Abstract EN:

Approximately 20 million people are infected by HTLV-1 (human T cell leukemia virus type-1). Although the majority of infected individuals remain asymptomatic, around 10% will develop HTLV-1-associated disease. HTLV-1 has been described to efficiently propagate through cell-cell contacts. Designated as virological synapses, these cellular contacts exhibit some of the characteristics of immunological synapses. This project has allowed a better comprehension of how HTLV-1 propagates from cell-to-cell and proposes a completely novel concept of virus transmission through 'viral biofilms'. Contrary to what was previously suggested we have shown that HTLV-1 is accumulated at the surface of infected cells, in extracellular viral assemblies. Viral assemblies are composed of extracellular matrix (HSPG agrin, collagen) and linker molecules (galectin, tetherin) that provide the adhesion and cohesion forces needed to maintain viruses at the cell surface. More importantly, we have shown that HTLV- 1 viral assemblies contribute to the majority of virus cell-cell transmission since their removal significantly inhibits infection (« 80%). Viral assemblies, store, concentrate, disseminate and protect the virus. These characteristics recapitulate most of the features of bacterial or fungal biofilms. Therefore, we propose the use of the term 'viral biofilm' to designate this new mode of cell-to-cell virus spread.