Identification and characterization of antigen-specific T lymphocytes during the course of an immune response is tedious and indirect. To address this problem, the peptide-major histocompatability complex (MHC) ligand for a given population of T cells was multimerized to make soluble peptide-MHC tetramers. Tetramers of human lymphocyte antigen A2 that were complexed with two different human immunodeficiency virus (HIV)-derived peptides or with a peptide derived from influenza A matrix protein bound to peptide-specific cytotoxic T cells in vitro and to T cells from the blood of HIV-infected individuals. In general, tetramer binding correlated well with cytotoxicity assays. This approach should be useful in the analysis of T cells specific for infectious agents, tumors, and autoantigens.

http://science.sciencemag.org/content/sci/274/5284/94.full.pdf

Phenotypic Analysis of Antigen-Specific T Lymphocytes

Virologic and immunologic studies were performed on five patients presenting with primary human immunodeficiency virus type 1 (HIV-1) infection. CD8+ cytotoxic T lymphocyte (CTL) precursors specific for cells expressing antigens of HIV-1 Gag, Pol, and Env were detected at or within 3 weeks of presentation in four of the five patients and were detected in all five patients by 3 to 6 months after presentation. The one patient with an absent initial CTL response had prolonged symptoms, persistent viremia, and low CD4+ T-cell count. Neutralizing antibody activity was absent at the time of presentation in all five patients. These findings suggest that cellular immunity is involved in the initial control of virus replication in primary HIV-1 infection and indicate a role for CTL in protective immunity to HIV-1 in vivo.

Temporal association of cellular immune responses with the initial control of viremia in primary human immunodeficiency virus type 1 syndrome.

Human immunodeficiency virus type 1 (HIV-1) Env-, Gag-, Pol-, Nef-, and Tat-specific cytotoxic T-lymphocyte (CTL) activities were quantitated temporally in five patients with symptomatic primary HIV-1 infection. A dominant CD8(+)-mediated, major histocompatibility complex class I-restricted CTL response to the HIV-1 envelope glycoprotein, gp160, was noted in four of the five patients studied. The level of HIV-1-specific CTL activity in the five patients paralleled the efficiency of control of primary viremia. Patients who mounted strong gp160-specific CTL responses showed rapid reduction of acute plasma viremia and antigenemia, while in contrast, primary viremia and antigenemia were poorly controlled in patients in whom virus-specific CTL activity was low or undetectable. These results suggest that HIV-1-specific CTL activity is a major component of the host immune response associated with the control of virus replication following primary HIV-1 infection and have important implications for the design of antiviral vaccines.

https://jvi.asm.org/content/jvi/68/9/6103.full.pdf

Virus-specific CD8+ cytotoxic T-lymphocyte activity associated with control of viremia in primary human immunodeficiency virus type 1 infection.

The HIV-1-specific cytotoxic T lymphocyte (CTL) response is temporally associated with the decline in viremia during primary HIV-1 infection, but definitive evidence that it is of importance in virus containment has been lacking. Here we show that in a patient whose early CTL response was focused on a highly immunodominant epitope in gp160, there was rapid elimination of the transmitted virus strain and selection for a virus population bearing amino acid changes at a single residue within this epitope, which conferred escape from recognition by epitope-specific CTL. The magnitude (> 100-fold), kinetics (30–72 days from onset of symptoms) and genetic pathways of virus escape from CTL pressure were comparable to virus escape from antiretroviral therapy, indicating the biological significance of the CTL response in vivo. One aim of HIV-1 vaccines should thus be to elicit strong CTL responses against multiple codominant viral epitopes.

Antiviral pressure exerted by HIV-1-specific cytotoxic T lymphocytes (CTLs) during primary infection demonstrated by rapid selection of CTL escape virus.

An international panel of experts prepared an evidenced-based guideline for vaccination of immunocompromised adults and children. These guidelines are intended for use by primary care and subspecialty providers who care for immunocompromised patients. Evidence was often limited. Areas that warrant future investigation are highlighted.

