Targeting tumour necrosis factor alpha during chronic neurodegeneration using enhanced delivery of biologics across the blood-brain barrier

Alzheimer’s disease (AD) is a progressive neurodegenerative disease that affects memory and higher cognitive functions. Currently available therapies only treat symptoms meaning there is a clinical unmet need for disease-modifying therapies. Systemic inflammation has been shown to exacerbate the progression of neurodegenerative diseases through modulation of neuroinflammation. Evidence shows that increases in serum tumour necrosis factor alpha (TNF-α) is associated with an increased rate of cognitive decline in AD patients and its neutralisation provides a potential novel therapeutic strategy. A clinical complication with treating neurodegenerative diseases is the requirement to reach therapeutic targets in the brain and this requires delivery across the blood-brain barrier (BBB). Evidence suggests that enhanced brain delivery of immunotherapies can be achieved by targeting the transferrin receptor (TfR). Recent developments in antibody engineering allow for binding of multiple targets in the same therapy, using bispecific antibodies or fusion proteins. I hypothesise that enhanced delivery of a bispecific anti-TfR-anti-TNF-α fusion protein across the BBB can slow disease progression in a model of neurodegeneration and limit the effects of systemic inflammation on neurodegeneration. The ME7 prion model of neurodegeneration (ME7 mice) is a robust model where disease progression can be followed non-invasively using behavioural tests and shows increased brain cytokine expression. Infection with Salmonella typhimurium in mice can effectively model systemic inflammation and in ME7 mice results in increased microglial activation and cytokine production, including TNF-α. Furthermore, the neuroinflammatory response is exaggerated when ME7 mice are exposed to a systemic bacterial infection at later stages of disease. To investigate neutralisation of TNF-α in peripheral and central compartments, I generated two novel bispecific fusion proteins that neutralise TNF-α in vitro: 8D3130 hIgG1 TM ∆K-mTNFR2, which binds mouse TfR for enhanced brain delivery and NIP228 hIgG1 TM ∆K-mTNFR2, which acts in the periphery. Treatment of ME7 mice with bispecific anti-TNF-α fusion proteins had no effect on mouse behaviours or neuroinflammation at the cellular and molecular level. In addition, administration of bispecific anti-TNF-α fusion proteins after infection with Salmonella typhimurium in ME7 mice had no effect on the increased microglial activation or cytokine expression. These data suggest that treatment with an anti-TNF-α fusion proteins, that can act in the periphery or in the brain, has no effect on disease progression in a model of neurodegeneration and is unable to attenuate the exacerbatory effects of systemic inflammation on neuroinflammation. Further work is required to establish whether intervention was administered at the optimum time and whether treatment prior to systemic inflammation could be beneficial in neurodegenerative diseases