Early CD4(+) T cell recovery in human immunodeficiency virus-infected patients receiving effective therapy is related to a down-regulation of apoptosis and not to proliferation

Raltegravir Inclusion Decreases CD4 T-Cells Intra-Cellular Viral Load and Increases CD4 and CD28 Positive T-Cells in Selected HIV Patients

Raltegravir (RLT) prevents the integration of HIV DNA in the nucleus, but published studies remain controversial, suggesting that it does not decrease proviral DNA. However, there are only a few studies focused on virus-targeted cells. We aimed our study on the impact of RLT inclusion on total intra-cellular viral DNA (TID) in cellular subsets and immune effects in patients with newly acquired undetectable plasmatic viral load (UVL). Six patients having UVL using an antiretroviral combination for 6 months and CD4 T-cells > 350/mL and <500/mL were selected to receive RLT for 3 months from M0 to M3. Patients had 7 sequential viro-immunological determinations from M-1 to M5. Immune phenotypes were determined by flow cytometry and TID quantification was performed using PCR assay on purified cells. TID (median values) at the initiation of RLT in CD4 T-cells was 117 copies/millions of cells, decreased to 27.5 on M3, and remained thereafter permanently under the cut-off (<10 copies/millions of cells) in 4 out of 6 patients. This was associated with an increase of CD4 and CD4 + CD28+ T-cells and a decrease of HLA-DR expression and apoptosis of CD4 T-cells. RLT inclusion led to decreases in the viral load along with positive immune reconstitution, mainly for CD4 T-cells in HIV patients.

An activating transcription factor 6 beta (ATF6β) regulates apoptosis of hemocyte during immune response in Crassostrea gigas

The homeostasis of immune cells during immune response is vital for hosts to defend against invaders. Activating transcription factor 6 (ATF6) is an important transcription factor in the unfolded protein response (UPR) to maintaining cellular homeostasis. In the present study, one ATF6 homologue was identified from Pacific oyster Crassostrea gigas (designated as CgATF6β). The full length cDNA of CgATF6β was of 2645 bp with a 1596 bp open reading frame (ORF) encoding a polypeptide of 531 amino acids. The deduced amino acid sequence of CgATF6β was predicted to contain a transmembrane region, a conserved basic leucine zipper (bZIP) domain, a site 1 protease cleavage site, a site 2 protease cleavage site, and a Golgi localization signal. CgATF6β mRNA was constitutively expressed in hemocytes, gill, mantle, gonad, hepatopancreas and labial palp, with a slightly higher expression level in muscle (2.45-fold of that in gill, p < 0.05). After oysters were challenged with Vibrio splendidus, the mRNA expression levels of CgATF6β in hemocytes were significantly up-regulated at 3 h (2.68-fold of that in seawater group, p < 0.01) and peaked at 12 h (3.14-fold of that in seawater group, p < 0.01). The endogenic CgATF6β protein was mainly located in the cytoplasm of oyster hemocytes, and it was significantly transported into the nuclei of hemocytes at 1.5 h after the challenge with V. splendidus. After an injection with CgATF6β dsRNA, the mRNA expression of CgATF6β was knocked down to 0.26-fold of that in dsGFP group (p < 0.01). In CgATF6β dsRNA-injected oysters, the mRNA expressions of glucose-regulated protein 78 (GRP78), calnexin (CNX) and anti-apoptotic B-cell lymphoma-2 (Bcl-2) in hemocytes were significantly decreased at 12 h after V. splendidus challenge, which were 0.65-fold (p < 0.01), 0.54-fold (p < 0.01) and 0.17-fold (p < 0.01) of that in dsGFP-injected oysters, while the apoptotic rate of hemocytes was significantly up-regulated (1.97-fold of that in dsGFP group, p < 0.05). Collectively, these results suggested that CgATF6β was involved in apoptosis inhibition of oyster hemocytes upon V. splendidus challenge by regulating the expression of CgGRP78, CgCNX and CgBcl-2.

