Induction of prolonged survival of CD4+ T lymphocytes by intermittent IL-2 therapy in HIV-infected patients

Immunological success is predicted by enfuvirtide but not interleukin-2 therapy in immunodepressed patients

OBJECTIVES

To evaluate the efficacy of adding interleukin-2 (IL-2) to an optimized background treatment in HIV-1 patients with advanced failure.

DESIGN

Randomized, open-label, multicentre controlled trial.

METHODS

Patients with CD4 T-cell count of less than 200 cells/microl, plasma HIV-1 RNA of more than 10 000 copies/ml and a genotypic sensitivity score showing two or less active drugs were randomized to either eight IL-2 cycles with optimized background treatment or optimized background treatment alone. Optimization was made according to genotypic sensitivity score. Enfuvirtide was added in enfuvirtide-naive patients. Evaluation was performed at week 52 on the proportions of patients with CD4 cell count of at least 200 cells/microl (primary outcome), of patients with a CD4 cell count increase of at least 50 cells/microl from week 0, on plasma HIV-1 RNA and HIV-related events.

RESULTS

Fifty-six patients were analysed. Median age was 43 years, 61% were at Center for Disease Control and Prevention stage C, 43% had a genotypic sensitivity score of 0, median baseline CD4 cell count and plasma HIV-1 RNA values were 64 cells/microl and 4.9 log10 copies/ml, respectively. Treatment could be optimized in 23 patients. At week 52, in the IL-2 and control groups, the proportion of patients with CD4 cell count of at least 200 cells/microl (14 and 18%) or a CD4 cell count increase of at least 50 cells/microl (25 and 32%) and median plasma HIV-1 RNA were not significantly different. In multivariate analysis, optimization with enfuvirtide and baseline CD4 cell count were statistically associated with CD4 cell count of at least 200 cells/microl at week 52 (P = 0.003 and P = 0.01). Optimization with enfuvirtide was the only factor associated with a CD4 cell count gain of at least 50 cells/microl (P < 0.001). There was no difference in the rate of AIDS events between groups.

CONCLUSION

IL-2 failed to increase CD4 cell count in immunocompromised patients with multiple therapeutic failures. Enfuvirtide use was highly associated with success.

Drug targets in hepatitis B virus infection

Hepatitis B virus infection (HBV) is a significant global health problem. Despite the success of universal hepatitis B vaccination in many countries, more than 350 million individuals worldwide are chronically infected and 15- 40% of those will develop cirrhosis and/or hepatocellular carcinoma if left untreated. Available therapies for chronic hepatitis B (CHB) infection are effective at decreasing viremia and improving measured clinical outcomes, however, no single therapy is optimal. As such, alternative drug therapies and the investigation of their role in the management of CHB are warranted. Significant improvements in the understanding of the HBV life cycle, viral genomics, and virus-host interactions continue to lead to the development of novel viral targets and immune modulators. Currently, two major classes of agents are utilized in CHB: the interferons and the nucleos(t)ide analogues. Each agent has individual advantages and drawbacks. The development of specific antiviral therapy has led to the emergence of HBV drug-resistant strains that has limited the long-term therapeutic potential of available agents. This necessitates the development of new agents that target both wild-type and drug-resistant strains. Further understanding of the basic mechanisms and clinical nuances of drug therapy is warranted. As most novel therapies are in the earliest stages of clinical development and testing, in the near future, treatment will continue to be long-term and likely involve the use of combination therapies to prevent viral resistance. In this review, we will highlight the HBV life cycle and genome, focusing in on current and potential novel antiviral drug targets as well as the benefits and clinical challenges with these therapies.

Functions of γC cytokines in immune homeostasis: current and potential clinical applications

Cytokines that signal through receptor complexes containing the common gamma (gammaC) chain receptor subunit are central regulators of lymphocyte homeostasis. In this review, we discuss the four major gammaC cytokines that have proven activity in or potential for immunotherapy: IL-2, IL-7, IL-15 and IL-21. Their shared and unique activities on specific lymphocyte populations suggest therapeutic applications such as enhancing lymphocyte reconstitution, expanding tumor and pathogen-specific lymphocytes, and optimizing vaccines. Because the responsiveness of individual lymphocyte subsets varies under different situations such as lymphopenia and active immune responses, understanding the dynamics of gammaC-containing receptor expression is important in deciding how to achieve the most desired effect. Current understanding of the biology of gammaC cytokines suggests several clinical applications, including their direct administration or use in generation of lymphocytes for adoptive transfer, increasing their endogenous production, and potentiating their activity by complex formation with specific antibodies or their specific receptor-alpha subunits. Overall, gammaC cytokines have great potential, through their targeted use alone or in combination, to be an integral part of clinical interventions with enhanced efficacy and decreased toxicity.

Lymphocyte kinetics in health and disease

Quantitative understanding of immunology requires the development of experimental and mathematical techniques for estimation of rates of division and death of lymphocytes under different conditions. Here, we review the advantages and limitations of several labelling methods that are currently used to quantify turnover of lymphocytes in vivo. In addition to highlighting insights into lymphocyte kinetics which have recently been gained thanks to the development of novel techniques, we discuss important directions for future experimental and theoretical work in the field of lymphocyte turnover.

The effect of continuous versus pericycle antiretroviral therapy on IL-2 responsiveness

BACKGROUND

Intermittent administration of interleukin-2 (IL-2) to human immunodeficiency virus (HIV)- infected patients on antiretroviral therapy (ART) is capable of inducing significant increases in CD4 T cell counts as a result of increased T cell survival and decreased cell turnover. However, its role in the setting of ART interruptions (STI) is less well characterized. We sought to compare the effect of continuous (C) versus intermittent (P) ART on CD4 responses in patients undergoing IL-2 therapy.

METHODS

CD4 cell responses were compared in 25 patients who underwent IL-2 therapy during periods of continuous ART (n = 90 cycles) as well as during STI (n = 45 cycles). During STI, patients resumed ART for only 10 days surrounding each IL-2 cycle.

RESULTS

C cycles resulted in a significantly greater CD4 gain than P cycles (Delta156 cells/microL, 95% CI = 68-243). In multivariate analyses, baseline CD4/CD25 expression and treatment arm remained strong predictors of CD4 gain while CD8/CD38+, CD8/DR+, and CD4 Ki67+ phenotype were not predictive.

CONCLUSIONS

Continuous ART was associated with a statistically significantly greater CD4 cell response to IL-2 therapy than was intermittent ART. These observations may have important implications for the appropriate integration of IL-2 therapy into STI strategies.

