Virus entry and replication in the brain precedes blood-brain barrier disruption during intranasal alphavirus infection

Abstract

Viral infections of the central nervous system (CNS) are often associated with blood-brain barrier (BBB) disruption, yet the impact of virus replication and immune cell recruitment on BBB integrity are incompletely understood. Using two-photon microscopy, we demonstrate that Venezuelan equine encephalitis virus (VEEV) strain TC83-GFP, a GFP expressing, attenuated strain with a G3A mutation within the 5′ UTR that is associated with increased sensitivity to type I interferons (IFNs), does not directly impact BBB permeability. Following intranasal infection of both wild-type and IFN-induced protein with tetratricopeptide repeats 1 (IFIT1)-deficient mice, which fail to block TC83-specific RNA translation, virus spreads to the olfactory bulb and cortex via migration along axonal tracts of neurons originating from the olfactory neuroepithelium. Global dissemination of virus in the CNS by 2 days post-infection (dpi) was associated with increased BBB permeability in the olfactory bulb, but not in the cortex or hindbrain, where permeability only increased after the recruitment of CX3CR1+ and CCR2+ mononuclear cells on 6 dpi, which corresponded with tight junction loss and claudin 5 redistribution. Importantly, despite higher levels of viral replication, similar results were obtained in IFIT1-deficient mice. These findings indicate that TC83 gains CNS access via anterograde axonal migration without directly altering BBB function and that mononuclear and endothelial cell interactions may underlie BBB disruption during alphavirus encephalitis.

Zika virus infects pericytes in the choroid plexus and enters the central nervous system through the blood-cerebrospinal fluid barrier

“…1d and Supplementary Fig. 1) that showed widely distributed strong positive staining around the capillaries in the cortex as previously reported by others (23).…”

EGR1 upregulation following Venezuelan equine encephalitis virus infection is regulated by ERK and PERK pathways contributing to cell death

“…Astrocytes and neurons are the primary targets of VEEV in the brain (Cain et al, 2017) inducing well-characterized cytopathic effects in neurons of the CNS. In this study, we showed that VEEV replication in human primary astrocytes and the apoptosis induced following VEEV infection can be suppressed by blocking either ERK or PERK pathways, both of which are responsible for upregulating EGR1 pathway, rescuing the cells from VEEV induced apoptosis.…”

Direct and indirect pro-inflammatory cytokine response resulting from TC-83 infection of glial cells

“…Cells were seeded at a density of 10 [4] cells per 100 µl in 96-well plates overnight, followed by the addition of DMEM with TC-83 (MOI of 2). The cells were incubated for 1h at 37.1°C.…”

“…Approximately 1% of all infections develop into severe encephalitic illness, which can result in coma and death. These deleterious outcomes are most closely associated with aerosol exposure, which allows the virus to quickly enter the brain via the olfactory nerve, where it can establish a robust infection [4–6]. Neuronal cells are highly permissive to VEEV infection, resulting in rapid viral dissemination, widespread neuroinflammation, and destruction of the blood brain barrier (BBB) [4].…”

“…These deleterious outcomes are most closely associated with aerosol exposure, which allows the virus to quickly enter the brain via the olfactory nerve, where it can establish a robust infection [4–6]. Neuronal cells are highly permissive to VEEV infection, resulting in rapid viral dissemination, widespread neuroinflammation, and destruction of the blood brain barrier (BBB) [4]. Similar to other neurotropic viral infections, viremia in the brain is associated with long term neurological sequelae, including the potential for development of seizures [7–9].…”