In vivo migration and function of transferred HIV-1-specific cytotoxic T cells

Adoptive T-Cell Therapy for B-Cell Acute Lymphoblastic Leukemia: Preclinical Studies

We have previously shown that leukemia-specific cytotoxic T cells (CTL) can be generated from the bone marrow of most patients with B-cell precursor acute leukemias. If these antileukemia CTL are to be used for adoptive immunotherapy, they must have the capability to circulate, migrate through endothelium, home to the bone marrow, and, most importantly, lyse the leukemic cells in a leukemia-permissive bone marrow microenvironment. We demonstrate here that such antileukemia T-cell lines are overwhelmingly CD8+ and exhibit an activated phenotype. Using a transendothelial chemotaxis assay with human endothelial cells, we observed that these T cells can be recruited and transmigrate through vascular and bone marrow endothelium and that these transmigrated cells preserve their capacity to lyse leukemic cells. Additionally, these antileukemia T-cell lines are capable of adhering to autologous stromal cell layers. Finally, autologous antileukemia CTL specifically lyse leukemic cells even in the presence of autologous marrow stroma. Importantly, these antileukemia T-cell lines do not lyse autologous stromal cells. Thus, the capacity to generate anti–leukemia-specific T-cell lines coupled with the present findings that such cells can migrate, adhere, and function in the presence of the marrow microenvironment enable the development of clinical studies of adoptive transfer of antileukemia CTL for the treatment of ALL.

Immune reconstitution in AIDS: oncologic implications and hematologic approaches

Combination anti-retroviral therapy for HIV disease has profoundly altered the nature of the AIDS epidemic. Mitigating the impact of an uncontrollable decline in immune function is no longer the focal point for AIDS therapy, but has evolved to an emphasis on maximizing the potential for immune regeneration. Improved control of HIV replication has diminished, albeit unevenly, the frequency of AIDS-related malignancies and has altered the focus of hematologic and oncologic interventions in HIV disease. Now, with adoptive cellular therapies and the genetic engineering of cells in the clinical arena, the potential for cellular therapeutics in enhancing immune restoration is being tested. These approaches are based on better understanding of the immunobiology of HIV and its impact on hematopoietic tissues.

The simian immunodeficiency virus envelope glycoprotein contains two epitopes presented by the Mamu-A*01 class I molecule

Cytotoxic T lymphocyte (CTL) responses against the simian immunodeficiency virus (SIV) envelope and Gag proteins were monitored in a Mamu-A*01-positive rhesus macaque infected with SIVsmE660. Peripheral blood mononuclear cells (PBMC) cultured with synthetic peptides spanning the entire gp160 and Gag coding region recognized a total of three epitopes. One located in Gag was identified as the previously described Mamu-A*01-restricted p11cC-->M epitope (CTPYDINQM). The other two epitopes, designated p15m and p54m, were located in the gp160 envelope protein. Both were nine amino acids in length and were predicted to bind Mamu-A*01 because they contained proline and leucine residues at positions 3 and 9, respectively. Indeed, expression of this class I major histocompatibility complex molecule was required for target cell recognition by envelope-specific CD8(+) T cells directed against both epitopes. These Mamu-A*01-restricted epitopes in the SIV envelope will be useful for monitoring immune responses in vaccinated or infected animals.

Cell-associated HIV-1 messenger RNA and DNA in T-helper cell and monocytes in asymptomatic HIV-1-infected subjects on HAART plus an inactivated HIV-1 immunogen

OBJECTIVE

We examined the effect of an HIV-1-specific immune-based therapy on cell-associated HIV-1 DNA and RNA.

DESIGN

Five HIV-1-infected subjects receiving HIV-1 immunogen plus HAART were compared with three HIV-1-infected subjects who received incomplete Freund's adjuvant (IFA) plus HAART.

METHODS

Cell-associated HIV-1 RNA or DNA in lymphocytes and monocytes was determined using a dual immunophenotyping/in situ hybridization assay with or without in situ PCR amplification.

RESULTS

Cell-associated HIV-1 RNA in CD4 cells correlated with plasma RNA overall. CD4, HIV-1 gag-pol messenger (m)RNA+ cells decreased in the immunogen plus HAART group compared with the IFA plus HAART group. Decreases in HIV-1 DNA+ CD4 cells were observed in the immunogen plus HAART compared with the IFA plus HAART group. Decreases in HIV-1 gag-pol mRNA+ monocytes were observed in the immunogen plus HAART group compared with the IFA plus HAART group. Consistent with the findings in CD4 cells, decreases in HIV-1 DNA+ monocytes were observed in the immunogen plus HAART group compared with the IFA plus HAART group.

CONCLUSIONS

These preliminary observations support the rationale for examining the combination of immune-based therapies and antiretroviral drugs for effective HIV-1 control.

T lymphocyte responses in HIV-1 infection: implications for vaccine development

Substantial progress has been made over the past year in understanding the cellular immune response in HIV pathogenesis. Cytotoxic T lymphocytes play a critical role in establishing the level of viremia and virus-specific Th cell responses appear to affect the in vivo efficacy of cytotoxic T lymphocytes. Together, these new data provide important insights to refocus efforts aimed at immunotherapeutic interventions and vaccine development.

