Objectives. To determine the association between the ability of a different strains of meningococci to survive in whole blood and the age of the donor.
Methods. A panel of serogroup B and a serogroup C strain of Neisseria meningitidis was tested in an ex vivo whole blood model. Blood from 81 healthy children and 20 adults and from children during convalescence from serogroup B (55 patients) or serogroup C (43 patients) meningococcal infection was assessed.
Results. Age-dependent acquisition of whole blood killing of serogroup B and C bacterial isolates was demonstrated in healthy children with an inverse relationship to the reported incidence of disease. After infection with serogroup B or C meningococci, evidence of whole blood killing of the bacteria was found even in blood from children <2 years of age, the survival of a serogroup B strain, MC58, being reduced compared with that in healthy children (median, 64% compared with 194.5% survival at 90 min). In both affected children and controls, there was a significant correlation between whole blood killing of strain MC58 and of other serogroup B and C meningococci.
Conclusions. The whole blood model measures both humoral and cellular mechanisms responsible for the bactericidal activity of blood. The model was first described 80 years ago, but this is the first description of its age dependency. Acquisition of bactericidal activity was more rapid in children infected and is directed at various strains of meningococci, indicating the presence of a cross-reactive antigen(s).