Orthopoxvirus extracellular enveloped virion surface antigen (EEV surface antigen)

Orthopoxvirus extracellular enveloped virion (EEV) surface antigens are a specialized set of viral proteins required for the assembly and release of the EEV form of orthopoxviruses, such as Variola (smallpox) and Monkeypox viruses (Smith et al., 2002). While the intracellular mature virion (IMV) remains within the cell until lysis, the EEV is wrapped in an additional host-derived lipid bilayer and is actively released to facilitate long-range dissemination and rapid cell-to-cell spread (Blasco & Moss, 1991). The most prominent of these antigens is the p37 protein, encoded by the highly conserved F13L gene, which acts as a critical scaffold for the wrapping process (Grosenbach et al., 2018). Other key antigens include B5R and A33R, which are involved in actin tail formation and protection from host complement and antibodies. The p37 protein is the specific molecular target of the antiviral drug Tecovirimat, which prevents the formation of EEVs and thus halts the progression of the infection (FDA, 2018). Targeting these antigens is a primary strategy for managing outbreaks of smallpox and mpox by limiting viral transmission within the host organism.

Other names

p37 proteinF13L proteinMajor envelope proteinEEV-specific proteinsA33RB5RA34RA36R

Tecovirimat inhibits the p37 protein (encoded by the F13L gene), which is required for the wrapping of intracellular mature virions (IMV) with a host-derived membrane to form extracellular enveloped virions (EEV), thereby preventing viral egress and systemic spread (Grosenbach et al., 2018; FDA, 2018). Vaccinia immune globulin intravenous provides passive immunity via neutralizing antibodies that target EEV surface antigens such as B5R and A33R (Wittek, 2006).