Deficient cellular immunity--finding and fixing the defects

The critical role of cellular immunity in resistance to infectious diseases is glaringly revealed by life-threatening infections if T cell function is disrupted by an inherited or acquired immunodeficiency. Although treatment has historically focused on infectious complications, understanding of the cellular and molecular basis of immunodeficiency and technologies useful for enhancing cellular immunity have both been rapidly evolving. A new era of molecular and cellular therapy is emerging as approaches to correct abnormal genes, the loss of T cell subpopulations, and aberrant T cell homeostasis make the transition from bench to bedside.

CD8(+) minor histocompatibility antigen-specific cytotoxic T lymphocyte clones eliminate human acute myeloid leukemia stem cells

Effective immunotherapy for human leukemia based on infusions of T lymphocytes requires the identification of effector T cells that target the leukemic stem cell. The transplantation of human acute myeloid leukemia into nonobese diabetic/severe combined immune deficient (SCID) mice has identified a rare leukemic progenitor termed the SCID leukemia-initiating cell, which is present in low frequency in the leukemic population and is essential for establishing leukemic hematopoiesis. Thus, this transplant model may be ideally suited to identify effector T cells with antileukemic activity. We report that CD8(+) cytotoxic T lymphocyte (CTL) clones specific for minor histocompatibility antigens inhibit the engraftment of human acute myeloid leukemia cells in nonobese diabetic/SCID mice and demonstrate that this inhibition is mediated by direct CTL recognition of SCID leukemia-initiating cells. These results indicate that CD8(+) minor histocompatibility antigen-specific CTL may be mediators of the graft-versus-leukemia effect associated with allogeneic hematopoietic cell transplantation and provide an experimental model to identify and select T cell clones for immunotherapy to prevent or treat relapse after allogeneic hematopoietic cell transplantation.

The Antiviral Activity of HIV-Specific CD8+ CTL Clones Is Limited by Elimination Due to Encounter with HIV-Infected Targets

Adoptive immunotherapy of virus infection with viral-specific CTL has shown promise in animal models and human virus infections and is being evaluated as a therapy for established HIV-1 infection. Defining the individual obstacles for success is difficult in human trials. We have therefore examined the localization, persistence, and antiviral activity of HIV-1 gag-specific CTL clones in both HIV-1-infected and uninfected haplotype-matched human (hu)-PBL-SCID mice. Injection of gag-specific clones but not control CTL into HIV-1-infected hosts reduced plasma viremia by >10-fold but failed to eliminate the virus infection from most treated animals. The failure to eradicate virus did not reflect selection of escape variants because the gag epitope remained unmutated in virus isolates obtained after CTL therapy. Injection of carboxyfluorescein diacetate succinimide ester-labeled CTL demonstrated markedly different fates for gag-specific CTL in the presence or absence of HIV-1 infection. HIV-1-specific CTL rapidly disappeared in infected recipients, whereas they were maintained at high numbers in uninfected mice. By contrast, control CTL were long lived in both infected and uninfected recipients. Thus, interaction of CTL with virus-infected target cells in vivo leads not only to target destruction but also to the rapid disappearance of the infused CTL, and it limits the capacity of CTL therapy to eliminate HIV-1 infection.

Pediatric AIDS-associated lymphocytic interstitial pneumonia and pulmonary arterio-occlusive disease: role of VCAM-1/VLA-4 adhesion pathway and human herpesviruses

Because the mechanisms of lymphocyte accumulation in the lungs of children with AIDS-associated lymphocytic interstitial pneumonia (LIP) are unknown, we studied the relative contributions of known adhesion pathways in mediating lymphocyte adherence to endothelium and the potential role of human herpesviruses in the expansion of these lesions. LIP was characterized by lymphoid hyperplasia of the bronchus-associated lymphoid tissue (BALT) and infiltration of the pulmonary interstitium with CD8(+) T lymphocytes. In some individuals there was expansion of the alveolar septae with dense aggregates of B lymphocytes, many containing the Epstein-Barr viral (EBV) genome. Patients with concurrent EBV infection also demonstrated large-vessel arteriopathy characterized by thickening of the intimae with collagen and smooth muscle. Venular endothelium from the lung of children with LIP, but not uninflamed lung from other children with AIDS or lung from children with nonspecific pneumonitis, expressed high levels of vascular cell adhesion molecule-1 (VCAM-1) protein. In turn, inflammatory cells expressing very late activation antigen-4 (VLA-4), the leukocyte ligand for VCAM-1, were the predominant perivascular infiltrate associated with vessels expressing VCAM-1. Expression of other endothelial adhesion molecules, including intracellular adhesion molecule-1 and E-selectin, was not uniformly associated with LIP. Using a tissue adhesion assay combined with immunohistochemistry for VCAM-1, we show that CD8(+) T cell clones that express VLA-4 bind preferentially to pulmonary vessels in sites of LIP: vessels that expressed high levels of VCAM-1. When tissues and cells were pretreated with antibodies to VCAM-1 or VLA-4, respectively, adhesion was inhibited by >/=80%. Thus, infiltration of alveolar septae with CD8(+) T cells was highly correlative with VCAM-1/VLA-4 adhesive interactions, and focal expansion of B cells was coincidental to co-infection with EBV.