Viruses manipulate the life cycle in host cells via the use of viral properties and host machineries. Development of antiviral peptides against dengue virus (DENV) infection has previously been concentrated on blocking the actions of viral structural proteins and enzymes in virus entry and viral RNA processing in host cells. In this study, we proposed DENV NS1, which is a multifunctional nonstructural protein indispensable for virus production, as a new target for inhibition of DENV infection by specific peptides. We performed biopanning assays using a phage-displayed peptide library and identified 11 different sequences of 12-mer peptides binding to DENV NS1. In silico analyses of peptide-protein interactions revealed 4 peptides most likely to bind to DENV NS1 at specific positions and their association was analysed by surface plasmon resonance. Treatment of Huh7 cells with these 4 peptides conjugated with N-terminal fluorescent tag and C-terminal cell penetrating tag at varying time-of-addition post-DENV infection could inhibit the production of DENV-2 in a time-and dosedependent manner. The inhibitory effects of the peptides were also observed in other virus serotypes (DENV-1 and DENV-4), but not in DENV-3. These findings indicate the potential application of peptides targeting DENV NS1 as antiviral agents against DENV infection. Dengue virus (DENV) infection is a major and increasing public health problem worldwide. There are approximately 390 million infections, 500,000 severe cases with hospitalization, and a 2.5% mortality rate each year 1,2. Although the majority of individuals experiencing DENV infection are asymptomatic, approximately one-fourth of the infected cases develop a wide range of clinical manifestations of dengue disease with unclear pathogenic mechanisms 3,4. To date, there is no specific anti-viral drug available for the treatment of DENV infection. A licensed dengue vaccine also has some limitations for use in naïve individuals not previously infected by DENV and in children less than 9 years of age 5,6. Consequently, the development of an alternative strategy to combat DENV infection and severe dengue is still needed. DENV is a positive, single-stranded, enveloped RNA virus belonging to the family Flaviviridae, and it has 4 distinct serotypes (DENV-1, DENV-2, DENV-3 and DENV-4) 7. Infection with any DENV serotype can generate

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Viral-cell entry and cell–cell viral spreading processes of SARS-CoV-2 are subjected to fast evolutionary optimization because of its worldwide spreading, requiring the need for new drug developments. However, this task is still challenging, because a detailed understanding of the underlying molecular processes, mediated by the key cellular proteases TMPRSS2 and furin, is still lacking. Here, we show by large-scale atomistic calculations that binding of the ACE2 cell receptor at one of the heteromers of the SARS-CoV-2 spike leads to a release of its furin cleavage site (S1/S2), enabling an enhanced furin binding, and that this latter process promotes the binding of TMPRSS2 through the release of the TMPRSS2 cleavage site (S2′) out of the ACE2-binding heteromer. Moreover, we find that, after proteolytic cleavage, improved furin binding causes that parts of the S2 subunit dissociate from the complex, suggesting that furin promotes the fusion of the S2 subunit with the cell membrane before transfer of the viral RNA. Graphical abstract Here we show by computational means that binding of the ACE2-cell receptor at one of the heteromers of the SARS-CoV-2 spike leads to an enhanced binding of the protease furin, promoting the binding of the protease TMPRSS2. Moreover, we show that, after proteolytic cleavage, improved furin binding causes that parts of the heteromer dissociate from the spike.