Pharmaceutical approaches to eradication of persistent HIV infection

Highly active antiretroviral therapy (HAART) has markedly decreased morbidity and mortality in human immunodeficiency virus type 1 (HIV-1)-infected individuals in the developed world. Successful therapy often results in stable plasma levels of HIV-1 RNA below the limits of detection of commercial assays. Nonetheless, HIV-1 has not been cured by HAART. The causes of persistence of HIV infection in the face of current therapy appear to be multifactorial: latent but replication-competent provirus in resting CD4+ T cells, cryptic viral expression below the limits of detection of clinical assays, and viral sanctuary sites might all contribute to persistence. Clearance of HIV infection will almost certainly require a multimodality approach that includes potent suppression of HIV replication, therapies that reach all compartments of residual HIV replication and depletion of any reservoirs of persistent, quiescent proviral infection. This review highlights the basic mechanisms for the establishment and maintenance of viral reservoirs and pharmaceutical approaches towards their elimination.

Back-burning to cure HIV: temporary depletion of all CD4+ cells and elimination of the extracellular reservoir with HIV immunotoxin therapy

Temporary elimination of all host cells for the human immunodeficiency virus (HIV) combined with dislodging HIV from its extracellular reservoir could cure acquired immunodeficiency syndrome (AIDS). This combination would be effective because the virus is dependent on host cell integration or on the membrane protection of B cells or of follicular dendritic cells (FDCs) for its survival and because the CD4(+) host cells are leukocytes that are naturally renewable through hematopoiesis. By treating HIV patients with a combination of humanized antibodies it should be possible to achieve both goals. To deplete HIV host cells, a humanized antibody against CD4 should be fused to an apoptosis-inducing toxin; and to void the extracellular reservoir, a fragment of a humanized antibody against CD21 should be used. Because only CD4(+) cells would be destroyed, hematopoietic stem cells would be spared, and would spontaneously replace the depleted cells. We call this hypothetical new HIV treatment "HIV Immunotoxin Therapy (HIT)". Once the HIV viral load reaches zero, the HIT would be withdrawn and IL-2 or luteinizing hormone releasing hormone analogues (LHRH-A) might be administered to accelerate the natural replacement of the CD4(+) T(H) cells and macrophages. Killing all HIV host cells may seem counterintuitive at first, because it requires the purposeful destruction of the very cells that we ultimately hope to preserve for AIDS patients, but just as controlled back-burning purposefully creates a trap to stop a wildfire from burning out of control, this method could provide a mechanism to extinguish HIV.

Inferiority of IL-2 alone versus IL-2 with HAART in maintaining CD4 T cell counts during HAART interruption: a randomized controlled trial

OBJECTIVE

To evaluate whether interleukin (IL)-2 in patients with chronic HIV infection can maintain CD4 T cell counts during 6 months of HAART interruption.

DESIGN

Prospective, randomized, controlled, open-label phase II noninferiority trial comparing IL-2 with HAART interruption or continuous HAART.

METHODS

Forty-one IL-2-experienced (three or more prior cycles) HIV-1-infected adults with CD4 cell count at least 500 cells/microl were randomized in the ratio 2: 1 to interrupted (I = 27) or continuous (C = 14) HAART for 6 months following an initial IL-2 cycle. Subsequent IL-2 cycles were triggered by CD4 T cell counts less than 90% of baseline. Immune, metabolic, and quality of life indices were compared (Mann-Whitney and Fisher's exact tests), defining noninferiority as a percentage difference (C- I) in treatment success (CD4 T cells > or =90% of baseline at 6 months) with a 95% confidence interval (CI) lower limit greater than -20%.

RESULTS

Demographic and immune parameters were similar between the groups at baseline. Median CD4 T cell count, HIV viral load, and treatment success differed significantly at 6 months (I: 866 cells/microl, 39,389 copies/ml, 48.1%; C: 1246 cells/microl, <50 copies/ml, 92.3%; P < or = 0.001). Group I was inferior to C (% difference = -44.2%; 95% CI: -64.2%, -11.2%; P = 0.013). Minor statistically significant differences in HgbA1c and energy level occurred at 6 months (I > C). Following HAART interruption, single cases of acute retroviral syndrome, secondary syphilis, non-Hodgkin's lymphoma, and Kaposi's sarcoma recurrence were observed.

CONCLUSION

IL-2 alone was inferior to IL-2 with HAART in maintaining baseline CD4 T cell counts. HAART interruption had a small impact on metabolic parameters and quality of life.

The common gamma-chain cytokines IL-2, IL-7, IL-15, and IL-21 induce the expression of programmed death-1 and its ligands

The programmed death (PD)-1 molecule and its ligands (PD-L1 and PD-L2), negative regulatory members of the B7 family, play an important role in peripheral tolerance. Previous studies have demonstrated that PD-1 is up-regulated on T cells following TCR-mediated activation; however, little is known regarding PD-1 and Ag-independent, cytokine-induced T cell activation. The common gamma-chain (gamma c) cytokines IL-2, IL-7, IL-15, and IL-21, which play an important role in peripheral T cell expansion and survival, were found to up-regulate PD-1 and, with the exception of IL-21, PD-L1 on purified T cells in vitro. This effect was most prominent on memory T cells. Furthermore, these cytokines induced, indirectly, the expression of PD-L1 and PD-L2 on monocytes/macrophages in PBMC. The in vivo correlate of these observations was confirmed on PBMC isolated from HIV-infected individuals receiving IL-2 immunotherapy. Exposure of gamma c cytokine pretreated T cells to PD-1 ligand-IgG had no effect on STAT5 activation, T cell proliferation, or survival driven by gamma c cytokines. However, PD-1 ligand-IgG dramatically inhibited anti-CD3/CD28-driven proliferation and Lck activation. Furthermore, following restimulation with anti-CD3/CD28, cytokine secretion by both gamma c cytokine and anti-CD3/CD28 pretreated T cells was suppressed. These data suggest that gamma c cytokine-induced PD-1 does not interfere with cytokine-driven peripheral T cell expansion/survival, but may act to suppress certain effector functions of cytokine-stimulated cells upon TCR engagement, thereby minimizing immune-mediated damage to the host.

CD4 T cell survival after intermittent interleukin-2 therapy is predictive of an increase in the CD4 T cell count of HIV-infected patients

Administration of interleukin (IL)-2 to human immunodeficiency virus (HIV)-infected patients leads to significant increases in CD4 T cell counts. We previously have shown that IL-2 induces increased proliferation and survival of CD4 T cells. Deuterium labeling studies were undertaken to study the relationship between IL-2-induced increases in the CD4 T cell count and the effects of IL-2 on cell proliferation and survival. A strong inverse correlation was noted between the rate of decay of the label in CD4 cells and increases in CD4 cell counts (R =or- 0.67; P<.001). This correlation was not seen with the level of proliferating cells. Although the CD4 cell count at baseline and the number of CD4 cells expressing CD25 were also predictive of increases in the CD4 cell count, the rate of decay remained the most statistically significant predictor in multivariate regression models. Thus, an increase in the survival of CD4 T cells appears to be the critical mechanism leading to sustained increases in the CD4 cell counts of HIV-infected patients receiving intermittent IL-2 therapy.

