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Clinical and Diagnostic Laboratory Immunology, May 1997, 264-269, Vol 4, No. 3
GA Losonsky, Y Lim, P Motamedi, LE Comstock, JA Johnson, JG Morris Jr, CO Tacket, JB Kaper and MM Levine
The emergence of a new agent of cholera, Vibrio cholerae O139, has prompted
a reevaluation of the vibriocidal antibody assay. This assay, primarily
directed to lipopolysaccharide, is an important correlate of O1 immunity.
V. cholerae O139 strains are encapsulated, rendering them relatively
resistant to killing by serum. Recent reports suggest that there is
strain-to-strain variability in the sensitivity of the vibriocidal assay to
fully encapsulated O139 strains. We have assessed a modified vibriocidal
assay for fully encapsulated O139 strain AI-1837 and its unencapsulated
mutant 2L in sera from 53 volunteers given wild- type AI-1837 or its
attenuated derivative CVD 112 and from 48 controls challenged with V.
cholerae O1 or strains of the family Enterobacteriaceae. Vibriocidal
responses to the AI-1837 and 2L strains were seen in 67 and 89% of
volunteers, respectively, following a single exposure to the wild-type
strain. However, >50% of all controls had low- level vibriocidal
responses to both strains. These nonspecific responses were transient and
of the immunoglobulin G isotype. No binding activity against purified O139
lipopolysaccharide (LPS) by immunoblotting was seen in control sera. In
contrast, vibriocidal assay and strain 2L LPS responses by immunoblotting
were detectable in 91% of tested volunteers following a single exposure to
O139. The presence of vibriocidal antibody to AI-1837 or 2L was not
associated with protection in rechallenge studies with O139 strain AI-1837.
The vibriocidal assay with unencapsulated strain 2L may be used to detect
exposure to O139 strain AI-1837 in controlled research trials. However, its
lack of specificity does not make it useful for determining exposure to V.
cholerae O139 in the field.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Vibriocidal antibody responses in North American volunteers exposed to wild-type or vaccine Vibrio cholerae O139: specificity and relevance to immunity
Center for Vaccine Development, University of Maryland School of Medicine, and Veterans Affairs Medical Center of Baltimore, 21201, USA.
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