Jumping species-a mechanism for coronavirus persistence and survival

Abstract

Zoonotic transmission of novel viruses represents a significant threat to global public health and is fueled by globalization, the loss of natural habitats, and exposure to new hosts. For coronaviruses (CoVs), broad diversity exists within bat populations and uniquely positions them to seed future emergence events. In this review, we explore the host and viral dynamics that shape these CoV populations for survival, amplification, and possible emergence in novel hosts.

Figure 1

Balancing coronavirus emergence. Bat populations maintain a unique environment that facilitates survival and maintenance of diverse pools of viruses. To overcome species barriers, CoV must modify some key viral factors while maintaining others. Two mechanisms govern this balance: fidelity and gene modulation. Using these processes, CoVs shape their proteins conserving some (viral enzymes, structural proteins, spike S2) while modifying others (non-structural proteins, accessory proteins, spike S1). The resulting pools therefore maintain viability while also possessing tools necessary for emergence.

Figure 2

Conservation and modification of spike protein. The CoV spike protein is critical receptor binding and entry. Therefore, while modification is likely required for infection of new species, the spike protein must also maintain its entry mechanism. (a) Structure of MHV-CoV spike trimer (adapted from Ref. [53]), dividing the protein into S1 globular head portions (blue), and S2 conserved stalk (green). (b) Heat maps were constructed from a set of representative coronaviruses from all four genogroups using alignment data paired with neighbor-joining phylogenetic trees built in Geneious (v.9.1.5) and visualized in EvolView (evolgenius.info). Trees show the degree of genetic similarity of S1 and S2 domains of the spike glycoprotein.

Figure 3

Maintenance and change the CoV backbone. Changes to the CoV backbone can aid emergence, but must be balanced against conservation of other elements. (a) Genomic structure of SARS-CoV with proteins predicted to be conserved (blue), variable (red), or in between (purple). (b) Heat maps were constructed from a set of representative coronaviruses from all four genogroups using alignment data paired with neighbor-joining phylogenetic trees built in Geneious (v.9.1.5) and visualized in EvolView (evolgenius.info). Trees show the degree of genetic similarity of ORF6, NSP2, nucleocapsid, and NSP14 across genera.