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Keith L Knutson

Publications and source records attributed to Keith L Knutson.

31 records · Page 2Linked to original sources
PubMed2003

Immunologic principles and immunotherapeutic approaches in ovarian cancer.

Ovarian cancer is an immunogenic tumor, and numerous antigens have been identified in recent years. Several of these antigens are important in regulating tumor growth and may be ideal targets for the development of immune-based strategies. In the absence of immunologic intervention, tumors evade the immune system by several mechanisms, most notably tolerance and immunosuppression. As understanding of the immune response improves, strategies are being designed to circumvent T-cell tolerance to self-antigens through modulation of APC function. In addition, techniques are being developed to identify reverse ovarian cancer-induced immune evasion tactics. The type of the immune-based therapy to apply varies with disease burden. It is hoped that discoveries at the bench along with lessons learned in prior clinical trials soon will allow clinicians to develop rationally based immunologic strategies to treat and prevent ovarian cancer.

Animals↗
PubMed2003

Pilot study of an HLA-A2 peptide vaccine using flt3 ligand as a systemic vaccine adjuvant.

A pilot vaccine study was conducted to test the safety and immunological efficacy of four monthly immunizations of an MHC class I peptide vaccine, the E75 HLA-A2 epitope from HER-2/neu, using flt3 ligand as a systemic vaccine adjuvant. Twenty HLA-A2-expressing subjects with advanced stage prostate cancer were randomly assigned to one of four immunization or treatment schedules: (a) Flt3 ligand (20 microg/kg per day) administered subcutaneously daily for 14 days on a 28-day cycle, monthly for four months; (b) flt3 ligand course as above with the E75 peptide vaccine administered on day 7 of each flt3 ligand cycle; (c) flt3 ligand course as above with the E75 peptide vaccine administered on day 14 of each flt3 ligand cycle; or (d) E75 peptide admixed with granulocyte-macrophage colony-stimulating factor and administered intradermally once every 28 days, as has previously been reported. The primary endpoints of the study were the determination of safety and immunological efficacy in generating E75-specific T cells as determined by peptide-specific interferon-gamma ELIspot. Adverse events included one grade 3 skin reaction and the development of grade 2 autoimmune hypothyroidism in two subjects with preexisting subclinical autoimmune hypothyroidism. Dendritic cells were markedly increased in the peripheral blood of subjects receiving flt3 ligand with each repetitive cycle, but augmentation of antigen-presenting cells within the dermis was not observed. Apart from a single subject, no significant peptide-specific T-cell responses were detected by ELIspot, whereas delayed-type hypersensitivity responses were detectable in control subjects and in subjects receiving peptide vaccine early in the course of flt3 ligand administration. The absence of robust peripheral immune responses in the current study may be attributable to the small numbers of subjects or differences in the subject population. In addition, the inability of fit3 ligand to augment the number of peripheral skin antigen-presenting cells may have contributed to the absence of robust peptide-specific immunity detectable in the peripheral blood of immunized subjects treated with flt3 ligand.

Adenocarcinoma↗
PubMed2003

Soluble cytokines can act as effective adjuvants in plasmid DNA vaccines targeting self tumor antigens.

There are few vaccination strategies available for the reproducible generation of a cytotoxic T cell (CTL) response, particularly in the setting of immunizing against a tumor antigen. Plasmid-based DNA vaccination offers several advantages as compared to MHC class I peptide-based vaccines or DNA immunization using viral vectors. Plasmid-based DNA vaccines are easily produced, can potentially elicit both an MHC class I and class II response, and have little infectious potential. Plasmid-based vaccines, however, have been poorly immunogenic. The systemic immune response generated after plasmid vaccination relies on in vivo transfection of local antigen presenting cells (APC) and both direct presentation and "cross priming" of antigen by professional and non-professional APC. Therefore, methods to enhance the function of APC, such as simultaneous inoculation with plasmids encoding cytokine genes, has resulted in an enhancement of detectable immunity after vaccination. We questioned whether local application of soluble cytokines would be effective in enhancing the systemic immune response elicited after DNA vaccination. Using a self-tumor antigen model, we vaccinated rats with a plasmid-based rat neu intracellular domain (ICD) DNA construct and either no adjuvant, soluble GM-CSF, or IL-12. We demonstrate that the addition of soluble GM-CSF or IL-12 to rat neu ICD DNA vaccination elicits detectable neu specific T cell immunity; specifically the generation of CTL. Antibodies directed against rat neu were not elicited with this approach, indicating that the neu specific T cell immune response elicited with plasmid DNA was skewed towards cell-mediated rather than humoral immunity.

