Recently, increasing natural infection cases and experimental animal challenge studies demonstrated domestic cats are susceptible to multiple subtypes influenza A virus (IAV) infections.  Notably, some subtype IAV strains could circulate in domestic cats after cross-species transmission and even infected humans, posing a threat to public health.  Host factors related to viral polymerase activity could determine host range of IAV and acidic nuclear phosphoprotein 32 (ANP32) is the most important one among them.  However, role of cat-derived ANP32 on viral polymerase activity and host range of IAV is still unknown.  In the present study, a total of 10 feline ANP32 (feANP32) splice variants (including 5 feANP32A, 3 feANP32B, and 2 feANP32E) were obtained from domestic cats by RT-PCR.  Sequence alignment results demonstrated amino acid deletions and/or insertions occurred among feANP32 variants, but all feANP32 proteins were primarily localized to cell nucleus.  Minigenome replication systems for several representative IAV strains were established and the support ability of feANP32 on IAV polymerase activity was estimated.  The results indicated that most feANP32A and feANP32B splice variants were able to support all the tested IAV strains, though the support activity of a single feANP32 protein on polymerase activity varied among different IAV strains.  In addition, the role of feANP32 in supporting H3N2 canine influenza virus was determined by investigating viral replication in vitro.  Collectively, our study systematically investigated the support activity of feANP32 on IAV, providing a clue for further exploring the mechanism of susceptibility of cats to IAV.

Coronaviruses are widely transmissible between humans and animals, causing diseases of varying severity.  Porcine enteric alphacoronavirus (PEAV) is a newly-discovered pathogenic porcine enteric coronavirus in recent years, which causes watery diarrhea in newborn piglets.  The host inflammatory responses to PEAV and its metabolic regulation mechanisms remain unclear, and no antiviral studies have been reported.  Therefore, we investigated the pathogenic mechanism and antiviral drugs of PEAV.  The transcriptomic analysis of PEAV-infected host cells revealed that PEAV could upregulate lipid metabolism pathways.  In lipid metabolism, steady-state energy processes, which can be mediated by lipid droplets (LDs), are the main functions of organelles.  LDs are also important in viral infection and inflammation.  In infected cells, PEAV increased LD accumulation, upregulated NF-κB signaling, promoted the production of the inflammatory cytokines IL-1β and IL-8, and induced cell death.  Inhibiting LD accumulation with a DGAT-1 inhibitor significantly inhibited PEAV replication, downregulated the NF-κB signaling pathway, reduced the production of IL-1β and IL-8, and inhibited cell death.  The NF-κB signaling pathway inhibitor BAY11-7082 significantly inhibited LD accumulation and PEAV replication.  Metformin hydrochloride also exerted anti-PEAV effects and significantly inhibited LD accumulation, downregulated the NF-κB signaling pathway, reduced the production of IL-1β and IL-8, and inhibited cell death.  LD accumulation in the lipid metabolism pathway therefore plays an important role in the replication and pathogenesis of PEAV, and metformin hydrochloride inhibits LD accumulation and the inflammatory response to exert anti-PEAV activity and reducing pathological injury.  These findings contribute new targets for developing treatments for PEAV infections.