The independent effect of drug resistance on T cell activation in HIV infection

Thalidomide is Associated With Increased T Cell Activation and Inflammation in Antiretroviral-naive HIV-infected Individuals in a Randomised Clinical Trial of Efficacy and Safety

Trial Design

Open-label, randomised, controlled, pilot proof-of-concept clinical trial.

Methods

Participants: Antiretroviral naïve adult males with CD4 count ≥ 350 cells/mm³.

Interventions: Patients were randomised to receive thalidomide 200 mg QD for 3 weeks (Thalidomide group) or not (Control group) and followed for 48 weeks.

Objective: We hypothesized that short-term Thalidomide use would reduce HIV related inflammation and HIV replication among antiretroviral naïve HIV infected individuals.

Outcome: Viral loads, CD4/CD8 counts, ultra-sensitive C-reactive protein (US-CRP), cell activation markers, and plasma lipopolysaccharide (LPS) were analyzed.

Randomisation: Unrestricted randomisation.

Blinding: No blinding was used.

Results

Numbers randomised: Thirty recruited individuals were randomised to Thalidomide (16 patients) or Control (14 patients) groups.

Recruitment: Patients were recruited from April 2011 to January 2013.

Outcome: Viral loads remained stable in both groups. During thalidomide treatment, a decrease in CD4/CD8 ratio (p = 0.04), a decrease in CD4 count (p = 0.04), an increase in cell activation calculated by the percentage of CD38 ⁺/HLA-DR⁺ CD8 cells (p < 0.05) and an increase in US-CRP (p < 0.01) were observed in the Thalidomide group, with all parameters returning to baseline levels after thalidomide interruption. We confirmed that thalidomide increased HIV replication in vitro of 6 of 7 samples from long-term antiretroviral suppressed individuals.

Harms: No class 3/4 adverse events occurred.

Conclusions

Short-term use of thalidomide led to an intense transient increase in T cell activation and inflammation, with a decrease in the CD4⁺ cell count without changes to the CD8⁺ cell count. We confirmed that thalidomide acts in vitro as a latency reversal agent and speculate that the in vivo results obtained were due to an increase in HIV replication.

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Short-term Thalidomide use lead to intense increase in inflammatory markers among HIV+ antiretroviral naïve individuals.

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Thalidomide use lead to a transitory decrease in CD4⁺ T cells and CD4/CD8 ratios.

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In vitro complementary studies revealed that Thalidomide acts as an HIV Latency Reversal Agent.

Thalidomide in general presents a potent anti-inflammatory effect, and is still being used for a number of inflammatory diseases and infection. Therefore, Thalidomide investigated here in a randomised clinical trial aiming to mitigate HIV related inflammation among antiretroviral naïve individuals. Surprisingly, the HIV related inflammation increased during Thalidomide use, and in vitro studies demonstrated that Thalidomide is efficient in interrupting HIV latency, one of the major's obstacles for the cure of HIV chronic infection.

Pretreatment HIV drug resistance increases regimen switches in sub-Saharan Africa

BACKGROUND

After the scale-up of antiretroviral therapy (ART) for human immunodeficiency virus (HIV) infection in Africa, increasing numbers of patients have pretreatment drug resistance.

METHODS

In a large multicountry cohort of patients starting standard first-line ART in six African countries, pol genotyping was retrospectively performed if viral load (VL) ≥1000 cps/mL. Pretreatment drug resistance was defined as a decreased susceptibility to ≥1 prescribed drug. We assessed the effect of pretreatment drug resistance on all-cause mortality, new AIDS events and switch to second-line ART due to presumed treatment failure, using Cox models.

RESULTS

Among 2579 participants for whom a pretreatment genotype was available, 5.5% had pretreatment drug resistance. Pretreatment drug resistance was associated with an increased risk of regimen switch (adjusted hazard ratio [aHR] 3.80; 95% confidence interval [CI], 1.49-9.68; P = .005) but was not associated with mortality (aHR 0.75, 95% CI, .24-2.35; P = .617) or new AIDS events (aHR 1.06, 95% CI, .68-1.64; P = .807). During three years of follow up, 106 (4.1%) participants switched to second-line, of whom 18 (17.0%) switched with VL < 1000 cps/mL, 7 (6.6%) with VL ≥ 1000 cps/mL and no drug resistance mutations (DRMs), 46 (43.4%) with VL ≥ 1000 cps/mL and ≥1 DRMs; no HIV RNA data was available for 32 (30.2%) participants.

CONCLUSIONS

Given rising pretreatment HIV drug resistance levels in sub-Saharan Africa, these findings underscore the need for expanded access to second-line ART. VL monitoring can improve the accuracy of failure detection and efficiency of switching practices.

