Human Macrophages and Dendritic Cells Can Equally Present MART-1 Antigen to CD8+ T Cells after Phagocytosis of Gamma-Irradiated Melanoma Cells

Dendritic cells (DC) can achieve cross-presentation of naturally-occurring tumor-associated antigens after phagocytosis and processing of dying tumor cells. They have been used in different clinical settings to vaccinate cancer patients. We have previously used gamma-irradiated MART-1 expressing melanoma cells as a source of antigens to vaccinate melanoma patients by injecting irradiated cells with BCG and GM-CSF or to load immature DC and use them as a vaccine. Other clinical trials have used IFN-gamma activated macrophage killer cells (MAK) to treat cancer patients. However, the clinical use of MAK has been based on their direct tumoricidal activity rather than on their ability to act as antigen-presenting cells to stimulate an adaptive antitumor response. Thus, in the present work, we compared the fate of MART-1 after phagocytosis of gamma-irradiated cells by clinical grade DC or MAK as well as the ability of these cells to cross present MART-1 to CD8+ T cells. Using a high affinity antibody against MART-1, 2A9, which specifically stains melanoma tumors, melanoma cell lines and normal melanocytes, the expression level of MART-1 in melanoma cell lines could be related to their ability to stimulate IFN-gamma production by a MART-1 specific HLA-A*0201-restricted CD8+ T cell clone. Confocal microscopy with Alexa Fluor®647-labelled 2A9 also showed that MART-1 could be detected in tumor cells attached and/or fused to phagocytes and even inside these cells as early as 1 h and up to 24 h or 48 h after initiation of co-cultures between gamma-irradiated melanoma cells and MAK or DC, respectively. Interestingly, MART-1 was cross-presented to MART-1 specific T cells by both MAK and DC co-cultured with melanoma gamma-irradiated cells for different time-points. Thus, naturally occurring MART-1 melanoma antigen can be taken-up from dying melanoma cells into DC or MAK and both cell types can induce specific CD8+ T cell cross-presentation thereafter

Induction de réponses immunes anti-tumorales in vivo à la suite du traitement par anticorps anti-CD20 (existence d'un effet << vaccinal >> des anticorps anti-tumoraux ?)

L anticorps monoclonal (AcM) anti-CD20 rituximab est utilisé pour le traitement de patients atteints de lymphomes B non-Hodgkiniens mais l obtention de réponses cliniques durables demeure un événement rare. Si les mécanismes d action directs des AcM anti-CD20 sont bien caractérisés in vitro, leur impact sur l efficacité clinique reste discuté. De plus, peu de choses sont connues sur le potentiel des anti-CD20 à induire des réponses immunes anti-tumorales. Mon travail de Thèse a mis en évidence qu une thérapie par AcM anti-CD20 chez la souris permet l induction d une réponse immune cellulaire impliquant les cellules CD4+ et CD8+. Ainsi, en plus des mécanismes directs, les AcM anti-CD20 peuvent initier le développement de réponses immunes anti-tumorales. L identification des résidus de la région Fc impliqués dans cet effet vaccinal et le développement de thérapies utilisant AcM et molécules immuno-stimulatrices sont des pistes de recherche prometteusesPARIS-BIUP (751062107) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Competition ELISA between anti-MART-1 1F9, 2A9 and A103 mAbs and biotinylated-2A9 mAb.

<p>96-well ELISA plates were coated with purified GST-MART-1 and incubated with purified 1F9, 2A9 or A103 mAbs (three-fold dilutions in duplicate). Biotinylated-2A9 mAb was then added. A streptavidin-HRP solution was used as detection reagent. Results shown correspond to one representative experiment out of three independent assays.</p

Kaff determination of anti-MART-1 mAbs.

*<p>Mean of 24 values (n = 4 independent experiments).</p

Table S2 from CD25^high Effector Regulatory T Cells Hamper Responses to PD-1 Blockade in Triple-Negative Breast Cancer

T cell and NK cell subpopulations gene features, related to Figure 1</p

Table S1 from CD25^high Effector Regulatory T Cells Hamper Responses to PD-1 Blockade in Triple-Negative Breast Cancer

Clinical characteristics of patients with breast cancer</p

Selective SIRPα blockade reverses tumor T cell exclusion and overcomes cancer immunotherapy resistance

International audienceT cell exclusion causes resistance to cancer immunotherapies via immune checkpoint blockade (ICB). Myeloid cells contribute to resistance by expressing signal regulatory protein-α (SIRPα), an inhibitory membrane receptor that interacts with ubiquitous receptor CD47 to control macrophage phagocytosis in the tumor microenvironment. Although CD47/SIRPα-targeting drugs have been assessed in preclinical models, the therapeutic benefit of selectively blocking SIRPα, and not SIRPγ/CD47, in humans remains unknown. We report a potent synergy between selective SIRPα blockade and ICB in increasing memory T cell responses and reverting exclusion in syngeneic and orthotopic tumor models. Selective SIRPα blockade stimulated tumor nest T cell recruitment by restoring murine and human macrophage chemokine secretion and increased anti-tumor T cell responses by promoting tumor-antigen crosspresentation by dendritic cells. However, nonselective SIRPα/SIRPγ blockade targeting CD47 impaired human T cell activation, proliferation, and endothelial transmigration. Selective SIRPα inhibition opens an attractive avenue to overcoming ICB resistance in patients with elevated myeloid cell infiltration in solid tumors