Andreas Ronit

Persisting inflammation and chronic immune activation but intact cognitive function in HIV-infected patients after long-term treatment with combination antiretroviral therapy.

Objectives:Impaired cognitive function in HIV-infected patients has been suggested. Treatment with combination antiretroviral therapy (cART) restores CD4+ cell counts and suppresses viral replication, but immune activation and inflammation may persist. The aim of the study was to examine if cognitive function in HIV-infected patients was related to immune activation and inflammation. Methods:Sixty-one HIV-infected patients and 31 healthy controls were included. All patients were on treatment with cART, had suppressed viral replication, and had a mean CD4+ cell count of 522 cells/&mgr;L. Cognitive function was assessed using a test battery of neurocognitive tests. Plasma concentrations of interleukin-6 (IL-6), tumor necrosis factor-&agr; (TNF-&agr;), and &bgr;-2-microglobulin were measured. Immune activation (CD8+HLR-DR+CD38+ cells) was determined using flow cytometry. Multiple linear regression analysis was performed to identify relationship between cognitive scores and markers of inflammation and immune activation. Results:HIV-infected patients had intact cognitive function compared with healthy controls. Higher levels of TNF-&agr;, &bgr;-2-microglobulin, and chronic activated CD8+ cells were found in HIV-infected patients (P = 0.0002, P < 0.0001, and P = 0.021, respectively). Weak negative correlations were found between chronic activated CD8+ cells (&bgr;-coefficient = −0.277, P = 0.044), IL-6 (&bgr;-coefficient = −0.280, P = 0.014), and memory and learning. Conclusions:HIV-infected patients on cART with undetectable viral load had an increased level of inflammation and immune activation. However, intact cognitive function was found, and only weak correlations were found between cognitive function and markers of inflammation and immune activation, indicating that peripheral inflammation and immune activation are not major drivers of cognitive decay in HIV-infected patients.

CD4+ and CD8+ Regulatory T Cells (Tregs) are Elevated and Display an Active Phenotype in Patients with Chronic HCV Mono‐Infection and HIV/HCV Co‐Infection

The aim of this study was to examine regulatory T cells (Tregs) in peripheral blood and liver tissue in patients with chronic hepatitis C virus (HCV) mono‐infection and in patients with HIV/HCV co‐infection. In a cross‐sectional study were included 51 patients with chronic HCV infection, 24 patients with HIV/HCV co‐infection and 24 healthy individuals. CD4+ and CD8+ Tregs were determined using flow cytometry. Fibrosis was examined by transient elastography. Inflammation, fibrosis and Tregs were determined in liver biopsies from 12 patients. Increased frequency of CD4+ and CD8+ Tregs was found in HIV/HCV co‐infected patients [median: 6.4% (IQR: 5.7–6.9) and 1.0% (0.7–1.2), respectively] compared to HCV mono‐infected patients [5.6% (4.2–6.3), P = 0.01 and 0.5% (0.3–0.7), P < 0.001, respectively]. Furthermore, HCV mono‐infected patients had increased frequencies of Tregs compared with healthy controls (P < 0.05). However, no associations between the frequency of Tregs and fibrosis were found. Furthermore, characterization of CD4+ Tregs using CD45RA demonstrated a higher frequency of activated Tregs in both HCV mono‐infected and HIV/HCV co‐infected patients compared with healthy controls. Finally, number of intrahepatic Tregs was associated with both peripheral CD8+ Tregs and intrahepatic inflammation. In conclusion, HCV mono‐infected patients and particularly HIV/HCV co‐infected patients have increased the frequency of CD4+ and CD8+ Tregs compared with healthy controls. Furthermore, CD4+ Tregs in infected patients displayed an active phenotype. Tregs were not associated with fibrosis, but a positive correlation between intrahepatic Tregs and inflammation was found. Taken together, these results suggest a role for Tregs in the pathogenesis of chronic HCV infection.

Disassociation of static and dynamic cerebral autoregulatory performance in healthy volunteers after lipopolysaccharide infusion and in patients with sepsis.

Sepsis is frequently complicated by brain dysfunction, which may be associated with disturbances in cerebral autoregulation, rendering the brain susceptible to hypoperfusion and hyperperfusion. The purpose of the present study was to assess static and dynamic cerebral autoregulation 1) in a human experimental model of the systemic inflammatory response during early sepsis and 2) in patients with advanced sepsis. Cerebral autoregulation was tested using transcranial Doppler ultrasound in healthy volunteers (n = 9) before and after LPS infusion and in patients with sepsis (n = 16). Static autoregulation was tested by norepinephrine infusion and dynamic autoregulation by transfer function analysis (TFA) of spontaneous oscillations between mean arterial blood pressure and middle cerebral artery blood flow velocity in the low frequency range (0.07-0.20 Hz). Static autoregulatory performance after LPS infusion and in patients with sepsis was similar to values in healthy volunteers at baseline. In contrast, TFA showed decreased gain and an increased phase difference between blood pressure and middle cerebral artery blood flow velocity after LPS (both P < 0.01 vs. baseline); patients exhibited similar gain but lower phase difference values (P < 0.01 vs. baseline and LPS), indicating a slower dynamic autoregulatory response. Our findings imply that static and dynamic cerebral autoregulatory performance may disassociate in sepsis; thus static autoregulation was maintained both after LPS and in patients with sepsis, whereas dynamic autoregulation was enhanced after LPS and impaired with a prolonged response time in patients. Hence, acute surges in blood pressure may adversely affect cerebral perfusion in patients with sepsis.

