Biomedical subjects

Mary Jo Turk

Publications and source records attributed to Mary Jo Turk.

15 recordsLinked to original sources

PubMed2006

Adjuvanticity of plasmid DNA encoding cytokines fused to immunoglobulin Fc domains.

PURPOSE: Plasmid DNAs encoding cytokines enhance immune responses to vaccination in models of infectious diseases and cancer. We compared DNA adjuvants for their ability to enhance immunity against a poorly immunogenic self-antigen expressed by cancer. EXPERIMENTAL DESIGN: DNAs encoding cytokines that affect T cells [interleukin (IL)-2, IL-12, IL-15, IL-18, IL-21, and the chemokine CCL21] and antigen-presenting cells [granulocyte macrophage colony-stimulating factor (GM-CSF)] were compared in mouse models as adjuvants to enhance CD8+ T-cell responses and tumor immunity. A DNA vaccine against a self-antigen, gp100, expressed by melanoma was used in combination with DNA encoding cytokines and cytokines fused to the Fc domain of mouse IgG1 (Ig). RESULTS: We found that (a) cytokine DNAs generally increased CD8+ T-cell responses against gp100; (b) ligation to Fc domains further enhanced T-cell responses; (c) adjuvant effects were sensitive to timing of DNA injection; (d) the most efficacious individual adjuvants for improving tumor-free survival were IL-12/Ig, IL-15/Ig, IL-21/Ig, GM-CSF/Ig, and CCL21; and (e) combinations of IL-2/Ig+IL-12/Ig, IL-2/Ig+IL-15/Ig, IL-12/Ig+IL-15/Ig, and IL-12/Ig+IL-21/Ig were most active; and (f) increased adjuvanticity of cytokine/Ig fusion DNAs was not related to higher tissue levels or greater stability. CONCLUSIONS: These observations support the potential of cytokine DNA adjuvants for immunization against self-antigens expressed by cancer, the importance of timing, and the enhancement of immune responses by Fc domains through mechanisms unrelated to increased half-life.

Acute-Phase Reaction↗

PubMed2006

Agonist anti-GITR antibody enhances vaccine-induced CD8(+) T-cell responses and tumor immunity.

Immunization of mice with plasmids encoding xenogeneic orthologues of tumor differentiation antigens can break immune ignorance and tolerance to self and induce protective tumor immunity. We sought to improve on this strategy by combining xenogeneic DNA vaccination with an agonist anti-glucocorticoid-induced tumor necrosis factor receptor family-related gene (GITR) monoclonal antibody (mAb), DTA-1, which has been shown previously both to costimulate activated effector CD4(+) and CD8(+) T cells and to inhibit the suppressive activity of CD4(+)CD25(+) regulatory T cells. We found that ligation of GITR with DTA-1 just before the second, but not the first, of 3 weekly DNA immunizations enhanced primary CD8(+) T-cell responses against the melanoma differentiation antigens gp100 and tyrosinase-related protein 2/dopachrome tautomerase and increased protection from a lethal challenge with B16 melanoma. This improved tumor immunity was associated with a modest increase in focal autoimmunity, manifested as autoimmune hypopigmentation. DTA-1 administration on this schedule also led to prolonged persistence of the antigen-specific CD8(+) T cells as well as to an enhanced recall CD8(+) T-cell response to a booster vaccination given 4 weeks after the primary immunization series. Giving the anti-GITR mAb both during primary immunization and at the time of booster vaccination increased the recall response even further. Finally, this effect on vaccine-induced CD8(+) T-cell responses was partially independent of CD4(+) T cells (both helper and regulatory), consistent with a direct costimulatory effect on the effector CD8(+) cells themselves.

Animals↗

PubMed2006

Optimization of a self antigen for presentation of multiple epitopes in cancer immunity.