CD127 and CD25 expression defines CD4+ T cell subsets that are differentially depleted during HIV infection

Decreased CD4(+) T cell counts are the best marker of disease progression during HIV infection. However, CD4(+) T cells are heterogeneous in phenotype and function, and it is unknown how preferential depletion of specific CD4(+) T cell subsets influences disease severity. CD4(+) T cells can be classified into three subsets by the expression of receptors for two T cell-tropic cytokines, IL-2 (CD25) and IL-7 (CD127). The CD127(+)CD25(low/-) subset includes IL-2-producing naive and central memory T cells; the CD127(-)CD25(-) subset includes mainly effector T cells expressing perforin and IFN-gamma; and the CD127(low)CD25(high) subset includes FoxP3-expressing regulatory T cells. Herein we investigated how the proportions of these T cell subsets are changed during HIV infection. When compared with healthy controls, HIV-infected patients show a relative increase in CD4(+)CD127(-)CD25(-) T cells that is related to an absolute decline of CD4(+)CD127(+)CD25(low/-) T cells. Interestingly, this expansion of CD4(+)CD127(-) T cells was not observed in naturally SIV-infected sooty mangabeys. The relative expansion of CD4(+)CD127(-)CD25(-) T cells correlated directly with the levels of total CD4(+) T cell depletion and immune activation. CD4(+)CD127(-)CD25(-) T cells were not selectively resistant to HIV infection as levels of cell-associated virus were similar in all non-naive CD4(+) T cell subsets. These data indicate that, during HIV infection, specific changes in the fraction of CD4(+) T cells expressing CD25 and/or CD127 are associated with disease progression. Further studies will determine whether monitoring the three subsets of CD4(+) T cells defined based on the expression of CD25 and CD127 should be used in the clinical management of HIV-infected individuals.

IL-15 acts as a potent inducer of CD4(+)CD25(hi) cells expressing FOXP3

IL-15 is a member of the gamma chain-dependent cytokines and known to affect innate and CD8(+) adaptive immune responses. Despite a growing interest in the use of IL-15 as an immunotherapeutic agent, the broad spectrum of immunoregulatory functions exerted by IL-15 has not been fully elucidated. Here, we demonstrate that IL-15 increases expression of CD25 and forkhead box transcription factor P3 (FOXP3), a master transcriptional regulator of regulatory T cells, in human peripheral CD4(+)CD25(-) T cells in the absence of antigenic stimulation. Comparisons involving IL-2 and IL-7 revealed that the induction of CD25(hi) and FOXP3 expression was most prominent with IL-15 and IL-2. More modest effects were seen with IL-7. Despite levels of FOXP3 expression comparable to that of conventional regulatory T cells, cytokine-induced CD4(+)CD25(hi)FOXP3(+) cells exerted only weak suppressor activity. Thus, the current study has demonstrated that IL-15 acts as a potent inducer of CD4(+)CD25(hi)FOXP3(+) cells in the periphery, and suggests a potential role for IL-15 in blunting immune activation. This study has provided further insights into the pleiotropic nature of IL-15 beyond the regulation of CD8(+) T cells.

Idiopathic CD4+ lymphocytopenia: natural history and prognostic factors

Idiopathic CD4(+) lymphocytopenia (ICL) is a rare non-HIV-related syndrome with unclear natural history and prognosis. This prospective natural history cohort study describes the clinical course, CD4 T lymphocyte kinetics, outcome, and prognostic factors of ICL. Thirty-nine patients (17 men, 22 women) 25 to 85 years old with ICL were evaluated between 1992 and 2006, and 36 were followed for a median of 49.5 months. Cryptococcal and nontuberculous mycobacterial infections were the major presenting opportunistic infections. Seven patients presented with no infection. In 32, CD4 T-cell counts remained less than 300/mm(3) throughout the study period and in 7 normalized after an average of 31 months. Overall, 15 (41.6%) developed an opportunistic infection in follow-up, 5 (13.8%) of which were "AIDS-defining clinical conditions," and 4 (11.1%) developed autoimmune diseases. Seven patients died, 4 from ICL-related opportunistic infections, within 42 months after diagnosis. Immunologic analyses revealed increased activation and turnover in CD4 but not CD8 T lymphocytes. CD8 T lymphocytopenia (< 180/mm(3)) and the degree of CD4 T cell activation (measured by HLA-DR expression) at presentation were associated with adverse outcome (opportunistic infection-related death; P = .003 and .02, respectively).

Sparse production but preferential incorporation of recently produced naive T cells in the human peripheral pool

In mice, recent thymic emigrants (RTEs) make up a large part of the naïve T cell pool and have been suggested to be a distinct short-lived pool. In humans, however, the life span and number of RTEs are unknown. Although (2)H(2)O labeling in young mice showed high thymic-dependent daily naïve T cell production, long term up- and down-labeling with (2)H(2)O in human adults revealed a low daily production of naïve T cells. Using mathematical modeling, we estimated human naïve CD4 and CD8 T cell half-lives of 4.2 and 6.5 years, respectively, whereas memory CD4 and CD8 T cells had half-lives of 0.4 and 0.7 year. The estimated half-life of recently produced naïve T cells was much longer than these average half-lives. Thus, our data are incompatible with a substantial short-lived RTE population in human adults and suggest that the few naïve T cells that are newly produced are preferentially incorporated in the peripheral pool.

Safety, tolerability, pharmacokinetics, and efficacy of an interleukin-2 agonist among HIV-infected patients receiving highly active antiretroviral therapy

We sought to determine the safety, maximum tolerated dose, optimal dose, and preliminary dose efficacy of intermittent subcutaneously (s.c.) administered BAY 50-4798 among patients with HIV infection receiving highly active antiretroviral therapy (HAART) compared with patients receiving HAART alone. A phase I/II randomized, double-blind, dose-escalation study was conducted of the safety, tolerability, pharmacokinetics, and efficacy of s.c. BAY 50-4798 administered to HIV-infected patients already receiving stable HAART. There were no unexpected safety findings in a population of HIV-infected patients receiving HAART plus SC BAY 50-4798 as adjunctive therapy. BAY 50-4798 exhibited nearly dose-proportional pharmacokinetics, and accumulation was minimal during multiple-dose treatment. Limited efficacy data indicated that treatment with BAY 50-4798 caused at least a transient increase in CD4(+) T cell counts in some recipients, particularly at the early time points. In general, this effect appeared to increase with increasing dose. Bay 50-4798 was generally well tolerated across the dose range tested, but a lack of potent, sustained immunologic activity suggests that further optimization of dose and schedule will be necessary.

