Long-term intrathecal infusion of outer surface protein C from Borrelia burgdorferi causes axonal damage

Persistent Borrelia burgdorferi Sensu Lato Infection after Antibiotic Treatment: Systematic Overview and Appraisal of the Current Evidence from Experimental Animal Models

Lyme borreliosis is caused by spirochetes belonging to the Borrelia burgdorferi sensu lato group, which are transmitted by Ixodes tick species living in the temperate climate zones of the Northern Hemisphere. The clinical manifestations of Lyme borreliosis are diverse and treated with oral or intravenous antibiotics. In some patients, long-lasting and debilitating symptoms can persist after the recommended antibiotic treatment. The etiology of such persisting symptoms is under debate, and one hypothesis entails persistent infection by a subset of spirochetes after antibiotic therapy. Here, we review and appraise the experimental evidence from in vivo animal studies on the persistence of B. burgdorferi sensu lato infection after antibiotic treatment, focusing on the antimicrobial agents doxycycline and ceftriaxone. Our review indicates that some in vivo animal studies found sporadic positive cultures after antibiotic treatment. However, this culture positivity often seemed to be related to inadequate antibiotic treatment, and the few positive cultures in some studies could not be reproduced in other studies. Overall, current results from animal studies provide insufficient evidence for the persistence of viable and infectious spirochetes after adequate antibiotic treatment. Borrelial nucleic acids, on the contrary, were frequently detected in these animal studies and may thus persist after antibiotic treatment. We put forward that research into the pathogenesis of persisting complaints after antibiotic treatment for Lyme borreliosis in humans should be a top priority, but future studies should most definitely also focus on explanations other than persistent B. burgdorferi sensu lato infection after antibiotic treatment.

Intracerebral Infection with E. coli Impairs Spatial Learning and Induces Necrosis of Hippocampal Neurons in the Tg2576 Mouse Model of Alzheimer’s Disease

Background:

In patients with Alzheimer’s disease (AD), bacterial infections are often associated with a cognitive decline. Animal models of genuine acute infections with viable bacteria which induce deterioration of neurodegenerative diseases are missing.

Objective:

We assessed the effect of an intracerebral infection with E. coli in a mouse model of AD.

Methods:

13-month-old Tg2576 +/- mice and transgene negative littermates (Tg2576 -/-) received an intracerebral injection with E. coli K1 or saline followed by treatment with ceftriaxone starting 41 h post infection (p.i.) for 5 days. For 4 weeks, mice were monitored for clinical status, weight, motor functions, and neuropsychological status using the Morris water maze. ELISAs, stainings, and immunohistochemistry in brains were performed at the end of the experiment.

Results:

Mortality of the infection was approximately 20%. After 4 weeks, spatial learning of infected Tg2576 +/- mice was compromised compared to non-infected Tg2576 +/- mice (p < 0.05). E. coli infection did not influence spatial learning in Tg2576 -/- mice, or spatial memory in both Tg2576 +/- and -/- mice within 4 weeks p.i.. Necrosis of hippocampal neurons was induced in infected compared to non-infected Tg2576 +/- mice 4 weeks p.i., whereas brain concentrations of Aβ_1–40, Aβ_1–42, and phosphoTau as well as axonal damage and microglia density were not altered.

Conclusion:

Here, we proved in principle that a genuine acute bacterial infection can worsen cognitive functions of AD mice. Mouse models of subacute systemic infections are needed to develop new strategies for the treatment of bacterial infections in patients with AD in order to minimize their cognitive decline.

ALS or ALS mimic by neuroborreliosis-A case report

Comprehensive investigation in motor neuron disease is vital not to miss a treatable differential diagnosis. Neuroborreliosis should be considered during an ALS work-up. However, false-positive CSF results do occur, and thus, results should be interpreted carefully in context of all clinical test results.

The inflammatory response and neuronal injury in Streptococcus suis meningitis

BACKGROUND

Many of the currently used models of bacterial meningitis have limitations due to direct inoculation of pathogens into the cerebrospinal fluid or brain and a relatively insensitive assessment of long-term sequelae. The present study evaluates the utility of a Streptococcus (S.) suis intranasal infection model for the investigation of experimental therapies in meningitis.

METHODS

We examined the brains of 10 piglets with S. suis meningitis as well as 14 control piglets by histology, immunohistochemistry and in-situ tailing for morphological alterations in the hippocampal dentate gyrus and microglial activation in the neocortex.

RESULTS

In piglets with meningitis, the density of apoptotic neurons was significantly higher than in control piglets. Moreover, scoring of microglial morphology revealed a significant activation of these cells during meningitis. The slight increase in the density of dividing cells, young neurons and microglia observed in piglets suffering from meningitis was not statistically significant, probably because of the short time frame between onset of clinical signs and organ sampling.

