A. Marceline van Furth

Meningeal and Perivascular Macrophages of the Central Nervous System Play a Protective Role During Bacterial Meningitis

Meningeal (MM) and perivascular macrophages (PVM) constitute major populations of resident macrophages in the CNS that can be distinguished from microglial cells. So far, there is no direct evidence that demonstrates a possible role of MM and PVM in the CNS during normal or pathologic conditions. To elucidate the role of the MM and PVM during CNS inflammation, we have developed a strategy using a single intraventricular injection of mannosylated clodronate liposomes, which results in a complete and selective depletion of the PVM and MM from the CNS. Depletion of the MM and PVM during experimental pneumococcal meningitis resulted in increased illness, which correlated with higher bacteria counts in the cerebrospinal fluid and blood. This was associated with a decreased influx of leukocytes into the cerebrospinal fluid, which occurred despite an elevated production of relevant chemokines (e.g., macrophage-inflammatory protein-2) and a higher expression of vascular adhesion molecules (e.g., VCAM-1). In contrast, the higher bacterial counts correlated with elevated production of local and systemic inflammatory mediators (e.g., IL-6) indicating enhanced local leukocyte and systemic immune activation, and this may explain the worsening of the clinical signs. These findings show that the PVM and MM play a protective role during bacterial meningitis and suggest that a primary action of these macrophages is to facilitate the influx of leukocytes at the blood-brain barrier. More in general, we demonstrate for the first time that the PVM and MM play a crucial role during inflammation in the CNS.

IL-1 Receptor Type 1 Gene-Deficient Mice Demonstrate an Impaired Host Defense Against Pneumococcal Meningitis

The fatality rate associated with Streptococcus pneumoniae meningitis remains high despite adequate antibiotic treatment. IL-1 is an important proinflammatory cytokine, which is up-regulated in brain tissue after the induction of meningitis. To determine the role of IL-1 in pneumococcal meningitis we induced meningitis by intranasal inoculation with 8 × 104 CFU of S. pneumoniae and 180 U of hyaluronidase in IL-1R type I gene-deficient (IL-1R−/−) mice and wild-type mice. Meningitis resulted in elevated IL-1α and IL-1β mRNA and protein levels in the brain. The absence of an intact IL-1 signal was associated with a higher susceptibility to develop meningitis. Furthermore, the lack of IL-1 impaired bacterial clearance, as reflected by an increased number of CFU in cerebrospinal fluid of IL-1R−/− mice. The characteristic pleocytosis of meningitis was not significantly altered in IL-1R−/− mice, but meningitis was associated with lower brain levels of cytokines. The mortality was significantly higher and earlier in the course of the disease in IL-1R−/− mice. These results demonstrate that endogenous IL-1 is required for an adequate host defense in pneumococcal meningitis.

Experimental Pneumococcal Meningitis in Mice: A Model of Intranasal Infection

Effective laboratory animal models of bacterial meningitis are needed to unravel the pathophysiology of this disease. Previous models have failed to simulate human meningitis by using a directly intracerebral route of infection. Hyaluronidase is a virulence factor of Streptococcus pneumoniae. In this study, a novel model of murine meningitis is described. Intranasal administration of S. pneumoniae with hyaluronidase induced meningitis in 50% of inoculated mice, as defined by a positive cerebrospinal fluid (CSF) culture and an inflammatory infiltrate in the meninges. None of the mice inoculated without hyaluronidase developed meningitis. Hyaluronidase was found to facilitate pneumococcal invasion of the bloodstream after colonization of the upper respiratory tract. Meningitis was characterized by pleocytosis of CSF and the induction of proinflammatory cytokines and CXC chemokines in brain tissue. These results indicate that this murine model mimics important features of human disease and allow for the use of this model for studying issues related to the pathophysiology and the treatment of pneumococcal meningitis.