Adjuvants, Immunologic↗
PubMed2003

Plasmid-based vaccines encoding rat neu and immune stimulatory molecules can elicit rat neu-specific immunity.

DNA vaccines are ideally suited for immunizing against tumor antigens because constructs can be formulated that not only encode the tumor antigen but also encode molecules chosen to improve the ability to elicit an antitumor response. Ligands expressed on antigen-presenting cells associated with stimulating a robust T-cell response are excellent candidates for inclusion in a DNA vaccine. Mice transgenic for the HER-2/neu homologue, rat neu, were immunized with full-length rat neu cDNA given alone or in combination with plasmids encoding costimulatory molecules CD80 or CD86 and the ligand for CD137 (CD137L). Intradermal injection of the plasmid constructs resulted in both plasmid transcript and antigen protein expression being detected in lymph nodes draining the injection site. Immunization with plasmids encoding the neu antigen along with plasmids encoding CD137L and either CD80 or CD86 resulted in the generation of neu-specific antibodies that induced phopshorylation of the neu tyrosine kinase and inhibited the growth of cultured tumor cells overexpressing neu. Survival of animals was significantly prolonged after immunization with vaccines encoding neu together with the costimulatory molecules. Although tumors eventually occurred in the vaccinated animals, they were markedly infiltrated with CD4+ T cells. DNA vaccines encoding neu, when given in combination with both CD137L and either CD80 or CD86, can induce cellular and humoral immunity and result in an antitumor effect.

Animals↗
PubMed2002

Generation of T-cell immunity to the HER-2/neu protein after active immunization with HER-2/neu peptide-based vaccines.

PURPOSE: The HER-2/neu protein is a nonmutated tumor antigen that is overexpressed in a variety of human malignancies, including breast and ovarian cancer. Many tumor antigens, such as MAGE and gp100, are self-proteins; therefore, effective vaccine strategies must circumvent tolerance. We hypothesized that immunizing patients with subdominant peptide epitopes derived from HER-2/neu, using an adjuvant known to recruit professional antigen-presenting cells, granulocyte-macrophage colony-stimulating factor, would result in the generation of T-cell immunity specific for the HER-2/neu protein. PATIENTS AND METHODS: Sixty-four patients with HER-2/neu-overexpressing breast, ovarian, or non-small-cell lung cancers were enrolled. Vaccines were composed of peptides derived from potential T-helper epitopes of the HER-2/neu protein admixed with granulocyte-macrophage colony-stimulating factor and administered intradermally. Peripheral-blood mononuclear cells were evaluated at baseline, before vaccination, and after vaccination for antigen-specific T-cell immunity. Immunologic response data are presented on the 38 subjects who completed six vaccinations. Toxicity data are presented on all 64 patients enrolled. RESULTS: Ninety-two percent of patients developed T-cell immunity to HER-2/neu peptides (stimulation index, 2.1 to 59) and 68% to a HER-2/neu protein domain (stimulation index range, 2 to 31). Epitope spreading was observed in 84% of patients and significantly correlated with the generation of a HER-2/neu protein-specific T-cell immunity (P =.03). At 1-year follow-up, immunity to the HER-2/neu protein persisted in 38% of patients. CONCLUSION: The majority of patients with HER-2/neu-overexpressing cancers can develop immunity to both HER-2/neu peptides and protein. In addition, the generation of protein-specific immunity, after peptide immunization, was associated with epitope spreading, reflecting the initiation of an endogenous immune response. Finally, immunity can persist after active immunizations have ended.

Adult↗
PubMed2002

Flt3 ligand as a vaccine adjuvant in association with HER-2/neu peptide-based vaccines in patients with HER-2/neu-overexpressing cancers.

