Apoptosis Induced by a Postbinding Step of Vaccinia Virus Entry into Chinese Hamster Ovary Cells

Abstract

Unlike most cell types examined, nonpermissive Chinese hamster ovary (CHO) cells readily underwent apoptosis upon infection with vaccinia virus (VV). Apoptosis was observed as early as 3 h postinfection with an electrophoretic assay of DNA fragmentation and by 8 h using an in situ (TUNEL) assay. The CHO hr gene from cowpox virus, which overcomes host range restriction of VV in CHO cells, merely delayed the onset of apoptosis by approximately 3 h. Intermediate and late viral protein synthesis were not necessary for apoptosis since these events do not proceed under nonpermissive conditions. Apoptosis also occurred in the presence of cytosine arabinoside or cycloheximide, which inhibits DNA or protein synthesis, respectively, and after infection with a mutant virus that is blocked in early transcription. We also demonstrated that viral early transcription was not required for induction of apoptosis by infecting CHO cells with psoralen/UV-inactivated virus. On the other hand, apoptosis was inhibited by a neutralizing antibody to the virion L1R protein added either before or after virus attachment to cells. These results indicate that a postbinding step associated with cell entry is sufficient and required for induction of apoptosis in CHO cells. Recent progress on apoptotic signaling pathways raises the possibility that a cellular receptor for VV may be involved in apoptosis.

Immune properties of recombinant vaccinia virus encoding CD154 (CD40L) are determined by expression of virally encoded CD40L and the presence of CD40L protein in viral particles

“…However, PS/UV treatment can also inhibit transcription of some genes under control of synthetic E/L vaccinia promoters 29,30 and we found that exposure of rV-CD40L to PS/UV prior to cell infection essentially prevented expression of CD40L in the infected cells (data not shown). To avoid this problem, MC38 cells were infected with rV-CD40L for 16 hours and then treated with PS/UV, which resulted in inactivation of virus while maintaining high levels of CD40L expression (MC38/rV-CD40L N ).…”

The Enhanced Tumor Selectivity of an Oncolytic Vaccinia Lacking the Host Range and Antiapoptosis Genes SPI-1 and SPI-2

“…Cells infected with vaccinia eventually die; this death does not occur via apoptosis in most cell lines studied (35)(36)(37). Vaccinia virus encodes a number of antiapoptotic genes, including SPI-1 and SPI-2.…”

“…These processes might change the conformation and structure of the plasma membrane to create Annexin V-positive staining, which normally is an indicator of early apoptosis. Second, based on previous studies, vaccinia induces cell death via nonapoptotic pathways in most cell types (35,36). Third, all previous experiments demonstrating antiapoptotic effects for SPI-1 and SPI-2 proteins were done under specific sets of conditions.…”

Glycoprotein of Nonpathogenic Rabies Viruses Is a Key Determinant of Human Cell Apoptosis

“…Human immunodeficiency virus gp120 and gp41 induce apoptosis by interacting with CD4 and CxCR4, whereas the Sindbis virus E2 protein targets an early step in the replication process that occurs shortly after entry. Similarly, the entry of vaccinia virus or herpes simplex virus type 1 can induce apoptosis (20,48). For RV, the direct interaction of virus particles with the membrane is not sufficient to induce apoptosis, as cells treated with inactivated noninfectious virus particles do not undergo apoptosis (25,57).…”