Host and Viral Factors in HIV-Mediated Bystander Apoptosis

Human immunodeficiency virus (HIV) infections lead to a progressive loss of CD4 T cells primarily via the process of apoptosis. With a limited number of infected cells and vastly disproportionate apoptosis in HIV infected patients, it is believed that apoptosis of uninfected bystander cells plays a significant role in this process. Disease progression in HIV infected individuals is highly variable suggesting that both host and viral factors may influence HIV mediated apoptosis. Amongst the viral factors, the role of Envelope (Env) glycoprotein in bystander apoptosis is well documented. Recent evidence on the variability in apoptosis induction by primary patient derived Envs underscores the role of Env glycoprotein in HIV disease. Amongst the host factors, the role of C-C Chemokine Receptor type 5 (CCR5), a coreceptor for HIV Env, is also becoming increasingly evident. Polymorphisms in the CCR5 gene and promoter affect CCR5 cell surface expression and correlate with both apoptosis and CD4 loss. Finally, chronic immune activation in HIV infections induces multiple defects in the immune system and has recently been shown to accelerate HIV Env mediated CD4 apoptosis. Consequently, those factors that affect CCR5 expression and/or immune activation in turn indirectly regulate HIV mediated apoptosis making this phenomenon both complex and multifactorial. This review explores the complex role of various host and viral factors in determining HIV mediated bystander apoptosis.

Strategies to limit immune-activation in HIV patients

INTRODUCTION

Antiretroviral treatment of HIV infection reduces, but does not eliminate, viral replication and down modulates immune activation. The persistence of low level HIV replication in the host, nevertheless, drives a smouldering degree of immune activation that is observed throughout the natural history of disease and is the main driving force sustaining morbidity and mortality. Areas covered: Early start of antiretroviral therapy (ART) and intensive management of behavioural risk factors are possible but, at best, marginally successful ways to manage immune activation. We review alternative, possible strategies to reduce immune activation in HIV infection including timing of ART initiation and ART intensification to reduce HIV residual viremia; switch of ART to newer molecules with reduced toxicity; use of anti inflammatory/immunomodulatory agents and, finally, interventions aimed at modifying the composition of the microbiota. Expert commentary: Current therapeutic strategies to limit immune activation are only marginally successful. Because HIV eradication is currently impossible, intensive studies are needed to determine if and how immune activation can be silenced in HIV infection.

HIV-1 Env Glycoprotein Phenotype along with Immune Activation Determines CD4 T Cell Loss in HIV Patients

The mechanism behind the selective depletion of CD4(+) cells in HIV infections remains undetermined. Although HIV selectively infects CD4(+) cells, the relatively few infected cells in vivo cannot account for the extent of CD4(+) T cell depletion, suggesting indirect or bystander mechanisms. The role of virus replication, Env glycoprotein phenotype, and immune activation (IA) in this bystander phenomenon remains controversial. Using samples derived from HIV-infected patients, we demonstrate that, although IA in both CD4(+) and CD8(+) subsets correlates with CD4 decline, apoptosis in CD4(+) and not CD8(+) cells is associated with disease progression. Because HIV-1 Env glycoprotein has been implicated in bystander apoptosis, we cloned full-length Envs from plasma of viremic patients and tested their apoptosis-inducing potential (AIP). Interestingly, AIP of HIV-1 Env glycoproteins were found to correlate inversely with CD4:CD8 ratios, suggesting a role of Env phenotype in disease progression. In vitro mitogenic stimulation of PBMCs resulted in upregulation of IA markers but failed to alter the CD4:CD8 ratio. However, coculture of normal PBMCs with Env-expressing cells resulted in selective CD4 loss that was significantly enhanced by IA. Our study demonstrates that AIP of HIV-1 Env and IA collectively determine CD4 loss in HIV infection.

