Induction of cell-cell fusion by ectromelia virus is not inhibited by its fusion inhibitory complex.
BACKGROUND
Ectromelia virus, a member of the Orthopox genus, is the causative agent of the highly infectious mousepox disease. Previous studies have shown that different poxviruses induce cell-cell fusion which is manifested by the formation of multinucleated-giant cells (polykaryocytes). This phenomenon has been widely studied with vaccinia virus in conditions which require artificial acidification of the medium.


RESULTS
We show that Ectromelia virus induces cell-cell fusion under neutral pH conditions and requires the presence of a sufficient amount of viral particles on the plasma membrane of infected cells. This could be achieved by infection with a replicating virus and its propagation in infected cells (fusion "from within") or by infection with a high amount of virus particles per cell (fusion "from without"). Inhibition of virus maturation or inhibition of virus transport on microtubules towards the plasma membrane resulted in a complete inhibition of syncytia formation. We show that in contrast to vaccinia virus, Ectromelia virus induces cell-cell fusion irrespectively of its hemagglutination properties and cell-surface expression of the orthologs of the fusion inhibitory complex, A56 and K2. Additionally, cell-cell fusion was also detected in mice lungs following lethal respiratory infection.


CONCLUSIONS
Ectromelia virus induces spontaneous cell-cell fusion in-vitro and in-vivo although expressing an A56/K2 fusion inhibitory complex. This syncytia formation property cannot be attributed to the 37 amino acid deletion in ECTV A56.
Erez
Noam
N
Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona, Israel. noame@iibr.gov.il
Paran
Nir
N
Maik-Rachline
Galia
G
Politi
Boaz
B
Israely
Tomer
T
Schnider
Paula
P
Fuchs
Pinhas
P
Melamed
Sharon
S
Lustig
Shlomo
S
D000818:Animals; D002459:Cell Fusion; D002460:Cell Line; D004481:Ectromelia virus / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000473:pathology / Q000821:virology; D051379:Mice; D014764:Viral Proteins / Q000502:physiology*
D014764:Viral Proteins