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Vaccimonitor

Print version ISSN 1025-028XOn-line version ISSN 1025-0298

Abstract

CAMARAZA, María Amalia et al. Preliminary evaluation of different concentrations of bacterial suspensions used in the Whole Blood Bactericidal Assay. Vaccimonitor [online]. 2000, vol.9, n.2, pp.14-18. ISSN 1025-028X.

The Serum Bactericidal Assay (SBA) has been considered the “golden standard” to evaluate the serological efficacy of meningococcal vaccines, taking into account that the presence of serum bactericidal antibodies is related with protection. The levels of A and C capsular polysaccharide antibodies against these serogroups has confirmed the reliability of this assay. The SBA has also been used to asses the efficacy of serogroup B vaccines, but in some studies, the correlation between serological efficacy and protection has been poor. Ison et al developed the Whole Blood Assay (WBA) that measures the complete bactericidal activity in blood. The results obtained indicate that this model is a more sensitive marker of immunity than SBA for serogroup B. The results from the evaluation of the Cuban meningococcal vaccine (VA-MENGOC-BC®) in infants using WBA showed that after the immunisation around 50% of infants exhibited >50% lysis of the vaccine strain (B:4:P1.19,15). The results against heterologous strains were poor. Taking into account these and other results we evaluated the behavior of the WBA using lower concentrations of the bacterial suspension used as inoculum. Blood from two healthy adults was screened for bactericidal activity using the WBA, against B:4:P1.19,15(Cu 385/83) and B:15:P1.7,16 (MC58) strains. In addition to the recommended concentration (106 or 107 CFU/mL), two lower concentrations were used (105 and 104 CFU/mL). The first donor showed a lytic activity of 40% against the homologous strain, at a concentration of 107 CFU/mL. At 105 and 104 CFU/mL concentrations, lysis was around 80%. The behavior against the heterologous strain showed 25% of lysis at a concentration of 107 CFU/mL and around 60% at lower concentrations. The second donor did not show lytic activity against the homologous strain at a concentration of 107 CFU/mL, while it showed 55% and 65% lysis at 105 and 104 CFU/mL concentrations, respectively. The results against the heterologous strain were 40% of lysis for the highest concentration and 70% and 80% for concentrations of 105 and 104 CFU/mL respectively.

Keywords : Serum Bactericidal Assay; Whole Blood Assay; Neisseria meningitidis.

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