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Clinical and Diagnostic Laboratory Immunology, 07 1996, 444-450, Vol 3, No. 4
IM Feavers, AJ Fox, S Gray, DM Jones and MC Maiden
The currently used serological subtyping scheme for the pathogen Neisseria
meningitidis is not comprehensive, a proportion of isolates are reported as
not subtypeable (NST), and few isolates are fully characterized with two
subtypes for each strain. To establish the reasons for this and to assess
the effectiveness of DNA-based subtyping schemes, dot blot hybridization
and nucleotide sequence analyses were used to characterize the genes
encoding antigenic variants of the meningococcal subtyping antigen, the
PorA protein. A total of 233 strains, including 174 serologically NST and
59 partially or completely subtyped meningococcal strains, were surveyed.
The NST isolates were chosen to be temporally and geographically
representative of NST strains, isolated in England and Wales, and submitted
to the Meningococcal Reference Unit in the period 1989 to 1991. The
DNA-based analyses demonstrated that all of the strains examined possessed
a porA gene. Some of these strains were serologically NST because of a lack
of monoclonal antibodies against certain PorA epitopes; in other cases,
strains expressed minor variants of known PorA epitopes that did not react
with monoclonal antibodies in serological assays. Lack of expression
remained a possible explanation for serological typing failure in some
cases. These findings have important implications for epidemiological
analysis and vaccine design and demonstrate the need for genetic
characterization, rather than phenotypic characterization using monoclonal
antibodies, for the identification of meningococcal strains.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Antigenic diversity of meningococcal outer membrane protein PorA has implications for epidemiological analysis and vaccine design
Division of Bacteriology, National Institute for Biological Standards and Control, Potters Bar, Hertfordshire, United Kingdom.
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