C1 Inhibitor Treatment Improves Host Defense in Pneumococcal Meningitis in Rats and Mice

In spite of antibiotic treatment, pneumococcal meningitis continues to be associated with significant morbidity and mortality. The complement system is a key component of innate immunity against invading pathogens. However, activation of complement is also involved in tissue damage, and complement inhibition by C1 inhibitor (C1-inh) is beneficial in animal models of endotoxemia and sepsis. In the present study, we demonstrate classical pathway complement activation during pneumococcal meningitis in rats. We also evaluate the effect of C1-inh treatment on clinical illness, bacterial clearance, and inflammatory responses in rats and mice with pneumococcal meningitis. C1-inh treatment was associated with reduced clinical illness, a less-pronounced inflammatory infiltrate around the meninges, and lower brain levels of proinflammatory cytokines and chemokines. C1-inh treatment increased bacterial clearance, possibly through an up-regulation of CR3. Hence, C1-inh may be a useful agent in the treatment of pneumococcal meningitis.

A hypothetical astrocyte–microglia lactate shuttle derived from a 1H NMR metabolomics analysis of cerebrospinal fluid from a cohort of South African children with tuberculous meningitis

Tuberculosis meningitis (TBM) is the most severe form of extra-pulmonary tuberculosis and is particularly intense in small children; there is no universally accepted algorithm for the diagnosis and substantiation of TB infection, which can lead to delayed intervention, a high risk factor for morbidity and mortality. In this study a proton magnetic resonance (1H NMR)-based metabolomics analysis and several chemometric methods were applied to data generated from lumber cerebrospinal fluid (CSF) samples from three experimental groups: (1) South African infants and children with confirmed TBM, (2) non-meningitis South African infants and children as controls, and (3) neurological controls from the Netherlands. A total of 16 NMR-derived CSF metabolites were identified, which clearly differentiated between the controls and TBM cases under investigation. The defining metabolites were the combination of perturbed glucose and highly elevated lactate, common to some other neurological disorders. The remaining 14 metabolites of the host’s response to TBM were likewise mainly energy-associated indicators. We subsequently generated a hypothesis expressed as an “astrocyte–microglia lactate shuttle” (AMLS) based on the host’s response, which emerged from the NMR-metabolomics information. Activation of microglia, as implied by the AMLS hypothesis, does not, however, present a uniform process and involves intricate interactions and feedback loops between the microglia, astrocytes and neurons that hamper attempts to construct basic and linear cascades of cause and effect; TBM involves a complex integration of the responses from the various cell types present within the CNS, with microglia and the astrocytes as main players.

Zygomycete infection following voriconazole prophylaxis.

A 14-year-old boy was treated with chemotherapy for T-cell acute lymphoblastic leukaemia. Trimethoprimsulfamethoxazole and itraconazole were given for infection prophylaxis. In the course of this treatment he developed aplastic anaemia that required dose reduction of chemotherapy. During chemotherapy he developed bilateral upper lobe pneumonia. He was treated with meropenem; amphotericin B was added after 48 hours due to lack of improvement. A computed tomography scan showed lesions suspect for fungal infection. After 2 days, the patient remained febrile, and we switched amphotericin B to voriconazole. The lesions resolved almost completely in 10 days, suggesting an infection with Aspergillus spp. We continued voriconazole as prophylaxis instead of itraconazole. 6 months later, while still on voriconazole, he again developed pneumonia, refractory to meropenem, and was treated with amphotericin B. Culture and histology findings of bronchoalveolar lavage fluid disclosed no microbial pathogens. Persisting fever led to resection of the infected lobe and discontinuation of chemotherapy. Microscopy of pulmonary tissue showed necrosis and broad hyphae suspect for zygomycetes. The dose of amphotericin B was doubled but nonetheless the infection disseminated. He suffered from convulsions, spondylodiscitis, and a thromboembolic mass in his left cardiac ventricle. Because of cardiac decompensation and high risk of embolism, the mass was resected. Cultures of the thrombus showed growth of Rhizopus microsporus (figure), susceptible in vitro to amphotericin B and posaconazole, an experimental triazole agent. The thrombus reappeared and posaconazole was added to the amphotericin B treatment. Unfortunately, the boy died of progressive cardiac obstruction. Voriconazole, a broad-spectrum triazole antifungal, is increasingly used as prophylaxis in patients with haematological malignancies. As this case illustrates, prolonged use of this agent may lead to an increase of infections with zygomycetes, all resistant to voriconazole.