Prospective immune dynamics during the first 24 weeks of efavirenz based-antiretroviral therapy in HIV-1-infected subjects, according to CD4+ T-cell counts at presentation: the IMMUNEF clinical trial

Background

Longitudinal characterization of immune recovery in the first-phase of antiretroviral therapy (ART) is poorly described. We compared immune kinetics in individuals who were diagnosed early or late with HIV-1 infection, (thus commencing ART with different CD4⁺ T-cell counts), in order to investigate possible mechanisms involved in subsequent poor immune recovery.

Methods

Immunophenotyping, immune activation, proliferation, apoptosis, regulatory T-cells and intracellular cytokine production were compared at baseline and during 24-week follow-up in two groups of HIV-1-infected patients initiating the same ART (tenofovir/emtricitabine/efavirenz) and divided according to baseline CD4⁺ T-cell counts (late: ≤200/μL; early: >200/μL). Wilcoxon-rank sum test and analysis for repeated measures were used to evaluate differences between groups over time.

Results

Twenty-four out of 30 enrolled subjects were evaluable for the analysis, 13 late and 11 early presenters. Significantly lower CD4⁺ naïve and memory T-cells, and higher plasma viral load, as well as augmented percentages of activated (CD4⁺/CD25⁺ cells), apoptotic (CD4⁺/AnnexinV⁺/7AAD⁻, CD4⁺/caspase 8⁺ and CD4⁺/caspase 9⁺), and proliferating (CD8⁺/Ki67⁺ cells) lymphocytes were present at baseline in late presenters; ART resulted in a reduction of apoptotic and proliferating lymphocytes within the follow-up period.

Conclusions

A skewing towards memory/activated/apoptotic phenotype is seen in HIV-1-infected subjects starting ART at low CD4⁺ T-cell counts; ART results in early (24 weeks) trend towards normalization of these parameters. Antiretroviral therapy may play a role in rapidly limiting aberrant immune exhaustion even in late presenters, while requiring more time for re-population of highly depleted naïve T-cells.

Trial Registration

EU Clinical Trial Register EUDRACT number 2008-006188-35 https://www.clinicaltrialsregister.eu/ctr-search/trial/2008-006188-35/IT

The majority of CD4+ T-cell depletion during acute simian-human immunodeficiency virus SHIV89.6P infection occurs in uninfected cells

Untreated human immunodeficiency virus (HIV) infection is characterized by depletion of CD4(+) T cells, ultimately leading to the impairment of host immune defenses and death. HIV-infected CD4(+) T cells die from direct virus-induced apoptosis and CD8 T-cell-mediated elimination, but a broader and more profound depletion occurs in uninfected CD4(+) T cells via multiple indirect effects of infection. We fit mathematical models to data from experiments that tested an HIV eradication strategy in which five macaques with a proportion of CD4(+) T cells resistant to simian-human immunodeficiency virus (SHIV) entry were challenged with SHIV89.6P, a highly pathogenic dual-tropic chimeric SIV-HIV viral strain that results in rapid loss of both SHIV-susceptible and SHIV-resistant CD4(+) T cells. Our results suggest that uninfected (bystander) cell death accounts for the majority of CD4(+) T-lymphocyte loss, with at least 60% and 99% of CD4(+) T cell death occurring in uninfected cells during acute and established infection, respectively. Mechanisms to limit the profound indirect killing effects associated with HIV infection may be associated with immune preservation and improved long-term survival.

IMPORTANCE

HIV infection induces a massive depletion of CD4(+) T cells, leading to profound immunodeficiency, opportunistic infections, and eventually death. While HIV induces apoptosis (programmed cell death) by directly entering and replicating in CD4(+) T cells, uninfected CD4(+) T cells also undergo apoptosis due to ongoing toxic inflammation in the region of infection. In this paper, we use mathematical models in conjunction with data from simian-human immunodeficiency virus SHIV89.6P infection in macaques (a model of HIV infection in humans) to estimate the percentage of cell death that occurs in uninfected cells during the initial period of infection. We reveal that the vast majority of cell death occurs in these cells, which are not infected. The "bystander effects" that lead to enormous reductions in the number of uninfected CD4(+) T cells may be a target for future interventions that aim to limit the extent of damage caused by HIV.

