Infection of Glia by Human Pegivirus Suppresses Peroxisomal and Antiviral Signaling Pathways

Abstract

Human pegivirus (HPgV) infects peripheral leukocytes but was recently shown to be a neurotropic virus associated with leukoencephalitis in humans. In the present study, we investigated the neural cell tropism of HPgV as well as its effects on host immune responses. HPgV wild type (WT) as well as a mutant virus with a deletion in the HPgV NS2 gene (ΔNS2) were able to productively infect human astrocytes and microglia but not neurons or an oligodendrocyte-derived cell line. Of note, the ΔNS2 virus replicated better than WT pegivirus in astrocytes with both viruses being able to subsequently infect and spread in fresh human astrocyte cultures. Infection of human glia by HPgV WT and ΔNS2 viruses resulted in suppression of peroxisome-associated genes including PEX11B, ABCD1, PEX7, ABCD3, PEX3 and PEX5L during peak viral production, which was accompanied by reduced expression of IFNB, IRF3, IRF1, and MAVS , particularly in ΔNS2-infected cells. These data were consistent with analyses of brain tissue from patients infected with HPgV in which we observed suppression of peroxisome and type I interferon gene transcripts including PEX11B, ABCD3, IRF1, and IRF3 with concurrent loss of PMP70 immunoreactivity in glia. Our data indicate that human astrocytes and microglia are permissive to HPgV infection resulting in peroxisome injury and suppressed antiviral signaling that is influenced by viral diversity. Importance: Human pegiviruses are detected in 1-5% of the general population, principally infecting leukocytes, although their effects on human health remain uncertain. Herein, we show that human pegivirus infects specific neural cell types in culture and human brain and like other neurotropic flaviviruses, it causes suppression of peroxisome and antiviral signalling pathways, which could favour ongoing viral infection and perhaps confer susceptibility to the development of neurological disease.

Human Pegivirus Type 1: A Common Human Virus That Is Beneficial in Immune-Mediated Disease?

“…HPgV-1 infection of human glia cells led to the suppression of peroxisome-associated gene expression which was accompanied by reduced expression of interferon-beta, interferon regulatory transcription factors 1 and 3, and mitochondrial antiviral signaling protein. These changes were consistent with findings in the brain tissue obtained from the patients with HPgV-1 and sporadic encephalitis ( 137 ). Given the high prevalence of HPgV, the high serum and PBMC viral load, and low rates of sporadic encephalitis, it remains unclear if HPgV-1 commonly infects neural tissue or has any direct neurological outcomes in those without encephalitis.…”

“…In several studies including a meta-analysis, HPgV-1 infection is associated with approximately a 2.8-fold increased risk of developing NHL ( 132 – 135 ). HPgV-1 has also been associated with sporadic encephalitis, and viral RNA and antigens were detected in post-mortem brain tissues from two people with this condition ( 136 , 137 ). A variant of HPgV-1 containing a deletion in the NS2 coding region was identified in the brain tissue of one subject, and this NS2 deletion virus appeared to replicate better in astrocytes than the wild type HPgV-1.…”

“…A variant of HPgV-1 containing a deletion in the NS2 coding region was identified in the brain tissue of one subject, and this NS2 deletion virus appeared to replicate better in astrocytes than the wild type HPgV-1. HPgV-1 replication has recently been demonstrated in human astrocytes and microglia in vitro , though replication was not identified in neurons or an oligodendrocyte-derived cell line ( 137 ). HPgV-1 infection of human glia cells led to the suppression of peroxisome-associated gene expression which was accompanied by reduced expression of interferon-beta, interferon regulatory transcription factors 1 and 3, and mitochondrial antiviral signaling protein.…”

“…Currently, the biggest problem hindering HPgV-1 development for therapeutic use relates to the difficulties in growing the virus in vitro . While virus replicates in lymphocytes, NK cells, and neural cells in vitro ( 110 – 113 , 115 , 116 , 120 , 137 , 203 ), infection cannot be maintained in cell culture for more than handful of passages, suggesting either abortive infection or slow infection with dilutional loss of infected cells. Specifically, most of the cells in PBMC cultures obtained from HPgV-1 infected individuals die rapidly, leaving a small subset of primary mononuclear cells that survive for weeks to months producing low levels of virus ( 115 ).…”

Peroxisome Injury in Multiple Sclerosis: Protective Effects of 4-Phenylbutyrate in CNS-Associated Macrophages

“…3A). In microglia, peroxisomes modulate antiviral Type I interferon responses, and previous studies from our laboratory reported reduced expression of peroxisome biogenesis and structural genes in pegivirus-infected microglia (Doan et al, 2021). Exposing human fetal microglia to TNF-a decreased expression of peroxisome transcripts as well as PEX11b and PMP70 immunoreactivity.…”