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Biomedical subjects

Linda A Snyder

Publications and source records attributed to Linda A Snyder.

7 recordsLinked to original sources
PubMed2006

A MUC1/IL-18 DNA vaccine induces anti-tumor immunity and increased survival in MUC1 transgenic mice.

MUC1 (mucin 1) is a tumor-associated antigen that is overexpressed in many adenocarcinomas. Active immunotherapy targeting tumors expressing MUC1 could have great treatment value. MUC1 DNA vaccines were evaluated in MUC1 transgenic (MUC1.Tg) mice challenged with MC38/MUC1+ tumor cells. Vaccination with MUC1 plasmid DNA (pMUC1) alone was insufficient to induce tumor protection. However, co-administration of pMUC1 with a plasmid encoding murine interleukin-18 (pmuIL-18) resulted in significant tumor protection and survival after tumor challenge. Protection was durable in the absence of additional vaccination, as demonstrated by continued protection of vaccinated mice following tumor rechallenge. Mice surviving challenges with MC38/MUC1+ cells showed significant protection after challenge with MUC1(-) MC38 tumor cells, suggesting that these mice had developed immune responses to epitopes shared between the tumor cell lines. Antibody-mediated depletion of lymphocyte subsets demonstrated that protection was due largely to CD4+ T cells. This work demonstrates that a naked DNA vaccine can break tolerance to MUC1 and induce an immune response capable of mediating both significant protection from tumor challenge and increased survival.

Adjuvants, Immunologic↗
PubMed2006

Engineering human IL-18 with increased bioactivity and bioavailability.

Cytokines in plasmid form can act as potent adjuvants when co-administered with DNA vaccines, resulting in an enhanced immune response to the DNA-encoded antigen. This is true of interleukin-18 (IL-18), which has been shown to serve as an adjuvant in conjunction with certain DNA vaccines. To determine if the properties of IL-18 could be optimized for use as a DNA vaccine adjuvant, a model of IL-18/IL-18R binding was developed to identify variants of human IL-18 that were predicted to improve receptor interactions and potentially bioactivity. The linkage of mature IL-18 to a secretion signal sequence provided improved protein expression from mammalian cells and signal peptidase cleavage of this protein produced the authentic N-terminus. The IL-18 variant proteins secreted this way were bioactive, as demonstrated by their ability to induce interferon gamma (IFNgamma) expression by human peripheral blood mononuclear cells (PBMCs) and to bind to IL-18R, as demonstrated by BIAcore analysis. The IL-18 variants were inhibited by IL-18 binding protein (IL-18BP), the soluble inhibitor of IL-18, as measured by neutralization of the IFNgamma response in PBMCs. One variant, V11I/T63A, demonstrated increases both in bioactivity and mammalian cell expression as compared to native IL-18, indicating that this molecule may be particularly well suited for use as a DNA-encoded vaccine adjuvant.

Amino Acid Sequence↗
PubMed2006

Cloning and sequencing of the cynomolgus monkey prostate specific antigen cDNA.

BACKGROUND: Prostate-specific antigen (PSA) is an invaluable tumor marker for the detection of early prostate cancer, and can be a target for active immunotherapy of prostate cancer. We wanted to assess the usefulness of the cynomolgus monkey (Macaca fascicularis) as a relevant animal model to evaluate PSA-specific therapies. METHODS: RNA was isolated from the prostate of cynomolgus monkeys, and PSA gene products were amplified by reverse transcriptase-polymerase chain reaction using primers from conserved regions of human and rhesus monkey (Macaca mulatta) PSA genes. These amplified products were then sequenced. RESULTS: The cynomolgus PSA amino acid sequence is 89.7% identical to the human PSA gene, and 99.2% identical to the rhesus PSA amino acid sequence. Like the human and rhesus PSA genes, an open-reading frame of 261 amino acids was identified for the cynomolgus gene. Expression of the cynomolgus PSA gene appears to be restricted to the prostate, as it is in humans. CONCLUSIONS: The high identity between human and cynomolgus PSA sequences suggests that the cynomolgus monkey should be studied further for its potential as a large animal model to evaluate PSA-specific therapies.

3' Untranslated Regions↗
PubMed2006

Regulation of vascular endothelial growth factor expression by EMMPRIN via the PI3K-Akt signaling pathway.