The early phase of human sepsis is characterized by a combination of apoptosis and proliferation of T cells

PURPOSE

T cell activation as well as unresponsiveness has been described in separate studies in sepsis. Our aim was to establish the coexistence of both T cell fate in human sepsis.

PATIENTS AND METHODS

This is a cross-sectional study of 48 patients presenting with severe sepsis or septic shock and 15 healthy controls. Cytofluorometric techniques were used to quantify T cell activation, apoptosis, proliferation, expression of costimulatory molecules, and cytokine secretion.

RESULTS

Patients with sepsis were characterized by a significant increase in the percentage of activated T cell subsets, as measured using CD69 marker, compared with healthy controls (P<.05). T cell proliferation as measured through Ki67 expression was obvious in infected patients for both CD4 and CD8 T cell subsets compared with controls (P ≤.006). T cell subset apoptosis as measured using Hoechst dye was also increased in infected patients compared with controls (P ≤.002). CD4 T cell proliferation was correlated with interleukin 2 secretion (R(2)=0.84, P<.001), whereas up-regulation of CD4 T cell apoptosis was correlated with CTLA-4 expression (R(2)=0.24, P=.001). No such similar relationship was observed for CD8(+) T cells.

CONCLUSIONS

Concomitant T cell proliferation and T cell apoptosis are observed in human sepsis, being related to a different pathway.

Enhanced T-cell apoptosis in human septic shock is associated with alteration of the costimulatory pathway

T-cell apoptosis during septic shock (SS) has been associated with deleterious outcome, but the mechanisms of apoptosis are not well understood. As T-cells are not infected in bacterial infection, our hypothesis was that deleterious interactions between lymphocytes and monocytes could be involved. This is a cross-sectional study of 27 patients presenting with community-acquired SS, 23 infected patients without SS and 18 controls. Cytofluorometric techniques were used to study apoptosis, the costimulatory pathway and cytokine synthesis. Apoptosis was increased in SS compared to infected patients without SS and controls: the median values were 18, 2 and 3%, respectively, for CD4(+) T-cells (P < 0.001), and 12, 5 and 2%, respectively, for CD8(+) T-cells (P < 0.001). Patients with SS exhibited significant CD152 over-expression on T-cells, while CD86 expression was decreased on monocytes (P = 0.004). The synthesis of interleukin-2 was decreased in patients with SS compared to the other groups, while secretions of interferon-gamma and TNF-alpha were not altered. Ten surviving patients with SS showed a trend towards the normalisation of these parameters on day 7. In SS, T-cell apoptosis is related, at least in part, to the alteration of the costimulatory pathway, which, in turn, leads to significant modification of the cytokine network.

Persistent apoptosis in HIV-1-infected individuals receiving potent antiretroviral therapy is associated with poor recovery of CD4 T lymphocytes

CD4 T-cell depletion in HIV-1 infection is partly the result of T-cell apoptosis. Spontaneous apoptosis (SA) and apoptosis markers Fas-associated death-domain-like IL-1 beta converting enzyme (FLICE)-like inhibitory protein (FLIP), Bcl-2, TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), TRAIL receptor 1, and Fas were determined in 55 HIV-1 infected persons treated with highly active antiretroviral therapy (HAART) for 48 months. Despite suppressive HAART, SA remained elevated. Increased SA of peripheral blood mononuclear cells (PBMCs) and CD8 T lymphocytes and increased TRAIL receptor 1 expression strongly predicted a poorer recovery of CD4 T-cell count. HAART did not significantly alter anti-or proapoptotic markers in cultured PBMCs and T lymphocytes. The significant relationship between residual T-lymphocyte apoptosis and CD4 T-cell recovery suggests that persistent apoptosis may impede immune restoration.