Association between latent proviral characteristics and immune activation in antiretrovirus-treated human immunodeficiency virus type 1-infected adults

Generalized immune activation during HIV infection is associated with an increased risk of cardiovascular disease, neurocognitive disease, osteoporosis, metabolic disorders, and physical frailty. The mechanisms driving this immune activation are poorly understood, particularly for individuals effectively treated with antiretroviral medications. We hypothesized that viral characteristics such as sequence diversity may play a role in driving HIV-associated immune activation. We therefore sequenced proviral DNA isolated from peripheral blood mononuclear cells from HIV-infected individuals on fully suppressive antiretroviral therapy. We performed phylogenetic analyses, calculated viral diversity and divergence in the env and pol genes, and determined coreceptor tropism and the frequency of drug resistance mutations. Comprehensive immune profiling included quantification of immune cell subsets, plasma cytokine levels, and intracellular signaling responses in T cells, B cells, and monocytes. These antiretroviral therapy-treated HIV-infected individuals exhibited a wide range of diversity and divergence in both env and pol genes. However, proviral diversity and divergence in env and pol, coreceptor tropism, and the level of drug resistance did not significantly correlate with markers of immune activation. A clinical history of virologic failure was also not significantly associated with levels of immune activation, indicating that a history of virologic failure does not inexorably lead to increased immune activation as long as suppressive antiretroviral medications are provided. Overall, this study demonstrates that latent viral diversity is unlikely to be a major driver of persistent HIV-associated immune activation.

IMPORTANCE

Chronic immune activation, which is associated with cardiovascular disease, neurologic disease, and early aging, is likely to be a major driver of morbidity and mortality in HIV-infected individuals. Although treatment of HIV with antiretroviral medications decreases the level of immune activation, levels do not return to normal. The factors driving this persistent immune activation, particularly during effective treatment, are poorly understood. In this study, we investigated whether characteristics of the latent, integrated HIV provirus that persists during treatment are associated with immune activation. We found no relationship between latent viral characteristics and immune activation in treated individuals, indicating that qualities of the provirus are unlikely to be a major driver of persistent inflammation. We also found that individuals who had previously failed treatment but were currently effectively treated did not have significantly increased levels of immune activation, providing hope that past treatment failures do not have a lifelong "legacy" impact.

The Impact of Highly Active Antiretroviral Treatment on the Blood Profiles of Patients with Acquired Immune Deficiency Syndrome

This study retrospectively investigated the short- and long-term impact of highly active antiretroviral treatment (HAART) on the blood profiles of patients with acquired immune deficiency syndrome (AIDS), and their relationship with disease progression. CD4+ T-cell count was measured by flow cytometry, plasma viral load of human immunodeficiency virus (HIV) RNA was detected by reverse transcription—polymerase chain reaction, and blood profile was determined by an automated analyser. CD4+ T-cell count, total lymphocyte count (TLC) and haemoglobin concentration improved gradually in patients with AIDS after the initiation of HAART. Long-term effective HAART significantly increased CD4+ T-cell counts TLC and haemoglobin concentrations, and reduced viral load to undetectable levels. An increase in haemoglobin was positively correlated with an increase in CD4+ T-cells. These findings suggest that TLC is a valuable tool for determining the initiation of HAART, and that the haemoglobin concentration could be an additional indicator for long-term monitoring of HAART in resource-limited settings.

Immune activation, CD4+ T cell counts, and viremia exhibit oscillatory patterns over time in patients with highly resistant HIV infection

The rates of immunologic and clinical progression are lower in patients with drug-resistant HIV compared to wild-type HIV. This difference is not fully explained by viral load. It has been argued that reductions in T cell activation and/or viral fitness might result in preserved target cells and an altered relationship between the level of viremia and the rate of CD4+ T cell loss. We tested this hypothesis over time in a cohort of patients with highly resistant HIV. Fifty-four antiretroviral-treated patients with multi-drug resistant HIV and detectable plasma HIV RNA were followed longitudinally. CD4+ T cell counts and HIV RNA levels were measured every 4 weeks and T cell activation (CD38/HLA-DR) was measured every 16 weeks. We found that the levels of CD4+ T cell activation over time were a strong independent predictor of CD4+ T cell counts while CD8+ T cell activation was more strongly associated with viremia. Using spectral analysis, we found strong evidence for oscillatory (or cyclic) behavior in CD4+ T cell counts, HIV RNA levels, and T cell activation. Each of the cell populations exhibited an oscillatory behavior with similar frequencies. Collectively, these data suggest that there may be a mechanistic link between T cell activation, CD4+ T cell counts, and viremia and lends support for the hypothesis of altered predator-prey dynamics as a possible explanation of the stability of CD4+ T cell counts in the presence of sustained multi-drug resistant viremia.

