Biomedical subjects

Michael I Nishimura

Publications and source records attributed to Michael I Nishimura.

At least 19 recordsLinked to original sources

PubMed2007

T cell immunotherapy.

Adoptive T cell immunotherapy is the isolation of tumor-specific T cells from a cancer patient, in vitro activation and expansion of these T cells, and re-infusion of the T cells to the patient. In a small percentage of patients with tumor types susceptible to immune modulation, adoptive therapy has proven to be highly effective. The use of adoptive therapy has several limitations which are being actively investigated today. T cells from various sources are being isolated for adoptive therapy: lymphocytes can be isolated from tumor lesions, from lymph nodes draining the tumor or a tumor vaccine site, or from peripheral blood lymphocytes stimulated with tumor antigens in vitro. Recent advances in T cell therapy include enhanced efficacy of T cell therapy following non-myeloablative chemotherapy and genetic modification of T cells for use in adoptive therapy. Clinical trials using gene-modified T cells with improved activation, lifespan, and tumor targeting are on the horizon. It is likely that adoptive immunotherapy will remain a fertile area for investigation resulting in advances in the fields of T cell biology and gene therapy. Adoptive therapy for cancer will become widespread only after its clinical benefit for sizeable patient populations has been established.

Animals↗

PubMed2006

Influence of human CD8 on antigen recognition by T-cell receptor-transduced cells.

The CD8 coreceptor on T cells has two functions. Namely, CD8 acts to stabilize the binding of the T-cell receptor (TCR) to the peptide-MHC complex while localizing p56(lck) (lck) to the TCR/CD3 complex to facilitate early signaling events. Although both functions may be critical for efficient activation of a CTL, little is known about how the structural versus signaling roles of CD8, together with the relative strength of the TCR, influences T-cell function. We have addressed these issues by introducing full-length and truncated versions of the CD8alpha and CD8beta chains into CD8(-) Jurkat cell clones expressing cloned TCRs with known antigen specificity and relative affinities. Using a combination of antigen recognition and tetramer-binding assays, we find that the intracellular lck-binding domain of CD8 is critical for enhanced T-cell activation regardless of the relative strength of the TCR. In contrast, the extracellular domain of CD8 seems to be critical for TCRs with lower affinity but not those with higher affinity. Based on our results, we conclude that there are different requirements for CD8 to enhance T-cell function depending on the strength of its TCR.

Antigens, Neoplasm↗

PubMed2006

Therapeutic implications of autoimmune vitiligo T cells.

Vitiligo is an autoimmune disease presenting with progressive loss of skin pigmentation. The disease strikes 1% of the world population, generally during teenage years. The progressive loss of melanocytes from depigmenting vitiligo skin is accompanied by cellular infiltrates containing both CD4+ and CD8+ T lymphocytes. Infiltrating cytotoxic T cells with high affinity T cell receptors have likely escaped clonal deletion in the thymus, allowing such T cells to enter the circulation. Through the expression of CLA, these T cells home to the skin where they express type 1-cytokine profiles and mediate melanocyte apoptosis via the granzyme/perforin pathway. T cells found juxtapositionally apposed to remaining melanocytes can be isolated from the skin. Vitiligo T cells have demonstrated reactivity to antigens previously recognized as target antigens for T cells infiltrating melanoma tumors. In a comparison to existing melanoma-derived T cells, vitiligo T cells displayed superior reactivity towards melanoma cells. It is thought that genes encoding the TCRs expressed by vitiligo skin infiltrating T cells can be cloned and expressed in melanoma T cells, thereby generating a pool of circulating T cells with high affinity for their targets that can re-direct the immune response towards the tumor.

Animals↗

PubMed2006

Adoptive transfer of allogeneic cytotoxic T lymphocytes equipped with a HLA-A2 restricted MART-1 T-cell receptor: a phase I trial in metastatic melanoma.

PURPOSE: We did a phase I dose-escalation trial to evaluate the feasibility and safety of intratumoral injections of C Cure 709, an allogeneic, continuous CTL cell line that, restricted by HLA-A2, recognizes MART-1-positive tumor cells through transduction with a T-cell receptor encoding gene. EXPERIMENTAL DESIGN: Cells were administered intratumorally in four dose levels ranging from 10(8) to 10(9) cells/d on days 1, 4, 7, 10, 14, and 28 of each treatment cycle to patients with metastatic melanoma. Main inclusion criteria were HLA-A2 tissue type, MART-1-positive tumor cells, and metastases suitable for ultrasound-guided injections. Patients were assessed for toxicity and response. Three to six patients were treated per dose level. Patients without progressive disease were offered up to three treatment cycles. RESULTS: Fifteen patients received a total of 24 treatment cycles with a total of 266 injections of C Cure 709. Toxicity was minor to moderate and most common injection site reactions were fever, fatigue, nausea/vomiting, and arthralgia/myalgia. Side effects disappeared in general within 24 hours. Toxicity was not dose dependent. One patient obtained a partial response, encompassing both metastases used and not used for intratumoral injections. Remaining patients did not achieve an overall response. In addition, we observed local regression of metastases used for injection in two patients and of metastases not used for injection in one patient. CONCLUSION: Intratumoral injections of C Cure 709 are feasible, safe, and capable of inducing tumor regression. Further investigation in a phase II setting is warranted.

