Maxwell Pistilli

Inability of plasmacytoid dendritic cells to directly lyse HIV-infected autologous CD4+ T cells despite induction of tumor necrosis factor-related apoptosis-inducing ligand.

ABSTRACT The function of plasmacytoid dendritic cells (PDC) in chronic human immunodeficiency virus type 1 (HIV-1) infection remains controversial with regard to its potential for sustained alpha interferon (IFN-α) production and induction of PDC-dependent tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-mediated cytotoxicity of HIV-infected cells. We address these areas by a study of chronically HIV-1-infected subjects followed through antiretroviral therapy (ART) interruption and by testing PDC cytolytic function against autologous HIV-infected CD4+ T cells. Rebound in viremia induced by therapy interruption showed a positive association between TRAIL and viral load or T-cell activation, but comparable levels of plasma IFN-α/β were found in viremic ART-treated and control subjects. While PDC from HIV-infected subjects expressed less interferon regulator factor 7 (IRF-7) and produced significantly less IFN-α upon Toll-like receptor 7/9 (TLR7/9) engagement than controls, membrane TRAIL expression in PDC from HIV+ subjects was increased. Moreover, no significant increase in death receptor 5 (DR5) expression was seen in CD4+ T cells from viremic HIV+ subjects compared to controls or following in vitro infection/exposure to infectious and noninfectious virus or exogenous IFN-α, respectively. Although activated PDC killed the DR5-expressing HIV-infected Sup-T1 cell line, PDC did not lyse primary autologous HIV+ CD4+ T cells yet could provide accessory help for NK cells in killing HIV-infected autologous CD4+ T cells. Taken together, our data show a lack of sustained high levels of soluble IFN-α in chronic HIV-1 infection in vivo and document a lack of direct PDC cytolytic activity against autologous infected or uninfected CD4+ T cells.

Delayed loss of control of plasma lipopolysaccharide levels after therapy interruption in chronically HIV-1-infected patients.

Objective:Increased circulating levels of lipopolysaccharide (LPS) have been demonstrated in HIV-1-infected progressors. We investigated the effect of antiretroviral therapy (ART) interruptions on plasma LPS levels. Design and methods:Overall, 77 individuals participated in this study (51 HIV-positive and 26 healthy). Ten out of 51 HIV-positive participants were viremic ART-naive patients and 41 out of 51 were chronically suppressed patients on ART (three or more drugs, CD4 cell count more than 400 cells/μl, HIV-1 RNA less than 500 copies/ml for more than 8 months, less than 50 copies/ml at recruitment) undergoing therapy interruption. The limulus amebocyte assay was used to measure plasma LPS levels; enzyme-linked immunosorbent assay to measure plasma levels of endotoxin-core antibodies (EndoCAb), soluble (s)CD14, LPS-binding protein and IFN-α; immunoblotting to measure plasma gelsolin levels; and same day whole blood flow cytometry to measure levels of T-cell-activation markers (CD8+/CD38+, CD8+/HLA-DR+ and CD3+/CD95+). Results:Increases in viremia and T-cell-activation markers were observed during therapy interruptions. During short-term therapy interruptions of less than 12 weeks, no change in LPS levels was found, whereas negative associations between viral load and LPS levels (Spearmans Rho = −0.612, P = 0.0152), viral load and EndoCAb change (ΔEndoCAb, correlation = −0.502, P = 0.0204), and between ΔLPS and ΔEndoCAb (correlation = −0.851, P = 0.0073) were observed. In contrast, increased LPS (P = 0.0171) and sCD14 (P < 0.0001) levels were observed during long-term therapy interruption of more than 12 weeks compared with levels during ART, together with no association between LPS and viral load or EndoCAb. No association between immune activation and LPS was evident at any time point. Conclusion:Increased plasma LPS levels were observed only after more than 12 weeks of ART interruption, despite presence of LPS-controlling host mechanisms.

