Microglia activation in a pediatric rabbit model of tuberculous meningitis

Abstract

Central nervous system (CNS) tuberculosis (TB) is the most severe form of extra-pulmonary TB and disproportionately affects young children where the developing brain has a unique host response. New Zealand white rabbits were infected with Mycobacterium tuberculosis via subarachnoid inoculation at postnatal day 4-8 and evaluated until 4-6 weeks post-infection. Control and infected rabbit kits were assessed for the development of neurological deficits, bacterial burden, and postmortem microbiologic and pathologic changes. The presence of meningitis and tuberculomas was demonstrated histologically and by in vivo magnetic resonance imaging (MRI). The extent of microglial activation was quantified by in vitro immunohistochemistry as well as non-invasive in vivo imaging of activated microglia/macrophages with positron emission tomography (PET). Subarachnoid infection induced characteristic leptomeningeal and perivascular inflammation and TB lesions with central necrosis, a cellular rim and numerous bacilli on pathologic examination. Meningeal and rim enhancement was visible on MRI. An intense microglial activation was noted in M. tuberculosis-infected animals in the white matter and around the TB lesions, as evidenced by a significant increase in uptake of the tracer 124I-DPA-713, which is specific for activated microglia/macrophages, and confirmed by quantification of Iba-1 immunohistochemistry. Neurobehavioral analyses demonstrated signs similar to those noted in children with delayed maturation and development of neurological deficits resulting in significantly worse composite behavior scores in M. tuberculosis-infected animals. We have established a rabbit model that mimics features of TB meningitis in young children. This model could provide a platform for evaluating novel therapies, including host-directed therapies, against TB meningitis relevant to a young child's developing brain.

Thalidomide and Phosphodiesterase 4 Inhibitors as Host Directed Therapeutics for Tuberculous Meningitis: Insights From the Rabbit Model

“…The developmental stages of the brain in children makes them highly vulnerable to TBM. To understand the pathogenesis of TB during early brain development, a pediatric rabbit model of TBM was created (Tucker et al, 2016). In this model, 4-8 day old NZW rabbits were inoculated with Mtb into the subarachnoid space, and the animals were monitored for 35 days post-infection.…”

Mycobacteria employ two different mechanisms to cross the blood-brain barrier

“…Several in vivo models to study mycobacterial pathogenesis exist, such as rabbits, guinea pig, and mice (Be et al, 2012; Be, Klinkenberg, Bishai, Karakousis, & Jain, 2011; Skerry et al, 2013; Tsenova et al, 2005; Tucker et al, 2016; van Well et al, 2007; Zucchi et al, 2012). However, none of these models could demonstrate the course of events during mycobacterial trafficking across the BBB in a living host.…”

“…Several in vivo models to study mycobacterial pathogenesis exist, such as rabbits, guinea pig, and mice Be, Klinkenberg, Bishai, Karakousis, & Jain, 2011;Skerry et al, 2013;Tsenova et al, 2005;Tucker et al, 2016;van Well et al, 2007;Zucchi et al, 2012).…”

Delamanid Central Nervous System Pharmacokinetics in Tuberculous Meningitis in Rabbits and Humans

“…For MDR-and XDR-TBM, both of which are particularly lethal forms of TBM, treatment options are limited and outcomes are nearly universally poor. We used our experimentally induced TBM model in young rabbits due to its ability to reproducibly reflect the heterogeneity of disease (exudative meningitis and tuberculomas) and neurologic deficits in TBM patients (12,34). In our rabbit study, we found that the concentrations of DLM were almost 5-fold higher in brain than plasma in rabbits with and without CNS TB, while CSF concentrations were low but above the average MIC of DLM against M. tuberculosis, and estimates of CSF/plasma ratios of free drug were generally Ͼ1.…”

“…M. tuberculosis H37Rv (from the S.K.J. laboratory) was prepared from frozen titrated stock as previously described (12,34). Female and male New Zealand White (NZW) rabbits (Oryctolagus cuniculus; Robinson Services Inc., NC) were anesthetized and injected with approximately 1.42 Ϯ 0.21 log 10 CFU for infected rabbits or with phosphate-buffered saline (PBS; Quality Biological, Inc., Gaithersburg, MD) for uninfected rabbits on postnatal day (PND) 5 or 6 using a 28-gauge insulin syringe (28-gauge, 1/2-in.…”