Adult↗

PubMed2006

Identification of a hepatitis C virus-reactive T cell receptor that does not require CD8 for target cell recognition.

Hepatitis C virus (HCV) has been reported to elicit B and T cell immunity in infected patients. Despite the presence of antiviral immunity, many patients develop chronic infections leading to cirrhosis, hepatocellular carcinoma, and liver failure that can require transplantation. We have previously described the presence of HLA-A2-restricted, HCV NS3-reactive cytotoxic T lymphocytes (CTL) in the blood of HLA-A2- liver transplantation patients that received an HLA-A2+ liver allograft. These T cells are analogous to the "allospecific" T cells that have been described in hematopoietic stem cell transplantation patients. It has been speculated that allospecific T cells express high-affinity T cell receptors (TCRs). To determine if our HCV-reactive T cells expressed TCRs with relatively high affinity for antigen, we identified and cloned a TCR from an allospecific HLA-A2-restricted, HCV:NS3:1406-1415-reactive CD8+ T cell clone and expressed this HCV TCR in Jurkat cells. Tetramer binding to HCV TCR-transduced Jurkat cells required CD8 expression, whereas antigen recognition did not. In conclusion, based on the reactivity of the TCR-transduced Jurkat cells, we have identified a TCR that transfers anti-HCV reactivity to alternate effectors. These data suggest this high affinity HCV-specific TCR might have potential new immunotherapic implications.

CD8 Antigens↗

PubMed2005

T-cell receptor tetramer binding or the lack there of does not necessitate antigen reactivity in T-cell receptor transduced T cells.

Genetic transfer of T-cell receptor (TCR) chains provides a means of transferring tumor antigen specificity onto an alternate T-cell population. To determine which tumor reactive TCRs are best suitable for such adoptive transfer, careful evaluation of the resulting TCR modified populations need to be performed. We have previously cloned, and expressed TCRs from melanoma, EBV, HCV, and HPV reactive T-cell clones and found that several routine indicators of T-cell function do not always predict the relative strength of a TCR. Using a combination of tetramer binding assays and antigen recognition assays, we identified TCRs that fall into three classes. One class of TCR did not bind tetramers yet resulted in cells with high avidity for antigen. A second TCR class bound tetramer but did not secrete cytokines in response to antigen. Finally, the third class of TCRs bound tetramer and reacted to antigen as would be expected. We conclude that tetramer binding is not always a good indicator of the function of a cloned TCR or the avidity of a TCR gene modified T cell. Furthermore, our data indicate that the use of tetramer binding alone to identify antigen reactive TCRs may result in the exclusion of TCRs that may be highly reactive or cross reactive to the relevant tumor antigen.

Cell Line, Tumor↗

PubMed2005

T cell avidity and tumor recognition: implications and therapeutic strategies.

In the last two decades, great advances have been made studying the immune response to human tumors. The identification of protein antigens from cancer cells and better techniques for eliciting antigen specific T cell responses in vitro and in vivo have led to improved understanding of tumor recognition by T cells. Yet, much remains to be learned about the intricate details of T cell-tumor cell interactions. Though the strength of interaction between T cell and target is thought to be a key factor influencing the T cell response, investigations of T cell avidity, T cell receptor (TCR) affinity for peptide-MHC complex, and the recognition of peptide on antigen presenting targets or tumor cells reveal complex relationships. Coincident with these investigations, therapeutic strategies have been developed to enhance tumor recognition using antigens with altered peptide structures and T cells modified by the introduction of new antigen binding receptor molecules. The profound effects of these strategies on T cell-tumor interactions and the clinical implications of these effects are of interest to both scientists and clinicians. In recent years, the focus of much of our work has been the avidity and effector characteristics of tumor reactive T cells. Here we review concepts and current results in the field, and the implications of therapeutic strategies using altered antigens and altered effector T cells.