Immunoregulatory T cells may be involved in preserving CD4 T cell counts in HIV-infected long-term nonprogressors and controllers.

Background:HIV-infected controllers control viral replication and maintain normal CD4 T cell counts. Long-term nonprogressors (LTNPs) also maintain normal CD4 T cell counts but have ongoing viral replication. We hypothesized that immunoregulatory mechanisms are involved in preserved CD4 T cell counts in controllers and in LTNPs. Methods:Twenty HIV-infected viremic controllers, 5 elite controllers (ECs), and 14 LTNPs were included in this cross-sectional study. For comparison, 25 progressors and 34 healthy controls were included. Regulatory T cells (Tregs), Treg subpopulations, CD161+Th17 cells, and CD3+CD8+CD161highTc17 cells in peripheral blood were measured using flow cytometry. Tregs in lymphoid tissue were determined in tonsil biopsies and evaluated using immunolabeling. The production of transforming growth factor beta (TGF-&bgr;), interleukin (IL)-10, and IL-17 upon stimulation with phytohemagglutinin in peripheral blood was determined by Luminex. Results:All groups of HIV-infected patients displayed similar percentages of Tregs in both peripheral blood and lymphoid tissue. However, a larger percentage of Tregs in ECs and LTNPs were activated compared with that in controls, progressors, and viremic controllers. Further, ECs as the only group of HIV-infected patients, displayed elevated percentages of CD161+Th17 cells, preserved CD3+CD8+CD161highTc17 cells, and preserved IL-10 production. Conclusions:Overall, Treg percentage was similar in both blood and lymphoid tissue in all groups of patients and controls. However, both ECs and LTNPs displayed a large proportion of activated Tregs suggesting immunoregulatory mechanisms to be involved in preserving CD4 T cell counts in HIV-infected nonprogressors.

Impaired thymic output in patients with chronic hepatitis C virus infection.

Altered T cell homeostasis in chronic hepatitis C virus (HCV) infection has been demonstrated. However, it is unknown whether fibrosis is associated with more perturbed T cell homeostasis in chronic HCV infection. The aim of this study was to examine and compare T cell subsets including recent thymic emigrants (RTE), naive, memory, senescent, apoptotic and IL‐7 receptor α (CD127) expressing CD4+ and CD8+ T cells as well as telomere length and interferon‐γ production in HCV‐infected patients with (n = 25) and without (n = 26) fibrosis as well as in healthy controls (n = 24). Decreased proportions of CD4+ and CD8+ RTE were found in HCV‐infected patients, especially in HCV‐infected patients with fibrosis (14.3% (9.7–23.0) and 28.8% (16.1–40.5), respectively) compared with healthy controls (24.2% (16.3–32.1), P = 0.004 and 39.1% (31.6–55.0), P = 0.010, respectively). Furthermore, HCV‐infected patients with fibrosis presented with a higher proportion of CD4+ T cells expressing CD127 compared with HCV‐infected patients without fibrosis [88.4% (84.5–91.0) versus 83.8% (79.9–86.8), P = 0.016]. Thus, impaired thymic output in HCV infection was found, and high proportion of CD127+ T cells may illustrate a compensatory mechanism to preserve T cell counts.

Different immunological phenotypes associated with preserved CD4+ T cell counts in HIV-infected controllers and viremic long term non-progressors.

Background HIV-infected controllers control viral replication and maintain normal CD4+ T cell counts. Long Term Non-Progressors (LTNP) also maintain normal CD4+ T cell counts, but have on-going viral replication. We hypothesized that different immunological mechanisms are responsible for preserved CD4+ T cell counts in controllers and LTNP. Methods 25 HIV-infected controllers and 14 LTNP were included in this cross-sectional study. For comparison, 25 progressors and 34 healthy controls were included. Production and destruction of T cells were addressed by determination of T cell receptor excision circles (TREC), recent thymic emigrants, naïve cells, immune activation, senescence and apoptosis. Furthermore, telomere length was determined, and the amount of lymphoid tissue in tonsil biopsies was quantified. Results Controllers presented with partly preserved thymic output, preserved expression of the IL-7 receptor and IL-7 receptor density, and lower levels of destruction of cells than progressors resembling HIV-negative healthy controls. In contrast, LTNP appeared much like progressors, and different from controllers in immune activation, senescence, and apoptosis. Interestingly, CD8+ RTE, TREC and telomere length were partly preserved. Finally, both controllers and LTNP displayed decreased amounts of lymphoid tissue compared to healthy controls. Conclusions Controllers presented with an immunological profile different from LTNP. While controllers resembled healthy controls, LTNP were similar to progressors, suggesting different immunological mechanisms to be responsible for preserved CD4+ T cell counts in LTNP and controllers. However, both controllers and LTNP presented with reduced amounts of lymphoid tissue despite preserved CD4+ T cell counts, indicating HIV to cause damage even in non-progressors.

