Sabin poliovirus type 2 capsid antigens (Sabin-2 capsid)

Sabin poliovirus type 2 capsid antigens are the structural proteins (VP1, VP2, VP3, and VP4) derived from the attenuated Sabin strain of Poliovirus Type 2. These proteins assemble into an icosahedral shell that protects the viral RNA genome and facilitates entry into host cells by binding to the poliovirus receptor, CD155 (UniProt, 2024; PubMed, 2021). In the context of pharmacology, these antigens are the critical components of the Oral Polio Vaccine (OPV) and Inactivated Polio Vaccine (IPV), designed to elicit a protective immune response against poliomyelitis. While highly effective at inducing mucosal and systemic immunity, the Sabin type 2 strain is notably prone to genetic reversion, where mutations in the capsid or 5' UTR can restore neurovirulence, leading to vaccine-derived outbreaks (CDC, 2023). Consequently, modern drug development has focused on 'novel OPV2' (nOPV2), which features a stabilized capsid and genome to prevent such reversions while maintaining the antigenic profile necessary for broad protection (Nature, 2020).

Other names

Poliovirus type 2 (Sabin) structural proteinsSabin strain type 2 VP1-VP4P2/712,Ch,2ab capsidOral poliovirus vaccine type 2 antigen

The capsid antigens serve as the primary targets for neutralizing antibodies. Vaccines containing these antigens (either live-attenuated or inactivated) induce B-cell activation and the production of IgG and IgA antibodies that prevent the virus from binding to the host receptor CD155, thereby neutralizing the virus and preventing infection of the central nervous system (NIH, 2023; WHO, 2022).