Targeting intracellular signaling: a novel approach to vaccination

Vaccination is well known to control many current infectious diseases. However, the development of cellular (Th1) immunity to control viral pathogens, among others, requires the development of new vaccine adjuvants. The use of Toll-like receptor ligands or cytokines has shown much promise, although specificity and toxicity are issues with these strategies. Targeting intracellular signaling pathways may allow for greater specificity of the adjuvant, as well as reducing systemic toxicity. Studies targeting these pathways are discussed, as well as their potential applications in the future.

Human T cell reconstitution in DiGeorge syndrome and HIV-1 infection

The thymus is essential for proper development and maintenance of a broad T cell repertoire capable of recognizing a wide-range of foreign antigens. Recent advances in multicolor flow cytometry, non-invasive imaging techniques, and molecular assessments of thymic function have enabled a more comprehensive characterization of human thymic output in clinical settings than in the past. These techniques have been particularly valuable in monitoring human T cells after therapeutic thymic grafting for complete DiGeorge syndrome and during HIV-1 infection and AIDS. By defining the degree and mechanisms of T cell reconstitution in these settings, clinical investigators and primary caregivers have been able to better diagnose, treat and care for individuals with congenital or acquired immune deficiencies associated with loss of thymic function.

Confronting proviral HIV infection

The course of HIV infection is arrested by antiretroviral therapy (ART). However, life-long ART is undesirable. To eradicate infection, strategies are needed to deplete the rare population of proviral genomes that persist and reemerge if ART is interrupted. Proviral HIV persists due to the simultaneous deficiency of factors required to allow proviral expression and virion production, and a predominance of factors that obstruct proviral expression. Combining ART with global inducers of T-cell activation has so far failed to eradicate HIV infection. One approach to the selective removal of obstacles to proviral expression, inhibition of the chromatin remodeling enzyme histone deacetylase, has entered clinical testing. Additional approaches may be needed. Ultimately, therapies that eliminate rare cells that persistently express HIV and interrupt low levels of viremia that persist in some patients may be required to render depletion of proviral HIV infection clinically relevant, and lead to the clearance of HIV infection.

Non-human primate models of T-cell reconstitution

Non-human primates (NHP) have become an indispensable model in studying the common and dangerous human chronic infections, including HIV/SIV, Hepatitis C virus, and tuberculosis. More recently, we and others have used aged NHP to model human immune aging. Chronic infections and aging are both characterized by a significant depletion of defined lymphocyte subsets and the compensatory attempts to regenerate the immune system. As the efficacious antiviral drugs and novel methods to improve and boost the immune system emerge, therapeutic immune regeneration has become a realistic goal in both the physiologic and pathologic settings. This article will summarize our current knowledge on this topic and will discuss future research directions as well as the potential and power of translational studies in non-human primate models of infection, aging and bone marrow transplantation.

Long-term effects of intermittent interleukin-2 therapy in chronic HIV-infected patients (ANRS 048-079 Trials)

OBJECTIVE

Interleukin (IL)-2 therapy leads to significant CD4 cell increases in HIV-infected patients. Since phase III trials are ongoing, studies supporting the long-term feasibility of this strategy are needed.

METHODS

We studied the long-term outcomes of 131 patients treated with IL-2 in two studies initiated either before (ANRS 048) or following (ANRS 079) the advent of HAART.

RESULTS

At the last assessment (median follow-up 3.4 years), these patients experienced a gain of 428 cells/microl and a decrease in plasma HIV RNA to 1.70 log10 copies/ml. In both studies, high CD4 cell counts were maintained with a median of ten 5-day cycles of subcutaneous IL-2. Median time since the last cycle was 2 years. At last assessment, 59% of 048 patients maintained a non-HAART regimen. Detailed analysis at week 170 showed that median CD4 cell counts were 856 (048) and 964 (079) cells/microl. This corresponded to a gain from baseline of 515 (048) and 627 (079) cells/microl. The median viral load decreases from baseline and corresponded to 1.70 (048) and 1.88 (079) log10 copies/ml. Comparisons across the studies showed that CD4 gains and viral load changes were similar whether HAART or non-HAART was used. The frequency of cycling, but not CD4 cell counts, viral loads or antiviral regimen at baseline, was predictive of long-term CD4 gain (P = 0.03).

CONCLUSION

Altogether, these observations support IL-2 as a long-term therapeutic strategy in HIV infection.

Interruption of antiretroviral therapy initiated during primary HIV-1 infection: impact of a therapeutic vaccination strategy combined with interleukin (IL)-2 compared with IL-2 alone in the ANRS 095 Randomized Study

HIV-specific T cell responses play a critical role in the control of infection. We evaluated the impact of immune-based interventions in patients first treated during primary HIV-1 infection (PHI). Forty-three patients were randomized within three groups, to receive either interleukin-2 (IL-2 group), or boosts of ALVAC-HIV (vCP1433) and LIPO-6T followed by interleukin-2 (Vac-IL2 group), compared with no immune intervention (control group), and were monitored for T cell responses. Impact of strategies on viral replication was subsequently assessed during long-term treatment interruption. HIV-specific CD4(+) T cell responses did not change during the study period in immunized patients relative to controls, and vaccination had only a transient effect on interferon-gamma-producing CD8 responses. Viral rebound after treatment interruption was similar in immunized patients and controls. Forty percent of patients had HIV RNA values <10,000 copies/ml 12 weeks after interruption. The cumulative time off treatment represented almost half the total follow-up period. Immunological and virological status during PHI and HIV DNA load at interruption were predictive of the level of viral rebound after treatment interruption, whereas HIV RNA level during PHI and HIV DNA level at interruption were predictive of the time off treatment. Treatment interruption is safe in patients treated early after primary HIV infection. On the basis of this pilot study, HIV immunizations and interleukin-2 appear to have no supplementary benefit.

Predicting memory: a prospective readout for malaria vaccines?

Malaria vaccines aim to induce long lasting protective immunity. Bejon and colleagues propose that levels of rapidly induced (effector memory) interleukin-2 and interferon gamma producing T-cells after vaccination with leading pre-erythrocytic stage vaccines predict the induction of resting memory responses (central memory). Herein we discuss Bejon's findings in the context of current thinking on the generation and maintenance of T cell memory, with particular emphasis on the role of cytokines.

