Stability of PorA during a meningococcal disease epidemic.
Meningococci causing New Zealand's epidemic, which began in 1991, are defined as group B, serosubtype P1.4 (subtype P1.7-2,4), belonging to the ST-41/ST-44 complex, lineage III. Of the 2,358 group B isolates obtained from disease cases from 1991 through 2003, 85.7% (2,021 of 2,358) were determined to be serosubtype P1.4. Of the remaining isolates, 156 (6.6%) were not serosubtypeable (NST). Molecular analysis of the porA gene from these B:NST meningococcal isolates was used to determine the reason. Most NST isolates (156, 88.5%) expressed a PorA that was distinct from P1.7-2,4 PorA. Fifteen isolates expressed variants of P1.7-2,4 PorA, and a further three expressed P1.7-2,4 PorA without any sequence variation. These three isolates expressed P1.7-2,4 PorA at very low levels, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and showed variation in the porA promoter region. Among the 15 meningococcal isolates expressing variants of P1.7-2,4 PorA, 11 different sequence variations were found. Compared with the P1.7-2,4 PorA sequence, the sequences of these variants contained deletions, insertions, or single-nucleotide substitutions in the VR2 region of the protein. Multilocus restriction typing was used to assess the clonal derivations of B:NST case isolates. Meningococcal isolates expressing distinct PorA proteins belonged mostly to clonal types that were unrelated to the epidemic strain, whereas all meningococcal isolates expressing variants of P1.7-2,4 PorA belonged to the ST-41/ST-44 complex, lineage III. These results, together with those obtained serologically, demonstrate that the P1.7-2,4 PorA protein of meningococci responsible for New Zealand's epidemic has remained relatively stable over 13 years and support the use of a strain-specific outer membrane vesicle vaccine to control the epidemic.
Devoy
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Communicable Disease Group, Institute of Environmental Science and Research, Porirua, New Zealand.
Dyet
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Martin
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D000595:Amino Acid Sequence; D001483:Base Sequence; D004196:Disease Outbreaks; D006801:Humans; D008589:Meningococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D022401:Meningococcal Vaccines / Q000008:administration & dosage; D008969:Molecular Sequence Data; D038541:Neisseria meningitidis, Serogroup B / Q000145:classification* / Q000235:genetics / Q000276:immunology; D009520:New Zealand / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D018272:Porins / Q000737:chemistry* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012703:Serotyping
D022401:Meningococcal Vaccines; D018272:Porins; C057699:porin protein, Neisseria