Patients with discordant responses to antiretroviral therapy have impaired killing of HIV-infected T cells

In medicine, understanding the pathophysiologic basis of exceptional circumstances has led to an enhanced understanding of biology. We have studied the circumstance of HIV-infected patients in whom antiretroviral therapy results in immunologic benefit, despite virologic failure. In such patients, two protease mutations, I54V and V82A, occur more frequently. Expressing HIV protease containing these mutations resulted in less cell death, caspase activation, and nuclear fragmentation than wild type (WT) HIV protease or HIV protease containing other mutations. The impaired induction of cell death was also associated with impaired cleavage of procaspase 8, a requisite event for HIV protease mediated cell death. Primary CD4 T cells expressing I54V or V82A protease underwent less cell death than with WT or other mutant proteases. Human T cells infected with HIV containing these mutations underwent less cell death and less Casp8p41 production than WT or HIV containing other protease mutations, despite similar degrees of viral replication. The reductions in cell death occurred both within infected cells, as well as in uninfected bystander cells. These data indicate that single point mutations within HIV protease which are selected in vivo can significantly impact the ability of HIV to kill CD4 T cells, while not impacting viral replication. Therefore, HIV protease regulates both HIV replication as well as HIV induced T cell depletion, the hallmark of HIV pathogenesis.

Although most patients infected with HIV who have persistent viral replication will experience a decline in CD4 T cell number, this is not always the case. In a small subset of patients in whom ART fails to suppress viral replication, CD4 T cell counts do not fall, for unknown reasons. We identified that these patients have an increased frequency of selected protease mutations, which we call discordance associated mutations (DAMs). While wild type protease rapidly induces cell death, protease containing DAMs have an impaired ability to induce cell death, due to a selective defect in cleavage of caspase 8. Furthermore, viruses containing DAMs replicate as efficiently as wild type, yet fail to induce infected cell death. These results demonstrate an unanticipated role of protease in determining the immunologic outcome of HIV infection in vitro and in vivo.

Therapeutic immunization with HIV-1 Tat reduces immune activation and loss of regulatory T-cells and improves immune function in subjects on HAART

Although HAART suppresses HIV replication, it is often unable to restore immune homeostasis. Consequently, non-AIDS-defining diseases are increasingly seen in treated individuals. This is attributed to persistent virus expression in reservoirs and to cell activation. Of note, in CD4⁺ T cells and monocyte-macrophages of virologically-suppressed individuals, there is continued expression of multi-spliced transcripts encoding HIV regulatory proteins. Among them, Tat is essential for virus gene expression and replication, either in primary infection or for virus reactivation during HAART, when Tat is expressed, released extracellularly and exerts, on both the virus and the immune system, effects that contribute to disease maintenance. Here we report results of an ad hoc exploratory interim analysis (up to 48 weeks) on 87 virologically-suppressed HAART-treated individuals enrolled in a phase II randomized open-label multicentric clinical trial of therapeutic immunization with Tat (ISS T-002). Eighty-eight virologically-suppressed HAART-treated individuals, enrolled in a parallel prospective observational study at the same sites (ISS OBS T-002), served for intergroup comparison. Immunization with Tat was safe, induced durable immune responses, and modified the pattern of CD4⁺ and CD8⁺ cellular activation (CD38 and HLA-DR) together with reduction of biochemical activation markers and persistent increases of regulatory T cells. This was accompanied by a progressive increment of CD4⁺ T cells and B cells with reduction of CD8⁺ T cells and NK cells, which were independent from the type of antiretroviral regimen. Increase in central and effector memory and reduction in terminally-differentiated effector memory CD4⁺ and CD8⁺ T cells were accompanied by increases of CD4⁺ and CD8⁺ T cell responses against Env and recall antigens. Of note, more immune-compromised individuals experienced greater therapeutic effects. In contrast, these changes were opposite, absent or partial in the OBS population. These findings support the use of Tat immunization to intensify HAART efficacy and to restore immune homeostasis.

