Ex vivo bactericidal activity against group C Neisseria meningitidis in seronegative subjects.

ABSTRACT

BACKGROUND: To determine the anti-meningococcal C immunological activity by adding functional tests (opsonophagocytosis) to the classical serology techniques. SUBJECTS AND METHODS: 42 adult volunteers were screened using serological methods (determination of total and bactericidal antibodies). Seronegative subjects were tested by opsonophagocytosis. RESULTS: 24 subjects (57%) showed serological evidence of previous contact with Neisseria meningitidis group C antigens 19 subjects had both total and bactericidal antibodies, two subjects had only total antibodies and three subjects had only bactericidal antibodies. Of the 18 seronegative subjects, five showed ex vivo activity in killing curves with or without polymorphonuclear cells two subjects exhibited only complement-mediated bactericidal activity, one subject only opsonophagocytosis, and two subjects exhibited both activities. CONCLUSION: The addition of functional tests to the classical serological determination increases the evidence of previous contact with N. meningitidis antigens by 12%.