Scientific Publications by FDA Staff

Clin Vaccine Immunol 2014 Sep;21(9):1330-8

Glycosylated and nonglycosylated complement control protein of the lister strain of vaccinia virus.

Meseda CA, Kuhn J, Atukorale V, Campbell J, Weir JP

The vaccinia virus complement control protein (VCP) is a secreted viral protein that binds the C3b and C4b complement components and inhibits the classical and alternative complement pathways. Previously, we reported that an attenuated smallpox vaccine, LC16m8, which was derived from the Lister strain of vaccinia virus (VV-Lister), expressed a glycosylated form of VCP, whereas published sequence data at that time indicated that the VV-Lister VCP has no motif for N-linked glycosylation. We were interested in determining whether the glycosylation of VCP impairs its biological activity, possibly contributing to the attenuation of LC16m8, and the likely origin of the glycosylated VCP. Expression analysis indicated that VV-Lister contains sub-strains expressing glycosylated VCP and those expressing non-glycosylated VCP. Other strains of smallpox vaccine, as well as laboratory strains of vaccinia virus, all expressed non-glycosylated VCP. Individual Lister virus clones expressing either the glycosylated VCP or the non-glycosylated species were isolated, and partially purified VCP from the isolates were found to be functional equivalents in binding human C3b and C4b complement proteins and inhibition of hemolysis, and in immunogenicity. Recombinant vaccinia viruses expressing FLAG-tagged glycosylated VCP (FLAG-VCPg) and non-glycosylated VCP (FLAG-VCP) were constructed based on the Western Reserve strain. Purified FLAG-VCP and FLAG-VCPg bind human C3b and C4b and blocked complement-mediated hemolysis. Our data suggest that glycosylation did not affect the biological activity of VCP, and thus may not have contributed to the attenuation of LC16m8. In addition, the LC16m8 virus likely originated from a sub-strain of VV-Lister that expresses glycosylated VCP.