Developing Interferon-β as a safe in-vivo experimental-medicine model of human inflammation.
BackgroundInflammation is increasingly implicated in a wide range of neuropsychiatric disorders ranging from depression through age- and infection-related cognitive decline to dementia. Arguably, the most important evidence supporting an aetiological role for inflammation in these conditions in humans has come from studies of patients receiving IFN- therapeutically or longitudinal follow-up of patients after naturalistic infections (e.g., hepatitis C). These experimental medicine-type approaches have identified a discrete set of brain regions e.g. amygdala-hippocampus-hypothalamus, insula and anterior cingulate as well as dopamine-rich subcortical structures that are particularly sensitive to systemic inflammation. Coupled with renewed interest in developing novel immune-targeted therapies for neuropsychiatric disorders as diverse as depression and neurodegenerative disorders, this has highlighted the urgent need for a safe, reliable in-vivo experimental medicine model of inflammation that can be used across the age range. To date, this need has been partially addressed by access to short-acting forms of Interferon-alpha or human (GMP) grade lipopolysaccharide (LPS). However, unpegylated IFN- is no longer commercially available and the costs and cardiovascular monitoring requirements of low-dose (i.e. 0.8-1ng/Kg i.v. endotoxin) LPS are prohibitive and particularly challenging to use in older or more vulnerable populations. AimDevelop a new experimental model of human inflammation that elicits robust sickness responses within a few hours but with minimal cardiovascular effects, thus avoiding the need for continuous cardiac monitoring and ensuring applicability across diverse experimental contexts and participant groups from the young to the elderly. MethodsUsing a randomized, placebo-controlled, repeated measures cross-over design, physiological, behavioural, immune and transcriptomic responses were collected from 30 healthy volunteers (15 young [18-34] and 15 old [60-75]) following both IFN-{beta} (EXTAVIA(R) [100 {micro}g]) and saline (placebo) injections. ResultsIFN-{beta} induced a robust systemic immune response, evidenced by significant increases in temperature, heart rate, immune cell activation (lymphocytes, monocytes and neutrophils) and levels of IFN-{beta}, IL-10 and TNF- cytokines. These physiological changes were accompanied by significant increases in negative mood, tiredness, tension and sickness symptoms aa well as by a decrease in vigour. ConclusionsFN-{beta} is a safe and robust new experimental model of mild acute inflammation, This minimally invasive and effective design can induce transient changes in systemic inflammation in healthy individuals from 18-75. A more refined, ecologically valid model similar to the mild inflammation typically reported in psychiatric disorders like depression or cognitive impairment.