Proteasome-Independent Major Histocompatibility Complex Class I Cross-Presentation Mediated by Papaya Mosaic Virus-Like Particles Leads to Expansion of Specific Human T Cells

Abstract

The development of versatile vaccine platforms is a priority that is recognized by health authorities worldwide; such platforms should induce both arms of the immune system, the humoral and cytotoxic-Tlymphocyte responses. In this study, we have established that a vaccine platform based on the coat protein of papaya mosaic virus (PapMV CP), previously shown to induce a humoral response, can induce major histocompatibility complex (MHC) class I cross-presentation of HLA-A*0201 epitopes from gp100, a melanoma antigen, and from influenza virus M1 matrix protein. PapMV proteins were able to assemble into stable virus-like particles (VLPs) in a crystalline and repetitive structure. When we pulsed HLA-A*0201؉ antigenpresenting cells (APCs) with the recombinant PapMV FLU or gp100, we noted that antigen-specific CD8 ؉ T cells were highly reactive to these APCs, demonstrating that the epitope from the VLPs were processed and loaded on the MHC class I complex. APCs were preincubated with two different proteasome inhibitors, which did not affect the efficiency of peptide presentation on MHC class I. Classical presentation from an endogenous antigen was abolished in the same conditions. Clearly, antigen presentation mediated by the PapMV system was proteasome independent. Finally, PapMV-pulsed APCs had the capacity to expand highly avid antigenspecific T cells against the influenza virus M1 HLA-A*0201 epitope when cocultured with autologous peripheral blood mononuclear cells. This study demonstrates the potential of PapMV for MHC class I crosspresentation and for the expansion of human antigen-specific T cells. It makes VLPs from PapMV CP a very attractive platform to trigger cellular responses for vaccine development against chronic infectious diseases and cancers.

Novel Plant Virus-Based Vaccine Induces Protective Cytotoxic T-Lymphocyte-Mediated Antiviral Immunity through Dendritic Cell Maturation

“…PapMV-like particles displaying the immunodominant p33 CTL epitope from LCMV are internalized by DCs and cross-presented to specific CTLs. We recently reported that this is achieved through a proteasome-independent pathway (14), as shown for another VLP-based system (30). Importantly, and in contrast to many VLPs described so far, PapMV-like particles directly prime protective CTL responses in vivo without an adjuvant (i.e., CpGs or anti-CD40).…”

“…PapMV VLPs, formed by the self-assembly of the CP after overexpression in Escherichia coli (39), can carry foreign epitopes and induce the production of specific antibodies in vaccinated mice (7). Moreover, we have recently shown that a human B-cell line can cross-present CTL epitopes displayed on PapMV VLPs to specific T cells in vitro in a proteasome-independent fashion (14). To determine whether such VLPs could also trigger the development of protective cellular immunity in vivo, PapMV VLPs carrying the H-2 b -restricted dominant p33 CTL epitope from LCMV (PapMV-p33 VLPs) were engineered and evaluated for the capacity to induce CTL responses against LCMV.…”

Nanoparticle Adjuvant Sensing by TLR7 Enhances CD8+ T Cell–Mediated Protection from Listeria Monocytogenes Infection

“…Vaccination with such nanoparticles generates a specific cellular and humoral immune response against displayed Ags and provides protection against various viral infection models (19,(22)(23)(24)(25). Moreover, we have demonstrated that the fused Ags are efficiently cross-presented on MHC class I of human APCs and cause the expansion of human Ag-specific T cells (26). Finally, we recently showed that PapMV used as an immunomodulator leads to the development of protective immune responses against influenza or Streptococcus pneumoniae challenges (27).…”

Human Activated T Lymphocytes Modulate IDO Expression in Tumors through Th1/Th2 Balance

“…Monocyte-derived dendritic cells (DC) were generated from PBMCs of healthy donors (35), followed by 24 h of stimulation with 500 ng/ml soluble trimeric CD40L (Immunex) and/or 10 3 U/ml IFN-␥ (Pierce Endogen) and/or 5 g/ml LPS (Sigma-Aldrich).…”