Identification of chicken CAR homology as a cellular receptor for the emerging highly pathogenic fowl adenovirus 4 via unique binding mechanism

Abstract

Since 2015, the prevalence of severe hepatitis-hydropericardium syndrome, which is caused by the novel genotype fowl adenovirus serotype 4 (FAdV-4), has increased in China and led to considerable economic losses. The replication cycle of FAdV-4, especially the emerging highly pathogenic novel genotype FAdV-4, remains largely unknown. The adenovirus fibre interacts with the cellular receptor as the initial step in adenovirus (AdV) infection. In our previous studies, the complete genome sequence showed that the fibre patterns of FAdV-4 were distinct from all other AdVs. Here, proteinblockage and antibody-neutralization assays were performed to confirm that the novel FAdV-4 short fibre was critical for binding to susceptible leghorn male hepatocellular (LMH) cells. Subsequently, fibre 1 was used as bait to investigate the receptor on LMH cells via mass spectrometry. The chicken coxsackie and adenovirus receptor (CAR) protein was confirmed as the novel FAdV-4 receptor in competition assays. We further identified the D2 domain of CAR (D2-CAR) as the active domain responsible for binding to the short fibre of the novel FAdV-4. Taken together, these findings demonstrate for the first time that the chicken CAR homolog is a cellular receptor for the novel FAdV-4, which facilitates viral entry by interacting with the viral short fibre through the D2 domain. Collectively, these findings provide an in-depth understanding of the mechanisms of the emerging novel genotype FAdV-4 invasion and pathogenesis.

Fiber modifications enable fowl adenovirus 4 vectors to transduce human cells

“… 44 It was reported recently that fiber1 was the major fiber for FAdV‐C4 adsorption. 45 , 46 We obtained the same findings and further confirmed that fiber2 was non‐essential for growing FAdV‐4 in a cultured chicken cell line, 31 which implies that fiber1 may only be slightly modified, whereas fiber2 is free for radical reconstruction. Recently, chicken CAR homology was identified as a cellular receptor for FAdV‐4.…”

“…44 It was reported recently that fiber1 was the major fiber for FAdV-C4 adsorption. 45,46 We obtained the same findings and further confirmed that fiber2 was non-essential for growing…”

Domain in Fiber-2 interacted with KPNA3/4 significantly affects the replication and pathogenicity of the highly pathogenic FAdV-4

“…However, little is known about the molecular basis for the infection and pathogenesis of FAdV-4. Recently, our group and other group both revealed that Fiber-1, but not Fiber-2, directly triggered the viral infection of FAdV-4 via its shaft and knob domains [ 11 , 12 ]. Zhang et al reported that Fiber-2, but not Fiber-1, was identified as one of the major virulent determiners for the highly pathogenic FAdV-4 endemic in China [ 10 ].…”

“…Zhang et al recently reported that Fiber-2 and Hexon, but not Fiber-1, were the virulent determiners for the highly pathogenic FAdV-4 isolates in comparison with the nonpathogenic strain [ 10 ]. Our group and other group’s recent studies found that the Fiber-1, not Fiber-2, directly triggered the viral infection of FAdV-4 via its shaft and knob domains [ 11 , 12 ]. However, the molecular basis of the Fiber-2 in the pathogenesis of the highly pathogenic FAdV-4 need to be further elucidated.…”

A novel fiber-2-edited live attenuated vaccine candidate against the highly pathogenic serotype 4 fowl adenovirus

“…Unlike other serotypes, serotypes FAdV-1, FAdV-4, and FAdV-10 have two fiber genes ( fiber-1 and fiber-2 ) [ 13 ]. Recently, our group and Wang’s group found that Fiber-1, but not Fiber-2, directly triggered the viral infection of FAdV-4 via its shaft and knob domains [ 14 , 15 ]. However, Zhang et al reported that Fiber-2, but not Fiber-1, was identified as one of the major virulent determiners for the highly pathogenic FAdV-4 endemic in China [ 16 ].…”