Effects of adoptive immunotherapy with autologous CD8+ T lymphocytes on immunologic parameters: lymphocyte subsets and cytotoxic activity

Generation and ex vivo expansion of HTLV-1 specific CD8+ cytotoxic T-lymphocytes for adoptive immunotherapy

CD8(+) cytotoxic T-lymphocytes (CTLs) have been proven, in multiple animal models, to be the most powerful antiviral and antitumor components of the immune system. We have developed a protocol to activate and expand tumor and virus peptide-specific CD8(+) T-lymphocytes from the peripheral blood of healthy, human trophic leukemia virus-1 (HTLV-1) seronegative human leucocyte antigen (HLA)-A*0201 individuals. A combination of density-based separation and culture conditions was employed to isolate dendritic cells (DCs), which are the most potent antigen-presenting cells (APCs), and T-lymphocytes. The DCs were pulsed with HLA-A*0201 binding peptides and cultured with autologous T-lymphocytes to generate peptide-specific CTLs. The CTLs were generated against a nine-amino-acid peptide from the Tax protein of HTLV-1. The CTLs were expanded according to a restimulation schedule employing peptide-pulsed autologous monocytes and low-dose interleukin-2 (IL-2) to numbers in excess of 100 x 10(6) cells following 5 weeks of culture. Expanded cells contained primarily CD3(+) T-cells, of which CD8(+) T-lymphocytes constituted greater than two-thirds of the cell population. Obtained CTLs exhibited potent antigen-specific lysis of peptide-pulsed target cells in a dose-dependent fashion in in vitro (51)Cr release cytotoxicity assay. This antigen-specific killing was shown to be HLA class I restricted and mediated by CD8(+) T-lymphocytes. Since the T-lymphocytes were obtained from HTLV-1 seronegative donors, the generation of peptide-specific CTLs represents reliable and reproducible elicitation of a primary immune response in vitro against naive antigens and subsequent expansion of generated CTLs for adoptive immunotherapy. (c) 1996 John Wiley & Sons, Inc.

Immunotherapy of viral infections

Among the microorganisms that cause diseases of medical or veterinary importance, the only group that is entirely dependent on the host, and hence not easily amenable to therapy via pharmaceuticals, is the viruses. Since viruses are obligate intracellular pathogens, and therefore depend a great deal on cellular processes, direct therapy of viral infections is difficult. Thus, modifying or targeting nonspecific or specific immune responses is an important aspect of intervention of ongoing viral infections. However, as a result of the unavailability of effective vaccines and the extended duration of manifestation, chronic viral infections are the most suitable for immunotherapies. We present an overview of various immunological strategies that have been applied for treating viral infections after exposure to the infectious agent.

Rational approaches to immune regulation

Our laboratory is interested in the properties of proteins that render them immunogenic, and how such immunogenicity may be modulated in vivo. We are attempting to enhance the immune response in the design of more effective vaccines against viral diseases, such as HIV, and against tumor antigens expressed on breast, ovarian, and cervical cancer and B cell lymphomas. Our main approach is to use a facultative intracellular bacterium, Listeria monocytogenes, which has the unusual ability to live and grow in the cytoplasm of the cell and is thus an excellent vector for targeting passenger antigens to the major histocompatibility complex (MHC) class I pathway of antigen processing with the generation of authentic cytotoxic T lymphocytes (CTL) epitopes. In the field of tumor immunotherapy, we are also developing nonliving vaccine vectors for tumor antigens.

Freezing characteristics of genetically modified lymphocytes for the treatment of MPS II

The freezing characteristics of genetically modified lymphocytes obtained from a donor with mucopolysaccharidosis type II (MPS II) were determined using cryomicroscopy and controlled rate freezing studies to determine postthaw viability. The cells from a donor with MPS II used in this investigation were cultured and transduced with a retroviral vector for the iduronate-2-sulfatase (IDS) enzyme for clinical studies for human gene therapy. The water transport and intracellular ice formation (IIF) characteristics of the cells were determined after completion of the culture and transduction protocol. The water transport parameters, I(pg) and E(lp), for the cultured and transduced cells were determined to be 4.4 +/- 1.3 x 10(-14) m3/Ns and 173 +/- 25 kJ/mol, respectively. The IIF nucleation parameters, kappa and omega, were 5.5 x 10(10) K5 and 3.5 x 10(11) (l/m2 s), respectively. The postthaw viability of the genetically modified cells was less than the viability of the freshly isolated cells from the same donor. The postthaw viability of the cultured and transduced cells from a donor with MPS II was also less than that observed with cells from a normal donor that were frozen and thawed under the same conditions. These studies are essential in understanding the biophysical changes resulting from the ex vivo culture of cells and the manner in which these changes influence the ability of the cells to be cryopreserved.