Journal Article↗

PubMed2005

Interferon-gamma renders tumors that express low levels of Her-2/neu sensitive to cytotoxic T cells.

Her-2/neu is a tumor-associated antigen that has been targeted with both antibodies and cytotoxic T lymphocytes (CTL). Despite the isolation of Her-2/neu-reactive CTL in vaccinated patients, their therapeutic use has been limited by the observation that they often do not robustly recognize Her-2/neu(+) tumors. We sought to determine the mechanism for this escape using Ag201P and Ag201M cells, which are murine osteosarcoma tumor lines that express a functional HLA-A2/K(b) molecule. We now demonstrate that Ag201P and Ag201M express low levels of murine Her-2/neu, and that Ag201M was modestly and inconsistently recognized by an HLA-A2-restricted, Her-2/neu-reactive human CTL clone. In order to determine whether inefficient antigen processing might account for the weak recognition, COS-A2 cells were transfected with a short Her-2/neu minigene coding for the immunodominant Her-2/neu:369 epitope that did not require antigen processing or a long Her-2/neu minigene that did require antigen processing. Her-2/neu-reactive CTL clones only recognized COS-A2 cells transfected with the short minigene, indicating that lack of proper antigen processing could be responsible for the poor recognition of target cells. To confirm these results, it was demonstrated that following treatment with interferon-gamma, both Ag201P and Ag201M robustly and consistently stimulated the CTL clones. Furthermore, CTL clone recognition was enhanced following interferon-gamma treatment using another murine tumor line that expressed low levels of Her-2/neu (B16-A2/K(b)). The enhanced recognition of Ag201P and Ag201M in the presence of interferon-gamma was not due to an upregulation of Her-2/neu protein expression. Collectively, these results suggest that inefficient antigen processing of Her-2/neu can contribute to the lack of tumor recognition by CTL. These results also suggest that even tissues that express low levels of Her-2/neu might become CTL targets under conditions in which antigen processing is enhanced.

Animals↗

PubMed2005

Recognition of host immune activation by Pseudomonas aeruginosa.

It is generally reasoned that lethal infections caused by opportunistic pathogens develop permissively by invading a host that is both physiologically stressed and immunologically compromised. However, an alternative hypothesis might be that opportunistic pathogens actively sense alterations in host immune function and respond by enhancing their virulence phenotype. We demonstrate that interferon-gamma binds to an outer membrane protein in Pseudomonas aeruginosa, OprF, resulting in the expression of a quorum-sensing dependent virulence determinant, the PA-I lectin. These observations provide details of the mechanisms by which prokaryotic organisms are directly signaled by immune activation in their eukaryotic host.

Adhesins, Bacterial↗

PubMed2005

Simultaneous generation of CD8+ and CD4+ melanoma-reactive T cells by retroviral-mediated transfer of a single T-cell receptor.

Adoptive immunotherapy of cancer requires the generation of large numbers of tumor antigen-reactive T cells for transfer into cancer patients. Genes encoding tumor antigen-specific T-cell receptors can be introduced into primary human T cells by retroviral mediated gene transfer as a potential method of providing any patient with a source of autologous tumor-reactive T cells. A T-cell receptor-specific for a class I MHC (HLA-A2)-restricted epitope of the melanoma antigen tyrosinase was isolated from a CD4(+) tumor-infiltrating lymphocyte (TIL 1383I) and introduced into normal human peripheral blood lymphocytes by retroviral transduction. T-cell receptor-transduced T cells secreted various cytokines when cocultured with tyrosinase peptide-loaded antigen-presenting cells as well as melanoma cells in an HLA-A2-restricted manner, and could also lyse target cells. Furthermore, T-cell clones isolated from these cultures showed both CD8(+) and CD4(+) transduced T cells could recognize HLA-A2(+) melanoma cells, giving us the possibility of engineering class I MHC-restricted effector and T helper cells against melanoma. The ability to confer class I MHC-restricted tumor cell recognition to CD4(+) T cells makes the TIL 1383I TCR an attractive candidate for T-cell receptor gene transfer-based immunotherapy.

CD4-Positive T-Lymphocytes↗

PubMed2005

Antigen recognition and T-cell biology.

Despite the wealth of information that has been acquired regarding the way T cells recognize their targets, we are left with far more questions than answers regarding how to manipulate the immune response to better treat cancer patients. Clearly, most patients have a broad repertoire of T cells capable of recognizing their tumor cells. Despite the presence of these tumor reactive T cells and our ability to increase their frequency though vaccination or adoptive transfer, patients still progress. From the T cell side, defects in T cell signaling may account for much of our failure to achieve significant numbers of objective clinical responses. In spite of these negatives, the horizon does remain bright for T cell based immune therapy of cancer. The periodic objective clinical response tells us that immune therapy can work. Now that we know that cancer patients have the capacity to mount immune responses against their tumors, current and future investigations with agents which alter T cell function combined with vaccination or adoptive T cell transfer may help tip the balance towards effective immune therapies.

