Role of NS1 for Dengue virus replication and pathogenicity and ways to counteract it

• Applicant: Professor Dr. Ralf Friedrich Wilhelm Bartenschlager
• Subject Area: Virology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 499982526

Dengue virus (DENV), the causative agent of dengue fever, belongs to the Flavivirus genus within the Flaviviridae family. DENV infects ~390 million people per year, of which ~500.000 experience severe disease and ~20.000 die. Within the last 20 years the number of dengue cases reported to WHO increased steadily from 500.000 in 2000 to over 4 million in 2019. Despite this alarming increase and the medical relevance, there is no direct antiviral therapy available to treat DENV infections and the only approved vaccine has limited efficacy and depends on baseline serostatus of the vaccine recipient. One known pathogenicity factor of Dengue virus infection is the multifunctional viral protein NS1, which is required for RNA replication and associated with dengue disease severity. Therefore, in this joint proposal we teamed up to unravel the mechanisms underlying NS1 production and secretion. Preliminary results obtained independently in our laboratories identified several host cell factors (proteins and lipids) possibly being involved in NS1 production and secretion. One of these factors is importin-beta 1 (IMPβ1) that can be targeted by the clinically approved drug ivermectin, which we found to affect NS1 abundance and secretion both in vitro and in infected patients. Based on these results, here we propose to characterize in-depth the role of IMPβ1 and ivermectin in NS1 production and secretion and to identify additional host factors and pathways critically involved in DENV NS1 synthesis and release from cells. Four complementary and highly inter-related aims will be pursued in close collaboration. These are as follows: First, to study the secretory pathway of NS1 and the mechanism how IMPβ1 contributes to NS1 stability and secretion; second, to decipher the mode-of-action of ivermectin and ways to increase its anti-NS1 potency; third, to go beyond IMPβ1 and ivermectin and search for additional host cell factors and pathways involved in NS1 production and secretion for which we will take advantage of the rich data source we have collected (complementary proteome and lipidome data); forth, to correlate our in vitro data on NS1 secretion and involved host factor(s) with clinical data. The reasons to join forces by the two laboratories are on the one hand the common interest in Dengue virus, especially the role of NS1 in the viral replication cycle and pathogenesis, on the other hand the complementary expertise and infrastructures. These include cutting-edge molecular virology and imaging approaches (light and electron microscopy) and NS1 pathogenicity models, clinical virology and patient cohorts. Given that NS1 is an important pathogenicity factor, gained knowledge might help to improve treatment of infected patients in order to lower severe dengue disease manifestations.

• DFG Programme: Research Grants
• International Connection: Thailand
• Partner Organisation: National Science and Technology Development Agency (NSTDA); National Innovation Agency; Program Management Unit for Human Resources ; and Institutional Development
• Cooperation Partner: Panisadee Avirutnan, Ph.D.