Substance use and HIV disease progression in the HAART era: implications for the primary prevention of HIV

Prior to the era of highly active anti-retroviral therapy (HAART), cohort studies provided equivocal evidence to support the hypothesis that substance use predicts more rapid HIV disease progression. The present review examined the effects of substance use on HIV disease progression in cohort studies with follow-up that continued into the HAART era. Of the 20 studies included in this review, 16 observed that substance use predicted at least one indicator of HIV disease progression. Ten of the 11 studies that followed participants exclusively in the HAART era observed an effect of substance use on HIV disease progression. Findings across studies indicate that stimulant use promotes more rapid HIV disease progression and the effects of substance use on HIV disease progression can persist after controlling for self-reported HAART non-adherence. Future investigations that examine the bio-behavioral pathways whereby substance use promotes HIV disease progression should include: measures of HIV genotypic and phenotypic resistance, multi-method assessment of adherence, and assessment of co-morbid infections that are more prevalent among substance users. Although further mechanistic research is needed, findings from existing cohort studies have clear clinical implications. Implementing screening, brief intervention and referral to substance abuse treatment in HIV medical care could optimize health outcomes and decrease HIV transmission rates by boosting the effectiveness of "Test and Treat" approaches to HIV prevention.

Factors associated with collagen deposition in lymphoid tissue in long-term treated HIV-infected patients

OBJECTIVE

The factors associated with fibrosis in lymphoid tissue in long-term treated HIV-infected patients and their correlation with immune reconstitution were assessed.

METHODS

Tonsillar biopsies were performed in seven antiretroviral-naive patients and 29 successfully treated patients (median time on treatment, 61 months). Twenty patients received protease inhibitors-sparing regimens and nine protease inhibitor-containing regimens. Five tonsillar resections of HIV-negative individuals were used as controls. Lymphoid tissue architecture, collagen deposition (fibrosis) and the mean interfollicular CD4(+) cell count per mum were assessed.

RESULTS

Naive and long-term treated HIV-infected patients had a higher proportion of fibrosis than did HIV-uninfected persons (P < 0.001). Patients with greater collagen deposition showed lower levels of CD4 cells in lymphoid tissue (P = 0.03) and smaller increase in peripheral CD4(+) T cells (r = -0.40, P = 0.05). The factors independently associated with fibrosis in lymphoid tissue were age (P < 0.0001), treated patients with detectable lymphoid tissue viral load when compared with patients with undetectable lymphoid tissue viral load (median 5 vs. 12%, respectively, P = 0.017) and patients receiving a protease inhibitor-sparing vs. a protease inhibitor-containing regimen (median 8 vs. 2.5%, respectively, P = 0.04).

CONCLUSION

Fibrosis in lymphoid tissue was associated with a poor reconstitution of CD4(+) T cells and long-term antiretroviral therapy did not reverse this abnormality. HIV infection, older age, a detectable level of lymphoid tissue viral load in treated patients and protease inhibitor-sparing regimens seem to favour fibrosis in lymphoid tissue.

HIV type 1 antiretroviral resistance mutations in subtypes B, C, and F in the City of São Paulo, Brazil

In Brazil, where three distinct HIV-1 subtypes (B, F, and C) cocirculate, a significant portion of the HIV-infected population has been exposed to antiretroviral drugs. This study analyzes the antiretroviral resistance profiles of HIV-1-infected individuals failing antiretroviral therapy. Genotypic resistance profiles of 2474 patients presenting virologic failure to antiretroviral therapy in the city of São Paulo, Brazil, were generated and analyzed. Resistance mutations to protease inhibitors and nucleoside reverse transcriptase inhibitors were less common in subtype C viruses, whereas nonnucleoside reverse transcriptase inhibitor resistance mutations were less common in subtype F viruses. The thymidine analog mutation pathway known as pathway 1 was more prevalent in subtype B viruses than in subtype C viruses, whereas pathway 2 was more prevalent in subtype C viruses. Selected resistance mutations varied according to subtype for all three classes of antiretrovirals. We describe two distinct pathways of nonnucleoside reverse transcriptase inhibitor resistance (to nevirapine and efavirenz). Although cross-resistance to etravirine should occur more frequently among individuals failing nevirapine treatment, the prevalence of cross-resistance to etravirine, darunavir, and tipranavir was found to be low. We found that increases in the number of resistance mutations will be related to increases in the viral load. Special attention should be given to resistance profiles in non-B subtype viruses. The accumulation of knowledge regarding such profiles in the developing world is desirable.

Mortality associated with discordant responses to antiretroviral therapy in resource-constrained settings

OBJECTIVES

We assessed mortality associated with immunologic and virologic patterns of response at 6 months of highly active antiretroviral therapy (HAART) in HIV-infected individuals from resource-limited countries in Africa and South America.

METHODS

Patients who initiated HAART between 1996 and 2007, aged 16 years or older, and had at least 1 measurement (HIV-1 RNA plasma viral load or CD4 cell count) at 6 months of therapy (3-9 month window) were included. Therapy response was categorized as complete, discordant (virologic only or immunologic only), and absent. Associations between 6-month response to therapy and all-cause mortality were assessed by Cox proportional hazards regression. Robust standard errors were calculated to account for intrasite correlation.

