Orthopoxvirus A27 protein (A27)

The Orthopoxvirus A27 protein is a highly conserved 14-kDa envelope protein essential for the attachment of the intracellular mature virus (IMV) to host cells (UniProt P06953). It functions by binding to cell surface heparin sulfate glycosaminoglycans, facilitating the initial stages of viral entry (PubMed: 15956310). Additionally, A27 is required for the transport of IMV particles to the site of wrapping, where they acquire an additional double membrane to become extracellular enveloped virus (EEV) (PubMed: 22438551). As a major surface antigen, it is a key target for the host immune response; neutralizing antibodies against A27 can prevent viral infection by blocking both attachment and fusion (NCBI: NBK574519). While current antivirals like Tecovirimat target other proteins, A27 remains a primary focus for vaccine development and monoclonal antibody therapies, such as those found in Vaccinia Immune Globulin (VIGIV) (PubMed: 35921475). Its structural stability and conservation across species like Variola and Mpox virus make it an ideal candidate for cross-protective countermeasures. Therapeutic interventions often aim to mimic the natural antibody response to this protein to provide passive immunity. Research into A27 also informs the design of subunit vaccines that could offer safer alternatives to live-virus vaccines.

Other names

A27L proteinHeparin-binding proteinEnvelope protein A27Vaccinia virus A27 proteinP14 protein

Neutralizing antibodies bind to the A27 protein to block viral attachment to cell surface glycosaminoglycans and prevent membrane fusion, thereby inhibiting viral entry into host cells (PubMed: 15956310).