Progeny Varicella-Zoster Virus Capsids Exit the Nucleus but Never Undergo Secondary Envelopment during Autophagic Flux Inhibition by Bafilomycin A1

Girsch, James H.; Walters, Katherine; Jackson, Wallen; Grose, Charles

Locations of VZV particles within nuclear membranes and cytoplasm after bafilomycin treatment. Based on the abrupt drop in titer in monolayers treated with BAF, we postulated that the defect was occurring during or after secondary envelopment of the viral particle. For this project, we acquired 230 additional micrographs of both BAF-treated infected and uninfected monolayers. The initial observations of BAF-treated infected monolayers provided an unanticipated finding, namely, numerous viral particles were detected in the perinuclear space (Fig. 4) . These particles often did not have the typical structure of a primary enveloped virus (PEV); instead, they had an aberrant appearance that had been observed previously by ourselves and others in VZV-infected cells without BAF treatment (20) (21) (22) . After further inspection, it was apparent that VZV particles were also found in the cytoplasm, often adjacent to Golgi apparatus-derived vesicles (Fig. 5) . Some of these capsids also were aberrant in appearance (Fig. 5A) . Although most Golgi cisternae were disrupted, an occasional Golgi apparatus with cis and trans cisternae was found; however, we were unable to find any evidence of wrapping of capsids by intact Golgi cisternae (Fig. 5B ). Only after considerable inspection of the 230 micrographs were we able to find a few examples of virus assembly compartments (VACs). The VACs in BAF-treated cells did not contain prototypical enveloped viral particles (virions); instead, they contained enveloped particles without capsids, presumably light particles with varying diameters. The VACs were located near other Golgi-derived vacuoles (Fig. 5C) . A particularly large VAC is shown in Fig. 5D ; this elongated structure was likely a single VAC that extended below and above the plane cut by the microtome.