Novel Exosome-Targeted CD4+ T Cell Vaccine Counteracting CD4+25+ Regulatory T Cell-Mediated Immune Suppression and Stimulating Efficient Central Memory CD8+ CTL Responses

Abstract

T cell-to-T cell Ag presentation is increasingly attracting attention. In this study, we demonstrated that active CD4+ T (aT) cells with uptake of OVA-pulsed dendritic cell-derived exosome (EXOOVA) express exosomal peptide/MHC class I and costimulatory molecules. These EXOOVA-uptaken (targeted) CD4+ aT cells can stimulate CD8+ T cell proliferation and differentiation into central memory CD8+ CTLs and induce more efficient in vivo antitumor immunity and long-term CD8+ T cell memory responses than OVA-pulsed dendritic cells. They can also counteract CD4+25+ regulatory T cell-mediated suppression of in vitro CD8+ T cell proliferation and in vivo CD8+ CTL responses and antitumor immunity. We further elucidate that the EXOOVA-uptaken (targeted)CD4+ aT cell’s stimulatory effect is mediated via its IL-2 secretion and acquired exosomal CD80 costimulation and is specifically delivered to CD8+ T cells in vivo via acquired exosomal peptide/MHC class I complexes. Therefore, EXO-targeted active CD4+ T cell vaccine may represent a novel and highly effective vaccine strategy for inducing immune responses against not only tumors, but also other infectious diseases.

Intercellular Trogocytosis Plays an Important Role in Modulation of Immune Responses

“…These Tc-APCs can play both negative and positive modulations in antitumor immune responses by eliminating DC OVA and neighbouring Tc-APCs, and by stimulating OVA-specific CD8 + central memory T responses and antitumor immunity via targeting role of acquired pMHC I complexes (85). More recently, we have further shown that the exosome-targeted CD4 + T cell vaccine using OVAspecific or non-specific CD4 + T cells with uptake of OVA-specific DC-released exosomes expressing pMHC I complexes are capable of breaking CD4 + 25 + regulatory T (Tr) cell-mediated immune suppression and stimulating efficient antigen-specific CD8 + CTL response (86,87). However, CD4 + T cells with uptake of exosomes without expression of OVA-specific pMHC I complexes are unable to stimulate OVA-specific CD8 + CTL responses.…”

A novel T cell-based vaccine capable of stimulating long-term functional CTL memory against B16 melanoma via CD40L signaling

“…12 Additional costimulations via 4-1BBL/4-1BB, OX40L/OX40 and CD40/CD40L interactions between DCs and CD8 1 T cells have also been found to promote effector CD8 1 T-cell responses during the priming phase 13,14 and CD8 1 Tm-cell development in the contraction phase. [15][16][17][18] However, whether these costimulatory events are also involved in priming and memory development in OVA-T EXO -stimulated CD8…”

Transgenic 4-1BBL-engineered vaccine stimulates potent Gag-specific therapeutic and long-term immunity via increased priming of CD44+CD62Lhigh IL-7R+ CTLs with up- and downregulation of anti- and pro-apoptosis genes

“…[8][9][10] To assess its therapeutic effect, C57BL/6 mice bearing 6-dayestablished OVA-expressing B16 melanoma BL6-10 OVA tumors were immunized with OVA-Texo in this study. We demonstrate that the OVA-Texo vaccine is unable to cure any mice bearing 6-day tumors, although OVA-Texo vaccination significantly reduces the average number of lung tumor colonies compared to the PBS control.…”

“…[8][9][10] We demonstrated that the OVA-Texo vaccine induces more efficient immunity than the DC vaccine and is capable of stimulating potent CD4 1 T cell-independent CTL responses and long-term antitumor immunity via IL-2/CD80 and CD40L signaling, counteracting regulatory T cellmediated immune suppression. [8][9][10] In addition, we also developed HIV-1 gp120-and Gag-specific T cell-based (gp120-Texo and Gag-Texo) vaccines using ConA-stimulated mouse CD8 1 T cells for the uptake of gp120-and Gag-specific DC-released EXOs. [11][12][13] We demonstrated that gp120-Texoand Gag-Texo-stimulated gp120-or Gag-specific CTL responses developed in transgenic HLA-A2 mice.…”

“…immunized with OVA-Texo /4-1BBL or OVA-Texo /Null cells (2310 6 cells/mouse) were taken 6 or 10 days after the immunization and were doubly stained with FITC-conjugated anti-CD8 Ab (FITC-CD8) and PE-conjugated H-2K b /OVA 257-264 tetramer (PE-Tetramer) or triply stained with FITC-CD8 Ab, PE-tetramer and PE-Cy5-conjugated anti-CD44, CD62L and IL-7R Abs, respectively, and then analyzed by flow cytometry. [8][9][10] To assess the intracellular expression of granzyme B and IFNc, splenocytes from immunized mice were stimulated with 2 mM OVAI (SIINFEKL) peptide in vitro in the presence of 2 mM monensin (GolgiStop, BD Biosciences, San Diego, CA) for 4 h and then stained with a FITC-anti-CD8 antibody. The cells were then fixed, and the cell membranes were permeabilized in Cytofix/Cytoperm solution (BD Biosciences, San Diego, CA) and stained with a PE-anti-granzyme B antibody or a PE-anti-IFN-c antibody for flow cytometry analysis.…”