Hypoxia-inducible factor 1α (HIF1α) Suppresses Virus Replication in Human Cytomegalovirus Infection by Limiting Kynurenine Synthesis

Abstract

Human cytomegalovirus (HCMV) replication depends on the activities of several host regulators of metabolism. Hypoxia-inducible factor 1α (HIF1α) was previously proposed to support virus replication through its metabolic regulatory function. HIF1α protein levels rise in response to HCMV infection in non-hypoxic conditions, but its effect on HCMV replication was not investigated. We addressed the role of HIF1α in HCMV replication by generating primary human cells with HIF1α knocked out using CRISPR/Cas9. When HIF1α was absent, we found that HCMV replication was enhanced, showing that HIF1α suppresses viral replication. We used untargeted metabolomics to determine if HIF1α regulates metabolite concentrations in HCMV infected cells. We discovered that in HCMV-infected cells, HIF1α suppresses intracellular and extracellular concentrations of kynurenine. HIF1α also suppressed the expression of the indoleamine 2,3-dioxygenase 1 (IDO1) rate-limiting enzyme in kynurenine synthesis. In addition to its role in tryptophan metabolism, kynurenine acts as a signaling messenger by activating aryl hydrocarbon receptor (AhR). Inhibiting AhR reduces HCMV replication while activating AhR with an exogenous ligand increases HCMV replication. Moreover, we found that feeding kynurenine to cells promotes HCMV replication. Overall, our findings indicate that HIF1α reduces HCMV replication by regulating metabolism and metabolite signaling.ImportanceViruses, like human cytomegalovirus (HCMV), reprogram cellular metabolism using host metabolic regulators to support virus replication. Alternatively, in response to infection, the host can use metabolism to limit virus replication. Here, our findings show that the host uses hypoxia-inducible factor 1α (HIF1α) as a metabolic regulator to reduce HCMV replication. Further, we found that HIF1α suppresses kynurenine synthesis, a metabolite that can promote HCMV replication by signaling through the aryl hydrocarbon receptor (AhR). In infected cells, the rate-limiting enzyme in kynurenine synthesis, indoleamine 2,3-dioxygenase 1 (IDO1), is suppressed by a HIF1α-dependent mechanism. Our findings describe a functional connection between HIF1α, IDO1, and AhR that allows HIF1α to limit HCMV replication through metabolic regulation, advancing our understanding of virus-host interactions.

TNFα-induced metabolic reprogramming drives an intrinsic anti-viral state

“…Separately, our data show that cells lacking Hif1α are more permissive to infection, suggesting Hif1α may play a role in limiting the initiation of infection. Consistent with this finding, Hif1α was recently shown to attenuate HCMV replication in human fibroblasts 40 . The anti-viral phenotype associated with Hif1α-mediated metabolic regulation is intriguing, yet the mechanisms responsible for TNFα-induced glycolysis still require elucidation.…”

“…Kynurenine accumulates in a variety of inflammatory conditions and is induced during Human Immunodeficiency Virus (HIV) infection 41, 42 . Others have described pro-viral effects of kynurenine on HCMV replication 40 , suggesting a potential complex relationship with infection that requires further analysis with respect to its roles in inflammation, intrinsic immunity and during viral infection.…”

Multi-omics reveals principles of gene regulation and pervasive non-productive transcription in the human cytomegalovirus genome

“…4 ). In addition to the TATA-binding protein (36 sites, p-value=8×10 −10 ), the most strongly enriched TF was HIF-1α (34 sites, p-value=10 −10 ), which has been described previously to be induced in the first few hours of HCMV infection 30 and to act as an antiviral host factor 31 . The enrichment of HIF-1α target sites in viral promoters indicates that HCMV usurped this host factor to regulate the expression of dozens of viral genes.…”

Role of aryl hydrocarbon receptors in infection and inflammation

“…The reduction of AhR has the potential to decrease the replication of HCMV, whereas the activation of AhR using an exogenous ligand can enhance virus proliferation. Wise et al propose that Hypoxiainducible factor 1a plays a significant role in the antiviral response by inhibiting the synthesis of Kyn and activating AhR during HCMV infection (71). Additionally, HCMV infection regulates the activation of AhR, which in turn modulates the transcription of infected cells.…”