Extracellular matrix metalloproteinase (MMP) inducer (EMMPRIN) is a cell surface glycoprotein overexpressed in many solid tumors. In addition to its ability to stimulate stromal MMP expression, tumor-associated EMMPRIN also induces vascular endothelial growth factor (VEGF) expression. To explore the underlying signaling pathways used by EMMPRIN, we studied the involvement of phosphoinositide 3-kinase (PI3K)-Akt, mitogen-activated protein kinase (MAPK), JUN, and p38 kinases in EMMPRIN-mediated VEGF regulation. Overexpression of EMMPRIN in MDA-MB-231 breast cancer cells stimulated the phosphorylation of only Akt and MAPKs but not that of JUN and p38 kinases. Conversely, inhibition of EMMPRIN expression resulted in suppressed Akt and MAPK phosphorylation. Furthermore, the PI3K-specific inhibitor LY294002 inhibited VEGF production by EMMPRIN-overexpressing cells in a dose- and time-dependent manner. On the other hand, the MAPK inhibitor U0126 did not affect VEGF production. In vivo, EMMPRIN-overexpressing tumors with elevated VEGF expression had a high level of phosphorylation of Akt and MAPK. Finally, when fibroblast cells were treated with recombinant EMMPRIN, Akt kinase but not MAPK was phosphorylated concomitant with an increase in VEGF production. Both the activation of Akt kinase and the induction of VEGF were specifically inhibited with a neutralizing antibody to EMMPRIN. Our results show that in both tumor and fibroblast cells EMMPRIN regulates VEGF production via the PI3K-Akt pathway but not via the MAPK, JUN, or p38 kinase pathways.

Animals↗
PubMed2005

Interleukin-18 enhances Th1 immunity and tumor protection of a DNA vaccine.

DNA vaccines show efficacy in many preclinical models, but these results have not yet translated to consistent clinical efficacy. Co-administration of molecularly encoded adjuvants is one approach that may enable DNA vaccines to achieve enhanced immune response induction in humans. Interleukin-18 (IL-18) is a Th1-type cytokine that has been shown to augment the activity of DNA vaccines in some preclinical models. A prostate-specific antigen (PSA) DNA vaccine was tested in a mouse tumor model system to explore the impact of co-administration of a pIL-18 plasmid. Low doses of the pPSA vaccine were not capable of inducing tumor protection, but when pIL-18 was co-administered, complete tumor protection was observed in all mice. Tumor protection was mediated by both CD4(+) and CD8(+) T cells. Detailed analysis of the immune response in mice immunized with either pPSA or pPSA/pIL-18 demonstrated that pIL-18 skewed the PSA-specific immune response toward Th1. More importantly, stronger CD4(+) and CD8(+) T cell responses developed in the pPSA/pIL-18-immunized mice, with faster kinetics. These results suggest that IL-18 is a powerful adjuvant molecule that can enhance the development of antigen-specific immunity and vaccine efficacy.

Adjuvants, Immunologic↗
PubMed2005

Induction of Th1-type immunity and tumor protection with a prostate-specific antigen DNA vaccine.

Prostate specific antigen (PSA) is a serum marker that is widely used in the detection and monitoring of prostate cancer. Though PSA is a self-antigen, T cell responses to PSA epitopes have been detected in healthy men and prostate cancer patients, suggesting it may be used as a target for active immunotherapy of prostate cancer. A PSA DNA vaccine (pPSA) was evaluated in mice and monkeys for its ability to induce antigen-specific immune responses. Mice immunized intradermally with pPSA demonstrated strong PSA-specific humoral and cellular immunity. The anti-PSA immune responses were skewed toward Th1, as shown by high IFNgamma and IL-2 production. The immune response was sufficient to protect mice from challenge with PSA-expressing tumor cells. Tumor protection was durable in the absence of additional vaccination, as demonstrated by protection of vaccinated mice from tumor rechallenge. Furthermore, pPSA vaccination induced PSA-specific antibody titers in male cynomolgus monkeys, which express a closely related PSA gene. These results demonstrate that vaccination with pPSA may be able to break tolerance and can induce an immune response that mediates tumor protection.

Animals↗