Poliovirus type 2 Sabin strain capsid (PV2 Sabin capsid)

The Poliovirus type 2 Sabin strain capsid is the proteinaceous shell of the live-attenuated virus used in the oral poliovirus vaccine (OPV). It is composed of 60 copies each of four structural proteins (VP1, VP2, VP3, and VP4) arranged in an icosahedral lattice, which protects the positive-sense single-stranded RNA genome (UniProt: P03300). The capsid is responsible for recognizing and binding to the host cell receptor, CD155 (poliovirus receptor), and undergoes complex conformational rearrangements to facilitate the injection of the viral genome into the cytoplasm (PubMed: 11967301). In the context of global polio eradication, the Sabin 2 capsid is a critical target for both vaccine design and the development of antiviral 'capsid inhibitors' like Pocapavir. These drugs bind to a hydrophobic 'pocket' in the VP1 protein, stabilizing the capsid to prevent the uncoating process required for infection (PubMed: 25183725). While the Sabin 2 strain is highly effective for immunization, its capsid can undergo genetic mutations that lead to the emergence of circulating vaccine-derived polioviruses (cVDPVs), which can cause paralytic disease similar to wild-type poliovirus (WHO, 2023).

Other names

Poliovirus type 2 Sabin strain structural proteinPV2 Sabin VP1-VP4 complexSabin 2 capsidOral Poliovirus Vaccine type 2 capsid

Capsid-binding inhibitors (WIN compounds) bind to a hydrophobic pocket within the VP1 subunit of the capsid, which increases the rigidity of the virion and prevents the conformational changes necessary for viral uncoating and the release of RNA into the host cell (PubMed: 25183725, 28834711).