Screening candidate intermediate hosts for porcine respiratory coronavirus using molecular docking

Emerging coronavirus-associated acute respiratory diseases have posed major global health and economic disruption, highlighting the ongoing risk of zoonotic spillover. Cross-species transmission is largely determined by the interaction between viral receptor-binding domains (RBDs) and host cellular receptors. This study utilizes Porcine Respiratory Coronavirus (PRCoV) as a model to investigate host adaptation via the Aminopeptidase N (APN) receptor. Using molecular docking and structural analysis, we evaluated the docking-estimated binding affinity between the PRCoV RBD and APN proteins from 18 vertebrate species. Sequence analysis revealed that Camelidae, Bovidae, and Hipposiderid bats share the highest similarity (70%-85%) with porcine APN (pAPN). Notably, Hipposiderid bats showed up to 80% similarity with both pAPN and human APN (hAPN), suggesting a significant ecological role in viral evolution. Meanwhile, avian, reptile, and aquatic species showed greater divergence from mammals, with 45-60% sequence similarity. Molecular docking results highlight the high predicted receptor compatibility among pigs, cats, bats, horses, rabbits, and cattle. While wild-type PRCoV displayed a tenfold lower affinity for hAPN (K_d 2971 pM) compared to pAPN (K_d 261 pM), specific single amino acid substitutions in the RBD enhanced binding compatibility to hAPN, reducing K_d values to below 100 pM. These RBD variants, analogous to mutations seen in SARS-CoV-2, suggest that minimal genetic shifts could increase predicted hAPN binding in the in-silico prediction. These findings highlight the potential for receptor-binding adaptation candidates and emphasize the importance of monitoring viral evolution and host receptor diversity to support early detection and support receptor-based surveillance and future validation.