Enhanced Efficacy of Therapeutic Cancer Vaccines Produced by Co-Treatment withMycobacterium tuberculosisHeparin-Binding Hemagglutinin, a Novel TLR4 Agonist

Abstract

Effective activation of dendritic cells (DCs) toward T helper (Th)-1 cell polarization would improve DC-based antitumor immunotherapy, helping promote the development of immunotherapeutic vaccines based on T-cell immunity. To achieve this goal, it is essential to develop effective immune adjuvants that can induce powerful Th1 cell immune responses. The pathogenic organism Mycobacterium tuberculosis includes certain constitutes, such as heparin-binding hemagglutinin (HBHA), that possess a strong immunostimulatory potential. In this study, we report the first clarification of the functions and precise mechanism of HBHA in immune stimulation settings relevant to cancer. HBHA induced DC maturation in a TLR4-dependent manner, elevating expression of the surface molecules CD40, CD80, and CD86, MHC classes I and II and the proinflammatory cytokines IL-6, IL-12, IL-1β, TNF-α, and CCR7, as well as stimulating the migratory capacity of DCs in vitro and in vivo. Mechanistic investigations established that MyD88 and TRIF signaling pathways downstream of TLR4 mediated secretion of HBHA-induced proinflammatory cytokines. HBHA-treated DCs activated naïve T cells, polarized CD4(+) and CD8(+) T cells to secrete IFN-γ, and induced T-cell-mediated cytotoxicity. Notably, systemic administration of DCs that were HBHA-treated and OVA(251-264)-pulsed ex vivo greatly strengthened immune priming in vivo, inducing a dramatic regression of tumor growth associated with long-term survival in a murine E.G7 thymoma model. Together, our findings highlight HBHA as an immune adjuvant that favors Th1 polarization and DC function for potential applications in DC-based antitumor immunotherapy.

Enhancement of Tumor-Specific T Cell–Mediated Immunity in Dendritic Cell–Based Vaccines by Mycobacterium tuberculosis Heat Shock Protein X

“…The recombinant HspX protein was produced using the pET28a (Promega, Madison, WI) vector and E. coli expression system, as recently described (6). Briefly, rv2301c encoding HspX was amplified by PCR using M. tuberculosis H37Rv genomic DNA (ATCC 27294) as a template and the following primers: forward, 59-GGG CCC GGA TCC ATG GCA AAG CTC TCC-39; and reverse, 59-GGG CCC GAA TTC CTT GAC GGT GAC GGT-39.…”

“…Ag uptake and in vitro and in vivo chemotaxis were performed as previously described (6). DC migration in vitro and in vivo.…”

“…Recently, it has been reported that certain Ags of the BCG vaccine can activate DCs through the TLR4 and TLR2 pathways and increase the differentiation and activity of CTLs (3)(4)(5)(6)(7). Previously, we reported an increase in the survival rate in an E.G7 thymoma model in which mice were vaccinated with DCs, and heparinbinding hemagglutinin protein extracted from Mycobacterium tuberculosis was used to stimulate the TLR4 levels (6). M. tuberculosis consists of various proteins that are involved in the maturation and activation of DCs, and during a screen for DC activators within the mycobacterial Ag, we identified heat shock protein X (HspX) as the strongest TLR4 agonist.…”

Cancer Vaccination, Will You Have To Pay The Toll?

“…In an effort to determine effective inducers of Th1 polarization and enhanced DC function, immunization with DCs treated with heparinbinding hemagglutinin (HBHA), a constituent of Mycobacterium tuberculosis, and pulsed with OVA peptide ex vivo resulted in decreased tumor growth and increased survival in a murine E.G7 thymoma model [35]. HBHA acts by stimulating TLR4 and upregulating the expression of costimulatory molecules, major histocompatibility complexes I and II, and the secretion of proinflammatory cytokines.…”

Blockade of Myd88 signaling induces antitumor effects by skewing the immunosuppressive function of myeloid‐derived suppressor cells

“…3,4 Accordingly, immunotherapies with TLR agonists boost immune responses. 5,6 Myeloid-derived suppressor cells (MDSCs) accumulate in the tumor, peripheral blood, spleen and bone marrow of tumorbearing mice and humans with cancer. 7,8 MDSCs are known to elicit immunosuppressive functions against many kinds of effectors including CD4 þ T cells and CD8 þ T cells.…”