Elevated LRRK2 and α-synuclein levels in CSF of infectious meningitis patients

Neurodegenerative diseases such as Parkinson’s (PD) have a complex aetiology consisting of an interplay of genetic and environmental factors. Inflammation and infection are proposed external factors that trigger disease progression. Tuberculous and cryptococcal meningitis frequently lead to long-term neurological sequelae but their association with the development of PD are unexplored. In this study, we protein profiled the CSF from 76 patients with or without infectious meningitis and found that proteins commonly associated with PD (LRRK2, tau and alpha-synuclein) were significantly elevated, establishing a link between neuroinflammation and infection. Importantly, these findings suggest that LRRK2, tau and alpha-synuclein could represent biomarkers of neuroinflammation.


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An increasing body of evidence implicates neuroinflammation in the aetiology of neurodegenerative

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Infectious meningitis caused by either M. tuberculosis or C. neoformans is characterised by the increase 52 of inflammatory and neural injury makers in the meninges 5-8 . In both tuberculous and cryptococcal 53 meningitis (TBM and CM), up to half of survivors experience neurological sequelae with deficits that 54 may be similar to those in neurodegenerative diseases, such as impaired cognition and movement 55 disorder.

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Here we report the results of a large-scale proteomic analysis comparing protein signatures in the CSF 58 from patients with or without infectious meningitis (TBM, CM, or viral meningoencephalitis, VM). We 59 identified a cluster of proteins that is functionally associated with neurodegenerative diseases, including 60 LRRK2, α-synuclein and tau. CSF abundance of these proteins was elevated in patients with TBM and 61 2 CM and positively correlated with inflammatory cytokines. Together, the data suggest that 62 neurodegeneration-associated proteins can be considered inflammatory markers themselves that 63 respond to infectious disease triggers.

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Adults (age ≥18) with suspected meningitis who underwent lumbar puncture as part of their diagnostic 68 workup were recruited into a diagnostic study 9

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SOMAscan, an aptamer-based multiplexed proteomics assay, was used to measure the abundance

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As previously reported, the proteomic analysis of CSF identified increased levels of inflammatory 112 cytokines, such as TNF-α, IL-1β and IFN-β in all meningitis samples (Fig 1A). This was paralleled by 113 an increase in cerebral injury markers such as matrix metallopeptidase 9 (MMP-9), glial fibrillary acidic 114 protein (GFAP) and ubiquitin C-terminal hydrolase L1 (UCH-L1) (Fig 1B). TBM induced the highest 115 increase in both inflammatory cytokines and injury markers, and VM consistently showed only a mild 116 increase of these proteins. In addition to the inflammatory protein pattern, we observed an unexpected 117 increase in a group of proteins typically associated with neurodegenerative diseases, such as LRRK2, 118 tau and α-synuclein in patients with CM and TBM. Specifically, TBM showed 2-fold higher median levels 119 in tau and α-synuclein and a striking 10-fold elevation in LRRK2 levels, when compared to non-120 meningitis controls (Fig 2A). We validated the proteomics findings by Western Blotting and confirmed 3 that LRRK2, α-synuclein and tau were significantly elevated in TBM, and to a lesser extent in CM, when 122 compared to CSF from control individuals (Fig 2B).

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Sub-analyses based on outcome were performed on CM and TBM where a subset of patients died, 125 thus were considered to have more severe infection at the time of sampling. While disease severity 126 impacted the CSF abundance of inflammatory cytokines (Figure 3A), there were no difference in the 127 levels of these neurodegenerative disease-associated proteins (Figure 3B)

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Studies in PD showed that the CSF levels of neurodegeneration-related proteins significantly correlate 133 with inflammatory cytokines including TNF-α and IL-6 11,12 . Similarly, we found a significant correlation 134 between LRRK2 and the inflammatory cytokines TNF-α and IL-1β and the neural injury marker UCH-135 L1 in TBM, CM and VM (Fig 4) suggesting that LRRK2 expression is associated with inflammatory 136 responses.

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In this study, we show a significant and selective upregulation of proteins associated with 142 neurodegenerative diseases in the CSF of patients suffering from tuberculous and cryptococcal 143 meningitis. Our findings implicate these proteins as potential markers of neuroinflammation and/or brain

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Overall, this proteomic analysis suggest that certain proteins associated with neurodegeneration, and 171 PD in particular, can be considered as markers of inflammation, and that inflammatory triggers such as