Broad Receptor Engagement of an Emerging Global Coronavirus may Potentiate its Diverse Cross-Species Transmissibility

May 15, 2018 — 

Coronaviruses exhibit a propensity for interspecies transmission, with SARS- and MERS-coronaviruses as notable examples. Cross-species transmission by coronaviruses is foremost determined by the virus' ability to bind receptors of new hosts. We here report that the recently identified, yet globally distributed porcine deltacoronavirus employs host aminopeptidase N (APN) as an entry receptor via S protein-mediated interaction with an interspecies conserved domain that allows for APN orthologue-mediated entry. Identification of APN as a deltacoronavirus receptor emphasizes the remarkable preferential employment of cell surface host peptidases as receptors by coronaviruses. Our findings provide important insight into how receptor usage of coronaviruses may fuel cross-host transmission between distantly related species and necessitate surveillance studies of deltacoronaviruses in thus far unappreciated potential reservoirs, including humans.

Abstract
Porcine deltacoronavirus (PDCoV), identified in 2012, is a common enteropathogen of swine with worldwide distribution. The source and evolutionary history of this virus is, however, unknown. PDCoV belongs to the Deltacoronavirus genus that comprises predominantly avian CoV. Phylogenetic analysis suggests that PDCoV originated relatively recently from a host-switching event between birds and mammals. Insight into receptor engagement by PDCoV may shed light into such an exceptional phenomenon. Here we report that PDCoV employs host aminopeptidase N (APN) as an entry receptor and interacts with APN via domain B of its spike (S) protein. Infection of porcine cells with PDCoV was drastically reduced by APN knockout and rescued after reconstitution of APN expression. In addition, we observed that PDCoV efficiently infects cells of unusual broad species range, including human and chicken. Accordingly, PDCoV S was found to target the phylogenetically conserved catalytic domain of APN. Moreover, transient expression of porcine, feline, human, and chicken APN renders cells susceptible to PDCoV infection. Binding of PDCoV to an interspecies conserved site on APN may facilitate direct transmission of PDCoV to nonreservoir species, including humans, potentially reflecting the mechanism that enabled a virus, ancestral to PDCoV, to breach the species barrier between birds and mammals. The APN cell surface protein is also used by several members of the Alphacoronavirus genus. Hence, our data constitute the second identification of CoVs from different genera that use the same receptor, implying that CoV receptor selection is subjected to specific restrictions that are still poorly understood.

Wentao Li, Ruben J. G. Hulswit, Scott P. Kenney, Ivy Widjaja, Kwonil Jung, Moyasar A. Alhamo, Brenda van Dieren, Frank J. M. van Kuppeveld, Linda J. Saif, and Berend-Jan Bosch; Broad Receptor Engagement of an Emerging Global Coronavirus may Potentiate its Diverse Cross-Species Transmissibility; PNAS May 14, 2018. 201802879; published ahead of print May 14, 2018.
https://doi.org/10.1073/pnas.1802879115