Characterization of virus inclusion bodies in bluetongue virus-infected cells

Abstract

A combined qualitative and quantitative approach has been used to examine the role of virus inclusion bodies (VIBs) in the morphogenesis ofbluetongue virus (BTV).VIBs were detected as early as 4h post-infection (p.i.), and their number and profile areas increased significantly between 12 and 16 h, and 20 and 28 h p.i.respectively. Core-and virus-like particles were found within and at the periphery of the VIB matrix, respectively, and their numerical density (number per area of VIB matrix) decreased during the course of infection whereas the numerical density of virus particles in the cytoplasm increased. Virus-like particles had a diameter of 57 + 8 nm and core-like particles appeared to fall into two size ranges, 32+3 nm and 38+__3 nm in diameter. Both pre-and post-embedding immunoelectron microscopy procedures were used to localize BTV structural and non-structural proteins within the VIBs. The VIB matrix was labelled with antibodies to structural proteins VP5 and VP7 and non-structural proteins NS1 and NS2. Cores within VIBs contained proteins VP5, VP7 and NS1 but not VP2. Virus-like particles at the periphery of VIBs contained VP2, VP5, VP7 and NS1. The results suggest that BTV particles are synthesized, assembled and released from the perimeter of VIBs and not from within the matrix. Cores embedded in the VIBs are likely to have been trapped there during expansion of the matrix during replication.

Grass carp reovirus activates RNAi pathway in rare minnow, Gobiocypris rarus

“…The virus inclusion bodies are the sites for virus synthesis and assembly (Brookes et al, 1993;Rivas et al, 1998). Uniform morphogenesis may indicate all the virions in the same inclusion body were replicated from a virus, which also indirectly verified that virus replication and assembly were originated in virus inclusion bodies.…”

Rice black streaked dwarf virus P9-1, an α-helical protein, self-interacts and forms viroplasms in vivo

“…Replication and assembly of viruses from the family Reoviridae are thought to take place in cytoplasmic inclusion bodies, and several non-structural viral proteins have been reported to be involved in the formation of these structures (Brookes et al, 1993;Dales, 1963;Fabbretti et al., 1999; Petrie et al, 1984;Rhim et al, 1962;Silverstein & Schur, 1970;Touris-Otero et al, 2004;Wei et al, 2006). To determine whether P9-1 is responsible for viroplasm formation, Arabidopsis protoplasts were transfected with plasmids encoding GFP or GFP-fused P9-1 and then observed by confocal laser-scanning microscopy at 16-24 h post-transfection.…”

“…The formation of viral inclusion bodies, or viroplasms, is a common feature of double-stranded (ds)RNA viruses from the family Reoviridae with genomes composed of 10-12 segments (Brookes et al, 1993;Fabbretti et al, 1999;Fukushi et al, 1962;Petrie et al, 1984;Rhim et al, 1962;Shikata & Kitagawa, 1977;Touris-Otero et al, 2004). These inclusion bodies are mainly composed of viral dsRNA, viral proteins and partially and fully assembled viral particles (Dales et al, 1965;Fabbretti et al, 1999;Isogai et al, 1998;Rhim et al, 1962;Silverstein & Schur, 1970;Touris-Otero et al, 2004;Wei et al, 2006).…”

Virus-derived Platforms for Visualizing Protein Associations inside Cells

“…These structures are variously called viral inclusion bodies (orbiviruses) (1), viral factories (orthoreoviruses) (2,3), or viroplasms (rotaviruses) (4) and are thought to be the sites of viral RNA replication and packaging into assembly intermediates that can later mature into infectious virions. The viral factories of some orthoreoviruses (such as certain isolates of strain Type 3 Dearing (T3D) 1 ), for example, have a globular morphology (5,6) and can attain large diameters (10 m or more) that make them easily identifiable by light microscopy (see Fig. 1a, left panel).…”