T cells recognizing self antigens expressed by cancer cells are prevalent in the immune repertoire. However, activation of these autoreactive T cells is limited by weak signals that are incapable of fully priming naive T cells, creating a state of tolerance or ignorance. Even if T cell activation occurs, immunity can be further restricted by a dominant response directed at only a single epitope. Enhanced antigen presentation of multiple epitopes was investigated as a strategy to overcome these barriers. Specific point mutations that create altered peptide ligands were introduced into the gene encoding a nonimmunogenic tissue self antigen expressed by melanoma, tyrosinase-related protein-1 (Tyrp1). Deficient asparagine-linked glycosylation, which was caused by additional mutations, produced altered protein trafficking and fate that increased antigen processing. Immunization of mice with mutated Tyrp1 DNA elicited cross-reactive CD8(+) T cell responses against multiple nonmutated epitopes of syngeneic Tyrp1 and against melanoma cells. These multi-specific anti-Tyrp1 CD8(+) T cell responses led to rejection of poorly immunogenic melanoma and prolonged survival when immunization was started after tumor challenge. These studies demonstrate how rationally designed DNA vaccines directed against self antigens for enhanced antigen processing and presentation reveal novel self epitopes and elicit multi-specific T cell responses to nonimmunogenic, nonmutated self antigens, enhancing immunity against cancer self antigens.

Animals↗

PubMed2006

Unraveling the complex relationship between cancer immunity and autoimmunity: lessons from melanoma and vitiligo.

A relationship between melanoma and vitiligo, a skin disorder characterized by the loss of melanocytes, has been postulated for many decades. In some cases, vitiligo is almost certainly a manifestation of autoimmune-mediated destruction of melanocytes. Melanocytes and melanoma cells share melanocyte differentiation antigens. Based on a number of observations, de novo vitiligo developing in patients with melanoma has been regarded as a sign of good prognosis. The immune system tolerates or ignores differentiation antigens because these antigens are self-derived. Therefore, immune tolerance or ignorance must be overcome to prime naive T and B cells to induce cancer immunity and autoimmunity against melanocyte differentiation antigens. Mouse models of concurrent melanoma and autoimmune vitiligo have revealed strategies to overcome immune ignorance or tolerance to melanocyte differentiation antigens: immunization with self-antigens as altered self (e.g., orthologues or mutated versions), expression in viral vectors, passive immunization with antibodies or T cells, incorporating potent adjuvants into active immunization, and blockade or removal of a downregulatory mechanism. Extensive investigations into the mechanisms that lead to tumor immunity and autoimmunity elicited by certain differentiation antigens have further revealed a variety of distinct cellular and molecular requirements, which are redundant and alternative.

Animals↗

PubMed2005

Folate receptor expression in carcinomas and normal tissues determined by a quantitative radioligand binding assay.

The folate receptor (FR) is a valuable therapeutic target that is highly expressed on a variety of cancers. The current development of folate-targeted cancer therapies has created the need for quantitating functional FRs in clinical specimens. In this article, we report on the creation of a highly sensitive radioactive binding method for quantitatively measuring FR expression in frozen tissue homogenates. Expression was positive in approximately 89% of human ovarian carcinomas but was negligible in both mucinous ovarian carcinomas and normal ovary. Expression was also significant in carcinomas of the kidney, endometrium, lung, breast, bladder, and pancreas. Normal tissues from humans and six different laboratory species were also analyzed; surprisingly, some interspecies variability in FR expression (especially in kidney, spleen, and lung tissue) was found. Interestingly, normal human lung tissue displayed high expression levels, whereas expression in normal lung of the other species was negligible. However, considering that folate-drug conjugates fail to accumulate in the lungs of patients, the consequence of this finding was not considered to be of clinical concern. Overall, this new methodology is reliable for determining functional FR expression levels in tissues, and it could possibly be a useful clinical test to determine patient candidacy for FR-targeted therapeutics.

Animals↗

PubMed2004

Folate-conjugated liposomes preferentially target macrophages associated with ovarian carcinoma.

