Abstract 2490: CD40 ligand expressing recombinant vaccinia virus (rVV40L) modulation of central memory CD8-mediated immune response
Authors: Trella Emanuele , Panopoulos Evangelos , Raafat Nermin , Mengus Chantal , Traunecker Emmanuel , Heidtmann Swantje , Heberer Michael , Oertli Daniel , Spagnoli Giulio Cesare , Zajac Paul 
Published: August 2015

In cancer immunotherapy, induction of tumor-reactive CD8+ T cells displaying phenotypic and functional profile of central memory T cells (TCM) is associated with favorable prognosis. A key element in the generation of TCM CD8+ cells is represented by the help provided by CD4+ T cells during the priming of naïve CD8+ T cells. In particular CD40 ligand (CD40L) expressed and/or secreted by activated CD4+ T cells triggers CD40 receptor expressed on antigen presenting cells (APCs) thereby enhancing their antigen presentation capacity. In order to bypass the requirement of CD4+ T cells we generated a non-replicating recombinant vaccinia virus encoding human CD40L (rVV40L) and compared its ability to shape CD8-mediated immune response to soluble CD40L recombinant protein (sCD40L).

In this regard, our data clearly underline the different biological properties of membrane-bound CD40L, as provided by rVV40L infection, as compared to its soluble form, in CD14+ APCs activation. Notably, considering expression of IL-12p40, IFN-a and -b genes, cytokines of proven relevance for memory T cell induction, rVV40L-infection was much more potent than s40L-treatment alone or combine with WT infection. In parallel, s40L-stimulation induced a much more significant expression of IL-10 and indoleamine-2, 3-dioxygenase (IDO) genes encoding immunosuppressive factors. Considering a panel of molecules involved in the generation of the immunological synapse with T cells on CD14+ cells, rVV40L appeared to promote a less intense up regulation of CD80 co-stimulatory molecules but, most importantly, only a minor increase of programmed death ligand-1 (PD-L1). Therefore, gene expression and phenotypic profiles suggested that rVV40L-infected CD14+ cells might be highly effective APC in the induction of TCM CD8+ cells. Indeed, a single in vitro stimulation of naïve CD8+ T cells by rVV40L-infected CD14+ cells, in the absence of CD4+ T cells, was able to promote the rapid generation of central memory TAA (MAGE and MART-1) specific CD8+ T cells. These TCM were characterized by the typical central memory phenotype, as indicated by co-expression of CD45RO, CD62L and IL-7Ra, and by the high proliferative potential upon antigen recognition.

Collectively our data indicate that rVV40L efficiently modulates the quality of different APC signals delivered during the formation of the immunological synapse with CD8+ T cells. These in-vitro observations validate the strong clinical potential of our recombinant vaccinia virus constructs co-expressing CD40L for cancer immunotherapies.

Citation Format: Emanuele Trella, Evangelos Panopoulos, Nermin Raafat, Chantal Mengus, Emmanuel Traunecker, Swantje Heidtmann, Michael Heberer, Daniel Oertli, Giulio Cesare Spagnoli, Paul Zajac. CD40 ligand expressing recombinant vaccinia virus (rVV40L) modulation of central memory CD8-mediated immune response. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2490. doi:10.1158/1538-7445.AM2015-2490