Regulatory T cells in HIV-infected immunological nonresponders are increased in blood but depleted in lymphoid tissue and predict immunological reconstitution.

Background:HIV-infected immunological nonresponders fail to immune reconstitute despite optimal treatment. We hypothesized that regulatory T cells (Tregs) are involved in immunological reconstitution. Tregs and Treg subpopulations were measured in blood and Foxp3+ cells in lymphoid tissue, and the impact of Tregs on immunological reconstitution was determined. Methods:HIV-infected individuals on combination antiretroviral therapy for a minimum of 2 years were included. The study population included 14 immunological nonresponders (INR; CD4 T-cell count <200 cells/&mgr;L), 33 intermediate responders (CD4 T-cell count 200–500 cells/&mgr;L), 30 responders (CD4 T-cell count >500 cells/&mgr;L), and 34 healthy controls. Tregs, Treg subpopulations, and intracellular staining for interleukin 10 in peripheral blood were measured using flow cytometry. Foxp3+ cells in lymphoid tissue were evaluated using immunolabeling. The CD4 T-cell count was determined at inclusion and after 1 year of follow-up. Results:INR displayed high percentage of Tregs and activated Tregs in peripheral blood accompanied by a high percentage of Tregs expressing interleukin 10, whereas numbers of Foxp3+ cells in lymphoid tissue were low. In contrast, responders resembled healthy controls. Finally, in INR, high level of Tregs in blood and Foxp3+ cells in lymphoid tissue were associated with higher level of immunological reconstitution after 1 year of follow-up. Conclusions:In conclusion, altered distribution of Tregs was found in INR. Interestingly, high level of Tregs predicted higher level of immunological reconstitution suggesting a role for Tregs in immunological reconstitution.

Dysregulation of toll‐like receptor (TLR) 2 expression on monocytes and upregulation of the frequency of T cells expressing TLR2 in patients with chronic hepatitis C virus infection

Toll‐like receptors (TLRs) initiate inflammatory responses that may play a role in disease progression in patients infected with hepatitis C virus (HCV). TLR2 and TLR4 surface expression were assessed on CD14+ monocytes, CD4+ and CD8+ T cells in treatment naïve patients with chronic HCV infection with fibrosis, without fibrosis, co‐infected with human immunodeficiency virus (HIV), and in healthy controls. Increased expression of TLR2 was found on monocytes in HCV‐infected patients with fibrosis (p < 0.01), co‐infected with HIV (p = 0.03), and possibly in patients without fibrosis (p = 0.07) when compared to controls. TLR2 positive CD4+ and CD8+ T cells were upregulated in patients with fibrosis only (p < 0.01). However, expression of TLR2 was not associated with T cell activation. TLR4 expression was similar in patients and healthy controls. In conclusion, TLR2 expression on monocytes and the frequency of T cells expressing TLR2 may contribute to disease progression in chronic HCV infection.

Inflammation-Induced Changes in Circulating T-Cell Subsets and Cytokine Production During Human Endotoxemia

Observational clinical studies suggest the initial phase of sepsis may involve impaired cellular immunity. In the present study, we investigated temporal changes in T-cell subsets and T-cell cytokine production during human endotoxemia. Endotoxin (Escherichia coli lipopolysaccharide 4 ng/kg) was administered intravenously in 15 healthy volunteers. Peripheral blood and bronchoalveolar lavage fluid (BALF) were collected at baseline and after 2, 4, 6, 8, and 24 hours for flow cytometry. CD4+CD25+CD127lowFoxp3+ regulatory T cells (Tregs), CD4+CD161+ cells, and activated Human leukocyte antigen, HLA-DR+CD38+ T cells were determined. Ex vivo whole-blood cytokine production and Toll-like receptor (TLR)-4 expression on Tregs were measured. Absolute number of CD3+CD4+ (P = .026), CD3+CD8+ (P = .046), Tregs (P = .023), and CD4+CD161+ cells (P = .042) decreased after endotoxin administration. The frequency of anti-inflammatory Tregs increased (P = .033), whereas the frequency of proinflammatory CD4+CD161+ cells decreased (P = .034). Endotoxemia was associated with impaired whole-blood production of tumor necrosis factor-α, interleukin-10, IL-6, IL-17, IL-2, and interferon-γ in response to phytohaemagglutinin but did not affect TLR4 expression on Tregs. No changes in the absolute count or frequency of BALF T cells were observed. Systemic inflammation is associated with lymphopenia, a relative increase in the frequency of anti-inflammatory Tregs, and a functional impairment of T-cell cytokine production.

T cell subsets in human airways prior to and following endobronchial administration of endotoxin

Bronchial instillation of lipopolysaccharide (LPS) provides a reversible model of lung inflammation that may resemble early stages of acute respiratory distress syndrome (ARDS). We investigated the distributions of T‐cell subsets in the human airways and sought to determine whether pro‐ and anti‐inflammatory T cells are involved in the local immune response to lung inflammation.