Quantitative longitudinal analysis of T cell receptor repertoire expression in HIV-infected patients on antiretroviral and interleukin-2 therapy

We have developed a single-step reverse transcriptase kinetic PCR assay (kRT-PCR) to accurately determine the expression of each of the 24 TCRbetaV gene families in CD8(+) cells. We analyzed the long-term effects of highly active antiretroviral therapy (HAART) on the stability of the CD8(+) T cell receptor (TCR) repertoire in a cohort of 15 treated and 10 untreated individuals diagnosed with human immunodeficiency virus (HIV) infection. The CD4(+) TCR repertoire was studied in a second cohort receiving interleukin-2 infusions in addition to HAART. Analysis was based on kinetic (quantitative) reverse-transcription PCR (kRT-PCR) of the TCR variable B gene (TCRbetaV). Expression of each of the 24 Vbeta families was assessed at baseline immediately after infection and following initiation of HAART at 2, 4, 12, 24, and up to 192 weeks in 24-week intervals. Statistically significant family-specific expression changes were observed between treated and untreated individuals for 10 TCRbetaV families. Overall, when compared to untreated patients, a more stable expression of TCR genes was observed for HAART-treated individuals. Interestingly, this difference did not correlate with either CD4 or CD8 counts, which follow the expected curves for treated and untreated patients. When we applied our quantitative analysis to IL-2-treated patients we observed a rapid polyclonal activation of the repertoire. These results suggest that homeostasis in the T cell receptor repertoire is more robust in those patients who stay on HAART for a long time and confirm the polyclonal stimulating capacity of IL-2.

Quantification of T-cell dynamics: from telomeres to DNA labeling

Immunology has traditionally been a qualitative science describing the cellular and molecular components of the immune system and their functions. Only quite recently have new experimental techniques paved the way for a more quantitative approach of immunology. Lymphocyte telomere lengths have been measured to get insights into the proliferation rate of different lymphocyte subsets, T-cell receptor excision circles have been used to quantify the daily output of new T cells from the thymus, and bromodeoxyuridine and stable isotope labeling have been applied to measure proliferation and death rates of naive and memory lymphocytes. A common problem of the above techniques is the translation of the resulting data into relevant parameters, such as the typical division and death rate of the different lymphocyte populations. Theoretical immunology has contributed significantly to the interpretation of such quantitative experimental data, thereby resolving diverse controversies and, most importantly, has suggested novel experiments, allowing for more conclusive and quantitative interpretations. In this article, we review a variety of different models that have been used to interpret data on lymphocyte kinetics in healthy human subjects and discuss their contributions and limitations.

Novel approaches towards conquering hepatitis B virus infection

Currently approved treatments for hepatitis B virus (HBV) infection include the immunomodulatory agent, IFN-α, and nucleos(t)ide analogues. Their efficacy is limited by their side effects, as well as the induction of viral mutations that render them less potent. It is thus necessary to develop drugs that target additional viral antigens. Chemicals and biomaterials by unique methods of preventing HBV replication are currently being developed, including novel nucleosides and newly synthesized compounds such as capsid assembling and mRNA transcription inhibitors. Molecular therapies that target different stages of the HBV life cycle will aid current methods to manage chronic hepatitis B (CHB) infection. The use of immunomodulators and gene therapy are also under consideration. This report summarizes the most recent treatment possibilities for CHB infection. Emerging therapies and their potential mechanisms, efficacy, and pitfalls are discussed.

CD8 apoptosis may be a predictor of T cell number normalization after immune reconstitution in HIV

Background

As part of the Houston Vanguard study, a subset of 10 patients randomized to receive IL-2 therapy were compared to 4 patients randomized to not receive IL-2, for markers of T cell activation and death during the first three cycles of IL-2. All patients were treated with combination antiretroviral therapy (ART) and were virally suppressed. The purpose of the study was to examine the role of CD8+ T cell death in responses to ART and IL-2 therapy.

Methods

Lymphocytes were examined at Day 0, 5 and 30 days during three cycles of IL-2 therapy. CD25, CD38, HLA-DR expression and annexin (cell death) were examined on CD4 and CD8 subpopulations. Follow up studies examined CD4 levels and CD4:CD8 reconstitution after 6 years using both univariant and multivariate analyses.

Results

Human lymphocytes responded to IL-2 therapy by upregulation of CD25 on CD4⁺ T cells, leading to an increase in CD4 cell counts. CD8⁺ T cells did not increase CD25 expression, but upregulated activation antigens (CD38 and DR) and had increased death. At baseline, 7 of the 14 patients had high CD8⁺ T cell apoptosis (mean 17.0% ± 6.0). We did an exploratory analysis of immune status after six years, and found that baseline CD8⁺ T cell apoptosis was correlated with CD4 cell count gain beginning two years post enrollment. Patients with low levels of CD8⁺ T cell apoptosis at baseline (mean 2.2% ± 2.1) had significantly higher CD4 cell counts and more normalized CD4:CD8 ratios than patients with high CD8⁺ T cell apoptosis (mean CD4 cell counts 1,209 ± 164 vs 754 ± 320 cells/mm³; CD4:CD8 ratios 1.55 vs. 0.70, respectively).

Conclusion

We postulate that CD8⁺ T cell apoptosis may reflect inherent activation status, which continues in some patients even though viral replication is suppressed which influences the ability of CD4⁺ T cells to rebound. Levels of CD8⁺ T cell apoptosis may therefore be an independent predictor of immune status, which should be shown in a prospective study.

[Cytokine therapies in HIV infection]

The theoretical objectives of cytokine therapies in HIV infection are to impact T cell homeostasis and/or to improve immune functions or the mobilization of the HIV reservoir. Among cytokines, IL-2 and IL-7 are promising agents under clinical evaluation. Intermittent administration of IL-2 is by far the furthest studied strategy in HIV infection. This cytokine increases CD4 T lymphocytes in HIV-infected individuals. Recent clinical data showed that this effect is sustained over years. IL-2 therapy induces a peripheral expansion of T cells as a consequence of prolonged survival of T cells and decreased immune activation. These effects suggest that a cytokine therapy may interfere with critical factors of HIV disease. Recent data provide arguments that IL-2 therapy improves immune functions in HIV-infected patients. Whether these effects may be translated into clinical benefits is under evaluation in ongoing phase III studies. The potential interest of IL-7 in the treatment of HIV-infection is based on its crucial role on T cell homeostasis both in thymic output and peripheral T proliferation and survival. Although no data in human are still available, recent studies provide arguments to assess this cytokine in HIV infection. Phase I studies are ongoing or planned.

