Explotando SR-B1 para el desarrollo de nuevos fármacos para la inmunoterapia

Abstract

Scavenger receptor class B type 1 (SR-B1) is a 509 amino acid glycoprotein containing a large extracellular domain and two transmembrane domains followed by two cytoplasmic domains. This receptor has a spatial configuration that forms a tunnel for lipid transfer, one of the main functions of SR-B1. The interaction between SR-B1 and Apolipoprotein A1 (Apo-A1) is required for cholesterol reverse transport by high-density lipoproteins (HDL). Additionally, SR-B1 has a dual function in inflammation. Under steady-state conditions, SR-B1 transmits anti-inflammatory signals, but under dangerous conditions, it can transmit pro-inflammatory signals. In this doctoral thesis, various applications have been developed based on the study of the complex role of SR-B1 in inflammation. In the first chapter of this thesis, we evaluated the sustained delivery of low doses of interferon α1 (IFN-α1) either alone or fused to Apo-A1 (IFN-α1 / Apo-A1) by an adeno-associated viral system in a mouse model of multiple sclerosis. The low levels of IFN-α1 or IFN-α1 / Apo-A1 generated are sufficient to prevent or control the symptoms of the disease in mice. These low drug levels are able to reduce the infiltration of immune cells in the spinal cord, prevent the destruction of myelin and decrease the immune response against the myelin-derived peptide, used to induce the disease. In the second chapter, a strategy to increase the effectiveness of cancer virotherapy was evaluated. Modified vaccinia Ankara virus (MVA) is an antitumor vaccine used in preclinical and clinical trials. This virus cannot replicate in human cells because it lacks the genes responsible for that function. However, MVA is immunogenic and generates type I interferon-mediated antiviral immune response. We conducted a screening of clinically approved drugs to find novel inhibitors that could decrease membrane levels of type 1 interferon receptor 1 (IFNAR1) in order to transiently block the type I interferon-mediated antiviral activity, which limits the antitumor efficacy of MVA. Statins such as simvastatin and atorvastatin were found to reduce both IFNAR1 membrane density in mouse fibroblasts, as well as clathrin-mediated bovine serum albumin endocytosis, a mechanism that acts in the IFNAR1 recycling pathway. Consequently, these drugs display a potent transient inhibitory activity of type I interferon signaling. In B16-OVA tumor-bearing mice, simvastatin increases the antitumor activity generated by MVA-OVA. This effect was due to the activity of cytotoxic T lymphocytes. The combination of simvastatin and MVA-OVA promotes a potent infiltration of immune cells in the tumor microenvironment. Finally, in the third chapter of this thesis, the role of SR-B1 in vitamin D metabolism was analyzed. Vitamin D plays an essential role in macrophage-mediated antitumor responses through the induction of cathelicidin production. We demonstrated that the cellular uptake of calcidiol is made through SR-B1 in human monocytes extracted from healthy volunteers, in a human leukemia monocytic cell line (THP-1) and in a breast cancer line (BT 474). Blockade of this receptor by a specific antibody, HDLs or chemical inhibitors such as ITX 5061 and BLT-1 prevents the transcriptional regulation of vitamin D-responsible genes. On a functional level, vitamin D promoted the increase of CD14 levels in the cellular membrane of THP-1 cells and increased IL-8 release upon LPS stimulation. This effect of vitamin D was inhibited by the monoclonal antibodies against the SR-B1 receptor. Altogether, the study of the role of SR-B1 in inflammation has led to the proposal of various applications that can lead to the development or optimization of drugs.