Cerebrospinal fluid in tuberculous meningitis exhibits only the L-enantiomer of lactic acid

BackgroundThe defining feature of the cerebrospinal fluid (CSF) collected from infants and children with tuberculous meningitis (TBM), derived from an earlier untargeted nuclear magnetic resonance (NMR) metabolomics study, was highly elevated lactic acid. Undetermined was the contribution from host response (L-lactic acid) or of microbial origin (D-lactic acid), which was set out to be determined in this study.MethodsIn this follow-up study, we used targeted ultra-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (UPLC–ESI–MS/MS) to determine the ratio of the L and D enantiomers of lactic acid in these CSF samples.ResultsHere we report for the first time that the lactic acid observed in the CSF of confirmed TBM cases was in the L-form and solely a response from the host to the infection, with no contribution from any bacteria. The significance of elevated lactic acid in TBM appears to be that it is a crucial energy substrate, used preferentially over glucose by microglia, and exhibits neuroprotective capabilities.ConclusionThese results provide experimental evidence to support our conceptual astrocyte–microglia lactate shuttle model formulated from our previous NMR-based metabolomics study — highlighting the fact that lactic acid plays an important role in neuroinflammatory diseases such as TBM. Furthermore, this study reinforces our belief that the determination of enantiomers of metabolites corresponding to infectious diseases is of critical importance in substantiating the clinical significance of disease markers.

Cushing’s Triad in Pneumococcal Meningitis Due to Brainstem Ischemia: Early Detection by Diffusion-Weighted MRI

An infant with pneumococcal meningitis developed signs of raised intracranial pressure during the progression of the disease, including loss of consciousness, hypertension, bradycardia, and respiratory depression. However, both the emergency computed tomography scan findings and intracranial pressure measured by lumbar puncture were normal. Diffusion-weighted magnetic resonance imaging identified multiple lesions with restricted diffusion suggestive of ischemia in the brainstem, explaining the signs observed in the patient. These lesions could not be identified on T(2)-weighted images at that time.

Paediatric ART Adherence in South Africa: A Comprehensive Analysis

Adherence to antiretroviral therapy (ART) remains a challenge for HIV-infected children. In this cross-sectional study, we used structured interview-administered questionnaires and medical records to measure adherence levels and factors associated with adherence and viral suppression. We included 195 South African children aged 2.1–12.9 on ART. Adherence levels ranged between 20.5% (pill count) and 89.1% (self-report). Boys were less adherent according to self-report, girls were less adherent according to pill count. Caregivers ensured medication was taken when the condition directly affected daily life. Well-functioning families and families with high SES provide a context supportive of adherence. Non-disclosure and difficulties administering medication negatively affected adherence and viral suppression. This study shows challenging levels of adherence impacting directly on viral suppression in a South African paediatric HIV program. Gender roles, non-disclosure and difficulty administering medication may undermine adherence and should be taken into account for clinical guidelines, policy design and inform strategies.

The church and paediatric HIV care in rural South Africa : A qualitative study

ABSTRACT Religion has substantial – positive and negative – influence on South Africas HIV context. This qualitative study explored possibilities for positive church engagement in paediatric HIV care in a rural district in Limpopo Province, South Africa. Opinions, attitudes and experiences of various stakeholders including religious leaders, healthcare workers and people infected/affected with/by HIV were investigated through participant observation, semi-structured interviews and focus group discussions. During the research the original focus on paediatric HIV care shifted to HIV care in general in reaction to participant responses. Participants identified three main barriers to positive church engagement in HIV care: (a) stigma and disclosure; (b) sexual associations with HIV and (c) religious beliefs and practices. All participant groups appreciated the opportunity and relevance of strengthening church involvement in HIV care. Opportunities for positive church engagement in HIV care that participants identified included: (a) comprehensive and holistic HIV care when churches and clinics collaborate; (b) the wide social reach of churches and (c) the safety and acceptance in churches. Findings indicate that despite barriers great potential exists for increased positive church engagement in HIV care in rural South Africa. Recommendations include increased medical knowledge and dialogue on HIV/AIDS within church settings, and increased collaboration between churches and the medical sector.