An open-label, multiple ascending dose study of the anti-CTLA-4 antibody ipilimumab in viremic HIV patients.

Expression of cytotoxic T-lymphocyte antigen 4 (CTLA-4), a negative regulator of T-cell function, is increased in chronic HIV-1 infection. It was hypothesized that CTLA-4 blockade may enhance immune response to HIV-1 and result in better control of viremia. This open-label, multiple ascending dose study (NCT03407105)-the first to examine ipilimumab in participants with HIV-1 infection-assessed the safety, tolerability, and pharmacokinetics of ipilimumab, as well as whether ipilimumab enhanced immune response to HIV-1 and improved control of viremia.

Allospecific CD4(+) T cells retain effector function and are actively regulated by Treg cells in the context of transplantation tolerance.

Although donor-specific transfusion (DST) plus CD154 blockade represents a robust protocol for inducing transplantation tolerance, the underlying mechanisms are incompletely understood. In a murine T-cell adoptive transfer model, we have visualized alloantigen-specific, TCR-transgenic for H2-A(b) /H2-K(d) 54-68 epitope (TCR75) CD4(+) T cells with indirect allospecificity during the course of tolerance induction. Three main observations were made.

Enhanced auto-antibody production and Mott cell formation in FcμR-deficient autoimmune mice.

The IgM-Fc receptor (FcμR) is involved in IgM homeostasis as evidenced by increased pre-immune serum IgM and natural auto-antibodies of both IgM and IgG isotypes in Fcmr-deficient C57BL/6 (B6) mice. To determine the impact of Fcmr-ablation on autoimmunity, we introduced the Fcmr null mutation onto the Fas-deficient autoimmune-prone B6.MRL Fas (lpr/lpr) mouse background (B6/lpr).

Antibody-mediated rejection of single class I MHC-disparate cardiac allografts.

Murine CCR5(-/-) recipients produce high titers of antibody to complete MHC-mismatched heart and renal allografts. To study mechanisms of class I MHC antibody-mediated allograft injury, we tested the rejection of heart allografts transgenically expressing a single class I MHC disparity in wild-type C57BL/6 (H-2(b)) and B6.CCR5(-/-) recipients.

A simple technique for augmentation of axonal ingrowth into chondroitinase-treated acellular nerve grafts using nerve growth factor.

Background And Purpose: Improvement in axonal regeneration may lead to the development of longer nerve grafts and improved outcomes for patients with peripheral nerve injury. Although the use of acellular nerve grafts has been well documented (Groves et al, Exp Neurol. 2005;195:278-292; Krekoski et al, J Neurosci.

The potency of allospecific Tregs cells appears to correlate with T cell receptor functional avidity.

CD4(+) CD25(+) regulatory T cells (T(reg) cells) are an attractive adoptive cell therapy in mediating transplantation tolerance. T-cell receptor (TcR) activation is critical for T(reg) function, suggesting that the TcR avidity of T(reg) cells used in therapy may affect the therapeutic outcome. To address this, we compared the regulatory capacity of T(reg) lines expressing TcRs derived from two TcR transgenic mice shown to have the same specificity but different functional avidities.

Comparison of immunologic assays for detecting immune responses in HIV immunotherapeutic studies: AIDS Clinical Trials Group Trial A5181.

This study was designed to evaluate which of several T-cell-specific, immune response assays are the most relevant in measuring the key characteristics of an effective immune response to HIV-1. Using 5 HIV-1 antigens as stimulants, we assessed lymphocyte proliferation, supernatant gamma interferon (IFN-gamma) cytokine production (CP), single-cell IFN-gamma production by enzyme-linked immunospot (ELISPOT) assay, with and without Epstein-Barr virus-transformed B-lymphoblastoid cell lines (B-LCLs), and intracellular cytokine production (ICC) for IFN-gamma and interleukin 2 (IL-2) by flow cytometry. We used these to compare specimens from HIV-1-infected subjects who were virally suppressed with a stable antiretroviral therapy (ART) regimen (group A) with specimens from subjects not on ART but with HIV-1 viremia of <3,000 copies/ml (group B).

Measurement of antiretroviral drugs in the lungs of HIV-infected patients.

AIMS: Prior studies have shown that HAART is associated with decreased HIV viral load in the lungs. The correlation between antiretroviral exposure in bronchoalveolar lavage (BAL) fluid and virologic response was evaluated in patients starting HAART and enrolled in The AIDS Clinical Trial Group Protocol 723. MATERIALS #ENTITYSTARTX00026; METHODS: A total of 24 subjects underwent blood and BAL sampling prior to starting HAART, and after 4 and 24 weeks of HAART.

Targeting MHC class I monomers to dendritic cells inhibits the indirect pathway of allorecognition and the production of IgG alloantibodies leading to long-term allograft survival.