The folate receptor (FR) is overexpressed on many epithelial cancers and has been exploited for targeted delivery of folate-linked liposomes to cancer cells in vitro. The present studies investigate the distribution of folate-targeted liposomes in a FR(+) mouse model of ovarian cancer. According to flow cytometric analysis, folate-conjugation of liposomes significantly enhanced their uptake into ovarian cancer cells and tumor-associated macrophages within tumor ascites fluid. Compared to ovarian cancer cells, macrophages acquired tenfold more liposomes, and approximately 50% of this uptake was FR-dependent. These results demonstrate that, in addition to their cancer cell-targeting properties, folate-liposomes may be useful for targeting drugs to tumor-associated macrophages in vivo.

Animals↗

PubMed2004

Concomitant tumor immunity to a poorly immunogenic melanoma is prevented by regulatory T cells.

Concomitant tumor immunity describes immune responses in a host with a progressive tumor that rejects the same tumor at a remote site. In this work, concomitant tumor immunity was investigated in mice bearing poorly immunogenic B16 melanoma. Progression of B16 tumors did not spontaneously elicit concomitant immunity. However, depletion of CD4(+) T cells in tumor-bearing mice resulted in CD8(+) T cell-mediated rejection of challenge tumors given on day 6. Concomitant immunity was also elicited by treatment with cyclophosphamide or DTA-1 monoclonal antibody against the glucocorticoid-induced tumor necrosis factor receptor. Immunity elicited by B16 melanoma cross-reacted with a distinct syngeneic melanoma, but not with nonmelanoma tumors. Furthermore, CD8(+) T cells from mice with concomitant immunity specifically responded to major histocompatibility complex class I-restricted epitopes of two melanocyte differentiation antigens. RAG1(-/-) mice adoptively transferred with CD8(+) and CD4(+) T cells lacking the CD4(+)CD25(+) compartment mounted robust concomitant immunity, which was suppressed by readdition of CD4(+)CD25(+) cells. Naturally occurring CD4(+)CD25(+) T cells efficiently suppressed concomitant immunity mediated by previously activated CD8(+) T cells, demonstrating that precursor regulatory T cells in naive hosts give rise to effective suppressors. These results show that regulatory T cells are the major regulators of concomitant tumor immunity against this weakly immunogenic tumor.

Adoptive Transfer↗

PubMed2004

Ligand binding and kinetics of folate receptor recycling in vivo: impact on receptor-mediated drug delivery.

Folate receptor-targeted cancer therapies constitute a promising treatment for the approximately one third of human cancers that overexpress the folate receptor (FR). However, the potencies of all folate-receptor targeted therapies depend on 1) the rate of folate-linked drug conjugate binding to the cancer cell surface, 2) the dose of folate conjugate that will saturate tumor cell surface FR in vivo, 3) the rate of FR internalization, unloading, and recycling back to the tumor cell surface for another round of conjugate uptake, and 4) the residence time of the folate conjugate before its metabolism or release from the cell. Because little information exists on any of these processes, we have undertaken to characterize them on both cancer cells in culture and solid tumors in live mice. We quantitate here the properties of FR saturation, internalization, recycling, and unloading in several cultured cancer cell lines and murine tumor models, and we describe the conditions that should maximize both the potencies and specificities of folate receptor-targeted therapies in vivo.

Animals↗

PubMed2004

Folate receptor-mediated targeting of therapeutic and imaging agents to activated macrophages in rheumatoid arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by inflammation of the joints and destruction of cartilage and bone, often compromising both the quality and duration of life. The disease pathology is complex, involving the infiltration and activation of various populations of immune cells along with the release of destructive inflammatory mediators into the synovium of affected joints. Although it is still debatable whether activated macrophages are the primary promoters of RA, emerging data clearly show that the biological activity of this subset of inflammatory cells greatly contributes to both the acute and chronic stages of the disease. The further discovery of folate receptor expression on these activated (but not quiescent) macrophages in both animal models and human patients with naturally occurring RA has opened the possibility of exploiting folic acid to target attached drugs to this population of pathologic cells. Indeed, recent studies have shown that folate-linked imaging and therapeutic agents can be selectively delivered to arthritic joints, allowing both visualization and treatment of RA, with little or no collateral toxicity to normal tissues. This review will first summarize data documenting specific expression of the folate receptor on activated macrophages and then focus on the development of folate-targeted diagnostic and therapeutic agents for guided intervention into rheumatoid arthritis.

