Cytopathological changes induced by selected Brazilian flaviviruses in mouse macrophages

Abstract

SummaryScanning and transmission electron microscopy were used to analyse the ultrastructure of peritoneal mouse macrophage cells infected with Brazilian flavivirus (yellow fever, Rocio, Bussuquara and Saint Louis encephalitis viruses). Macrophage cells collected 3 days after viral infection had a flattened shape, with an increased number of large spikes of cytoplasm prolongations, giving an appearance of hairy cells. Cytopathological changes to the macrophage cells were similar regardless of the infecting flavivirus. Rough and smooth endoplasmic reticulum of the macrophage cells infected with flavivirus were abundant, hypertrophic and enlarged. A large number of free ribosomes were seen in the cytoplasm of these infected cells. Spherical particles approximately 50-70 nm in diameter, some of which were empty, were observed in the cytoplasm, generally inside vesicles. These particles probably correspond to viral particles.

Restricted replication and lysosomal trafficking of yellow fever 17D vaccine virus in human dendritic cells

“…Many viruses that enter cells by receptor-mediated endocytosis undergo a pH-dependent endosomal/virus fusion that allows virus uncoating and escape of viral nucleocapsids into cytoplasmic sites for initiation of the replication cycle (Gruenberg, 2001;Lakadamyali et al, 2003). In marked contrast to DCs, but similar to Vero cells, replication of YF-VAX in monocytes and the macrophage-like cell line U937 is highly productive (Barros et al, 2004;Liprandi & Walder, 1983;Marianneau et al, 1999b) and we speculate that the difference between these cell types and DCs is related to uptake and processing of YF-VAX. An additional consideration is that the disproportionate number of envelope protein mutations carried by YF-VAX in comparison with the parental Asibi strain (Hahn et al, 1987) alters host binding and penetration properties, as has been described previously for attenuated variants of JEV and Murray Valley encephalitis virus (Lee & Lobigs, 2002), with implications for their intracellular distribution sites.…”

“…Both YFV-17D and wild-type YFV replicate productively in human monocytes and macrophages including Kupffer cells (Barros et al, 2004;Liprandi & Walder, 1983;Marianneau et al, 1999b). Replication of YFV-17D in human DCs has also been detected using plaque assays (Barba-Spaeth et al, 2005;Brandler et al, 2005) and by detection of intracellular non-structural protein NS4A and NS4B (Barba-Spaeth et al, 2005;Querec et al, 2006).…”

A Shorter Fixation Protocol for Transmission Electron Microscopy: An Alternative to Spend Less Time

“…This procedure takes between 1 and 2 h. A postfixation with osmium tetroxide for 30 min and some wash and dehydration steps after the fixation are also required. The embedding process in epoxy resin is the final step, and it lasts approximately 2 days [3].…”