Naive T-cell depletion related to infection by X4 human immunodeficiency virus type 1 in poor immunological responders to highly active antiretroviral therapy

The reasons for poor CD4+ T-cell recovery in some human immunodeficiency virus (HIV)-infected subjects despite effective highly active antiretroviral therapy (HAART) remain unclear. We recently reported that CXCR4-using (X4) HIV-1 could be gradually selected in cellular reservoirs during sustained HAART. Because of the differential expression of HIV-1 coreceptors CCR5 and CXCR4 on distinct T-cell subsets, the residual replication of R5 and X4 viruses could have different impacts on T-cell homeostasis during immune reconstitution on HAART. We examined this hypothesis and the mechanisms of CD4+ T-cell restoration by comparing the virological and immunological features of 15 poor and 15 good immunological responders to HAART. We found a high frequency of X4 viruses in the poor immunological responders. But the levels of intrathymic proliferation of the two groups were similar regardless of whether they were infected by R5 or X4 virus. The frequency of recent thymic emigrants in the poor immunological responders was also similar to that found in the good immunological responders, despite their reduced numbers of naïve CD4+ T cells. Our data, rather, suggest that the naïve T-cell compartment is drained by a high rate of mature naïve cell loss in the periphery due to bystander apoptosis or activation-induced differentiation. X4 viruses could play a role in the depletion of naïve T cells in poor immunological responders to HAART by triggering persistent T-cell activation and bystander apoptosis via gp120-CXCR4 interactions.

Decreased CD127 expression on T Cells in HIV-1-infected adults receiving antiretroviral therapy with or without intermittent IL-2 therapy

BACKGROUND

The interleukin-7 (IL-7)/IL-7 receptor alpha (IL-7Ralpha) system is an important regulator of T-cell homeostasis. We evaluated the IL-7/IL-7Ralpha system in a large cohort of HIV-infected patients, including a subset treated with intermittent IL-2.

METHODS

IL-7 serum levels and CD127 (IL-7Ralpha) expression on T cells were evaluated in a cross-sectional study of 36 healthy volunteers, 151 HIV-infected patients, and 83 HIV-infected patients who had received IL-2 therapy. Multivariate regression models were used to determine predictors of CD127 expression.

RESULTS

HIV-infected patients had higher IL-7 levels compared with healthy volunteers (P = 0.022) and IL-2-treated patients (P = 0.012). CD127 expression was significantly lower on CD4 and CD8 T cells of HIV-infected patients compared with healthy volunteers (P = 0.008 and P < 0.001, respectively), and CD127 median fluorescence intensity was lowest on CD4 T cells in IL-2-treated patients (P < 0.001 compared with HIV-infected patients). The proportion of naive and effector memory/effector T cells were significant predictors of CD127 expression on T cells. IL-2 immunotherapy led to the expansion of a CD25/CD127-low subset of CD4 T cells.

CONCLUSIONS

CD127 expression on T cells remains low in HIV-infected patients despite antiretroviral therapy, reflecting persistent aberration in the subset composition of the T-cell pool.

Immunostimulatory combinations: designing the next generation of vaccine adjuvants

Agents that activate dendritic cells are essential components for vaccines and can be conceptualized as molecular adjuvants. Other molecular adjuvants affect downstream factors that shape the resulting immune response. This review provides a compendium of recently studied molecular adjuvants, focusing on CD8+ T cell responses, which have important roles in HIV vaccines. Reference is also made to CD8+ T cell antitumor responses, where parallel studies of molecular adjuvants are being pursued. Molecular adjuvants can be considered in the following groups: TNF superfamily molecules such as CD40 ligand; agonists for TLRs; agonists for NAIP, CIITA, HET-E, TP-1-leucine-rich repeat pathway receptors, such as nucleotide-binding and oligomerization domain (NOD)1, NOD2, and cryopyrin; chemokines; ILs; CSFs; IFNs; alarmins; and purinergic P2X7 receptor agonists. Complementing these positively acting agents are strategies to reduce the immunosuppressive effects of CD4+CD25+ regulatory T cells and negatively acting factors such as TGF-beta, IL-10, suppressor of cytokine signaling 1, and programmed cell death-1 using neutralizing antibodies, antisense, and small interfering RNA. Especially effective are combinations of molecular adjuvants, which can elicit a massive expansion of antigen-specific CD8+ T cells and show unprecedented efficacy in vaccine and tumor models. Taken together, these new approaches provide significant incremental progress in the development of vaccines to elicit cell-mediated immunity against HIV and other pathogens.

Idiopathic CD4 lymphocytopenia

PURPOSE OF REVIEW

A severe decrease of CD4 T cells predisposes humans to opportunistic infections. In adults, HIV is certainly the most common cause of CD4 lymphocytopenia, but other causes, such as infections, autoimmune diseases, immunosuppressive therapy, lymphoma and idiopathic forms need to be considered. This review summarizes the current knowledge of the poorly understood syndrome of idiopathic CD4 lymphocytopenia.

RECENT FINDINGS

Little research has tried to systematically dissect this probably heterogeneic syndrome after its initial description in 1992. Numerous cases presenting with opportunistic infections have been reported. Disturbed differentiation of stem cell precursors may contribute to CD4 lymphocytopenia. Because infections and lymphoma may also cause CD4 lymphocytopenia, the distinction between cause and effect may evolve only during follow-up.

SUMMARY

The manifestation of opportunistic infections calls for the evaluation of the immune system for CD4 lymphocytopenia. The differential diagnosis of this condition in adults comprises primarily HIV infection and less often other diseases or drugs. Idiopathic CD4 lymphocytopenia is very rare. The clinical significance of low CD4 cell counts in HIV negative patients still awaits its systematic analysis. Prophylaxis of opportunistic infections is oriented at the recommendations of HIV-infected individuals and causal treatment remains experimental.

A randomised trial of subcutaneous intermittent interleukin-2 without antiretroviral therapy in HIV-infected patients: the UK-Vanguard Study

Objective:

The objective of the trial was to evaluate in a pilot setting the safety and efficacy of interleukin-2 (IL-2) therapy when used without concomitant antiretroviral therapy as a treatment for HIV infection.

Design and Setting:

This was a multicentre randomised three-arm trial conducted between September 1998 and March 2001 at three clinical centres in the United Kingdom.

Participants:

Participants were 36 antiretroviral treatment naïve HIV-1-infected patients with baseline CD4 T lymphocyte counts of at least 350 cells/mm³.

Interventions:

Participants were randomly assigned to receive IL-2 at 15 million international units (MIU) per day (12 participants) or 9 MIU/day (12 participants) or no treatment (12 participants). IL-2 was administered by twice-daily subcutaneous injections for five consecutive days every 8 wk.