Adoptive immunotherapy of feline leukemia virus infection using autologous lymph node lymphocytes

Adoptive immunotherapy using autologous cells expanded ex vivo from lymph nodes was examined in cats infected with the retrovirus feline leukemia virus (FeLV). Cells were obtained from popliteal lymph nodes from 18 FeLV-antigen-positive cats without complications; a mean of 6.2 x 10(7) cells were obtained. Lymph node cells were cultured with 600 IU/ml interleukin-2 (IL-2) for 7 days. Cells expanded 0.8- to 11-fold (mean, 2.7; median, 2.4); were 80% +/- 8.0% CD3+, 29% +/- 8.1% CD4+, and 41% +/- 7.0% CD8+, and exhibited cytolytic activity against FeLV-transformed FL74 cells. Sixteen cats received a single intravenous infusion of 0.13 to 3.9 x 10(8) cells. Cell infusion was well tolerated; fever developed approximately 1 hour postinfusion. Clinical activity, antiviral activity, or both was observed in 10 cats. Nine cats had clinical responses with improvement in weight, activity, appearance, or a combination of these that began 2 to 4 weeks after cell infusion and that lasted for up to 13 or more months. FeLV antigen became undetectable in 4 cats. These results indicate that adoptive immunotherapy using autologous lymph node cells, activated and expanded ex vivo in short-term cultures with low concentrations of IL-2, can modulate the course of a retroviral infection.

Anthrax toxin-mediated delivery in vivo and in vitro of a cytotoxic T-lymphocyte epitope from ovalbumin

We reported earlier that a nontoxic form of anthrax toxin was capable of delivering a cytotoxic T-lymphocyte (CTL) epitope in vivo, such that a specific CTL response was primed against the epitope. The epitope, of bacterial origin, was fused to an N-terminal fragment (LFn) from the lethal-factor component of the toxin, and the fusion protein was injected, together with the protective antigen (PA) component, into BALB/c mice. Here we report that PA plus LFn is capable of delivering a different epitope--OVA(257-264) from ovalbumin. Delivery was accomplished in a different mouse haplotype, H-2Kb and occurred in vitro as well as in vivo. An OVA(257-264)-specific CTL clone, GA-4, recognized EL-4 cells treated in vitro with PA plus as little as 30 fmol of the LFn-OVA(257-264) fusion protein. PA mutants attenuated in toxin self-assembly or translocation were inactive, implying that the role of PA in epitope delivery is the same as that in toxin action. Also, we showed that OVA(257-264)-specific CTL could be induced to proliferate by incubation with splenocytes treated with PA plus LFn-OVA(257-264). These findings imply that PA-LFn may serve as a general delivery vehicle for CTL epitopes in vivo and as a safe, efficient tool for the ex vivo expansion of patient-derived CTL for use in adoptive immunotherapy.

A preliminary study to determine the effect of an infusion of cryopreserved autologous lymphocytes on immunocompetence and viral load in HIV-infected patients

Therapeutic measures aimed at boosting the immunity of HIV-infected patients are a critical component of strategies for effective therapy of HIV and AIDS. To improve immunocompetence in patients with progressive disease, autologous lymphocytes that were collected and cryopreserved earlier in the course of HIV-infection were reinfused. None of the 12 patients receiving cell infusions experienced any adverse effects. Improvements in immunologic parameters (CD4+ counts, CD8+ counts, or both; HIV-specific cytotoxic T-lymphocyte (CTL) activity; or viral load) were seen in seven patients. Restoration of the CD4+ count to the level recorded at the time of cell harvest was achieved in two patients with less advanced disease. Plasma HIV RNA was reduced by >0.5 logs in two of the four patients tested. These preliminary results suggest that cellular immunotherapy using cryopreserved autologous lymphocytes has the potential to improve some measures of immunity in patients with HIV/AIDS and warrants further investigation.