Animals↗

PubMed2005

Regulatory balance between the immune response of tumor antigen-specific T-cell receptor gene-transduced CD8 T cells and the suppressive effects of tolerogenic dendritic cells.

Tumor immune responses, including some immunotherapy strategies, can fail because of a number of reasons, such as poor tumor cell immunogenicity or local suppressive cytokine release by dendritic cells (DC) at tumor sites. The retroviral transfer of T-cell receptor (TCR) genes encoding tumor-specific receptors into T cells is a fascinating approach to bypass antigen-presenting cells and allow T cells to directly recognize antigen. It also allows the generation and expansion of potent antitumor cytotoxic T lymphocytes with defined cancer antigen specificities more readily than naive T cells. However, interleukin-10 (IL-10)-exposed dendritic cells (IL-10-DC) have been labeled tolerogenic because of the suppressive effects they have on T cell responses. Whether TCR gene-transduced effector CD8(+) T cells can break through suppressive functions mediated by IL-10-DC is not known. In the current study, we demonstrate the role of IL-10 in modifying the function of DC that otherwise would activate potent TCR gene-transduced T cells against tumor antigens. TCR gene-transduced T cells maintained their cytolytic activity in the presence of DC exposed to low doses of IL-10 during maturation; however, they lost this activity in an antigen-specific manner when exposed to DC matured with high doses of IL-10.

CD8-Positive T-Lymphocytes↗

PubMed2004

A new murine tumor model for studying HLA-A2-restricted anti-tumor immunity.

HLA-A2/K(b) transgenic mice have been powerful tools for studying HLA-A2-restricted anti-tumor immunity. Two tumor lines were established from an aged HLA-A2/K(b) transgenic mouse that developed spontaneous tumors in the right limb and lung. Histopathologic analysis of the tumor was consistent with an osteosarcoma that had metastasized to the lung. The cells from the primary tumor and the lung metastasis were adapted to culture and are designated Ag201P and Ag201M, respectively. Both Ag201P and Ag201M induced tumors in mice, indicating that the established cell lines are tumorigenic. Both tumor lines expressed HLA-A2/K(b) as assessed by RT-PCR and immunofluorescence analysis. Furthermore, the HLA-A2/K(b) molecules were functional on both tumor lines as demonstrated by their ability to present exogenously loaded HLA-A2-restricted peptides to human HLA-A2-restricted T cells. More importantly, endogenously expressed HLA-A2-restricted epitopes were processed and presented in the context of HLA-A2/K(b) in Ag201P and Ag201M cells to human HLA-A2-restricted T cells. Thus, Ag201P and Ag201M are two new murine tumor lines that express functional HLA-A2/K(b), and represent potentially invaluable tools to study HLA-A2-restricted anti-tumor immunity in mice.

Animals↗

PubMed2004

Retroviral transduction of peptide stimulated t cells can generate dual t cell receptor-expressing (bifunctional) t cells reactive with two defined antigens.

BACKGROUND: Tumors and viruses have developed many mechanisms to evade the immune system, including down-regulation of target antigens and MHC molecules. These immune escape mechanisms may be able to be circumvented by adoptively transferring T cells engineered to express two different T cell receptors, each specific for a different antigen or MHC restriction molecule. METHODS: PBMC from the blood of normal healthy donors were stimulated for three days with an antigenic peptide from cytomegalovirus (CMV) pp65. These CMV reactive cultures were transduced with a encoding the TIL 5 T cell receptor (TCR) that mediates recognition of the dominant epitope of the melanoma antigen MART-1. Following selection for transduced cells, the cultures were evaluated for recognition of CMV pp65 and MART-1 expressing targets. RESULTS: We were able to rapidly create bifunctional T cells capable of recognizing both CMV pp65 and MART-1 using a combination of HLA-A2 tetramer staining and intracellular staining for interferon-gamma. These bifunctional T cells were sensitive to very low levels of antigen, recognize MART-1+ tumor cells, and maintained their bifunctionality for over 40 days in culture. CONCLUSION: Bifunctional T cells can be engineered by transducing short term peptide stimulated T cell cultures. These bifunctional T cells may be more effective in treating patients with cancer or chronic virus infections because they would reduce the possibility of disease progression due to antigen and/or MHC loss variants.

