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Chitosan is a surprising negative modulator of cytotoxic CD8+ T cell responses elicited by adenovirus cancer vaccines
Journal article   Peer reviewed

Chitosan is a surprising negative modulator of cytotoxic CD8+ T cell responses elicited by adenovirus cancer vaccines

Caitlin D Lemke, Jessica B Graham, Sean M Geary, Gideon Zamba, David M Lubaroff and Aliasger K Salem
Molecular pharmaceutics, Vol.8(5), pp.1652-1661
10/03/2011
DOI: 10.1021/mp100464y
PMCID: PMC3562499
PMID: 21780831
url
https://www.ncbi.nlm.nih.gov/pmc/articles/3562499View
Open Access

Abstract

Adjuvants modulate protective CD8(+) T cell responses generated by cancer vaccines. We have previously shown that immunostimulatory cytosine-phosphodiester-guanine (CpG) oligodeoxynucleotide (ODN) significantly augments tumor protection in mice given adenovirus cancer vaccines. Here, we examined the impact of chitosan, another candidate vaccine adjuvant, on protection conferred by adenovirus cancer vaccines. Unexpectedly, immunization of mice with adenovirus cancer vaccines in combination with chitosan provided little protection against tumor challenge. This directly correlated with the reduced detection of Ag-specific CD8(+) T cells, interferon-γ (IFN-γ) production, and cytotoxic T cell activity. We ruled out immunosuppressive regulatory T cells since the frequency did not change regardless of whether chitosan was delivered. In mammalian cell lines, chitosan did not interfere with adenovirus transgene expression. However, infection of primary murine bone marrow-derived dendritic cells with adenovirus complexed with chitosan significantly reduced viability, transgene expression, and upregulation of major histocompatability (MHC) class I and CD86. Our in vitro observations indicate that chitosan dramatically inhibits adenovirus-mediated transgene expression and antigen presenting cell activation, which could prevent CD8(+) T cell activation from occurring in vivo. These surprising data demonstrate for the first time that chitosan vaccine formulations can negatively impact the induction of CD8(+) T cell responses via its effect on dendritic cells, which is clinically important since consideration of chitosan as an adjuvant for vaccine formulations is growing.
Dendritic Cells - immunology Male Histocompatibility Antigens Class I - metabolism Bone Marrow Cells - virology T-Lymphocytes, Cytotoxic - drug effects Cancer Vaccines - therapeutic use Genes, Viral - drug effects Bone Marrow Cells - immunology Immunologic Factors - toxicity Adenoviridae - genetics Adenoviridae - immunology Dendritic Cells - virology Dendritic Cells - metabolism T-Lymphocytes, Cytotoxic - immunology Interferon-gamma Release Tests Mice, Inbred C57BL Cells, Cultured Down-Regulation - drug effects Chitosan - toxicity Cancer Vaccines - antagonists & inhibitors B7-2 Antigen - metabolism Animals Lymphocyte Activation - drug effects Transgenes - drug effects Cell Line, Tumor Antigen Presentation - drug effects Mice Mice, Inbred BALB C Bone Marrow Cells - metabolism

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