CONCLUSIONS

The morphological changes found during S. suis meningitis are in accordance with abnormalities in other animal models and human autopsy cases. Therefore, the pig should be considered as a model for evaluating effects of experimental therapeutic approaches on neurological function in bacterial meningitis.

Primary Human Microglia Are Phagocytically Active and Respond to Borrelia burgdorferi With Upregulation of Chemokines and Cytokines

The Lyme disease causing bacterium Borrelia burgdorferi has an affinity for the central nervous system (CNS) and has been isolated from human cerebral spinal fluid by 18 days following Ixodes scapularis tick bite. Signaling from resident immune cells of the CNS could enhance CNS penetration by B. burgdorferi and activated immune cells through the blood brain barrier resulting in multiple neurological complications, collectively termed neuroborreliosis. The ensuing symptoms of neurological impairment likely arise from a glial-driven, host inflammatory response to B. burgdorferi. To date, however, the mechanism by which the bacterium initiates neuroinflammation leading to neural dysfunction remains unclear. We hypothesized that dead B. burgdorferi and bacterial debris persist in the CNS in spite of antibiotic treatment and contribute to the continuing inflammatory response in the CNS. To test our hypothesis, cultures of primary human microglia were incubated with live, antibiotic-killed and antibiotic-killed sonicated B. burgdorferi to define the response of microglia to different forms of the bacterium. We demonstrate that primary human microglia treated with B. burgdorferi show increased expression of pattern recognition receptors and genes known to be involved with cytoskeletal rearrangement and phagocytosis including MARCO, SCARB1, PLA2, PLD2, CD14, and TLR3. In addition, we observed increased expression and secretion of pro-inflammatory mediators and neurotrophic factors such as IL-6, IL-8, CXCL-1, and CXCL-10. Our data also indicate that B. burgdorferi interacts with the cell surface of primary human microglia and may be internalized following this initial interaction. Furthermore, our results indicate that dead and sonicated forms of B. burgdorferi induce a significantly larger inflammatory response than live bacteria. Our results support our hypothesis and provide evidence that microglia contribute to the damaging inflammatory events associated with neuroborreliosis.

CRAMP deficiency leads to a pro-inflammatory phenotype and impaired phagocytosis after exposure to bacterial meningitis pathogens

BACKGROUND

Antimicrobial peptides are important components of the host defence with a broad range of functions including direct antimicrobial activity and modulation of inflammation. Lack of cathelin-related antimicrobial peptide (CRAMP) was associated with higher mortality and bacterial burden and impaired neutrophil granulocyte infiltration in a model of pneumococcal meningitis. The present study was designed to characterize the effects of CRAMP deficiency on glial response and phagocytosis after exposure to bacterial stimuli.

METHODS

CRAMP-knock out and wildtype glial cells were exposed to bacterial supernatants from Streptococcus pneumoniae and Neisseria meningitides or the bacterial cell wall components lipopolysaccharide and peptidoglycan. Cell viability, expression of pro- and anti-inflammatory mediators and activation of signal transduction pathways, phagocytosis rate and glial cell phenotype were investigated by means of cell viability assays, immunohistochemistry, real-time RT-PCR and Western blot.

RESULTS

CRAMP-deficiency was associated with stronger expression of pro-inflammatory and weakened expression of anti-inflammatory cytokines indicating a higher degree of glial cell activation even under resting-state conditions. Furthermore, increased translocation of nuclear factor 'kappa-light-chain-enhancer' of activated B-cells was observed and phagocytosis of S. pneumoniae was reduced in CRAMP-deficient microglia indicating impaired antimicrobial activity.

CONCLUSIONS

In conclusion, the present study detected severe alterations of the glial immune response due to lack of CRAMP. The results indicate the importance of CRAMP to maintain and regulate the delicate balance between beneficial and harmful immune response in the brain.

Fungal encephalitis in human autopsy cases is associated with extensive neuronal damage but only minimal repair

AIMS

The present study aimed at examining neuronal injury and repair in post mortem brain sections of humans who died from fungal central nervous system infections.

METHODS

Histological and immunohistochemical abnormalities in 15 autopsy cases with fungal central nervous system infections from 1990 to 2008 were compared with findings in 10 age- und sex-matched control cases that died from acute non-neurological causes. The fungal pathogens were identified by culture or polymerase chain reaction and morphology in post mortem tissue. Seven patients with fungal encephalitis had either an organ transplantation or a malignant haematological disorder; five out of 15 did not have a classical predisposing illness but suffered from severe septic infections as the principal cause of immunosuppression, and three from alcoholism.