Rational approaches to immune regulation

Our studies are mainly focused on developing strategies of immune regulation. In the case of infectious and neoplastic disease, our approach is to upregulate cell-mediated immunity to viral of tumor antigens using an intracellular bacterium as a vector for targeting these antigens to the major histocompatibility complex (MHC) class I and class II pathways of antigen processing, in addition to exploiting the adjuvant properties of the vector to stimulate innate immunity. In the area of autoimmunity, we are attempting to downregulate the immune response by specific immune intervention directed against autoreactive T cells. In these studies we use murine models for multiple sclerosis. Our approach is to use both rationally designed T cell receptor (TCR) peptide analogs and recombinant viral vectors that express TCR components to regulate the disease.

Safety of Autologous, Ex Vivo-Expanded Human Immunodeficiency Virus (HIV)-Specific Cytotoxic T-Lymphocyte Infusion in HIV-Infected Patients

We infused six human immunodeficiency virus (HIV)-seropositive subjects with autologous CD8+ cytotoxic T cells (CTLs) enriched for HIV-specific cytotoxicity targeted against a diversity of HIV epitopes in gp120, gag p17 and p24, and nef. There was no toxicity and no subject deteriorated clinically. In the first 2 weeks, CD4 counts increased for all subjects and plasma viremia decreased in five of six subjects. Twenty-four weeks later, the mean values of all measures of viral burden and surrogate markers of HIV infection were either unchanged or improved, but none of the changes was statistically significant. Two subjects continued to have decreased cell-associated viral burden and another subject had more than doubled CD4 cell count. HIV-specific CTL activity increased in most subjects. The increase in CD4 T-cell counts in the first weeks after the infusion suggests that antiviral CTLs of diverse specificities do not play a significant role in CD4 T-cell decline. The lack of any acute toxicity or adverse effect on viral burden suggests that therapy with antiviral CTLs deserves further study.

Safety of Autologous, Ex Vivo-Expanded Human Immunodeficiency Virus (HIV)-Specific Cytotoxic T-Lymphocyte Infusion in HIV-Infected Patients

We infused six human immunodeficiency virus (HIV)-seropositive subjects with autologous CD8+ cytotoxic T cells (CTLs) enriched for HIV-specific cytotoxicity targeted against a diversity of HIV epitopes in gp120, gag p17 and p24, and nef. There was no toxicity and no subject deteriorated clinically. In the first 2 weeks, CD4 counts increased for all subjects and plasma viremia decreased in five of six subjects. Twenty-four weeks later, the mean values of all measures of viral burden and surrogate markers of HIV infection were either unchanged or improved, but none of the changes was statistically significant. Two subjects continued to have decreased cell-associated viral burden and another subject had more than doubled CD4 cell count. HIV-specific CTL activity increased in most subjects. The increase in CD4 T-cell counts in the first weeks after the infusion suggests that antiviral CTLs of diverse specificities do not play a significant role in CD4 T-cell decline. The lack of any acute toxicity or adverse effect on viral burden suggests that therapy with antiviral CTLs deserves further study.

CD8+ cell-mediated immune responses: relation to disease resistance and susceptibility in lentivirus-infected primates

Immune responses mediated by CD8+ lymphocytes have been correlated with protection from HIV infection and disease progression in humans and nonhuman primates. The CD8+ cell population is heterogeneous in terms of biological function and phenotype. We have undertaken a review of the current state of knowledge of subtypes of CD8+ cells and their role in immune responses directed to HIV and related primate lentiviruses. Differences in the pathogenesis of lentivirus infections in various primate hosts were examined and the possible roles of the various subpopulations of CD8+ lymphocytes in the resistance and/or susceptibility to lentivirus-related disease were compared.