Dendritic cells (DCs) are potent antigen-presenting cells and have shown promise to function as "natural" vaccine adjuvants. Currently, most cancer vaccine trials using DCs generate autologous DCs ex vivo for each patient. Systemic treatment with Flt3 ligand (FL) results in a marked increase of DCs in tissues such as spleen and lymph nodes in mice and in the peripheral blood and skin of humans. In light of these observations, we questioned whether FL could be used systemically as a vaccine adjuvant to stimulate DC mobilization in vivo, circumventing the need to generate DCs ex vivo. Ten patients with HER-2/neu-overexpressing cancer were enrolled in a phase 1 study to receive a HER-2/neu peptide-based vaccine targeting the intracellular domain of the HER-2/neu protein. All patients received 20 microg/kg FL per day subcutaneously for 14 days. Five patients received the HER-2/neu peptide-based vaccine alone on day 7 of the 14-day cycle, and 5 patients received the vaccine admixed with 150 microg granulocyte macrophage-colony-stimulating factor (GM-CSF) on day 7 of the FL cycle. T-cell proliferative responses to HER-2/neu peptides and intracellular domain protein suggest that vaccine regimens including FL as an adjuvant were not effective in eliciting a significant HER-2/neu protein-specific T-cell proliferative response. However, including FL as a vaccine adjuvant was effective in boosting the precursor frequency of interferon-gamma-secreting HER-2/neu-specific T cells. The small sample size of each group, however, did not allow a statistically significant comparison of immune responses between the FL alone and FL with GM-CSF arms. Finally, vaccine regimens including FL as a vaccine adjuvant were associated with the development of apparent autoimmune phenomena in some patients.

Adjuvants, Immunologic↗
PubMed2002

Clonal diversity of the T-cell population responding to a dominant HLA-A2 epitope of HER-2/neu after active immunization in an ovarian cancer patient.

Natural antigen processing and presentation of antigen is thought to be important for the generation of a broad functional repertoire of antigen-specific T cells. In this study, the T-cell repertoire to an immunodominant human leukocyte antigen A2 (HLA-A2) binding peptide epitope of HER-2/neu, p369-377, was examined in a patient following immunization with a peptide-based vaccine consisting of helper peptides encompassing HLA-A2 peptide epitopes. The responding T-cell repertoire generated was both phenotypically and functionally diverse. A total of 21 p369-377 clones were generated from this patient. With the exception of two clones, all clones were CD3(+). Sixteen of the clones were CD8(+)/CD4(-). Five of the clones were CD4(+)/CD8(-), despite being generated with an HLA-A2 binding peptide. Nineteen of 21 of clones expressed the alpha beta-T-cell receptor (TCR). The remaining two clones expressed the gamma delta T-cell response (TCR). Selected alpha beta-TCR clones, both CD8(+) and CD4(+), could lyse HLA-A2 transfected HER2 overexpressing tumor cells and p369-377-loaded B-lymphoblastic cell line. In addition to their lytic capabilities these clones could be induced to produce interferon-gamma (IFN-gamma) specifically in response to p369-377 peptide stimulation. The 2 gamma delta-TCR clones expressed CD8 and lysed HLA-A2(+) HER-2/neu(+) tumor cells, but not HLA-A2(-) HER-2/neu(+) tumor cells. One of gamma delta-TCR clones also released IFN-gamma directly in response to p369-377 stimulation. These results suggest that a tumor antigen TCR, directed against a specific epitope, can be markedly polyclonal at multiple levels including CD4/CD8 and TCR.

Amino Acid Sequence↗
PubMed2002

Adoptive T-cell therapy for the treatment of solid tumours.

Solid tumours can be eradicated by infusion of large amounts of tumour-specific T-cells in animal models. The successes seen in preclinical models, however, have not been adequately translated to human disease due, in part, to the inability to expand tumour antigen-specific T-cells ex vivo. Polyclonality and retention of antigen-specificity are two important properties of infused T-cells that are necessary for successful eradication of tumours. Investigators are beginning to evaluate the impact of attempting to reconstitute full T-cell immunity representing both major T-cell subsets, cytolytic T-cells and T-helper (Th) cells. One of the more important and often overlooked steps of successful adoptive T-cell therapy is the ex vivo expansion conditions, which can dramatically alter the phenotype of the T-cell. A number of cytokines and other soluble activation factors that have been characterised over the last decade are now available to supplement in vitro antigen presentation and IL-2. Newer molecular techniques have been developed and are aimed at genetically altering the characteristics of T-cells including their antigen-specificity and growth in vivo. In addition, advanced imaging techniques, such as positron emission tomography (PET), are being implemented in order to better define the in vivo function of ex vivo expanded tumour-specific T-cells.

Animals↗
PubMed2002

Immunization of cancer patients with a HER-2/neu, HLA-A2 peptide, p369-377, results in short-lived peptide-specific immunity.

