Hypoxia Induces the Gene Expression and Extracellular Transmission of Persistent Lymphocytic Choriomeningitis Virus

Abstract

The physiological context of virus-infected cells can markedly affect multiplication and spread of the virus progeny. During persistent infection, the virus exploits the host cell without disturbing its vital functions. However, microenvironmental hypoxia can uncouple this intimate relationship and escalate virus pathogenesis. Accumulating evidence suggests that hypoxia-inducible factor (HIF) modulates gene expression of the viruses that pass through a DNA stage, contain hypoxia-responsive promoter elements, and replicate in the nucleus. Here we show that hypoxia can influence the gene expression and transmission of the cytoplasmic RNA virus lymphocytic choriomeningitis virus (LCMV), which is a neglected human pathogen and teratogen. The MX strain of LCMV, which we used as a model, replicates in a persistent mode in human HeLa cells, fails to produce mature envelope glycoproteins, and spreads through cell-cell contacts in the absence of extracellular infectious virions. Both exposure of MX-infected HeLa cells to chronic hypoxia and gene transfer approaches led to increased virus RNA transcription and higher levels of the viral proteins via a HIFdependent mechanism. Moreover, hypoxia enhanced the formation of infectious virions capable of transmitting LCMV by cell-free medium. This LCMV "reactivation" might have health-compromising consequences in hypoxia-associated situations, such as fetal development and ischemia-related pathologies.The prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) provides an important model for investigations of the mechanisms of viral persistence and pathogenesis. Studies using this model led to major advances in virology and immunology that apply universally to other viral and microbial infections of humans (5,7,43,45). Even though LCMV infections are mostly asymptomatic and often remain unnoticed, compelling evidence indicates that LCMV is a neglected human pathogen of clinical significance, especially in cases of congenital infections leading to an increased risk of spontaneous abortion or central nervous system (CNS) disorders and chorioretinitis (3,4,17,44). Moreover, LCMV poses a special threat to immunocompromised individuals, as tragically illustrated by recent cases of transplant-associated infections by LCMV with fatal outcomes in the United States (13) and Australia (25). LCMV has a bisegmented single-stranded RNA genome and a life cycle confined to the cell cytoplasm. The genome consists of a small segment (S) (3.4 kb) and a large segment (L) (7.2 kb). Each genomic segment uses an ambisense coding strategy to direct the synthesis of two polypeptides from two opposite open reading frames separated by an intergenic region. The S segment encodes a major viral protein nucleoprotein (NP) and a glycoprotein precursor (GPC), which is posttranslationally cleaved into peripheral glycoprotein 1 (GP1) and transmembrane glycoprotein 2 (GP2). The L segment encodes a viral RNA-dependent RNA polymerase (L) and a small regulatory RING domain-containing Z protein (Z) (6, 42). S...

Hypoxia promotes the phenotypic change of aldehyde dehydrogenase activity of breast cancer stem cells

“…GFP‐expressing Aldefluor pos cells were established using MISSION TurboGFP Control Particle (SHC003V; Sigma‐Aldrich) as control cells. And, to suppress HIF‐2α expression, cells were transfected with either HIF‐2α siRNA or negative control siRNA (Qiagen, Basel, Switzerland), using Lipofectamine LTX (Invitrogen) . All kits were used according to the manufacturer's instructions.…”

“…And, to suppress HIF-2a expression, cells were transfected with either HIF-2a siRNA or negative control siRNA (Qiagen, Basel, Switzerland), using Lipofectamine LTX (Invitrogen). (21) All kits were used according to the manufacturer's instructions.…”

Lymphocytic choriomeningitis virus: invisible but not innocent

“…Hypoxic transactivation was also accompanied by the production of infectious virus particles that were released to the medium as is typical of acute or productive chronic infections. Notably, we provided the first evidence of a hypoxia-induced "reactivation" and spread of a virus with an RNA genome, which replicates in the cytoplasm in a persistent mode without disrupting cell integrity (Tomaskova et al, 2011).…”

Lymphocytic choriomeningitis virus: ways to establish and maintain non-cytolytic persistent infection

“…LCMV infection during pregnancy has been associated with spontaneous abortions and birth defects (Barton et al, 1993) or in transplant patients with fatal illness (Barry et al, 2008;Hadler et al, 2006;MMWR-Dispatch, 2005;Schafer et al, 2014;Waggoner et al, 2013). Th ere is also evidence of reactivation of the persistent virus during hypoxia (Tomaskova et al, 2011). Physiologically, this can occur during heart attack, ischemia, stroke or pregnancy.…”