T cell depletion strategies are an efficient therapy for the treatment of acute rejections and are an essential part of tolerance induction protocols in various animal models; however, they are usually nonselective and cause wholesale T cell depletion leaving the individual in a severely immunocompromised state. So far it has been difficult to selectively delete alloreactive T cells because the majority of protocols either delete all T cells, subsets of T cells, or subpopulations of T cells expressing certain activation markers, ignoring the Ag specificity of the TCR. We have developed a model in which we were able to selectively deplete alloreactive T cells with an indirect specificity by targeting intact MHC molecules to quiescent dendritic cells using 33D1 as the targeting Ab.

A randomized therapeutic vaccine trial of canarypox-HIV-pulsed dendritic cells vs. canarypox-HIV alone in HIV-1-infected patients on antiretroviral therapy.

Targeting canarypox (CP)-HIV vaccine to dendritic cells (DCs) elicits anti-HIV-1 immune responses in vitro. We conducted a phase I/II clinical trial to evaluate whether adding DC to a CP-HIV vaccine improved virologic control during analytic treatment interruption (ATI) in HIV-1-infected subjects. Twenty-nine subjects on suppressive antiretroviral therapy were randomized to vaccination with autologous DCs infected with CP-HIV+keyhole limpet hemocyanin (KLH) (arm A, n=14) or CP-HIV+KLH alone (arm B, n=15).

Preferential priming of alloreactive T cells with indirect reactivity.

The relative contributions of the direct and indirect pathways in alloimmune responses have not been fully elucidated. We report a novel murine TCR transgenic system that can simultaneously track the CD4-direct (CD4-d), CD4-indirect (CD4-i) and CD8-direct (CD8-d) pathways after transplantation. Using this system, we have observed a profoundly greater proliferation of CD4-i T cells relative to CD4-d and CD8-d T cells after transplantation.

Conferring indirect allospecificity on CD4+CD25+ Tregs by TCR gene transfer favors transplantation tolerance in mice.

T cell responses to MHC-mismatched transplants can be mediated via direct recognition of allogeneic MHC molecules on the cells of the transplant or via recognition of allogeneic peptides presented on the surface of recipient APCs in recipient MHC molecules - a process known as indirect recognition. As CD4(+)CD25(+) Tregs play an important role in regulating alloresponses, we investigated whether mouse Tregs specific for allogeneic MHC molecules could be generated in vitro and could promote transplantation tolerance in immunocompetent recipient mice. Tregs able to directly recognize allogeneic MHC class II molecules (dTregs) were obtained by stimulating CD4(+)CD25(+) cells from C57BL/6 mice (H-2(b)) with allogeneic DCs from BALB/c mice (H-2(d)).

CD8+ suppressor T cells resurrected.

This review focuses on the role of antigen-specific T cells that mediate active inhibition of immune responses over the past 35 years since their initial description. The field has experienced several changes in the accepted paradigm of such suppressor/regulatory T cells, from initial indications that such cells were CD8(+), to the view that such cells did not exist, to the identification of the transcription factor Foxp3 as a key orchestrator of inhibitory function. Although most Foxp3(+) cells in a resting animal are CD4(+)CD25(+) cells, Foxp3 expression and inhibitory function can be induced by antigens in the periphery by selective cytokine conditions, particularly TGF-beta.

Treatment response in acute/early infection versus advanced AIDS: equivalent first and second phases of HIV RNA decline.

Objective: Compare the initial phases of virologic decay when acute/early and advanced HIV-infected adults are administered the same treatment regimen.

Design: Mathematical modeling of a previously completed prospective treatment pilot study involving treatment-naive patients with early and advanced immunosuppression.

Methods: We analyzed data from a treatment protocol in which 18 individuals with acute or recent HIV-1 seroconversion and six patients with advanced AIDS were administered the same four-drug antiretroviral regimen.

Effect of highly active antiretroviral therapy on viral burden in the lungs of HIV-infected subjects.

Background: Human immunodeficiency virus (HIV) is readily detectable in the lungs of infected subjects and leads to an accumulation of CD8(+) lymphocytes in the alveolar space. Although highly active antiretroviral therapy (HAART) is effective in reducing viremia, less is known about its effect on tissue compartments. The AIDS Clinical Trials Group Protocol 723 Team evaluated the effect of HAART on lung viral load and cellular constituents.

Antigen, in the presence of TGF-beta, induces up-regulation of FoxP3gfp+ in CD4+ TCR transgenic T cells that mediate linked suppression of CD8+ T cell responses.

CD4(+)CD25(+) regulatory T cells (Tregs) inhibit immune responses to a variety of Ags, but their specificity and mechanism of suppression are controversial. This controversy is largely because many studies focused on natural Tregs with undefined specificities and suppression has frequently been measured on polyclonal T cell responses. To address the issue of specificity further, we have bred K(d)-specific, CD4(+) TCR (TCR75) transgenic mice to Foxp3(gfp) knockin reporter mice to permit sorting of Tregs with a known specificity.

