Opposing roles of ACE2 and TMPRSS2 in IBV Beaudette infection

Infectious bronchitis virus (IBV) is an economically important avian gammacoronavirus. IBV uses sialic acids and heparan sulfate for cellular attachment, but the host proteins governing its infection remain poorly defined. Here, we investigated the roles of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) during IBV Beaudette (IBV BD) infection. ACE2 knockout impaired IBV replication in DF-1 cells, whereas ACE2 reconstitution restored infection. Furthermore, ACE2 overexpression enhanced infection of DF-1 and primary chicken embryo kidney cells, supporting the role of chicken ACE2 as a proviral host factor. In contrast, TMPRSS2 exerted a restrictive function on IBV BD infection as demonstrated in TMPRSS2 KO DF-1 cells and upon pharmacological inhibition, which significantly increased IBV BD infection in DF-1 and Vero cells. RNA sequencing revealed significant changes in lipid metabolism and membrane-related processes following TMPRSS2 knockout and pharmacological inhibition. These findings highlight the opposing roles of ACE2 and TMPRSS2 in IBV BD infection, emphasizing the combined impact of proviral host factors, protease activity, and the cellular membrane environment during gammacoronavirus infections.