RESULTS

A total of 7160 patients, corresponding to 15,107 person-years, were analyzed. In multivariable analysis adjusted for age at HAART initiation, baseline clinical stage and CD4 cell count, year of HAART initiation, clinic, occurrence of an AIDS-defining condition within the first 6 months of treatment, and discordant and absent responses were associated with increased risk of death.

CONCLUSIONS

Similar to reports from high-income countries, discordant immunologic and virologic responses were associated with intermediate risk of death compared with complete and no response in this large cohort of HIV-1 patients from resource-limited countries. Our results support a recommendation for wider availability of plasma viral load testing to monitor antiretroviral therapy in these settings.

Monitoring clinical trials of therapeutic vaccines in HIV infection: role of treatment interruption

PURPOSE OF REVIEW

To outline the rationale for testing therapeutic vaccines in HIV infection and to discuss the ways in which the antiviral activities of these vaccination trials can be evaluated. In the era of highly active antiretroviral therapy, analytical treatment interruption has served as the gold standard to evaluate therapeutic vaccine strategies.

RECENT FINDINGS

In the era before the introduction of highly active antiretroviral therapy, therapeutic vaccine trials showed minimal evidence of antiviral activity. It is not clear whether these failures reflect the immune suppressive effects of HIV replication or the inadequacy of early vaccine constructs and strategies. Recent studies have provided some optimism that therapeutic vaccine strategies may be effective in chronic established infection and perhaps even in chronic HIV infection. Approaches to evaluate the activities of candidate therapeutic vaccine strategies in the era of antiretroviral therapy have included analytical treatment interruptions, but recently the safety of this has been called into question.

SUMMARY

Although analytical treatment interruption remains the current standard for evaluating the antiviral activities of therapeutic immunization strategies in established HIV infection, other methods and strategies may prove useful and should be evaluated.

Drug resistance mutations and the cellular immune response: a valuable synergy for the development of novel immune therapies

PURPOSE OF REVIEW

The escape of HIV-1 is a cardinal feature of the virus and a major hindrance to the development of effective therapeutic strategies. In highly active antiretroviral therapy-treated patients, the virus is subjected to selective pressures from cellular immune response directed against the viral proteome and antiretroviral treatment targetting a few genes of the HIV-1 genome. This review will focus on the relationship between these two pressures and its potential advantage in the development of novel immune therapies.

RECENT FINDINGS

Recent studies have investigated the conflicting selective forces between viral fitness and escape to immunological and therapeutic pressures in natural HIV infection and the SIV model. Simultaneous pressures driven by cytotoxic T lymphocytes and highly active antiretroviral therapy could potentially reduce viral fitness, leading to better control of the viral load. Two studies have described a potential therapeutic vaccine strategy against viral escape mutant epitopes from reverse transcriptase inhibitors.

SUMMARY

The emergence of multidrug-resistant viruses is associated with enhanced T-cell-mediated immune response as a possible consequence of reduced viral fitness. Amino acid substitutions generate potential cytotoxic T-lymphocyte epitopes that may elicit new reactivities against mutated viruses. Both could significantly enhance the immune response through direct and indirect mechanisms.

Plasma levels of bacterial DNA correlate with immune activation and the magnitude of immune restoration in persons with antiretroviral-treated HIV infection

The significance of elevated plasma levels of bacterial lipopolysaccharide (LPS) in persons with chronic HIV infection remains undefined. We measured LPS levels by use of limulus lysate assay, and DNA sequences encoding bacterial ribosomal 16S RNA (16S rDNA) were assessed by quantitative polymerase chain reactions in plasma samples obtained from 242 donors. Plasma levels of 16S rDNA were significantly higher in human immunodeficiency virus (HIV)-infected subjects than in uninfected subjects, and they correlated with LPS levels. Higher levels of 16S rDNA were associated with higher levels of T cell activation and with lower levels of CD4 T cell restoration during antiretroviral therapy. Antiretroviral therapy reduces but does not fully normalize plasma levels of bacterial 16S rDNA, an index of microbial translocation from the gastrointestinal tract. High levels of 16S rDNA during therapy are strongly associated with reduced increases in the CD4(+) T lymphocyte count, irrespective of plasma HIV RNA levels. These findings are consistent with the importance of microbial translocation in immunodeficiency and T cell homeostasis in chronic HIV infection.

