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Updated: Jan 21, 2026
Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature
Published on: April 1, 2014
Targeting the complement system in bacterial meningitis
Diederik L H Koelman1, Matthijs C Brouwer1, Diederik van de Beek1
1Amsterdam UMC, University of Amsterdam, Department of Neurology, Amsterdam Neuroscience, Meibergdreef 9, AZ, Amsterdam, The Netherlands.
Abstract:
Bacterial meningitis is most commonly caused by Streptococcus pneumoniae and Neisseria meningitidis and continues to pose a major public health threat. Morbidity and mortality of meningitis are driven by an uncontrolled host inflammatory response. This comprehensive update evaluates the role of the complement system in upregulating and maintaining the inflammatory response in bacterial meningitis. Genetic variation studies, complement level measurements in blood and CSF, and experimental work have together led to the identification of anaphylatoxin C5a as a promising treatment target in bacterial meningitis. In animals and patients with pneumococcal meningitis, the accumulation of neutrophils in the CSF was mainly driven by C5-derived chemotactic activity and correlated positively with disease severity and outcome. In murine pneumococcal meningitis, adjunctive treatment with C5 antibodies prevented brain damage and death. Several recently developed therapeutics target C5 conversion, C5a, or its receptor C5aR. Caution is warranted because treatment with C5 antibodies such as eculizumab also inhibits the formation of the membrane attack complex, which may result in decreased meningococcal killing and increased meningococcal disease susceptibility. The use of C5a or C5aR antagonists to specifically target the harmful anaphylatoxins-induced effects, therefore, are most promising and present opportunities for a phase 2 clinical trial.
Insights
Bacterial meningitis inflammation is driven by the complement system. Targeting C5a offers a promising therapeutic strategy for treating this severe public health threat.
Area of Science:
- Immunology
- Neuroscience
- Infectious Diseases
Background:
- Bacterial meningitis, primarily caused by Streptococcus pneumoniae and Neisseria meningitidis, remains a significant public health concern.
- The severe outcomes of meningitis are largely attributed to an excessive and uncontrolled host inflammatory response.
- The complement system plays a critical role in mediating and sustaining this detrimental inflammation.
Purpose of the Study:
- To comprehensively review the role of the complement system in bacterial meningitis pathogenesis.
- To evaluate the potential of targeting complement components, specifically C5a, as a therapeutic strategy.
- To assess the implications of complement-targeted therapies on disease severity and treatment outcomes.
Main Methods:
- Analysis of genetic variation studies related to complement components.
- Measurement of complement levels in cerebrospinal fluid (CSF) and blood.
- Review of experimental models (murine pneumococcal meningitis) and patient data.
- Evaluation of therapeutic strategies targeting C5 conversion, C5a, and its receptor C5aR.
Main Results:
- Accumulation of neutrophils in CSF during pneumococcal meningitis is primarily driven by C5-derived chemotaxis, correlating with disease severity.
- Experimental treatment with C5 antibodies in murine models demonstrated prevention of brain damage and mortality.
- Emerging therapeutics target C5 conversion, C5a, or C5aR, showing therapeutic potential.
Conclusions:
- The complement anaphylatoxin C5a is identified as a key mediator of inflammation and a promising therapeutic target in bacterial meningitis.
- While C5 inhibition shows promise, potential risks include impaired bacterial clearance due to inhibition of the membrane attack complex.
- Targeting C5a or C5aR specifically offers a more refined approach, warranting further clinical investigation, including Phase 2 trials.
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