Degenerate PCR method for identification of an antiapoptotic gene in BHV-1

Modulation of apoptosis by caprine herpesvirus 1 infection in a neuronal cell line

Caprine herpesvirus type 1 (CpHV-1), like other members of the alpha subfamily of herpesviruses, establishes latent infections in trigeminal ganglion neurons. Our groups previously demonstrated that CpHV-1 induces apoptosis in goat peripheral blood mononuclear cells and in an epithelial bovine cell line, but the ability of CpHV-1 to induce apoptosis in neuronal cells remains unexplored. In this report, the susceptibility of Neuro 2A cells to infection by CpHV-1 was examined. Following infection of cultured cells with CpHV-1, expression of cell death genes was evaluated using real-time PCR and Western blot assays. Analysis of virus-infected cells revealed activation of caspase-8, a marker for the extrinsic pathway of apoptosis, and caspase-9, a marker for the intrinsic pathway of apoptosis at 12 and 24 h post-infection. Significant increase in the levels of cleaved caspase-3 was also observed at the acme of cytopathic effect at 24 h post-infection. In particular, at 3 and 6 h post-infection, several proapototic genes were under-expressed. At 12 h post-infection several proapototic genes such as caspases, TNF, Cd70, and Traf1 were over expressed while Bcl2a1a, Fadd, and TNF genes were underexpressed. In conclusion, the simultaneous activation of caspase-8 and caspase-9 suggests that CpHV-1 can trigger the death-receptor pathway and the mitochondrial pathway separately and in parallel. Our findings are significant because this is the first published study showing the effect of CpHV-1 infection in neuronal cells in terms of gene expression and apoptosis modulation.

Screening and identification of host factors interacting with UL14 of herpes simplex virus 1

The UL14 protein of herpes simplex virus type 1 (HSV-1) is highly conserved in herpesvirus family. However, its exact function during the HSV-1 replication cycle is little known. In the present study, a high throughput yeast two-hybrid system was employed to screen the cellular factors interacting with UL14, and five target candidates were yielded: (1) TSC22 domain family protein 3 (TSC22D3); (2) Mediator of RNA polymerase II transcription subunit 8 isoform 1(MED8); (3) Runt-related transcription factor 3 (RUNX3); (4) Arrestin beta-2 (ARRB2); (5) Cereblon (CRBN). Indirect immunofluorescent assay showed that both TSC22D3 and MED8 co-localized with UL14. Co-immunoprecipitation assay demonstrated that UL14 could be immunoprecipitated by TSC22D3, suggesting that UL14 interacted with TSC22D3 under physiological condition. In summary, this study opened up new avenues toward delineating the function and physiological significance of UL14 during the HSV-1 replication cycle.

2,3,7,8-tetrachlorodibenzo-p-dioxin regulates bovine herpesvirus type 1 induced apoptosis by modulating Bcl-2 family members

Exposure to environmental contaminants, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), leads to an increased susceptibility to infectious agents. Infection of bovine cells (MDBK) with Bovine Herpesvirus 1 (BHV-1) anticipates virus-induced apoptosis, suggesting an involvement of TCDD in virus infection. Herein we analyzed the effects of TCDD on apoptotic pathway in MDBK cells infected with BHV-1. After 12 h of infection, TCDD induced a significant increase in apoptotic cells. TCDD caused a dose-dependent up-regulation and anticipated activation of caspases 3, 8 and 9, with respect to unexposed groups. TCDD anticipated cleavage of PARP, compared to controls. Furthermore TCDD increased Bax and Bid levels, and decreased Bcl-2 and Bcl-XL levels. Such events took place earlier in exposed than unexposed cells. These results showed that TCDD influences BHV-1 induced apoptosis through members of Bcl-2 family and up-regulating activation of caspases.

Bovine herpesvirus type 1 induces cell death by a cell-type-dependent fashion

Bovine herpesvirus 1 (BHV-1), a member of the alpha-herpesvirinae sub-family, causes significant losses to the cattle industry. BHV-1 establishes latency in trigeminal ganglionic sensory neurons, but periodically reactivates from latency. Previous studies suggested that infection with BHV-1-induced novel morphological changes in rabbit skin (RS) cells versus bovine kidney cells (MDBK). Consequently, we hypothesized that viral infection led to a novel form of cell death in RS cells compared to MDBK cells. To test this hypothesis, we examined the levels of apoptosis in these cell types following infection with BHV-1. Infection of RS, but not MDBK, cells leads to high levels of apoptosis compared to mock-infected cells. Previous studies indicated that a BHV-1 recombinant virus that does not express the bICP0 protein grows poorly in permissive cells and induces a persistent-like infection. This suggested that bICP0 played an important role in regulating cell death following infection. To test this hypothesis, we compared the levels of apoptosis in cells infected with the bICP0 null mutant versus viral strains that expressed bICP0. The bICP0 null mutant induces low levels of apoptosis in RS or MDBK cells. When MDBK cells are treated with UV light prior to infection, bICP0 expressing viral strains, but not the bICP0 null mutant, inhibited UV-induced apoptosis. Infection of MDBK cells with the bICP0 null mutant, leads to an accumulation of autophagosomes that are not detected following infection with bICP0 expressing viruses. These studies suggest that the bICP0 null mutant induces autophagy in MDBK cells, and bICP0 protein expression mediates cell-type specific cytotoxicity.