The online version of this article (https://doi.org/10.1186/s12974-017-1041-0) contains supplementary material, which is available to authorized users.
Varicella zoster virus (VZV) reactivation spans the spectrum from uncomplicated segmental herpes zoster to life-threatening disseminated CNS infection. Moreover, in the absence of a small animal model for this human pathogen, studies of pathogenesis at the organismal level depend on analysis of human biosamples. Changes in cerebrospinal fluid (CSF) metabolites may reflect critical aspects of host responses and end-organ damage in neuroinfection and neuroinflammation. We therefore applied a targeted metabolomics screen of CSF to three clinically distinct forms of VZV reactivation and infectious and non-infectious disease controls in order to identify biomarkers for CNS involvement in VZV reactivation.
Metabolite profiles were determined by targeted liquid chromatography-mass spectrometry in CSF from patients with segmental zoster (shingles, n = 14), facial nerve zoster (n = 16), VZV meningitis/encephalitis (n = 15), enteroviral meningitis (n = 10), idiopathic Bell’s palsy (n = 11), and normal pressure hydrocephalus (n = 15).
Concentrations of 88 metabolites passing quality assessment clearly separated the three VZV reactivation forms from each other and from the non-infected samples. Internal cross-validation identified four metabolites (SM C16:1, glycine, lysoPC a C26:1, PC ae C34:0) that were particularly associated with VZV meningoencephalitis. SM(OH) C14:1 accurately distinguished facial nerve zoster from Bell’s palsy. Random forest construction revealed even more accurate classifiers (signatures comprising 2–4 metabolites) for most comparisons. Some of the most accurate biomarkers correlated only weakly with CSF leukocyte count, indicating that they do not merely reflect recruitment of inflammatory cells but, rather, specific pathophysiological mechanisms. Across all samples, only the sum of hexoses and the amino acids arginine, serine, and tryptophan correlated negatively with leukocyte count. Increased expression of the metabolites associated with VZV meningoencephalitis could be linked to processes relating to neuroinflammation/immune activation, neuronal signaling, and cell stress, turnover, and death (e.g., autophagy and apoptosis), suggesting that these metabolites might sense processes relating to end-organ damage.
The results provide proof-of-concept for the value of CSF metabolites as (1) disease-associated signatures suggesting pathophysiological mechanisms, (2) degree and nature of neuroinflammation, and (3) biomarkers for diagnosis and risk stratification of VZV reactivation and, likely, neuroinfections due to other pathogens.
Not applicable (non-interventional study).
Additional file 1: Figure S1. Biclustering analysis based on differentially abundant metabolites. Fold changes (ratio of mean concentrations in each group relative to control) of metabolites with significant across-group differences (uncorrected Kruskal-Wallis P value < 0.05, n = 39) were used as input using the R function gplots::heatmap.2 ( www.r-project.org, Authors: Andy Liaw; revised by R. Gentleman, M. Maechler, W. Huber, G. Warnes). Between-group relationships support those identified in the nonmetric MDS analysis (Fig. 2). The greatest concentration changes are evident in Z. meningoencephalitis. Some co-regulation of metabolites is evident in the dendrogram, in particular clustering of five almost exclusively downregulated metabolites (including Arg, Trp and Ser, and the sum of hexoses (H1), all of which correlated negatively with CSF leukocyte count, see Fig. 5). The apparent upregulation of C5 in the Z. facial group was due to four patients with high concentrations of unknown significance. (TIFF 337 kb)
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- Mass-spectrometric profiling of cerebrospinal fluid reveals metabolite biomarkers for CNS involvement in varicella zoster virus reactivation
Manas K. Akmatov
- BioMed Central