Cytotoxic T lymphocytes and viral turnover in HIV type 1 infection

To understand the role of the immune system in limiting HIV type 1 replication, it is critical to know to what extent the rapid turnover of productively infected cells is caused by viral cytopathicity or by immune-mediated lysis. We show that uncultured peripheral blood mononuclear cells of many patients contain cytotoxic T lymphocytes (CTL) that lyse target cells-at plausible peripheral blood mononuclear cell-to-target ratios-with half-lives of less than 1 day. In 23 patients with CD4 counts ranging from 10 to 900 per microliter, the average rate of CTL-mediated lysis corresponds to a target cell half-life of 0.7 day. We develop mathematical models to calculate the turnover rate of infected cells subjected to immune-mediated lysis and viral cytopathicity and to estimate the fraction of cells that are killed by CTL as opposed to virus. The models provide new interpretations of drug treatment dynamics and explain why the observed rate of virus decline is roughly constant for different patients. We conclude that in HIV type 1 infection, CTL-mediated lysis can reduce virus load by limiting virus production, with small effects on the half-life of infected cells.

Detection of human immunodeficiency virus type 1-specific memory cytotoxic T lymphocytes in freshly donated and frozen-thawed peripheral blood mononuclear cells

Loss of anti-human immunodeficiency virus type 1 (HIV-1) memory cytotoxic T-lymphocyte (CTLm) responses is associated with disease progression in HIV-1 infection. In this study, nonspecific stimulation of peripheral blood mononuclear cells (PBMC) from HIV-1-infected homosexual men with anti-CD3 monoclonal antibody (MAb) was compared with antigen-specific stimulation with inactivated, autologous B lymphoblastoid cells (B-LCL) infected with a vaccinia virus vector encoding HIV-1 IIIb Gag, Pol, and Env (VV-GPE) for activation of HIV-1-specific CTLm responses in a bulk lysis assay and by precursor frequency analysis. The results show that VV-GPE-infected B-LCL stimulated on average 10-fold greater anti-HIV-1 CTLm activity, as detected in the bulk lysis assay, and 55-fold-greater CTLm precursor frequencies specific for the three HIV-1 structural proteins than did stimulation with anti-CD3 MAb. This effect was noted with both freshly donated and frozen-thawed PBMC. The lysis was mediated by CD8+ T cells and was restricted by the major histocompatibility class I complex. These data indicate that antigen-specific stimulation with VV-GPE-infected B-LCL is a highly efficient method for detection of anti-HIV-1 CTLm responses that is applicable to noncurrent prospective studies with frozen PBMC.

High levels of anti-human immunodeficiency virus type 1 (HIV-1) memory cytotoxic T-lymphocyte activity and low viral load are associated with lack of disease in HIV-1-infected long-term nonprogressors

Lack of disease in long-term nonprogressors with human immunodeficiency virus type 1 (HIV-1) infection was strongly associated with very low copy numbers of HIV-1 DNA and RNA in peripheral blood mononuclear cells and plasma and the presence of high levels of anti-HIV-1 CD8+ memory cytotoxic T lymphocytes specific for Gag, Pol, and Env, compared with levels present in intermediate and advanced progressors. CD8+ memory cytotoxic T lymphocytes may have an important role in controlling HIV-1 replication and preventing disease in long-term nonprogressors.

Anti-HIV type 1 cytotoxic T lymphocyte effector activity and disease progression in the first 8 years of HIV type 1 infection of homosexual men

Cytotoxic T lymphocytes (CTL) may play an important role in host defense against HIV-1 infection. In this study, we examined the responses of circulating effector CTL (CTLe) specific for Gag, Pol, Env, and Tat in 57 HIV-1-infected men, 49 of whom were asymptomatic and had documented time since seroconversion of < 8 years. CTLe responses to at least one of the four HIV-1 gene products were detected in 83% of the subjects. The magnitude and prevalence of the anti-Tat responses were significantly less than the responses to Gag, Pol, and Env. Cell depletion studies indicated that the lytic activity against the HIV-1 structural proteins was mediated by CD8+ T cells, although 30% of Env-specific lysis was mediated by CD16+ natural killer cells. Anti-HIV-1 CTLe responses against Gag and Pol were significantly less in subjects infected for over 6 years as compared to those infected for shorter periods of time. We found no correlation, however, between anti-HIV-1 CTLe responses and either CD4+ or CD8+ T cell counts, rates of CD4+ T cell loss, HIV-1 infectious viral load, use of antiviral medications, or subsequent progression to AIDS. Our results indicate that anti-HIV-1 CTLe activity is relatively stable in asymptomatic subjects infected < 6 years, and is not an early marker for risk of disease progression.