Animals↗

PubMed2003

Immunity to melanoma: unraveling the relation of tumor immunity and autoimmunity.

Cancer cells express self-antigens that are weakly recognized by the immune system. Even though responses against autologous cells are difficult to induce, the immune system is still able to mount a response against cancer. The discovery of the molecular identity of antigens that are recognized by the immune system of melanoma patients has led to the elucidation of tumor immunity at a cellular and molecular level. Multiple pathways in both the priming and effector phases of melanoma rejection have been described. Animal models' active immunotherapies for melanoma show a requirement for the cellular compartment of the immune system in the priming phase, primarily CD4+T cells. More diverse elements are required for the effector phase, including components from the innate immune system (macrophages, complement and/or natural killer cells) and from the adaptive immune system (CD8+T cells and B cells). Minor differences in amino-acid sequences of antigens must determine the particular mechanisms involved in tumor rejection. Since the immune system contains T and B cells that recognize and reject autologous cells, a consequence of tumor immunity is potential autoimmunity. There are distinct pathways for tumor immunity and autoimmunity. The requirements for autoimmunity at the priming phase seem to be CD4+/IFN-gamma dependent while the effector mechanisms are alternative and redundant. Vitiligo (autoimmune hypopigmentation) can be mediated by T cells, FcgammaR+macrophages and/or complement.

Animals↗

PubMed2003

Immunity to cancer through immune recognition of altered self: studies with melanoma.

The adaptive immune system is capable of recognizing cancer through T- and B-cell receptors. However, priming adaptive immunity against self antigens is potentially a difficult task. Presentation of altered self to the immune system is a strategy to elicit immunity against poorly immunogenic antigens. We have shown that immunization with conserved paralogues of tumor antigens can induce adaptive immunity against self antigens expressed by cancer. Remarkably, cancer immunity elicited by closely related paralogues can generate distinct adaptive immune responses, either antibody or T-cell dependent. Cancer immunity induced by xenogeneic immunization follows multiple and alternative pathways. The effector phase of tumor immunity can be mediated by cytotoxic T cells or macrophages and perhaps natural killer cells for antibody-dependent immunity. Helper CD4+ T cells are typically, but not always, required to generate immunity. Autoimmunity is frequently observed following immunization. Cancer immunity and autoimmunity use overlapping mechanisms, and therefore they are difficult to uncouple, but distinct pathways can be discerned that open the eventual possibility of uncoupling tumor immunity from autoimmunity. Studies examining the molecular basis for immunogenicity of conserved paralogues are facilitating the development of new strategies to rationally design vaccines that trigger adaptive immune responses to cancer.

Animals↗

PubMed2002

Characterization of a novel pH-sensitive peptide that enhances drug release from folate-targeted liposomes at endosomal pHs.

Although liposomes have proven useful for the delivery of drugs and gene therapy vectors, their potencies are often compromised by poor unloading following uptake into their target cells. We have consequently explored the properties of a novel 29-residue amphipathic peptide that was designed by arrangement of hydrophobic and hydrophilic residues to disrupt liposomes at lower peptide concentrations than previously tested peptides. The peptide was indeed found to promote pH-dependent liposome unloading with improved efficiency. A peptide of the same sequence, but half the length, however, promoted pH-dependent permeabilization only at much higher concentrations. Further characterization of the longer peptide revealed that release of liposome contents (i) occurred at a pH of approximately 6, (ii) became less efficient as the size of the encapsulated cargo increased, and (iii) was moderately suppressed in cholesterol-containing liposomes. Use of this peptide to enhance the cytotoxicity of cytosine arabinoside encapsulated in folate-targeted liposomes demonstrated an increase in drug potency of approximately 30-fold. Gene expression by a serum-stable folate-targeted liposomal vector was also measurably enhanced by inclusion of the peptide. We conclude that intracellular unloading of liposomal contents can be significantly improved by co-encapsulation of an optimally designed, pH-sensitive peptide.

