Combined TLR Stimulation With Pam3Cys and Poly I

Abstract

The cytokines granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4 are frequently used for generating dendritic cells (DCs) for therapeutic vaccination against cancer. These in vitro DCs share several characteristics with inflammatory monocyte-derived DCs in vivo. In contrast, culture of bone marrow cells in Flt3-ligand (Flt3L) generates a heterogeneous population of DCs, which comprise conventional DCs (cDCs) and plasmacytoid DCs similar to the steady-state populations found in vivo. Although previous studies have identified combinations of toll-like receptor ligands (TLR-Ls) that induce optimal activation of GM-CSF/IL-4 DCs in vitro, the conditions for optimal activation of Flt3L-DCs have not been established. In this study, we show that various combinations of the TLR-Ls Pam3Cys, Poly I:C, lipopolysaccharide, and CpG all increased Flt3L-DC maturation, but only the combination of Pam3Cys/Poly I:C showed a trend to enhanced production of IL-12p70 and tumor necrosis factor-α by cDCs. Pam3Cys/Poly I:C-treated cDCs also displayed enhanced capacity to present antigen to CD4(+) T cells, and cross-present to CD8(+) T cells, increasing T-cell proliferation in vitro. Within a prophylactic vaccination setting, cDCs activated with Pam3Cys/Poly I:C conferred tumor protection in mice. However, the numbers of cDCs required for protection were higher than the numbers of optimally activated GM-CSF/IL-4 DCs required for a similar effect. Our results show that combined TLR stimulation can enhance both the phenotypic and functional properties of Flt3L-DCs, but even under conditions of optimal activation these cells are not superior in activity to GM-CSF/IL-4 DCs in vivo.

Combination therapy targeting toll like receptors 7, 8 and 9 eliminates large established tumors

“…It was also shown that combinations of TLR 2, 3 and 9 ligands could enhance DC function and the induction of T cell immunity following vaccination [50]. Finally, a DC based vaccine delivered with TLR3 and TLR 2 provided enhanced protection to mice challenged with tumor [51]. …”

Immunotherapy of Metastatic Colorectal Cancer: Prevailing Challenges and New Perspectives

“…Immunopotentiators optimize DC-based vaccines and enhance production of the type-1 T-cell mediator IL-12. These include toll-like receptor agonists poly I:C, LPS, Pam3Cys and R848 [136–138]. The final study to be discussed in this review designed a vaccine with hyperstimulatory potential by loading DCs with a poxvector containing genes for CEA and other costimulatory molecules, including CD80.…”

Trial Watch

“…(NCT01984892); (2) in melanoma patients, who receive Hiltonol™ to improve the immunogenicity of a personalized, neoantigen-targeting peptide-based vaccine (NCT01970358); (3) in individuals with glioblastoma, who are treated with Hiltonol™ as adjuvant to a multipeptide-based vaccine (IMA950) 160 given in combination with temozolomide-based radiochemotherapy 82 , 161 (NCT01920191); (4) in cutaneous T-cell lymphoma patients, receiving Hiltonol™ to boost the therapeutic potential of radiation therapy coupled to the histone deacetylase inhibitor romidepsin 162 - 165 (NCT02061449); and (5) in B-cell lymphoma patients, who are concurrently treated with recombinant human FLT3 ligand (FLT3L, also known as CDX-301) 166 - 168 i.t. plus low-dose radiation therapy in the attempt to recruit DCs to neoplastic lesions and thus promote clinically relevant anticancer immune responses (NCT01976585).…”