Intracellular lipid droplet accumulation occurs early following viral infection and is required for an efficient interferon response.

Lipid droplets (LDs) are increasingly recognized as critical organelles in signalling events, transient protein sequestration and inter-organelle interactions. However, the role LDs play in antiviral innate immune pathways remains unknown. Here we demonstrate that induction of LDs occurs as early as 2 h post-viral infection, is transient and returns to basal levels by 72 h. This phenomenon occurs following viral infections, both in vitro and in vivo. Virally driven in vitro LD induction is type-I interferon (IFN) independent, and dependent on Epidermal Growth Factor Receptor (EGFR) engagement, offering an alternate mechanism of LD induction in comparison to our traditional understanding of their biogenesis. Additionally, LD induction corresponds with enhanced cellular type-I and -III IFN production in infected cells, with enhanced LD accumulation decreasing viral replication of both Herpes Simplex virus 1 (HSV-1) and Zika virus (ZIKV). Here, we demonstrate, that LDs play vital roles in facilitating the magnitude of the early antiviral immune response specifically through the enhanced modulation of IFN following viral infection, and control of viral replication. By identifying LDs as a critical signalling organelle, this data represents a paradigm shift in our understanding of the molecular mechanisms which coordinate an effective antiviral response.

The interferon stimulated gene viperin, restricts Shigella. flexneri in vitro.

The role of interferon and interferon stimulated genes (ISG) in limiting bacterial infection is controversial, and the role of individual ISGs in the control of the bacterial life-cycle is limited. Viperin, is a broad acting anti-viral ISGs, which restricts multiple viral pathogens with diverse mechanisms. Viperin is upregulated early in some bacterial infections, and using the intracellular bacterial pathogen, S. flexneri, we have shown for the first time that viperin inhibits the intracellular bacterial life cycle. S. flexneri replication in cultured cells induced a predominantly type I interferon response, with an early increase in viperin expression. Ectopic expression of viperin limited S. flexneri cellular numbers by as much as 80% at 5hrs post invasion, with similar results also obtained for the intracellular pathogen, Listeria monocytogenes. Analysis of viperins functional domains required for anti-bacterial activity revealed the importance of both viperin's N-terminal, and its radical SAM enzymatic function. Live imaging of S. flexneri revealed impeded entry into viperin expressing cells, which corresponded to a loss of cellular cholesterol. This data further defines viperin's multi-functional role, to include the ability to limit intracellular bacteria; and highlights the role of ISGs and the type I IFN response in the control of bacterial pathogens.

A novel I-TAC promoter polymorphic variant is functional in the presence of replicating HCV in vitro.

BACKGROUND: Chemokines are strong candidate genes for outcome of HCV infection. I-TAC is a chemokine known to be involved in the inflammatory process of HCV infection, and its expression is upregulated in chronic hepatitis C (CHC). OBJECTIVES: The aim of this study was to investigate genetic variability in the I-TAC promoter and to determine the correlation of these variants with HCV disease progression. STUDY DESIGN: I-TAC genotyping was performed in 60 chronic HCV patients and 60 controls using GeneScan analysis. Functional analysis of the I-TAC promoter was performed with the aid of luciferase reporter constructs transfected into Huh-7 cells or Huh-7 cells harbouring HCV genomic and sub-genomic replicons. Cytokine induced production of I-TAC from whole blood cultures was measured using enzyme-linked immunosorbent assay (ELISA). RESULTS: Sequencing of approximately 1 kb upstream of the I-TAC gene start codon revealed the presence of a novel 5 bp deletion mutant (-599del5) in a number of chronic HCV patients. Analysis of the functional potential of this deletion revealed no transcriptional change in Huh-7 cells transfected with luciferase reporter constructs, and this was confirmed in cytokine stimulated whole blood cultures where similar levels of I-TAC were liberated regardless of -599del5 genotype. Conversely, the -599del5 deletion variant significantly reduced transcriptional activity of the I-TAC promoter in the presence of replicating HCV. The distribution frequency of the allele was found to be significantly increased in a chronically HCV infected population compared to healthy controls. CONCLUSIONS: The novel I-TAC -599del5 promoter polymorphism is a functional variant in the presence of replicating HCV. Furthermore, this deletion mutant is significantly increased in a chronic HCV cohort and may predispose to HCV disease susceptibility.

Variation in immune response genes and chronic Q fever. Concepts: preliminary test with post-Q fever fatigue syndrome.

Acute primary Q fever is followed by various chronic sequelae. These include subacute Q fever endocarditis, granulomatous reactions in various organs or a prolonged debilitating post-infection fatigue syndrome (QFS). The causative organism, Coxiella burnetii, persists after an initial infection. The differing chronic outcomes may reflect variations within cytokine and accessory immune control genes which affect regulation of the level of persistence. As a preliminary test of the concept we have genotyped QFS patients and controls for gene variants spanning 15 genes and also examined HLA-B and DR frequencies. QFS patients exhibited a significantly increased frequency of HLA-DR-11 compared with controls and also significant differences in allelic variant frequencies within the NRAMP, and IFNgamma genes. These results indicate a possible genetic role in the expression of overt chronic Q fever. Further studies will be undertaken to increase sample sizes, to survey other forms of chronic Q fever and to examine Q fever patients who have recovered without sequelae.