BINDING OF MANNAN-BINDING PROTEIN TO VARIOUS BACTERIAL PATHOGENS OF MENINGITIS

Mannan-binding protein (MBP), a calcium-dependent plasma lectin, may p lay a role in the innate defence against microorganisms. After binding to carbohydrate structures at the bacterial surface, MBP activates th e classical pathway of the complement system. To investigate the bindi ng capacity of MBP to various bacteria associated with meningitis, an assay was developed to study the binding of MBP to bacteria grown in a semisynthetic fluid culture medium. Salmonella montevideo (containing a mannose-rich lipopolysaccharide (LPS)), used as a positive control strain, showed binding of radiolabelled MBP at a level of 80% compared with binding of MBP to zymosan. Binding of labelled MBP to Salm. mont evideo was time-dependent, temperature-dependent and saturable. The bi nding was inhibited by unlabelled MBP, by mannose and by N-acetyl-D-gl ucosamine. Among bacterial pathogens often found to cause meningitis, a wide range of MBP binding capacities could be determined. The encaps ulated Neisseria meningitidis (representatives from 11 serogroups othe r than group A were included: n = 22), N. mucosa (n = 1), Haemophilus influenzae type b (n = 10) and Streptococcus agalactiae (n = 5) had a low MBP binding capacity of 21.7% (95% confidence interval (CI) 3.3-40 .1%). Escherichia coli K1 (n = 11), Strep. suis (n = 5), Strep. pneumo niae (n = 10) and N. meningitidis serogroup A (n = 2) showed intermedi ate MBP binding capacity of 58.4% (95% CI 40.0-76.8%). A third group c onsisting of non-encapsulated Listeria monocytogenes (n = 11), non-enc apsulated H. influenzae (n = 2), nonencapsulated N. meningitidis (n = 2), N. cinera (n = 1) and N. subflava (n = 1) strains had a high MBP b inding capacity of 87.5% (95% CI 62.5-112.5%). The majority of encapsu lated pathogens causing bacterial meningitis seem to have a rather low MBP binding capacity.