Plateformes Lilloises en Biologie et Santé

Drug repurposing has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to its favorable safety profile and pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC50 measured against SARS-CoV-2 in human pulmonary cells. This compound inhibits SARS-CoV-2 at a post-entry step. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and lowered pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients.

Acute myeloid leukemia (AML) is characterized by an increased proliferation of hematopoietic progenitors or precursors (blasts) of the different myeloid lineages. Studies performed in AML-affected patients revealed a T-cell immunodeficiency, characterized by a decreased number of peripheral T lymphocytes' TRECs and a restricted repertoire. To study thymus dysfunction during AML, we used an AML mouse model in which we previously showed a thymic atrophy notably due to an increased cell death among double-positive (CD4+CD8+) thymocytes. To better understand this massive thymocytes’ loss, we collected ex vivo thymi from control and leukemic mice and immunophenotyped them for cell death. In parallel, we also assessed for the expression of different actors of cell death signaling pathways by RT-qPCR or Western Blotting. When comparing leukemic to control mice, there was a significant increase in the expression of Mlkl gene, phosphorylated MLKL and RIPK3 proteins and TNF-alpha receptors on double-positive (CD4+CD8+) thymocytes. These findings revealed an abnormal cell death of double-positive (CD4+CD8+) thymocytes by necroptosis (in addition to apoptosis) during AML. Such cell death was also observed in vitro using cultured wild-type thymocytes and recombinant TNF-alpha protein in the presence or absence of apoptosis inhibitors. Thus, we demonstrated that TNF-alpha plays a deleterious role in thymic function during AML by contributing to extensive thymocytes’ loss. Further investigations will help to better characterize its impact on the peripheral T-cell repertoire and antigens recognition.