Increased microbial translocation in ≤180 days old perinatally human immunodeficiency virus-positive infants as compared with human immunodeficiency virus-exposed uninfected infants of similar age

Background: The effect of early versus deferred antiretroviral treatment (ART) on plasma concentration of lipopolysaccharide (LPS) and host LPS-binding molecules in human immunodeficiency virus (HIV)-infected infants up to 1 year of age was investigated. Methods: We evaluated 54 perinatally HIV-infected and 22 HIV-exposed uninfected infants (controls) at the first and second semester of life. All HIV-infected infants had a baseline CD4 of ≥25%, participated in the Comprehensive International Program of Research on AIDS Children with HIV Early Antiretroviral Therapy trial in South Africa, and were randomized in the following groups: group 1 (n = 20), ART deferred until CD4 <25% or severe HIV disease; and group 2 (n = 34), ART initiation within 6 to 12 weeks of age. LPS, endotoxin-core antibodies, soluble CD14 (sCD14), and LPS-binding protein (LBP) were measured in cryopreserved plasma. T-cell activation was measured in fresh whole blood. Results: At the first semester, LPS concentration was higher in HIV-infected infants than in controls; sCD14, LBP, and T-cell activation were higher in group 1 than in group 2 and controls. Although LPS was not correlated with study variables, viral load was positively associated with sCD14, LBP, or endotoxin-core antibodies. At the second semester, LPS was not detectable and elevated host LPS-control molecules values were sustained in all groups and in conjunction with ART in all HIV-infected infants. Conclusions: Although plasma concentration of LPS was higher in perinatally HIV-infected infants 0 to 6 months of age than in controls independent of ART initiation strategy, concentration of LPS-control molecules was higher in infants with deferred ART, suggesting the presence of increased microbial translocation in HIV-infected infants with sustained early viral replication.

Increased soluble vascular cell adhesion molecule-1 plasma levels and soluble intercellular adhesion molecule-1 during antiretroviral therapy interruption and retention of elevated soluble vascular cellular adhesion molecule-1 levels following resumption of antiretroviral therapy

Objective:We investigated the effect of short viremic episodes on soluble markers associated with endothelial stress and cardiovascular disease risk in chronically HIV-1-infected patients followed during continuous antiretroviral therapy, antiretroviral therapy interruption and antiretroviral therapy resumption. Design and methods:We assessed changes in plasma levels of von Willebrand factor, soluble vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 by enzyme-linked immunosorbent assay, as well as T-cell activation (CD8+/CD38+, CD8+/HLA-DR+ and CD3+/CD95+) by flow cytometry, in 36 chronically HIV-1-infected patients participating in a randomized study. Patients were divided into the following three groups: a, on continuous antiretroviral therapy; b, on a 6-week antiretroviral therapy interruption; or c, on antiretroviral therapy interruption extended to the achievement of viral set point. Results:Although all measurements remained stable over a 40-week follow-up on antiretroviral therapy, plasma levels of soluble vascular cell adhesion molecule-1 (P < 0.0001) and soluble intercellular adhesion molecule-1 (P = 0.003) increased during treatment interruption in correlation with viral rebound and T-cell activation. No significant changes in von Willebrand factor were observed in any of the groups. After resuming antiretroviral therapy, soluble vascular cell adhesion molecule-1 levels remained elevated even after achievement of viral suppression to less than 50 copies/ml. Conclusion:The prompt rise in plasma soluble vascular cell adhesion molecule-1 and soluble intercellular adhesion molecule-1 upon viral rebound suggests an acute increase in endothelial stress upon treatment interruption, which may persists after viral resuppression of virus. Thus, viral replication during short-term treatment interruption may increase the overall cardiovascular risk during and beyond treatment interruption.

Presence of Human Immunodeficiency Virus–1–Specific CD4 and CD8 Cellular Immune Responses in Children with Full or Partial Virus Suppression

The present study assessed antiviral T cell immune responses in 48 human immunodeficiency virus (HIV)-infected children with a stable or decreasing CD4(+) T cell counts and different levels of viral control, in the presence or absence of antiretroviral therapy. Children with full (<40 copies/mL) or partial (<50,000 copies/mL) virus suppression and with a history of stable CD4(+) T cell counts had significantly increased levels of anti-HIV CD4(+) T cell lymphoproliferative responses, lower levels of CD38(+), and higher CD8(+)/CD28(+) T cell percentage, compared with those in treated children with a lack of virus suppression (>50,000 copies/mL). Levels of anti-HIV CD8(+) T cell activity, although higher in treated children with a lack of virus suppression, were not significantly different between the groups. Although levels of anti-HIV CD4(+) and CD8(+) T cell responses were not associated, these levels of responses were associated with the percentage of specific T cell subsets. Overall, a history of stable CD4(+) T cell counts, as a result of therapy that imparted full or partial virus suppression, was associated with increased levels of anti-HIV CD4(+) T helper responses and decreased T cell activation.

Increased CD34+/KDR+ cells are not associated with carotid artery intima-media thickness progression in chronic HIV-positive subjects.

