Cerebrospinal fluid inflammatory cytokine profiles of patients with neurotropic parasitic infections

The pathogenesis of chronic parasitic central nervous system (CNS) infections, including granulomatous amoebic meningoencephalitis (GAE), cerebral toxoplasmosis (CT), and neurocysticercosis (NCC), is primarily due to an inflammatory host reaction to the parasite. Inflammatory cytokines produced by invading T cells, monocytes, and CNS resident cells lead to neuroinflammation which underlie the immunopathology of these infections. Immune molecules, especially cytokines, can therefore emerge as potential biomarker(s) of CNS parasitic infections. In this study, cerebral spinal fluid (CSF) samples from suspected patients with parasitic infections were screened for pathogenic free-living amoebae by culture (n=2506) and PCR (n=275). Six proinflammatory cytokines in smear and culture-negative CSF samples from patients with GAE (n = 2), NCC (n = 7), and CT (n = 23) as well as control (n = 7) patients were measured using the Multiplex Suspension assay. None of the CSF samples tested was positive for neurotropic free-living amoebae by culture and only two samples showed Acanthamoeba 18S rRNA by PCR. Of the six cytokines measured, only IL-6 and IL-8 were significantly increased in all three infection groups compared to the control group. In addition, TNFa levels were higher in the GAE and NCC groups and IL-17 in the GAE group compared to controls. The levels of IL-1b and IFNg were very low in all the infection groups and the control group. There was a correlation between CSF cellularity and increased levels of IL-6, IL-8, and TNFa in 11 patients. Thus, quantifying inflammatory cytokine levels in CSF might help with understanding the level of neuroinflammation in patients with neurotropic parasitic diseases. Further studies with clinico-microbiological correlation in the form of reduction of cytokine levels with treatment and the correlation with neurological deficits are needed.