The vaccinia virus fusion inhibitor proteins SPI-3 (K2) and HA (A56) expressed by infected cells reduce the entry of superinfecting virus

• Published in: Virology (New York, N.Y.) N.Y.), 2008-10, Vol.380 (2), p.226-233
• Main Authors: Turner, Peter C, Moyer, Richard W
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Animals; ANTIBODIES; Cell–cell fusion; Cercopithecus aethiops; Cowpox virus; Hemagglutinin (A56R); INACTIVATION; Infectious Disease; LUCIFERASE; Luciferases - genetics; Luciferases - metabolism; Orthopoxvirus; RNA POLYMERASES; SPI-3 (K2L); Staining and Labeling - methods; Superinfection; VACCINIA VIRUS; Vaccinia virus - genetics; Vaccinia virus - physiology; Vero Cells; Viral Proteins - metabolism; Virus Attachment; Virus entry; Virus Internalization
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2008.07.020

Abstract The orthopoxvirus SPI-3 (K2) and A56 (hemagglutinin, HA) proteins interact and together prevent cell–cell fusion. SPI-3/A56 has been proposed to prevent the superinfection of previously infected cells by reducing virus–cell fusion. Binding of mature virions of vaccinia virus (VV) to VV-infected cells was unaffected by SPI-3 or A56 on the surface of infected cells. Entry of VV into infected cells was assessed using VV-PT7 -luc carrying the luciferase reporter under T7 control. Cells infected with VV or cowpox virus (CPV) expressing T7 RNA polymerase and lacking SPI-3 and/or A56 were superinfected with VV-PT7 -luc, and luciferase activity was measured. Inactivation of SPI-3 or A56 from the pre-infecting virus resulted in greater luciferase expression from the superinfecting VV-PT7 -luc. Antibody against SPI-3 present during infection with wild-type CPV-T7 increased luciferase expression from superinfecting VV-PT7 -luc. The SPI-3/A56 complex on the infected cell surface therefore appears to reduce the entry of virions into infected cells.