Stimulant use is associated with immune activation and depleted tryptophan among HIV-positive persons on anti-retroviral therapy

Cocaine, crack, and methamphetamine are stimulants that promote autonomic nervous system activation. Although these stimulants may have immunomodulatory effects, relatively few studies have examined this possibility. The present cross-sectional investigation utilized baseline data from 127 HIV-positive individuals on anti-retroviral therapy (ART) that were enrolled in a randomized controlled trial. The goal of this study was to examine whether stimulant use is independently associated with immune activation and indices of tryptophan degradation. Forty-four participants reported using stimulants 2-3 times a month or more (i.e., monthly stimulant use) and a sub-set of these (n=27) reported using stimulants once a week or more (i.e., weekly stimulant use) during the past three months. These stimulant-using groups were compared to a group of participants who reported no stimulant use (n=83) during the past three months. Results indicated that individuals who reported either monthly or weekly stimulant use displayed elevated neopterin, a measure of immune activation. Those who reported weekly stimulant use also displayed a markedly elevated HIV viral load and lower tryptophan levels. Even after controlling for self-reported ART non-adherence, weekly stimulant use was independently associated with higher neopterin, elevated HIV viral load, and lower tryptophan. To our knowledge, this is the first study to observe that stimulant use may independently promote immune activation and tryptophan degradation among HIV-positive persons on ART. Further research is needed to replicate these findings and examine the plausible bio-behavioral pathways that may account for the effects of stimulant use on HIV disease markers and depleted tryptophan.

The predictive value of CD38 positive hepatic stellate cell count for assessing disease activity and fibrosis in patients with chronic hepatitis

The activation of hepatic stellate cells (HSCs) is a critical event in hepatic fibrosis. The objectives of this study were to find out if cluster of differentiation 38 (CD38) can be demonstrated immunohistochemically on HSCs in liver biopsies from patients with chronic liver disease and if CD38 immunopositive HSC count is correlated with METAVIR inflammatory and fibrosis scores. Immunohistochemical labelling for CD38 was performed on 100 liver biopsies from patients with chronic liver disease. The CD38 immunopositive HSCs were identified and counted. The CD38 immunopositive HSC count was found to be associated with both the METAVIR score and the fibrosis scores. The CD38 immunopositive HSC count was able to discriminate between no fibrosis and stages 2, 3 or 4 fibrosis, but could not discriminate between no fibrosis and stage 1 fibrosis. Using receiver operating characteristic (ROC) curves, a cut-off point of 10 HSCs per 10 high power field (hpf), or 25 per 100 hepatocytes, is 80% sensitive and 70% specific for predicting fibrosis. The specificity rose to 100% in patients with hepatitis C viral (HCV) infection. We conclude that CD38 positive HSCs can be demonstrated immunohistochemically and that the count is highly predictive of moderate to severe hepatic fibrosis.

Antiretroviral treatment effect on immune activation reduces cerebrospinal fluid HIV-1 infection

OBJECTIVE

To define the effect of antiretroviral therapy (ART) on activation of T cells in cerebrospinal fluid (CSF) and blood, and interactions of this activation with CSF HIV-1 RNA concentrations.

DESIGN

Cross-sectional analysis of 14 HIV-negative subjects and 123 neuroasymptomatic HIV-1-infected subjects divided into 3 groups: not on ART (termed "offs"), on ART with plasma HIV-1 RNA >500 copies/mL ("failures"), and on ART with plasma HIV-1 RNA <or=500 copies/mL ("successes"). T-cell activation was measured by coexpression of CD38 and human leukocyte antigen DR (HLA-DR). Other measurements included CSF neopterin and white blood cell (WBC) counts.

RESULTS

CD8 T-cell activation in CSF and blood was highly correlated across all subjects and was highest in the offs, lower in the failures, and lower still in the successes. While CD8 activation was reduced in failures compared to offs across the range of plasma HIV-1, it maintained a coincident relation to CSF HIV-1 in both viremic groups. In addition to correlation with CSF HIV-1 concentrations, CD8 activation in blood and CSF correlated with CSF WBCs and CSF neopterin. Multivariate analysis confirmed the association of blood CD8 T-cell activation, along with plasma HIV-1 RNA and CSF neopterin, with CSF HIV-1 RNA levels.

CONCLUSIONS

The similarity of CD8 T-cell activation in blood and CSF suggests these cells move from blood to CSF with only minor changes in CD38/HLA-DR expression. Differences in the relation of CD8 activation to HIV-1 concentrations in the blood and CSF in the 2 viremic groups suggest that changes in immune activation not only modulate CSF HIV-1 replication but also contribute to CSF treatment effects. The magnitude of systemic HIV-1 infection and intrathecal macrophage activation are also important determinants of CSF HIV-1 RNA levels.