Journal Article↗

PubMed2004

Cutting edge: identification of hepatitis C virus-specific CD8+ T cells restricted by donor HLA alleles following liver transplantation.

By necessity, human liver transplantation is performed across HLA barriers. As a result, intracellular infection of the allograft presents a unique immunologic challenge for the recipient's immune system. In this study, we describe the presence of HLA-A2-restricted, hepatitis C virus (HCV)-specific CD8+ T cells in liver transplant recipients in whom the allograft is HLA-A2 positive and the recipient is HLA-A2 negative. These memory-effector T cells are recipient derived and recognize HCV peptide uniquely in the context of HLA-A2. Furthermore, these cells were absent before the transplant, suggesting that the allograft is capable of selectively expanding naive CD8+ T cells. The in vitro specificity to donor HLA allele-restricted CD8+ T cells suggests that these cells may function to control HCV spread in the allograft.

Alleles↗

PubMed2003

Cutting edge: the NK cell receptor 2B4 augments antigen-specific T cell cytotoxicity through CD48 ligation on neighboring T cells.

2B4 is expressed on all NK and a subset of memory/effector CD8(+) T cells. 2B4 binds to CD48 and activates NK cytotoxicity, but its function on CD8(+) T cells is not clear. Furthermore, two isoforms of 2B4 (2B4S and 2B4L) exist in mice but the role of individual isoforms is not known. To address these questions, we generated primary T cell cultures from L(d)-specific 2C/Rag2(-/-) TCR transgenic mice and transduced them with 2B4S or 2B4L. 2B4S- or 2B4L-transduced T cells showed greater cytotoxicity over control cells against CD48(+) and CD48(-) targets, suggesting that ligation of 2B4 by CD48 on target cells was not necessary for 2B4 function. Rather, 2B4/CD48 interaction on adjacent T cells appeared to be critical for cytotoxicity. Therefore, 2B4 functions as a costimulator of CD8(+) T cells in MHC-restricted cytotoxicity. We conclude that 2B4/CD48 interactions among T cells themselves can augment CTL lysis of their specific targets.

Adjuvants, Immunologic↗

PubMed2003

CD8-independent tumor cell recognition is a property of the T cell receptor and not the T cell.

The CD8 coreceptor enhances T cell function by stabilizing the TCR/peptide/MHC complex and/or increasing T cell avidity via interactions with the intracellular kinases Lck and LAT. We previously reported a CD4(+) T cell (TIL 1383I), which recognizes the tumor-associated Ag tyrosinase in the context of HLA-A2. To determine whether CD8 independent tumor cell recognition is a property of the TCR, we used retroviral transduction to express the TIL 1383I TCR in the CD8(-) murine lymphoma, 58 alpha(-)/beta(-). Immunofluorescent staining of TCR-transduced cells with human TCR V beta subfamily-specific and mouse CD3-specific Abs confirmed surface expression of the transferred TCR and coexpression of mouse CD3. Transduced effector cells secreted significant amounts of IL-2 following Ag presentation by tyrosinase peptide-pulsed T2 cells as well as stimulation with HLA-A2(+) melanoma lines compared with T2 cells alone or HLA-A2(-) melanoma cells. Further analysis of TCR-transduced clones demonstrated a correlation between T cell avidity and cell surface expression of the TCR. Therefore, the TIL 1383I TCR has sufficient affinity to mediate recognition of the physiologic levels of Ag expressed by tumor cells in the absence of CD8 expression.

Animals↗

PubMed2003

Transfer of TCR genes into mature T cells is accompanied by the maintenance of parental T cell avidity.

The adoptive transfer of tumor-specific T cells expanded in vitro can be of significant therapeutic value in select cancer patients. This strategy is limited though, as it is often difficult, if not impossible, to obtain T cells of clinical value. The transfer of TCR genes to mature T cells to generate tumor-reactive T cells provides a potential mechanism to overcome these limitations. To evaluate the feasibility of such an approach and the quality of the resulting T cells, we generated replication-deficient retroviral vectors using the well-characterized OT-1 TCR genes. After transducing murine T cells, we were able to expand large numbers of Ag-specific T cells that were functionally active against tumor cells expressing the relevant Ag. Furthermore, we found that T cells expressing retrovirally encoded TCR had avidity that was similar to that of the parental clone. This maintenance of avidity was despite variable expression of the retrovirally encoded TCR and the presence of potentially competing endogenous TCRs. These results suggest that the inherent qualities of the TCR, as dictated by the coding sequence, are the most critical parameters in the generation of high-avidity T cells.

Animals↗