Clinical and Diagnostic Laboratory Immunology, May 2001, p. 616-623, Vol. 8, No. 3
1071-412X/01/$04.00+0 DOI: 10.1128/CDLI.8.3.616-623.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Chiron Corporation, Emeryville,1 and Children's Hospital, Oakland Research Institute, Oakland,3 California, and Biologics Consulting Group, Alexandria, Virginia2
Received 20 October 2000/Returned for modification 4 January 2001/Accepted 14 March 2001
Complement-mediated bactericidal antibodies in serum confer
protection against meningococcal disease. The minimum protective titer
is estimated to be between 1:4 and 1:8 when measured by the
Goldschneider assay performed with human complement, the assay used in
the 1960s to establish the correlation between bactericidal antibodies
and protection. A more recently described bactericidal assay
standardized by an international consortium uses rabbit complement,
which is known to augment bactericidal titers. To define a protective
titer measured by the standardized assay, we compared bactericidal
titers against serogroup C strains measured by this assay to titers
measured by the assay described by Goldschneider et al. A titer of
1:128 measured by the standardized assay was needed to predict with
80% certainty a positive titer of
1:4 as measured by the
Goldschneider assay. However, the majority of samples with titers of
1:4 measured by the Goldschneider assay had titers of <1:128 when
measured by the standardized assay. Therefore, by the results of the
standardized assay such persons would be falsely categorized as being
susceptible to disease. In conclusion, high bactericidal titers
measured with the standardized assay performed with rabbit complement
are predictive of protection, but no threshold titer is both sensitive
and specific for predicting a positive titer measured by the
Goldschneider assay using human complement. Up to 10% of the U.S.
adult population lacks intrinsic bactericidal activity against
serogroup C strains in serum and can serve as complement donors.
Therefore, use of the Goldschneider assay or an equivalent assay
performed with human complement is preferred over assays that use
rabbit complement.
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