The virologic, immunologic, and clinical effects of interleukin 2 with potent antiretroviral therapy in patients with moderately advanced human immunodeficiency virus infection: a randomized controlled clinical trial--AIDS Clinical Trials Group 328.

Background: Interleukin 2 (IL-2) administration increases CD4 counts in persons with higher counts. This study investigated persons with moderately advanced human immunodeficiency virus infection receiving highly active antiretroviral therapy (HAART).

Methods: Two hundred four patients with CD4 T-cell counts from 50/microL to 350/microL who were treatment naive or had been treated only with reverse transcriptase inhibitors began a specified protease inhibitor HAART regimen.

A randomized, partially blinded phase 2 trial of antiretroviral therapy, HIV-specific immunizations, and interleukin-2 cycles to promote efficient control of viral replication (ACTG A5024).

Strategies to limit life-long dependence on antiretroviral therapy (ART) are needed. We randomized 81 human immunodeficiency virus (HIV)-infected subjects to 4 interventional arms involving continued ART plus ALVAC vCP1452 (or placebo) with or without interleukin (IL)-2 infusions. Viral load rebound 12 weeks after ART interruption was then analyzed to assess immune control.

TCR transgenic CD8+ T cells activated in the presence of TGFbeta express FoxP3 and mediate linked suppression of primary immune responses and cardiac allograft rejection.

Although CD4+CD25+FoxP3+ regulatory T cells play a role in allograft tolerance, the role of CD8+ cells with immunosuppressive function is less clear. To address this issue, spleen cells from Rag-1-deficient TCR transgenic (Tg) mice expressing a receptor for ovalbumin (OVA) in the context of MHC class I (OT1) were activated with OVA expressing antigen-presenting cell (APC) in the presence or absence of exogenous transforming growth factor beta (TGFbeta). TGFbeta inhibited the expression of IFN-gamma, granzyme B and the lytic activity of the OT1 T cells while inducing FoxP3 expression in 5-15% of the cells.

Enhanced responsiveness to antigen contributes more to immunological memory in CD4 T cells than increases in the number of cells.

Although immunological memory is characterized by both an increase in the frequency of antigen-specific T cells and a qualitative change in the pattern of their subsequent response, it is not clear which of these components is more significant in the overall enhanced response to secondary stimulation. To address this question for the CD4+ T-cell response, T-cell receptor (TCR) Tg T cells were adoptively transferred to normal syngeneic mice that were immunized with the relevant peptide. After the initial expansion of TCR Tg T cells, the size of the subsequent memory population of T cells was approximately the same as the size of the starting population, independent of the number of TCR Tg cells initially transferred.

Viral and cellular dynamics in HIV disease.

The control mechanisms that maintain a steady state viral load during chronic HIV-1 infection are critical to understanding the pathophysiology of HIV disease. The conceptual features of the two alternative models of viral control, referred to in this article as target cell limitation and immune control, are compared to the data regarding the viral and cellular dynamics of HIV-1 infection and the pattern of changes induced by effective antiretroviral drug therapy. The available data support the model that an antigen-driven immune response is the primary mechanism that limits viral growth in vivo.

Intratumoral administration of a recombinant canarypox virus expressing interleukin 12 in patients with metastatic melanoma.

The aim of this study was to evaluate the tolerability and activity of intratumoral administered human interleukin 12 encoded by a vector derived from the canarypox virus (ALVAC-IL-12). Nine patients with surgically incurable metastatic melanoma who had subcutaneous nodules available for injection were enrolled. ALVAC-IL-12 was administered by intratumoral injection on days 1, 4, 8, and 11.

Activation and migration of allo-peptide specific TCR transgenic T cells in cardiac allograft rejection.

T cells from TCR transgenic mice, expressing receptors specific for an allogeneic MHC class I peptide, were used to track T cell activation and migration in normal adoptive recipients that were subsequently transplanted with heterotopic hearts that were syngeneic except for a transgenic MHC class I antigen. T cells rapidly disappeared from the blood into the lymphoid tissues where they were activated within one day after transplantation. T cells initially formed discrete clusters in the spleen and lymph nodes.

Evidence for cooperativity in the rejection of cardiac grafts mediated by CD4 TCR Tg T cells specific for a defined allopeptide.

Understanding the mechanisms of rejection of organs transplanted between unrelated individuals is confounded by the complexity of the alloantigens and the diversity of T cells responding to these alloantigens. To circumvent these problems, we developed a transgenic (Tg) C57BL/6 model system in which the T-cell receptor (TCR) expressed by CD4 T cells is specific for a defined allogeneic H-2Kd peptide and the cardiac donor expressed H-2Kd as a transgene on the C57BL/6 background (B6.Kd).