Stunned silence: gene expression programs in human cells infected with monkeypox or vaccinia virus.

Kathleen H Rubins,Patrick O Brown,David A Relman,Lisa E Hensley,Frank R Deleo

doi:10.1371/journal.pone.0015615

Abstract

Poxviruses use an arsenal of molecular weapons to evade detection and disarm host immune responses. We used DNA microarrays to investigate the gene expression responses to infection by monkeypox virus (MPV), an emerging human pathogen, and Vaccinia virus (VAC), a widely used model and vaccine organism, in primary human macrophages, primary human fibroblasts and HeLa cells. Even as the overwhelmingly infected cells approached their demise, with extensive cytopathic changes, their gene expression programs appeared almost oblivious to poxvirus infection. Although killed (gamma-irradiated) MPV potently induced a transcriptional program characteristic of the interferon response, no such response was observed during infection with either live MPV or VAC. Moreover, while the gene expression response of infected cells to stimulation with ionomycin plus phorbol 12-myristate 13-acetate (PMA), or poly (I-C) was largely unimpaired by infection with MPV, a cluster of pro-inflammatory genes were a notable exception. Poly(I-C) induction of genes involved in alerting the innate immune system to the infectious threat, including TNF-alpha, IL-1 alpha and beta, CCL5 and IL-6, were suppressed by infection with live MPV. Thus, MPV selectively inhibits expression of genes with critical roles in cell-signaling pathways that activate innate immune responses, as part of its strategy for stealthy infection.

Highlights

Monkeypox virus (MPV), an emerging human pathogen in the Democratic Republic of the Congo (DRC) and elsewhere in central and western Africa, produces an illness that shares clinical features with smallpox but is somewhat less lethal, with case fatality rates of approximately 10% [1,2,3]
To assess the permissiveness of primary human fibroblasts and HeLa cells to infection with MPV and VAC, we first examined the cytopathic effects (CPE) of infection
Our choice of primary human macrophages and primary human fibroblasts as the principal host cells in these studies followed from observations of smallpox and MPV infection in non-human primates, in which macrophages and fibroblasts were typically infected [54,55]

Summary

Introduction

Monkeypox virus (MPV), an emerging human pathogen in the Democratic Republic of the Congo (DRC) and elsewhere in central and western Africa, produces an illness that shares clinical features with smallpox but is somewhat less lethal, with case fatality rates of approximately 10% [1,2,3]. An outbreak of monkeypox in the United States in 2003 demonstrated the potential for this virus to spread from traditional endemic regions [4,5]. Despite the potential threat this virus poses to public health [3,6], relatively little is known about the host cellular responses to MPV. Vaccinia virus (VAC), in contrast, has been widely used as a model for understanding poxvirus biology and exploited for vaccine purposes. Vaccinia encodes proteins that suppress the host interferon response by binding double-stranded RNA (dsRNA) and inhibiting RNA-dependent protein kinase (PKR) and 2–5 oligoadenlylate synthase (OAS) activation [9,10,11,12,13,14,15], an eIF2a homolog that acts as a pseudosubstrate inhibitor of PKR [16,17,18], proteins that serve as a decoy receptors for IFNgamma [19,20,21] and IFN-alpha/beta [22,23,24], and two antagonists of host TLR signaling (A46R and A52R)

Methods

Results

Conclusion