BACKGROUND Endothelial progenitor cells (EPCs) are involved in the endothelium repair. Low circulating EPC levels are predictive of cardiovascular events in HIV-negative subjects. The impact of HIV infection on EPCs, and the role of EPCs in HIV-associated cardiovascular disease, is not known. We hypothesized that circulating EPCs would be inversely associated with carotid artery intima-media thickness (c-IMT) changes in HIV-infected subjects. METHODS EPCs (CD34(+)/KDR(+), CD133(+)/KDR(+) and CD34(+)/CD133(+)/KDR(+)) were defined retrospectively by flow cytometry in cryopreserved peripheral blood mononuclear cells collected longitudinally from 66 chronic HIV-infected subjects and cross-sectionally from 50 at-risk HIV-negative subjects. The HIV-infected subjects participated in the Study of the Consequences of the Protease Inhibitor Era (SCOPE) cohort, were receiving antiretroviral therapy (59/66) and had two sequential measurements of c-IMT 1 year apart. Two distinct groups of HIV-infected subjects were identified a priori: rapid c-IMT progressors (subjects with rapid c-IMT progression, n=13, Δc-IMT>0.2 mm) and slow c-IMT progressors (subjects with slow or no c-IMT progression, n=53, Δc-IMT<0.2 mm). RESULTS Although cryopreservation reduced sensitivity of detection, EPC frequency in HIV-infected subjects was still significantly higher compared to at-risk HIV-negative subjects (CD34(+)/KDR(+); P=0.01) and correlated positively with CD4(+) T-cell count (CD34(+)/KDR(+), r=0.27; P=0.03). No association was found between the change of EPC frequencies over time (ΔEPC) and Δc-IMT or between EPC frequencies and c-IMT or Δc-IMT. CONCLUSIONS The lack of an association between EPCs and c-IMT in our cohort does not support HIV-associated reductions in EPC frequency as a cause of accelerated atherosclerosis.

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

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

Retention of Functional DC-NK Cross-Talk Following up to 18 Weeks Therapy Interruptions in Chronically Suppressed HIV Type 1+ Subjects

Editor: Chronic viral replication during HIV-I infection results, among other effects, in the depletion of dendritic cell (DC) subsets,1, 2 and decrease of natural killer cells (NK) frequency and function.3 An inverse correlation between chronic viral replication and numbers of mature NK or DC cells1,3 together with a lack of DC-associated functions has been reported.1,4 However, introduction of suppressive antiretroviral therapy (ART) is associated with a variable degree of recovery of frequency and function among innate effector cells.1 Following ART initiation, delayed kinetics of recovery of the innate compartment are observed in contrast to acute changes on T cell activation, suggesting a differential relationship between ART-mediated control of viremia and recovery of innate effector function.5 Although the effect of structured therapy interruptions (TI) in ART-suppressed subjects has been described for adaptive immune responses6 indicating an acute onset of T cell activation, no data are available regarding the effects of acute viral replication on innate immune system parameters following the absence of therapy. We therefore analyzed the effects of temporal viral replication on levels of innate cell immune reconstitution in ART-treated HIV-infected subjects who were participating on an observational study of the immune consequences of repeated therapy interruptions.

Short Communication: HIV Type 1 Viremia on ART Is Positively Associated with Polyclonal T Cell Proliferation in Subjects with T Cell IFN-γ Secretion Levels Comparable to Those of Uninfected Subjects

We investigated the association between plasma HIV-1 RNA, immune activation, and polyclonal T cell function in viremic subjects whether on or off antiretroviral therapy (ART). The surface expression of activation/functional molecules on T cells and monocytes as well as cytokine secretion and T cell proliferation were assessed in 23 HIV-1(-) and 79 HIV-1(+)-infected subjects with different levels of viral suppression and CD4(+) T cell count >250 cells/mm(3) for >6 months. Viral replication was associated with increased T cell and monocyte activation irrespective of ART. In subjects with a detectable viral load on ART, we found a positive association with anti-CD3/CD28-induced T cell proliferation compared to patients with undetectable viral load (<400 copies/ml). No difference among groups was observed for anti-CD3/CD28-mediated IFN-gamma responses. The presence of an unexpected positive association between polyclonal T cell proliferation and viral load in subjects with levels of T cell IFN-gamma responses comparable to those of uninfected subjects is of potential relevance to an increase in T cell activation response before the loss of polyclonal cytokine secretion and proliferation observed with disease progression. This finding suggests that T cell hyperresponsiveness may play a role in the pathogenesis of immune comorbidities on ART.