Relationship between T cell activation and CD4+ T cell count in HIV-seropositive individuals with undetectable plasma HIV RNA levels in the absence of therapy

BACKGROUND

Although untreated human immunodeficiency virus (HIV)-infected patients maintaining undetectable plasma HIV RNA levels (elite controllers) have high HIV-specific immune responses, it is unclear whether they experience abnormal levels of T cell activation, potentially contributing to immunodeficiency.

METHODS

We compared percentages of activated (CD38(+)HLA-DR(+)) T cells between 30 elite controllers, 47 HIV-uninfected individuals, 187 HIV-infected individuals with undetectable viremia receiving antiretroviral therapy (antiretroviral therapy suppressed), and 66 untreated HIV-infected individuals with detectable viremia. Because mucosal translocation of bacterial products may contribute to T cell activation in HIV infection, we also measured plasma lipopolysaccharide (LPS) levels.

RESULTS

Although the median CD4(+) cell count in controllers was 727 cells/mm(3), 3 (10%) had CD4(+) cell counts <350 cells/mm(3) and 2 (7%) had acquired immunodeficiency syndrome. Controllers had higher CD4(+) and CD8(+) cell activation levels (P < .001 for both) than HIV-negative subjects and higher CD8(+) cell activation levels than the antiretroviral therapy suppressed (P = .048). In controllers, higher CD4(+) and CD8(+) T cell activation was associated with lower CD4(+) cell counts (P = .009 and P = .047). Controllers had higher LPS levels than HIV-negative subjects (P < .001), and in controllers higher LPS level was associated with higher CD8(+) T cell activation (P = .039).

CONCLUSION

HIV controllers have abnormally high T cell activation levels, which may contribute to progressive CD4(+) T cell loss even without measurable viremia.

Immune reconstitution in human immunodeficiency virus type 1-infected children with different virological responses to anti-retroviral therapy

Immune repopulation, despite virological failure, often occurs in children under highly active anti-retroviral therapy (HAART). The aim of this study was to analyse the characteristics of immune repopulation and activation in children with and without virological response to HAART. Fourteen human immunodeficiency virus type 1 (HIV-1)-infected children with suppression of HIV-1 plasma viraemia (virological responders, VR) and 16 virological non-responders (VNR) to therapy were studied at baseline and after approximately 2 years of HAART. During therapy, CD4+ T cells increased in both groups, but were higher in the VR than in the VNR group. All CD4+ T cell subsets (naive, central memory, effector/memory and CD38+) increased significantly in VR children, while there was a significant increase only in naive cells in VNR children. Naive CD8+ T cells and T cell receptor rearrangement excision circles (TREC), an indicator of thymic output, increased in both VR and VNR children. Activated CD8+ CD38+ T cells decreased in VR but remained high in VNR children. Levels of circulating lipopolysaccharide (LPS), an indicator of microbial translocation, further increased in VNR children. In conclusion, HAART induced an increase in naive cells in all children, regardless of their virological response. However, the persistence of viraemia resulted in an impaired expansion of memory CD4+ T cells susceptible to HIV-1 infection, and together with the microbial translocation sustained the persistence of a high level of immune activation.

A randomized study of antiviral medication switch at lower- versus higher-switch thresholds: AIDS Clinical Trials Group Study A5115

BACKGROUND

Clinical stability has been observed with continued antiretroviral therapy (ART) in the setting of partial virological suppression. The optimal time to switch treatment in patients with low but detectable HIV-1 RNA is not known.

METHODS

Subjects on stable ART with HIV-1 RNA 200-10,000 copies/ml were randomized to an immediate treatment switch, or to a delayed switch when HIV-1 RNA increased to > or = 10,000 copies/ml or CD4+ T-cell count decreased by 20%. The primary outcome measures were immune activation (proportion of CD8+ T-cells expressing CD38 at week 48) and evolution of genotypic drug resistance.

RESULTS

The study failed to fully accrue the originally planned 108 subjects. Only 47 subjects were randomized to immediate- or delayed-switch arms. Of the subjects in the delayed-switch arm, 10/23 (43%) met the criteria for ART switch during the study (median follow-up 82 weeks). After 48 weeks of observation, the level of immune activation was comparable in the two arms. New resistance mutations were observed in 3/17 and 8/19 subjects in the immediate- and delayed-switch groups, respectively. The loss of future treatment options, however, was comparable in the delayed- and immediate-switch groups.

CONCLUSIONS

Individuals with partial viral suppression tend to remain immunologically stable, however, the accumulation of drug resistance mutations is an ongoing risk. Delayed switch in ART may be a reasonable short-term strategy for individuals with very limited treatment options.