Intrahepatic CD4+ T-Cell Apoptosis is Related to METAVIR Score in Patients With Chronic Hepatitis C Virus

Hepatitis C virus (HCV) infection leads to liver injury, which is thought to be immune-mediated. Apoptosis of hepatic T cells could influence histological damage. We quantified peripheral and intrahepatic T-cell apoptosis in 28 patients with chronic hepatitis C by using cytofluorometric techniques. METAVIR score and HCV plasma viral load were determined. Six liver biopsies, obtained from controls without chronic hepatitis during hepatobiliary surgery, served as controls. In patients, liver T-cell apoptosis was upregulated compared to peripheral T cells: 35 versus 7% for CD4+ and 56 versus 13% for CD8+ T cells (P < 0.001). Liver T-cell apoptosis levels from patients were increased compared to controls for both CD4+ (P = 0.041) and CD8+ T cells (P = 0.007). Nine patients exhibiting METAVIR scores A and F < or = 1 showed higher intrahepatic CD4+ T-cell apoptosis compared to the 19 patients with a higher METAVIR score (P = 0.001) and both histological activity and fibrosis were related to apoptosis level. There was also an inverse relationship between the level of intrahepatic CD8+ T-cell apoptosis and serum transaminase activity (P = 0.023). Our study shows immune compartmentalization, suggesting that the study of peripheral blood lymphocytes may not be fully relevant to the pathophysiology of HCV hepatitis, and that the severity of liver injury is inversely correlated with intrahepatic CD4+ T-cell apoptosis.

Apoptosis of naive CD4+ T-cells from HIV-infected patients with poor immune response to HAART is enhanced in vitro by steroid

OBJECTIVE

Because the absence of immune restoration in HIV-infected patients efficiently treated by highly active antiretroviral therapy (HAART) may be due to excessive immune activation, we prospectively studied the effect of hydrocortisone on T-cell apoptosis in a cohort of patients with satisfactory virologic response.

METHODS

Apoptosis of T-cell subsets including naïve CD45RA(+)CD4+ T-cells was determined at baseline and at months 1 and 3 after initiation of HAART. A satisfactory immune response was defined as an increase >100/microL CD4+ T-cells at month 3 compared to baseline.

RESULTS

Twenty out of 63 patients showed undetectable viral load at month 3, among whom eight exhibited a satisfactory immune response. Down-regulation spontaneous CD4+T-cell apoptosis was significant in the group of patients with a satisfactory immune response compared to the other patients. However, hydrocortisone up-regulated apoptosis of naïve CD4+ CD45RA+ T-cells, specifically in group of patients with poor immune response, whatever the time point considered: percentage of apoptotic CD4 T-cells was 16+/-16% without hydrocortisone and 22+/-22% with hydrocortisone at month 1, and respectively, 10+/-9 and 17+/-15% at month 3 (P < 0.05) Hydrocortisone had no impact on CD8+ T-cell apoptosis, whatever the considered group.

CONCLUSION

Our results suggest to not use steroid therapy as adjuvant immunotherapy in patients with less than optimal immunologic response to HAART.

Immune reconstitution in HIV infection and its relationship to cancer

HIV infection results in formidable immune dysfunction, widely affecting the immune system, but typified by T lymphopenia. This dysfunction includes a perturbed immune response to several persistent viruses that have a propensity to cause tumors. Effective control of HIV replication by highly active antiretroviral therapy (HAART) results in regeneration of the damaged immune system, and recent advances have allowed this immune reconstitution to be better defined. This article describes the immunodeficiency caused by HIV and the response of the immune system to HAART, with specific reference to the immune response to cancers associated with HIV infection.