EMERGENCE OF A NEW VIRULENT CLONE WITHIN THE ELECTROPHORETIC TYPE 5 COMPLEX OF SEROGROUP-B MENINGOCOCCI IN NORWAY

An increase in B:15:P1.12 meningococci among isolates from patients wi th Neisseria meningitidis infection in Norway in recent years led to f urther characterization of such strains. Between 1987 and 1992, B:15:P 1.12 strains constituted 9.8% (24 strains) of B:15 isolates. The B:15: P1.12 strains belonged to the electrophoretic type 5 (ET-5) complex, b ut 17 (71%) strains were a new clone (ET-5c) not found elsewhere in th e world, All but one strain of ET-Sc were responsible for a localized outbreak of systemic meningococcal disease in western Norway. A novel monoclonal antibody (202,G-12), developed against the unknown variable region 2 on the class 1 protein of one of these strains, bound to 19 of the 15:P1.12 strains, 4 strains bound the subtype P1.13 reference m onoclonal antibody MN24H10.75, and the remaining strain showed no reac tion, Sequencing of porA genes demonstrated a series of nine threonine residues in the deduced variable region 2 of the latter strain, while four and five threonine residues were found in the corresponding regi ons of strains reacting with the monoclonal antibodies 202,G-12 and MN 24H10.75, respectively, Epitope mapping with synthetic peptides showed that 202,G-12 bound to a sequence of 11 amino acids which included th e four threonine residues specific for subtype P1.13a. Immunoglobulin G antibodies against the P1.7,16 subtype protein, induced in volunteer s after vaccination with the Norwegian meningococcal vaccine, did not cross-react on immunoblots with the subtype protein of clone ET-5c. Th us, postvaccination class 1 protein antibodies, assumed to be protecti ve, may not be effective against infection with the new clone.