/pdf/2013-idsa-clinical-practice-guideline-for-vaccination-of-the-2qw25jra11.pdf

2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host

CTL specific for the HIV belong to the CD8 subset of T lymphocytes, and their activity is restricted by class I HLA transplantation Ag. In this report, HIV-specific CTL and their precursor cells were quantified by limiting dilution analysis. CTL were recovered from the lungs, lymph nodes, and blood of asymptomatic seropositive carriers and of patients with AIDS. HIV was found to be very immunogenic. High frequencies of both HIV-specific CTL and CTL precursor cells were detected in infected individuals. These CTL killed autologous HIV-infected macrophages and T4 lymphoblasts. They also killed doubly transfected P815-A2-env-LAV mouse tumor cells, which express the human HLA-A2 gene and the HIV-1 env gene. In the longitudinal studies of two HIV-infected patients, CTL and CTL precursor cell frequencies decreased as the clinical and immunologic status of the patients deteriorated. Most surprisingly, PBL from seronegative donors also responded to HIV stimulation in vitro and generated large numbers of HLA-restricted, HIV-specific CTL.

Unusually high frequencies of HIV-specific cytotoxic T lymphocytes in humans.

Legionnaires' disease related to gastric lavage with tap water

CTL specific for HIV have been described in lungs of infected patients at early stages of HIV disease. In order to characterize the evolution over time of HIV-specific CTL, we have analyzed the cytotoxic function and the cell surface phenotype of the alveolar lymphocytes from 41 patients at various stages of HIV disease. We demonstrated a progressive decline of alveolar anti-HIV CTL activity and detected Ts cells from the lungs of patients with advanced HIV disease. These alveolar T cells strongly suppressed the effector phase of anti-HIV CTL lysis. They lacked a marked specificity of function because they also block anti-HLA CTL response and were not restricted by the HLA-class-I transplantation Ag. They displayed the CD3, CD8, and HNK1 markers, were CD4 and CD16 negative, and lacked NK activity. The presence of Ts cells at late stages of HIV disease could thus partly explain the inefficiency of host defenses against HIV.

Cell-mediated suppression of HIV-specific cytotoxic T lymphocytes.

A T8 lymphocyte alveolitis occurs in HIV-positive patients, even in the absence of any lung infections or tumors. Using the monoclonal antibody (MAb) D44, the CD8+ T cells can be further subdivided into two functional subsets of cytotoxic T lymphocytes (CTL; CD8+, D44+) and suppressor T cells (CD8+, D44-). A dual fluorescence analysis of alveolar and peripheral lymphocytes has been used in HIV-positive patients without lung infections or tumors to reveal a dramatic increase in alveolar T8 lymphocytes (83%), compared to peripheral values (52%), which was mainly composed (89%) of CD8+ D44+ CTLs. Functional studies confirmed the cytolytic activity of these phenotypically defined alveolar CTLs on autologous alveolar macrophages used as target cells, excluding a natural killer-like activity. An immuno-enzyme analysis concomitantly revealed the co-expression of the p18 HIV antigen and the CD4 molecule on the autologous alveolar macrophages. These data suggest that CTL alveolitis occurs during HIV infection and is directed against HIV-infected alveolar macrophages which are presumably the targets of the locally recruited lung CTLs.

Evidence for a cytotoxic T-lymphocyte alveolitis in human immunodeficiency virus-infected patients.

The CTL response to HIV was analyzed in humans and in mice. By using a novel and strictly autologous lymphocyte culture system, human CTL lines were established with PBL from seropositive asymptomatic donors and from patients suffering from AIDS or presenting AIDS-related complex. CTL from HLA-A2 donors recognize and kill murine P815 mastocytoma cells doubly transfected with the human HLA-A2 gene and the HIV env gene; they also kill HLA-compatible human macrophages infected with HIV. CTL specific for the HIV env Ag were also generated in BALB/c mice by immunization with syngeneic murine cells transfected with the HIV env gene. Human and murine HIV-immune CTL populations belong to the CD8 subset of T lymphocytes and are restricted by class I HLA or H-2 transplantation Ag, respectively, in the recognition of HIV env Ag. The two different experimental systems presented here can be used to study CD8 lymphocyte immunity against HIV. The murine model of CTL immunity offers the additional advantage of avoiding the manipulation of infectious virus isolates.

C Mayaud

Papers

Unusually high frequencies of HIV-specific cytotoxic T lymphocytes in humans.

Legionnaires' disease related to gastric lavage with tap water

Cell-mediated suppression of HIV-specific cytotoxic T lymphocytes.

Evidence for a cytotoxic T-lymphocyte alveolitis in human immunodeficiency virus-infected patients.

Immune recognition of AIDS virus antigens by human and murine cytotoxic T lymphocytes.