RESULTS

Fungal organisms detected were Aspergillus spp. and other moulds, Candida spp. and black yeast-like fungi including Cladosporium spp. Histological analyses identified microglial activation, astrocytosis and axonal injury in the white matter without additional demyelination as characteristic features of this infectious disease. An increased rate of hippocampal neuronal apoptosis was detected in fungal encephalitis, while the number of recently generated TUC-4 and calretinin-expressing neurones in the dentate gyrus did not differ between patients and controls.

CONCLUSIONS

Unlike in other infectious diseases of the nervous system where a coexistence of damage and repair was observed, fungal encephalitis is characterized by strong damage and minimal neuronal regeneration.

Quantitative gait analysis of long-term locomotion deficits in classical unilateral striatal intracerebral hemorrhage rat model

Gait analysis is a systematic collection of quantitative information on bodily movements during locomotion. Gait analysis has been employed clinically in stroke patients for their rehabilitation planning. In animal studies, gait analysis has been employed for the assessment of their locomotive disturbances in ischemic stroke, spinal cord injury and Parkinson's disease. The aims of the work reported here were to identify the gait parameters, collected from the computer-generated CatWalk System, that change after unilateral intracerebral hemorrhage (ICH) in the acute stage and long term up to 56 days post-ICH. The results showed that with the collagenase-induced unilateral striatal lesion, the rats displayed a significant contralateral decrease in print and maximum contact area and paw intensity, a diagonal increase in the stance duration of the left front and right hind paws, a significant decrease in the stride length of all four limbs, and foot pattern instability as reflected by the base of support, support on styles, and cadence. These deficits, including those in print area, stance and pressure, were demonstrated throughout the long-term period following ICH. The correlations between the gait parameters, lesion volume and asymmetrical forelimb use were also reported in this paper. This work has provided a systematic description on gait parameters in the classical striatal ICH model, which might become an essential assessment tool in future studies of pathophysiology and the development of novel treatments for experimental unilateral intracerebral hemorrhage with gait deficits.

The Lyme disease spirochete Borrelia burgdorferi induces inflammation and apoptosis in cells from dorsal root ganglia

Background

Lyme neuroborreliosis (LNB), caused by the spirochete Borrelia burgdorferi, affects both the peripheral and the central nervous systems. Radiculitis or nerve root inflammation, which can cause pain, sensory loss, and weakness, is the most common manifestation of peripheral LNB in humans. We previously reported that rhesus monkeys infected with B. burgdorferi develop radiculitis as well as inflammation in the dorsal root ganglia (DRG), with elevated levels of neuronal and satellite glial cell apoptosis in the DRG. We hypothesized that B. burgdorferi induces inflammatory mediators in glial and neuronal cells and that this inflammatory milieu precipitates glial and neuronal apoptosis.

Methods

To model peripheral neuropathy in LNB we incubated normal rhesus DRG tissue explants with live B. burgdorferi ex vivo and identified immune mediators, producer cells, and verified the presence of B. burgdorferi in tissue sections by immunofluorescence staining and confocal microscopy. We also set up primary cultures of DRG cells from normal adult rhesus macaques and incubated the cultures with live B. burgdorferi. Culture supernatants were subjected to multiplex ELISA to detect immune mediators, while the cells were evaluated for apoptosis by the in situ TUNEL assay. A role for inflammation in mediating apoptosis was assessed by evaluating the above phenomena in the presence and absence of various concentrations of the anti-inflammatory drug dexamethasone. As Schwann cells ensheath the dorsal roots of the DRG, we evaluated the potential of live B. burgdorferi to induce inflammatory mediators in human Schwann cell (HSC) cultures.

Results

Rhesus DRG tissue explants exposed to live B. burgdorferi showed localization of CCL2 and IL-6 in sensory neurons, satellite glial cells and Schwann cells while IL-8 was seen in satellite glial cells and Schwann cells. Live B. burgdorferi induced elevated levels of IL-6, IL-8 and CCL2 in HSC and DRG cultures and apoptosis of sensory neurons. Dexamethasone reduced the levels of immune mediators and neuronal apoptosis in a dose dependent manner.

Conclusion

In this model, B. burgdorferi induced an inflammatory response and neuronal apoptosis of DRG. These pathophysiological processes could contribute to peripheral neuropathy in LNB.

Unilateral phrenic nerve lesion in Lyme neuroborreliosis

Background

Among a variety of more common differential diagnoses, the aetiology of acute respiratory failure includes Lyme neuroborreliosis.

Case presentation

We report an 87-years old huntsman with unilateral phrenic nerve palsy as a consequence of Lyme neuroborreliosis.

Conclusion

Although Lyme neuroborreliosis is a rare cause of diaphragmatic weakness, it should be considered in the differential workup because of its potentially treatable nature.