Introduction:

Vaccine strategies to enhance CTLs response are still a challenge since it is necessary to favor the exogenous antigens (Ag) cross-presentation by antigen presenting cells (APCs). For this purpose, liposomes encapsulating bacteria pore-forming proteins (PFPs) have been used. Objective. To explore the ability of liposomes co-encapsulating the Ag ovalbumin (OVA) and sticholysin II (StII), a PFP produced by Stichodactyla helianthus, to induce a CTL response, functional in a tumor model.

Methods:

Liposomes co-encapsulating OVA and StII were prepared by dehydration-rehydration (Lp/OVA/StII). The response of CTLs was evaluated, as well as the antitumor activity in a preventive setting. The ability of StII to stimulate maturation of dendritic cells (DCs) in vitro was also explored.

Results:

Lp/OVA/StII enhanced the OVA-specific CTL response and antitumor activity in mice challenged with the E.G7-OVA tumor. StII induced the maturation of DCs in vitro, which was dependent on the Toll-like receptor 4 (TLR4), with a contribution to the response of CTLs induced by the liposomal formulation in vivo. Lp/OVA/StII favored in vitro the cross-presentation of OVA and the activation of CD8+ T cells by macrophages, but not by DCs. These results are the first evidence that StII encapsulated into liposomes functions as a vaccine platform to induce a robust CTL response, with a contribution that goes beyond its ability to form pores in membranes.

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