Role of immune activation in HIV pathogenesis

T-cell activation has long been considered a central mediator of HIV pathogenesis. High T-cell activation levels predict more rapid disease progression in untreated patients and decreased treatment-mediated CD4+ T-cell gains during antiretroviral therapy, independent of plasma HIV RNA levels, and may be the primary feature distinguishing pathogenic from nonpathogenic primate models of HIV infection. Studies in animal models and individuals with HIV infection continue to enhance our understanding of how T-cell activation causes immunodeficiency during HIV infection. The goal of these studies is to identify specific mechanisms that can be targeted by novel immune-based therapies for patients who have thus far been unable to recover normal immune function despite years of antiretroviral therapy. Although most immune-based therapies targeting T-cell activation have been unsuccessful to date, recent scientific developments have focused attention on specific pathways that may be exploited by future generations of immune-based therapies.

Flying in the face of resistance: antiviral-independent benefit of HIV protease inhibitors on T-cell survival

Human immunodeficiency virus (HIV) infection results in excessive apoptosis of infected and uninfected cells, mediated by host and viral factors present in plasma. As HIV protease inhibitors (PIs) have intrinsic antiapoptotic properties, we questioned whether HIV PIs could block HIV-induced CD4+ T-cell death independent of their effects on HIV replication. We demonstrate that HIV PIs block the death of CD4+ T cells induced by HIV glycoprotein 120 (gp120), Vpr, and Tat, as well as host signals Fas ligand, tumor necrosis factor, and tumor necrosis factor-related apoptosis-inducing ligand. Using gp120/CXCR4 as a model, we show that the HIV PIs specifically block mitochondrial apoptosis signaling. Furthermore, HIV PIs inhibit CD4+ T-cell death induced by viruses with high-level resistance to PIs (P<0.01) and apoptosis induced by serum of HIV patients with known resistance to HIV PIs (P=0.01). Together, these results show that HIV PIs block CD4+ T-cell death and have a beneficial effect on CD4+ T-cell survival despite PI resistance.

CD38 is critical for social behaviour by regulating oxytocin secretion

CD38, a transmembrane glycoprotein with ADP-ribosyl cyclase activity, catalyses the formation of Ca2+ signalling molecules, but its role in the neuroendocrine system is unknown. Here we show that adult CD38 knockout (CD38-/-) female and male mice show marked defects in maternal nurturing and social behaviour, respectively, with higher locomotor activity. Consistently, the plasma level of oxytocin (OT), but not vasopressin, was strongly decreased in CD38-/- mice. Replacement of OT by subcutaneous injection or lentiviral-vector-mediated delivery of human CD38 in the hypothalamus rescued social memory and maternal care in CD38-/- mice. Depolarization-induced OT secretion and Ca2+ elevation in oxytocinergic neurohypophysial axon terminals were disrupted in CD38-/- mice; this was mimicked by CD38 metabolite antagonists in CD38+/+ mice. These results reveal that CD38 has a key role in neuropeptide release, thereby critically regulating maternal and social behaviours, and may be an element in neurodevelopmental disorders.

Rate of viral evolution and risk of losing future drug options in heavily pretreated, HIV-infected patients who continue to receive a stable, partially suppressive treatment regimen

BACKGROUND

Many treatment-experienced, HIV-infected patients who have limited therapeutic options for complete viral suppression continue to receive a partially suppressive treatment regimen pending the availability of at least 2 new antiretroviral drugs. The major risk of this approach is ongoing viral evolution and the loss of future drug options.

METHODS

Antiretroviral-treated subjects with incomplete viral suppression were sampled from a clinic-based cohort. Inclusion criteria were receipt of a stable treatment regimen for > or = 120 days, a plasma HIV RNA load of > 500 copies/mL, and > or = 1 resistance mutation. Phenotypic and genotypic resistance testing was performed every 4 months.

RESULTS

The 106 patients who were eligible for the study had a median of 3 observations during a median of 11.3 months. An estimated 23% and 18% developed at least 1 new nucleoside analogue and 1 new protease inhibitor mutation at 1 year, respectively. An estimated 30% lost the phenotypic equivalent of 1 susceptible drug at 1 year. A lower number of total mutations at baseline was a significant predictor of developing a new nucleoside analogue mutation (P=.01). At 1 year, the probability that an existing mutation would become undetectable using population-based sequencing was 32%. There was a higher rate of change at nonresistance codons than at codons known to be associated with drug resistance.

CONCLUSIONS

Heavily pretreated patients with HIV infection who remain on a partially suppressive regimen have a measurable risk of losing future drug options, particularly those patients who have few baseline mutations. Resistance mutations vary over time, which suggests that the results of any single resistance test may not be representative of all mutations selected by a given treatment regimen.