Understanding cerebral inflammation in viral encephalitis - how does neuron-glial signalling drive blood-brain barrier permeability?

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CONTEXTBrain inflammation, termed 'encephalitis', is a devastating disease commonly caused by the cold-sore virus (herpes simplex virus-HSV). Inflammation occurs due to breakdown of the natural barrier with the bloodstream and the migration of immune-cells in. Despite antivirus medication the inflammation continues. Consequently, most patients die or have significant brain injury.Sometimes patients are given steroids but their broad immune-suppression action risks increasing the virus, so targeted treatments are needed.Immune-cells are attracted by inflammation-proteins; I identified several such proteins in patients with the greatest blood-brain barrier (BBB) breakdown and worst outcome, and developed a mouse-model to study this by visualising immune-cell movement in the brain.To what extent BBB breakdown leads to immune cell migration or vice versa is not clear and it is not known how infected nerves communicate with other brain cells, and BBB cells.Understanding this network of interactions is critical to develop targeted immune therapy which reduces brain inflammation and improves patient outcome, without increasing the amount of virus.AIMS1. Establish the inflammation proteins which most closely associated with BBB breakdown in HSV encephalitis and which are/are not steroid responsive2. Interrogate how blocking these inflammation proteins alters BBB breakdown, immune cell migration and viral control3. Determine how these immune proteins communicate between infected nerves, the other brain cells and the BBB cellsOBJECTIVES1.From a unique cohort of HSV encephalitis patients who have received either steroids or placebo, I have collected blood and spinal fluid.a.I will analyse these by both looking for specific inflammation proteins and also by assessing all proteinsb.I will compare them to the degree of BBB permeability from:i.Amount of albumin protein which has leaked from the blood into the spinal fluidii.The volume of brain swelling on the brain scan (magnetic resonance imaging)2.Take forward key inflammation proteins by determining their action, in a mouse model I established, using mice lacking the receptor for these inflammation proteins and/or block the inflammation protein using a neutralising antibody and determine:a.Is morbidity decreased, using an established score?b.Is BBB breakdown reduced, measuring the leakage of an intravenous dye into the brain?c.Is viral control affected, using a plaque assay?d.Is immune cell migration altered, using intravital microscopy to visualise immune cell movements in real time in the brain of an anaesthetised mouse?3. In this model, I will analyse the generation of inflammation proteins and associated signals from each cell type in the brain and BBB over time to determine networks of communication up-stream and down-stream to key inflammation proteins.a.I will then confirm these findings by examining the interaction between nerve cells, other brain cells, and BBB cells in a BBB modeli.In response to HSV infection of single cells and cultures of different cells which may interactii.I will interrogate whether blocking these communications alters BBB breakdown and immune cell migrationPOTENTIAL APPLICATIONS AND BENEFITSThis is important so that I can develop targeted immune treatments to control inflammation, BBB breakdown, and leucocyte migration, without risking uncontrolled viral replication. By establishing this for HSV it opens up treatment opportunities for a wide range of other brain infections.Having built the capacity to generate hypotheses from clinical samples and with both a mouse model and a BBB model of brain infection, I will be excellently placed to determine the commonalities and differences between the immune response to HSV and other brain infections. Consequently, I will be able to drive forward targeted therapies and will be in a strong position to become a leader in the field.