Biology subjects

Rusnati, M.

Publications and source records attributed to Rusnati, M..

3 recordsLinked to original sources

bioRxiv2025

K5 polysaccharides inhibit SARS-CoV-2 infection by preventing spike-proteolytic priming

SARS-CoV-2 spike glycoprotein is a promising drug target due to its crucial role in viral infection. Heparin, a long linear polysaccharide that inhibits SARS-CoV-2 infection by acting on spike, has limited antiviral applications due to its anticoagulant effect. E. coli K5 polysaccharides share the same structure as the heparin precursor and can be chemically modified to devoid anticoagulant activity. Here, biochemical assays and computer simulations reveal that K5 with a high degree of sulfation at O-(K5OSH) or N- and O-positions (K5NOSH) bind spike with higher affinity than heparin, preventing its binding to ACE2 and cleavage by furin. This mechanism is supported by a cell syncytia assay showing that K5OSH and K5NOSH inhibit viral infection by blocking membrane fusion. Infection assays for SARS-CoV-2 Wuhan-Hu-1 and Omicron BA.1 variants corroborate their antiviral activity. These results support the therapeutic potential of K5OSH and K5NOSH against SARS-CoV-2, with K5OSH displaying the more promising activity profile.

biochemistry↗

bioRxiv2024

Validation of plasmonic-based biosensors for rapid and sensitive detection of rabbit hemorrhagic and foot-and-mouth disease viruses in biological samples

Biosensing technologies and monoclonal antibodies (MAbs) are gaining increasing importance as powerful tools in the field of virology. Surface plasmon resonance (SPR) is an optical biosensing technology already used in virus detection and in the screening of MAbs of diagnostic and therapeutic value. Rabbit haemorrhagic disease virus 2 (RHDV) and foot-and-mouth disease virus (FMDV) are top veterinary issues for whom, the development of novel methods for their detection in biological samples represents a priority with important livestock healthcare and economic implications. With these premises, here we prepared a series of SPR biosensors containing RHDV2 or its 6S subunit immobilized to the surface by different strategies. The biosensors were then used to characterize the binding capacity of a panel of anti-RHDV2 MAbs. From the comparison of the results obtained, the biosensor composed of intact RHDV2 captured with catcher-MAb covalently immobilized to the surface showed the best analytical performances, that were retained also when the same strategy was adopted to prepare a biosensor containing a different virus (namely, FMVD). The results obtained are discussed in view of the exploitation of SPR in the rapid, sensitive and resilient detection of viruses in biological materials and in the screening of antiviral MAbs libraries.

biochemistry↗

bioRxiv2024

The accomplices: Heparan sulfates and N-glycans foster SARS-CoV-2 spike:ACE2 receptor binding and virus priming

Although it is well established that the SARS-CoV-2 spike glycoprotein binds to the host cell ACE2 receptor to initiate infection, far less is known about the tissue tropism and host cell susceptibility to the virus. Differential expression across different cell types of heparan sulfate (HS) proteoglycans, with variably sulfated glycosaminoglycans (GAGs), and their synergistic interactions with host and viral N-glycans may contribute to tissue tropism and host cell susceptibility. Nevertheless, their contribution remains unclear since HS and N-glycans evade experimental characterization. We, therefore, carried out microsecond-long all-atom molecular dynamics simulations, followed by random acceleration molecular dynamics simulations, of the fully glycosylated spike:ACE2 complex with and without highly sulfated GAG chains bound. By considering the model GAGs as surrogates for the highly sulfated HS expressed in lung cells, we identified key novel cell entry mechanisms of spike SARS-CoV-2. We find that HS promotes structural and energetic stabilization of the active conformation of the spike receptor binding domain (RBD) and reorientation of ACE2 toward the N-terminal domain in the same spike subunit as the RBD. Spike and ACE2 N-glycans exert synergistic effects, promoting better packing, strengthening the protein:protein interaction, and prolonging the residence time of the complex. ACE2 and HS binding trigger rearrangement of the S2 functional protease cleavage site through allosteric interdomain communication. These results thus show that HS has a multifaceted role in facilitating SARS-CoV-2 infection and they provide a mechanistic basis for the development of novel GAG derivatives with anti-SARS-CoV-2 potential. Significance StatementA key to blocking SARS-CoV-2 infection is to understand why it infects some cell types more than others. Heparan sulfate (HS) proteoglycans are differentially expressed on the surface of host cells and, with ACE2 receptors, provide an entry route for SARS-CoV-2. Here, we used computer simulations to investigate how highly sulfated glycosaminoglycans, a model for HS expressed in lungs, impact the interaction between virus spike and host ACE2. The simulations indicate that HS, together with host and spike N-glycans, stabilizes the spike:ACE2 complex and triggers structural changes, including host protease cleavage, contributing to the SARS-CoV-2 infection mechanism. This study lays the basis for a better understanding of the cell-specificity of SARS-CoV-2 infection and for developing strategies for inhibiting SARS-CoV-2 infection.

biophysics↗