Human Rhinovirus Capsid (HRV Capsid)

The Human Rhinovirus (HRV) capsid is an icosahedral protein shell composed of 60 copies each of four structural proteins: VP1, VP2, VP3, and VP4. It serves as the primary interface between the virus and the host, facilitating attachment to cellular receptors like ICAM-1, LDLR, or CDHR3 through a surface depression known as the 'canyon.' Beyond attachment, the capsid protects the viral RNA genome and undergoes critical structural transitions to allow for genome release (uncoating) upon entry into the host cell. Rhinoviruses are the leading cause of the common cold and are major triggers for severe exacerbations of chronic respiratory diseases such as asthma and COPD. Therapeutic strategies targeting the capsid involve small-molecule 'capsid binders' that lodge in a hydrophobic pocket within VP1. These drugs, such as pleconaril and vapendavir, inhibit viral replication by stabilizing the capsid against uncoating and, in some cases, blocking initial receptor attachment. Despite extensive development, challenges such as high serotype diversity and the rapid emergence of resistance have hindered the clinical approval of these agents.

Other names

Rhinovirus capsid proteinHRV VP1-VP4 complexRhinovirus attachment structurePicornavirus capsidViral protein 1 (VP1)Viral protein 2 (VP2)Viral protein 3 (VP3)Viral protein 4 (VP4)

Capsid-binding drugs typically enter a hydrophobic pocket located within the VP1 structural protein, beneath the surface 'canyon' used for receptor binding. This interaction stabilizes the viral capsid, preventing the conformational changes and 'uncoating' required to release the viral RNA genome into the host cell cytoplasm. Additionally, drug binding can distort the canyon structure, sterically hindering the virus's ability to attach to host cell receptors such as ICAM-1 or LDLR.