Reactivation of latent herpes simplex virus by adenovirus recombinants encoding mutant IE-0 gene products

Abstract

We have previously shown that adenovirus recombinants expressing functional ICPO reactivate latent herpes simplex virus type 2 (HSV-2) in an in vitro latency system. This study demonstrated that ICPO, independent of other HSV gene products, is sufficient to reactivate latent HSV-2 in this in vitro system. To assess the effects of defined mutations in the sequence encoding ICPO (IE-0) on reactivation, seven in-frame insertion and three in-frame deletion mutants were moved into an adenovirus expression vector. Each recombinant directed the synthesis of stable ICPO of the correct size. The transactivation activity of the mutated sequences in these recombinants was similar to that when they were tested in plasmids. When these recombinants were examined for their ability to reactivate in the in vitro latency system, mutants with dramatic defects in transactivation (Ad-0/125, Ad-0/89, Ad-0/2/7, and Ad-0/88/93) were unable to reactivate latent HSV-2 independent of the multiplicity of infection. An exception to this correlation was the finding that Ad-0/89, which transactivated poorly, was able to reactivate latent virus after prolonged incubation whereas other transactivation-deficient mutants could not. Moreover, the presence of ICP4 did not compensate for the inability of any of the recombinants tested to reactivate HSV-2. These results show that (i) the transactivation domains of ICPO are also used in reactivation, (ii) the presence of another essential HSV regulatory protein ICP4 does not alter the pattern of reactivation by ICPO, and (iii) mutations in some regions of IE-0 previously shown to affect viral growth and plaque formation did not alter its ability to reactivate in this in vitro system.

Extracellular Vpr protein increases cellular permissiveness to human immunodeficiency virus replication and reactivates virus from latency

“…It has been proposed that the tegument protein brought into cells during infection influences the decision between lytic and latent HSV infection. Tegument proteins ICP0 and Vmw110 are capable of reactivating virus expression in latently infected cells through transcriptional activation of early HSV genes, including themselves, in a probable positive feedback loop (23,72). In support of this analogy, HIV-2 Vpx protein is structurally and evolutionarily similar to Vpr (42,63,64), and virionassociated Vpx has been shown to increase the efficiency of viral replication immediately after infection (27).…”

A novel ubiquitin-specific protease is dynamically associated with the PML nuclear domain and binds to a herpesvirus regulatory protein

“…The Vmw110‐mutant virus particles which fail to begin replication enter a quiescent state from which they can be reactivated by superinfection (Stow and Stow, 1989). Tissue culture systems have been developed in which HSV‐1 genomes can be established in a quiescent or latent state, and their reactivation can be induced by provision of exogenous Vmw110 (Harris et al ., 1989; Zhu et al ., 1990). Furthermore, Vmw110‐deficient viruses reactivate inefficiently in mouse latency models (Clements and Stow, 1989; Lieb et al ., 1989; Cai et al ., 1993).…”

Mutational analysis of the herpes simplex virus type 1 ICP0 C3HC4 zinc ring finger reveals a requirement for ICP0 in the expression of the essential alpha27 gene

“…Latent HSV-1 and HSV-2 appear to express primarily the latency-associated transcripts, whose function(s) is unknown (26,69). Current evidence suggests that ICP0 functions in the reactivation of latent HSV-1, since it was shown to be both necessary and sufficient for the reactivation of latent virus in model systems (33,82).…”

“…All alphaherpesviruses for which the DNA sequence is available encode proteins related to HSV-1 ICP0 (27). Although the function(s) of these proteins has yet to be established, they all appear to participate in the regulation of virus gene expression (11,12,19,20,22,33,48,49,74,79,82). Structural analysis of the C 3 HC 4 zinc finger domain from one of these proteins, the product of equine herpesvirus gene 63 (EHV- 63), demonstrates that this domain conforms to a ␤␤␣␤ structure, comprising three antiparallel beta-strands and an amphipathic alpha-helix (4,24).…”