Outcome Measures:

Primary outcome was the change from baseline CD4 T lymphocyte count at 24 wk. Safety and plasma HIV RNA levels were also monitored every 4 wk through 24 wk. The two IL-2 dose groups were combined for the primary analysis.

Results:

Area under curve (AUC) for change in the mean CD4 T lymphocyte count through 24 wk was 129 cells/mm³ for those assigned IL-2 (both dose groups combined) and 13 cells/mm³ for control participants (95% CI for difference, 51.3–181.2 cells/mm³; p = 0.0009). Compared to the control group, significant increases in CD4 cell count were observed for both IL-2 dose groups: 104.2/mm³ (p = 0.008) and 128.4 cells/mm³ (p = 0.002) for the 4.5 and 7.5 MIU dose groups, respectively. There were no significant differences between the IL-2 (0.13 log₁₀ copies/ml) and control (0.09 log₁₀ copies/ml) groups for AUC of change in plasma HIV RNA over the 24-wk period of follow-up (95% CI for difference, −0.17 to 0.26; p = 0.70). Grade 4 and dose-limiting side effects were in keeping with those previously reported for IL-2 therapy.

Conclusions:

In participants with HIV infection and baseline CD4 T lymphocyte counts of at least 350 cells/mm³, intermittent subcutaneous IL-2 without concomitant antiretroviral therapy was well tolerated and produced significant increases in CD4 T lymphocyte counts and did not adversely affect plasma HIV RNA levels.

Background: There is very good trial evidence that combinations of antiretroviral drugs improve the prognosis of people with HIV infection. However, these drugs can have major side effects, and HIV can become resistant to them. The development of alternative treatments might allow antiretroviral use to be delayed in some people, thereby reducing toxicity and the emergence of resistant strains of HIV.

What this trial shows: The researchers studied 36 adult patients in the United Kingdom who were infected with HIV and who had not previously been prescribed antiretrovirals. Participants in the trial were given either one of two different dosage levels of IL-2 (a chemical messenger normally produced in the body by particular immune cells) by injection under the skin or no treatment at all. Patients given IL-2 at either dosage experienced an increase in levels of CD4 T lymphocytes, the type of immune cell depleted by HIV infection, as compared to patients receiving no treatment. The viral load in patients receiving IL-2 did not differ from that of patients in the control arm.

Strengths and limitations: The rationale for this trial—to delay administration of antiretroviral drugs—is sound, as is the experimental design. The results are limited, however, by the short follow-up of patients in the trial and by the lack of clinical endpoints (such as disease progression), so it is not possible to tell whether patients in the trial benefited directly from the IL-2 treatment.

Contribution to the evidence: The clinical effectiveness and safety of IL-2 together with antiretrovirals as a treatment for HIV infection is currently being evaluated in other, large-scale trials. To date, no other study has assessed the outcomes arising from administration of IL-2 alone. Data from the current trial will be useful in planning further research to examine whether IL-2 might help delay antiretrovirals in HIV-positive people.

Immunological recovery and antiretroviral therapy in HIV-1 infection

Potent antiretroviral therapy has dramatically improved the prognosis of patients infected with HIV-1. Primary and secondary prophylaxis against Pneumocystis carinii, Mycobacterium avium, cytomegalovirus, and other pathogens can be discontinued safely once CD4 cell counts have increased beyond pathogen-specific thresholds. Approximately one-third of individuals receiving antiretroviral therapy will not reach CD4 cell counts above 500 cells per muL after 5 years despite continuous suppression of plasma HIV-1 RNA. Whether this failure represents a risk factor for the long-term incidence of opportunistic diseases--eg, tuberculosis or malignancies--remains uncertain. We describe the time course of CD4 cell concentrations in patients whose plasma HIV-1 RNA is durably suppressed by antiretroviral therapy, in patients with incomplete suppression of plasma HIV-1 RNA, and during treatment interruptions. In addition, immune reconstitution disease, an inflammatory syndrome associated with immunological recovery occurring days to weeks after the start of antiretroviral therapy, is briefly described.

IL-15 induces CD4 effector memory T cell production and tissue emigration in nonhuman primates

HIV infection selectively targets CD4+ effector memory T (T EM) cells, resulting in dramatic depletion of CD4+ T cells in mucosal effector sites in early infection. Regeneration of the T EM cell compartment is slow and incomplete, even when viral replication is controlled by antiretroviral therapy (ART). Here, we demonstrate that IL-15 dramatically increases in vivo proliferation of rhesus macaque (RM) CD4+ and CD8+ T EM cells with little effect on the naive or central memory T (T CM) cell subsets, a response pattern that is quite distinct from that of either IL-2 or IL-7. T EM cells produced in response to IL-15 did not accumulate in blood. Rather, 5-bromo-2'-deoxyuridine (BrdU) labeling studies suggest that many of these cells rapidly disperse to extralymphoid effector sites, where they manifest (slow) decay kinetics indistinguishable from that of untreated controls. In RMs with uncontrolled SIV infection and highly activated immune systems, IL-15 did not significantly increase CD4+ T EM cell proliferation, but with virologic control and concomitant reduction in immune activation by ART, IL-15 responsiveness was again observed. These data suggest that therapeutic use of IL-15 in the setting of ART might facilitate specific restoration of the CD4 + T cell compartment that is the primary target of HIV with less risk of exhausting precursor T cell compartments or generating potentially deleterious regulatory subsets.

Immunomodulants for the treatment of HIV infection: the search goes on

The natural history of HIV infection has been greatly modified by the introduction of powerful antiretroviral agents that act on multiple steps of HIV replication. Thus, antiretroviral therapy (ART) has prolonged the life of HIV-infected individuals, significantly impacting on the progression to AIDS. It was assumed that ART-induced suppression of HIV would have resulted in a degree of immune recovery sufficient enough to allow immune control over HIV replication independently of the use of drugs. Unfortunately, interruption of therapy, even after long periods of full suppression of viral replication, is almost inevitably associated with a prompt rebound of HIV viraemia. The outcome of this observation is that ART has to be considered as a lifelong therapy, with the associated resulting problems of the emergence of multi-drug resistant viral strains, toxic effects, costs and compliance. The use of immunomodulants in association with ART could achieve the goal of boosting the immune response to a threshold, permitting the immune response to indefinitely suppress HIV replication.

Change in T-Lymphocyte Count after Initiation of Highly Active Antiretroviral Therapy in HIV-Infected Patients with History of Mycobacterium Avium Complex Infection

Objective

To compare changes in CD4+, CD8+ and total lymphocyte counts after initiation of highly active anti-retroviral therapy (HAART) between HIV-infected patients with and without a recent history of Mycobacterium avium complex (MAC) infection.

