antiretroviral resistance in nine patients (14.3%) during HAART treatment, that in some cases could be attributed to excess G to A transitions. In six of the nine patients, the mutations conferred resistance to inhibitors administered in the treatment regime, although the mutations did not result in treatment failure. Sequence comparisons revealed viral evolution during the period of treatment in 47.5% of the patients. The results indicate successful suppression of HIV-1 under HAART for extended time periods, indistinguishable for patients in which evidence of virus evolution could or could not be documented.

Immunologic and virologic evolution during periods of intermittent and persistent low-level viremia

BACKGROUND

HIV replication, HIV-specific T-cell responses and T-cell activation each contributes to disease outcome during untreated HIV infection. The interaction of these factors is not well understood, particularly in the setting of antiretroviral therapy.

METHODS

This is a longitudinal study of antiretroviral-treated patients with plasma HIV RNA levels < 1000 copies/ml. Patients were divided into three groups: suppressed viremia, intermittent viremia ('blips') and persistent low-level viremia. HIV-specific immunity was measured using interferon-gamma ELISPOT. T-cell activation was defined by CD38 and HLA-DR co-expression. Drug resistance was quantified using a phenotypic susceptibility assay.

RESULTS

The breadth and the magnitude of the HIV-specific CD8 T-cell response was greater in patients with either intermittent or persistent viremia compared to patients with suppressed viremia. In contrast, T-cell activation was significantly elevated only in those patients with persistent viremia. Patients with persistent low-level viremia had moderate levels of phenotypic antiretroviral drug resistance that increased over time. Virologic failure (confirmed increase in viral load > 1000 HIV RNA copies/ml) was primarily observed in the persistently viremic group.

CONCLUSIONS

Antiretroviral-treated individuals with intermittent viremia appear to mount an effective HIV-specific T-cell response while not experiencing increases in the level of immune activation. This may limit viral evolution and emergence of drug resistance. In contrast, antiretroviral-treated individuals with persistent low-level viremia exhibit significant increases in overall immune activation and a substantial risk of subsequent treatment failure. It is likely that higher viremia and stronger immune activation act synergistically to accelerate the development of systemic drug resistance.

HIV-1 dynamics in vivo: implications for therapy

The advent of potent combination antiretroviral therapy has been an important breakthrough in the treatment of HIV-1 infection, resulting in marked reductions in HIV-1-related morbidity and mortality. Antiretroviral therapy has also provided researchers with a powerful tool to perturb the equilibrium of viral production and viral clearance, allowing them to dissect the underlying dynamics that control the pathogenesis of AIDS. Here, we review our current understanding of the sources of HIV-1 production, the estimates for the virion and the host-cell half-lives, and the pathways of virion trafficking and clearance. We also discuss the obstacles that result from the ability of HIV-1 to remain dormant for a prolonged period of time in a subset of long-lived cells, despite an apparently effective antiretroviral treatment.

Long-Term Virological Response to Multiple Sequential Regimens of Highly Active Antiretroviral Therapy for HIV Infection

Objective

Information about the virological response to sequential highly active antiretroviral therapy (HAART) for HIV infection is limited. The virological response to four consecutive therapies was evaluated in the Swiss HIV Cohort.

Design

Retrospective analysis in an observational cohort.

Methods

1140 individuals receiving uninterrupted HAART for 4.8 ±0.6 years were included. The virological response was classified as success (<400 copies/ml), low-level (LF: 400–5000 copies/ml) or high-level failure (HF: >5000 copies/ml). Potential determinants of the virological response, including patient demographics, treatment history and virological response to previous HAART regimens were analysed using survival and logistic regression analyses.

Results

40.1% failed virologically on the first (22.0% LF; 18.1% HF), 35.1% on the second (14.2% LF; 20.9% HF), 34.2% on the third (9.9% LF; 24.3% HF) and 32.7% on the fourth HAART regimen (9% LF; 23.7% HF). Nucleoside pre-treatment (OR: 2.34; 95% CI: 1.67–3.29) and low baseline CD4 T-cell count (OR: 0.79/100 cells rise; 95% CI: 0.72–0.88) increased the risk of HF on the first HAART. Virological failure on HAART with HIV-1 RNA levels exceeding 1000 copies/ml predicted a poor virological response to subsequent HAART regimens. A switch from a protease inhibitor- to a non-nucleoside reverse transcriptase inhibitor-containing regimen significantly reduced the risk of HF. Multiple switches of HAART did not affect the recovery of CD4 T lymphocytes.

Conclusion

Multiple sequential HAART regimens do not per se reduce the likelihood of long-term virological suppression and immunological recovery. However, early virological failure increases significantly the risk of subsequent unfavourable virological responses. The choice of a potent initial antiretroviral drug regimen is therefore critical. This study has been presented in part at the 10th Conference on Retroviruses & Opportunistic Infections. Boston, Mass., USA, 2003. Abstract #571.

Treatment of antiretroviral-drug-resistant HIV-1 infection

Drug-resistant HIV-1 is a cause of growing clinical and public-health concern. In many patients, combination antiretroviral therapy fails to achieve complete viral suppression (virological failure). Continuing viral replication during therapy leads to the accumulation of drug-resistance mutations, resulting in increased viral load and a greater risk of disease progression. Patients with drug-resistant HIV-1 infection have three therapeutic options: a change to a salvage regimen with the aim of fully suppressing viral replication; interruption of therapy; or continuation of a partially effective regimen. The first strategy is preferred for most patients failing their first or perhaps their second regimen. However, the best approach remains unclear for patients who have failed multiple treatment regimens and who have limited options for complete viral suppression. The management of such patients requires a careful understanding of the pathogenesis of drug-resistant HIV-1, the clinical consequences of virological failure, the potential benefits and limitations of diagnostic assays, and the likelihood that agents in development will be effective.

Viral blip dynamics during highly active antiretroviral therapy

Although intermittent episodes of low-level viremia are often observed in well-suppressed highly active antiretroviral therapy (HAART)-treated patients, the timing and amplitude of viral blips have never been examined in detail. We analyze here the dynamics of viral blips, i.e., plasma VL measurements of >50 copies/ml, in 123 HAART-treated patients monitored for a mean of 2.6 years (range, 5 months to 5.3 years). The mean (+/- the standard deviation) blip frequency was 0.09 +/- 0.11/sample, with about one-third of patients showing no viral blips. The mean viral blip amplitude was 158 +/- 132 human immunodeficiency virus type 1 (HIV-1) RNA copies/ml. Analysis of the blip frequency and amplitude distributions suggest that two blips less than 22 days apart have a significant chance of being part of the same episode of viremia. The data are consistent with a hypothetical model in which each episode of viremia consists of a phase of VL rise, followed by two-phase exponential decay. Thus, the term "viral blip" may be a misnomer, since viral replication appears to be occurring over an extended period. Neither the frequency nor the amplitude of viral blips increases with longer periods of observation, but the frequency is inversely correlated with the CD4(+)-T-cell count at the start of therapy, suggesting that host-specific factors but not treatment fatigue are determinants of blip frequency.