Speaker
Description
Activation of the hemagglutinin (HA) of influenza A viruses by host proteases is a prerequisite for infectivity. The HA of low pathogenic avian influenza A (LPAI) H7N9 viruses is cleaved at a single arginine by TMPRSS2. In 2016, the HA of the H7N9 virus mutated into highly pathogenic avian influenza A (HPAI) variants with multiple basic amino acids at the cleavage site. These novel viruses have caused severe human infections and poultry farm outbreaks in China.
We investigated the changes in protease specificity of H7N9 HA with a monobasic compared to multibasic cleavage sites with regard to the cleavability by different proteases and structural aspects. Therefore, 42 FRET-substrates derived from the HA cleavage sites of H1-H18 with a focus on various H7 subtypes were synthesized and tested with recombinant enzymes in a fluorescence assay. Based on this screening, the contribution of several serine proteases of the trypsin-like and subtilisin family in the activation of the HPAI H7N9 HA was studied in cell culture. The novel multibasic HA of HPAI H7N9 viruses is more susceptible to be cleaved by a broader spectrum of proteases compared to the LPAI variant. However, siRNA-mediated knockdown of furin in HeLa cells leads to a clearly reduced HA activation compared to a control. Furthermore, a comparative model shows an extended HA cleavage loop for the multibasic compared to the monobasic variant which is required for furin cleavage.
Taken together, these data suggest that furin is the major processing protease of the newly emerged HPAI H7N9 virus.
| Choose secondary Session | Evolution and Emerging viruses |
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| Choose primary session | Virus host cell interaction |