Method

Matched exposed-non-exposed retrospective cohort study.

Results

Fifty-one patients with a recent history of MAC infection (MAC+) started a combination of at least three antiretroviral drugs. They were individually matched to 145 patients without any history of MAC infection (MAC-) according to CD4+ T-cell count (±30 cells/mm3), previous experience of antiretroviral treatment, AIDS clinical stage at the time of HAART initiation (baseline), age (±10 years) and gender. MAC+ and MAC- patients presented comparable median levels of total lymphocytes (488 vs 688/mm3, P=0.09), CD4+ (11 vs 16/mm3, P=0.15), CD8+ count (359 vs 386/mm3, P=0.39) and plasma HIV RNA (5.3 vs 5.1 log10 copies/ml, P=0.22) at baseline. After 6 months on HAART, the median increase of CD4+ T-cell count was 28 cells/mm3 (interquartile range [IQR]: 1–63) in MAC+ and 72 cells/mm3 (IQR: 34–120) in MAC- patients ( P<0.0001), whereas the percentage of CD4+ T cells was not significantly different between the two groups ( P=0.13). Comparable differences were observed for total lymphocytes and CD8+ T cells ( P<0.001). The 6 months decline of plasma HIV RNA was not significantly different according to MAC exposure (-1.6 in MAC+ vs -1.8 log10 copies/ml in MAC- patients, P=0.65). Results were confirmed after adjustment for other characteristics than the matching variables and after taking into account potential informative bias due to unbalanced number of deaths between the two groups.

Conclusion

MAC infection at the time of HAART initiation is an important deleterious factor for immune reconstitution. A better understanding of the underlying mechanism and an evaluation of additional treatment strategies are necessary to help immune restoration in such circumstances.

Interruption of antiretroviral therapy blunts but does not abrogate CD4 T-cell responses to interleukin-2 administration in HIV infected patients

BACKGROUND

Intermittent administration of interleukin (IL)-2 to HIV infected patients leads to CD4 T-cell expansions that are associated with decreased CD4 T-cell turnover. IL-2 is under evaluation in antiretroviral therapy (ART) interruption studies, but it is unclear how the emergence of viremia may affect CD4 expansions.

METHODS

CD4 T-cell responses were evaluated in 27 HIV infected patients on long-term intermittent IL-2 therapy who underwent ART interruption immediately after an IL-2 cycle ('IL-2/off') and compared with responses from a previous IL-2 cycle while on continuous ART ('IL-2/on'). Immunophenotypic analysis, including intracellular Ki67 staining, of cryopreserved peripheral blood mononuclear cells was performed.

RESULTS

CD4 T-cell increases, in naive and central memory CD4 T-cell subsets, were observed in the IL-2/on (106 and 327 cells/microl, respectively) and IL-2/off (84 and 184 cells/microl, respectively) cycles 1 month following IL-2 administration. These increases were greater during the IL-2/on cycle (P = 0.05, P = 0.01, respectively). In both cycles, the change in CD4 T-cell count correlated with the change in CD4/CD25 T cells. In the IL-2/off cycle, the change in the proportion of CD4 T cells expressing Ki67 was associated with both the changes in viral load (r = 0.64, P = 0.001) and the changes in CD4 T cells (r = -0.56, P = 0.01).

CONCLUSIONS

IL-2 administration followed by ART interruption led to significant, although blunted, CD4 T-cell increases. IL-2 induced CD4 T-cell increases in the setting of emergent viremia were associated with decreased CD4 T-cell activation that counteracted the viremia-induced increases in CD4 T-cell activation.

Novel Approaches to New Therapies for Hepatitis B Virus Infection

Hepatitis B is one of the most prevalent viral diseases in the world. It leads to chronic liver disease in 10% of infected individuals, putting them at an increased risk for liver-related morbidity and mortality from complications of cirrhosis and hepatocellular carcinoma. Despite the success of universal hepatitis B vaccination in many countries, this disease remains a major public health problem, resulting in more than 500,000 deaths per year. Although the current therapy for chronic hepatitis B (CHB) is effective, it is not optimal; novel approaches to the management of CHB are needed. An improved understanding of virus-host interactions, advances in gene therapy, the development of molecular therapies targeted at different stages of the hepatitis B virus life cycle, and new insights into various approaches of immune modulation will lead to the development of better therapeutic agents for the management of CHB. These advances herald a new era of combination therapy. In this review, we will discuss emerging therapies and potential mechanisms, and highlight the promises and pitfalls of these new treatment strategies.

Change in T-lymphocyte count after initiation of highly active antiretroviral therapy in HIV-infected patients with history of Mycobacterium avium complex infection

OBJECTIVE

To compare changes in CD4+, CD8+ and total lymphocyte counts after initiation of highly active antiretroviral therapy (HAART) between HIV-infected patients with and without a recent history of Mycobacterium avium complex (MAC) infection.

METHOD

Matched exposed-non-exposed retrospective cohort study.

RESULTS

Fifty-one patients with a recent history of MAC infection (MAC+) started a combination of at least three antiretroviral drugs. They were individually matched to 145 patients without any history of MAC infection (MAC-) according to CD4+ T-cell count (+/- 30 cells/mm3), previous experience of antiretroviral treatment, AIDS clinical stage at the time of HAART initiation (baseline), age (+/- 10 years) and gender. MAC+ and MAC- patients presented comparable median levels of total lymphocytes (488 vs 688/mm3, P=0.09), CD4+ (11 vs 16/mm3, P=0.15), CD8+ count (359 vs 386/mm3, P=0.39) and plasma HIV RNA (5.3 vs 5.1 log10 copies/ml, P=0.22) at baseline. After 6 months on HAART, the median increase of CD4+ T-cell count was 28 cells/mm3 (interquartile range [IQR]: 1-63) in MAC+ and 72 cells/mm3 (IQR: 34-120) in MAC- patients (P<0.0001), whereas the percentage of CD4+ T cells was not significantly different between the two groups (P=0.13). Comparable differences were observed for total lymphocytes and CD8+ T cells (P<0.001). The 6 months decline of plasma HIV RNA was not significantly different according to MAC exposure (-1.6 in MAC+ vs -1.8 log10 copies/ml in MAC- patients, P=0.65). Results were confirmed after adjustment for other characteristics than the matching variables and after taking into account potential informative bias due to unbalanced number of deaths between the two groups.

CONCLUSION

MAC infection at the time of HAART initiation is an important deleterious factor for immune reconstitution. A better understanding of the underlying mechanism and an evaluation of additional treatment strategies are necessary to help immune restoration in such circumstances.