Unknown,Transcriptomics,Genomics,Proteomics

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Studies in a murine B16 melanoma model show that persistent antigen at vaccination sites induces CD8+ T cell sequestration, dysfunction and deletion

ABSTRACT: To understand why cancer vaccine-induced T cells often fail to eradicate tumors, we studied immune responses in mice vaccinated with gp100 peptide emulsified in incomplete Freund's adjuvant (IFA), commonly used in clinical cancer vaccine trials. After gp100 peptide/IFA vaccination, tumor-specific CD8+ T cells (adoptively transferred from gp100-specific TCR-transgenic pmel-1 mice) accumulated not in tumors but at the persisting, antigen-rich vaccination site. Once there, primed T cells became dysfunctional and underwent antigen-driven, IFN-γ and FasL-mediated apoptosis, resulting in systemic hyporesponsiveness to subsequent vaccination. Provision of anti-CD40 antibody, TLR7 agonist and interleukin-2 (covax) reduced T cell apoptosis but did not prevent vaccination site sequestration. A non-persisting vaccine formulation shifted T cell localization towards tumors, inducing superior anti-tumor activity. Short-lived formulation also reduced systemic T cell dysfunction and promoted memory formation, as shown by gene expression profiling and other measures. Persisting peptide/IFA vaccine depots, currently used to vaccinate cancer patients, can induce specific T cell sequestration at vaccination sites followed by dysfunction and deletion; short-lived depot formulations may overcome these limitations and result in greater therapeutic efficacy of peptide-based cancer vaccines. To study the fate of melanoma-specific CD8+ T cells after peptide vaccination, we tracked T cell receptor-transgenic pmel-1 T cells in mice vaccinated with heteroclitic gp100_25-33 peptide emulsified in IFA. Splenic pmel-1 CD8+ T cells were purified at 6 and 21 days after vaccination with either gp100/IFA/covax or gp100/saline/covax, and then their total RNA was extracted and used for comparison by gene expression profiling.

ORGANISM(S): Mus musculus

SUBMITTER: Wencai Ma

PROVIDER: E-GEOD-43929 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The activation of TLR-MyD88 (Toll like receptor- Myeloid differentiation factor 88) signaling within T cells functions as a potent costimulatory signal that boosts antitumor and antiviral responses. However, the molecular mechanisms underlying the costimulatory processes are poorly understood. We compared microarray gene analysis data between TLR1-TLR2 stimulated and unstimulated T cell receptor transgenic âpmelâ and MyD88-/-pmel CD8+ T cells and identified changes in the expression levels of several TNF family members. In particular, TLR-stimulation increased 4-1BB levels in pmel but not in MyD88-/-pmel T cells. A link between 4-1BB and TLR1-TLR2 signaling in CD8+ T cells was highlighted by in fact that 4-1BB-/- T cells exhibited suboptimal responses to TLR1-TLR2 agonist, but responded normally to CD28 or OX40 costimulation. Moreover, blocking 4-1BB signaling with antibodies also hindered the costimulatory effects of the TLR1-TLR2 agonist. The elevated levels of 4-1BB transcripts in TLR1-TLR2âstimulated cells were not due to increased mRNA stability nor increased histone activation but instead were associated with increased binding of p65 and c-Jun to two distinct 4-1BB promoter sites. Combining TLR1-TLR2 ligand with an agonistic anti-4-1BB antibody enhanced the antitumor activity in mice with established melanoma tumors. These studies reveal that the costimulatory effects of TLR1-TLR2 signaling in CD8+ T cells are in part mediated by 4-1BB and are important for mounting an effective antitumor immune response. CD8+ T cells from the B6.Cg-Thy1/Cy Tg(TcraTcrb)8Rest/J mice, referred to as âpmelâ T cells or from MyD88 knockout pmel mice (MyD88â/âpmel) were sorted. pmel and MyD88â/âpmel T cells were activated using MyD88â/â CD8 T cell-depleted splenocytes pulsed with 10ng/ml of mgp100. This was with or without 10Âµg/ml of Pam3CSK4. pmel or MyD88â/âpmel CD8 T cells were enriched and used for the extraction of RNA used for genomic analysis.

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Studies in a murine B16 melanoma model show that persistent antigen at vaccination sites induces CD8+ T cell sequestration, dysfunction and deletion

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