Amino Acid Sequence↗

PubMed2002

Folate-targeted imaging of activated macrophages in rats with adjuvant-induced arthritis.

OBJECTIVE: To determine whether overexpression of the high-affinity folate receptor (FR) on activated macrophages can be exploited to selectively target imaging agents to sites of inflammation in rats with adjuvant-induced arthritis (AIA). METHODS: Folic acid was conjugated to a (99m)Tc chelator (the complex termed EC20), and its distribution was visualized using gamma scintigraphy in healthy rats, rats with AIA, and arthritic rats that had been depleted of macrophages. To confirm that uptake was mediated by the FR, excess folic acid competition studies were conducted, and tissue FR levels were quantitated using a radioligand binding assay. Flow cytometry was also used to investigate uptake of folate conjugates into macrophages of both arthritic and healthy rats. RESULTS: EC20 concentrated in the arthritic extremities of diseased rats but not in the extremities of healthy rats. The intensity of images of affected tissues was greatly reduced in the presence of excess competing folic acid. The livers and spleens of arthritic animals also showed enhanced uptake of EC20 and increased levels of FR. Depletion of macrophages from arthritic animals reduced tissue FR content and concomitantly abolished uptake of EC20. In addition, macrophages isolated from livers of rats with AIA exhibited a significantly higher binding capacity for folate conjugates than did macrophages obtained from healthy rats. CONCLUSION: Although EC20 is currently undergoing clinical evaluation for use in the imaging of ovarian carcinomas, the present results suggest that it may also be useful for assaying the participation of activated macrophages in inflammatory processes such as rheumatoid arthritis.

Animals↗

PubMed2002

Multiple pathways to tumor immunity and concomitant autoimmunity.

The immune repertoire contains T cells and B cells that can recognize autologous cancer cells. This repertoire is directed against self, and in some cases altered self (mutations). Priming immune responses against self antigens can be difficult. Strategies are presented using altered self to elicit immunity against self in poorly immunogenic tumor models. Mechanisms underlying immunity to self antigens on cancer cells show that the immune system can use diverse strategies for cancer immunity, in both the immunization and the effector phases. CD4+ T cells are typically, but not always, required for immunization. The effector phase of tumor immunity can involve cytotoxic T cells, macrophages with activating Fc receptors, and/or killer domain molecules. This diversity in the effector phase is observed even when immunizing with conserved paralogs. A consequence of tumor immunity is potentially autoimmunity, which may be undesirable. Autoimmunity uses similar mechanisms as tumor immunity, but tumor immunity and autoimmunity can uncouple. These studies open up strategies for active immunization against cancer.

Animals↗

PubMed2002

GM-CSF DNA induces specific patterns of cytokines and chemokines in the skin: implications for DNA vaccines.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) enhances immune responses by inducing the proliferation, maturation, and migration of dendritic cells, and the expansion and differentiation of B and T lymphocytes. Similar biological effects have been observed with the use of GM-CSF DNA in mouse models for therapy of cancer and infectious diseases, and its use is currently being investigated in clinical trials in combination with DNA vaccines. To further understand the adjuvant mechanisms of GM-CSF DNA, we examined early events following its administration. We found measurable levels of GM-CSF protein in the skin and muscle, as well as in serum. Measurements of other cytokine and chemokine levels revealed differential expression patterns over time. The early response was characterized by high levels of inflammatory molecules, including IL-1beta, IL-6, TNFalpha, RANTES, MIP-1alpha and MCP-1, later followed by expression of precursor Th1 cytokines, IL-12 and IL-18, concomitant with IFNgamma production. Local production of GM-CSF protein also resulted in the early recruitment of polymorphonuclear cells and later recruitment of mononuclear cells, including dendritic cells. These results have implications for understanding early events in the immune response to DNA vaccines, and provide a basis for development of new approaches to cancer vaccines, including the use of cytokine genes as adjuvants.

Adjuvants, Immunologic↗