Ideally, vaccines should be designed to elicit long-lived immunity. The goal of this study was to determine whether HER-2/neu peptide-specific CD8+ T-cell immunity could be elicited using an immunodominant HER-2/neu-derived HLA-A2 peptide alone in the absence of exogenous help. Granulocyte macrophage colony-stimulating factor (GM-CSF) was used as adjuvant. Six HLA-A2 patients with HER-2/neu-overexpressing cancers received 6 monthly vaccinations with a vaccine preparation consisting of 500 microg of HER-2/neu peptide, p369-377, admixed with 100 microg of GM-CSF. The patients had either stage III or IV breast or ovarian cancer. Immune responses to the p369-377 were examined using an IFN-gamma enzyme-linked immunosorbent spot assay. Before vaccination, the median precursor frequency (range), defined as precursors per 10(6) peripheral blood mononuclear cell, to p369-377 was 0 (no range). After vaccination, the median precursor frequency to p369-377 in four evaluable patients was 0 (0-116). Overall, HER-2/neu peptide-specific precursors developed to p369-377 in two of four evaluable subjects. The responses were short-lived and not detectable at 5 months after the final vaccination. Immunocompetence was evident, because patients had detectable enzyme-linked immunosorbent spot responses to tetanus toxoid and influenza. These results demonstrate that HER-2/neu MHC class I epitopes can induce HER-2/neu peptide-specific IFN-gamma-producing CD8+ T cells. However, the magnitude of the responses were low, as well as short-lived, suggesting that CD4+ T-cell help is required for lasting immunity to this epitope.

Aged↗
PubMed2002

GMK (Progenics Pharmaceuticals).

Progenics Pharmaceuticals is developing GMK vaccine (a ganglioside conjugate vaccine coupled to keyhole limpet hemocyanin and formulated with the adjuvant QS-21), licensed from the Memorial Sloan-Kettering Cancer Center, for the potential treatment of melanoma and other cancers [194258], [325284]. It was previously under co-development with Bristol-Myers Squibb, but in May 2001, all rights to the GMK vaccine were returned to Progenics [409168]. It was the first of a new class of ganglioside conjugate vaccine evaluated by Progenics [194258]. GMK vaccination induces antibodies against GM2 ganglioside capable of specifically killing melanoma cells. Melanoma patients with antibodies against GM2 ganglioside have significantly improved disease-free and overall survival compared to antibody-negative subjects. The vaccine is undergoing two phase III trials, the first comparing GMK to high-dose IFNalpha in melanoma patients with more serious disease and at a high risk of relapse, and the second, in collaboration with the European Organization for Research and Treatment of Cancer, comparing GMK (14 doses of GMK over three years) to no treatment other than close monitoring of malignant melanoma patients at immediate risk of relapse [409168]. In February 1999, Lehman Brothers predicted that the vaccine had a 50% probability of reaching market, with an estimated first launch date in 2002. The analysts predicted potential peak sales in 2008 of $150 million in the US and $100 million in the rest of the world at that time [319225]. In January 2000, Lehman Brothers expected that an NDA filing would take place in 2002, with possible launch of the vaccine in 2003. In addition, Lehman Brothers estimated potential peak sales at $500 million [357788]. In August 2000, Punk, Ziegel & Company predicted that Progenics Pharmaceuticals will become sustainably profitable in 2003 following the launch of GMK and PRO-542 in 2002 [390063]. In July 2001, Ladenburg Thalmann predicted a $257 million market potential for GMK in the US, with the non-US market equivalent to the US market. A launch date of 2005 in the US, with a worldwide launch in 2006, was estimated [433347].

Animals↗
PubMed2002

Technology evaluation: DCVax, Northwest Biotherapeutics.

DCVax, a dendritic cell-based immunotherapy, is an active immunization platform being developed by Northwest Biotherapeutics for the potential treatment of multiple malignancies, including hormone-refractory metastatic prostate cancer, non-small-cell lung cancer, renal cancer and glioblastoma multiforme. The DCVax platform is tailored to a specific cancer type with either purified tumor-specific antigen or tumor cell extracts derived from patients at the time of resection. Phase I/II clinical trials of DCVax-Prostate have been completed, and phase III clinical trials have recently been initiated. DCVax-Brain is currently undergoing phase II clinical trials, and DCVax-Lung recently received approval from the US FDA for phase I clinical trials.

Brain Neoplasms↗