Distribution of Neisseria meningitidis serogroup B serosubtypes and serotypes circulating in the United States

Because the Neisseria meningitidis serogroup B (NMSB) capsule is poorly imm unogenic in humans, immunization strategies have focused on noncapsular ant igens, Both PorA and to a lesser extent PorB are noncapsular protein antige ns capable of inducing protective bactericidal antibodies, and vaccines bas ed on the outer membrane protein (OMP) components of serogroup B meningococ ci have been shown to be effective in clinical trials. Multiple PorA antige ns seem to be needed to prevent endemic meningococcal disease around the wo rld, and a hexavalent PorA-based meningococcal vaccine has recently been de veloped in The Netherlands. To evaluate the distribution of NMSB PorA and P orB antigens in the United States, serosubtyping and serotyping were done o n 444 NMSB strains isolated in the active surveillance areas of the United States (total population, 32 million) during the period 1992 to 1998, A tot al of 244 strains were isolated from sporadic cases of meningococcal diseas e, and 200 strains were isolated from an epidemic in Oregon. A panel of 16 mouse monoclonal antibodies reactive with PorA and 15 monoclonal antibodies reactive with PorB were used. Among the NMSB isolates obtained from sporad ic cases, the most prevalent serosubtypes were P1.7,16 (14.3%), P1.19,15 (9 .8%), P1.7,1 (8.6%), P1.5,2 (7.8%), P1.22a, 14 (7.8%), and P1.14 (5.3%) and the most prevalent serotypes were 4,7 (27.5%), 15 (16%), 14 (8.6%), 10 (6. 1%), 1 (4.9%), and 2a (3.7%). A multivalent PorA-based OMP vaccine aimed at the six most prevalent serosubtypes could have targeted about half of the sporadic cases of NMSB disease that occurred between 1992 and 1998 in the s urveillance areas. Twenty serosubtypes would have had to be included in a m ultivalent vaccine to achieve 80% coverage of strains causing sporadic dise ase. The relatively large number of isolates that did not react with murine monoclonal antibodies indicates that DNA sequence-based variable region ty ping of NMSB will be necessary to provide precise information on the distri bution and diversity of PorA antigens and correlation with nonserosubtypeab le isolates. The high degree of variability observed in the PorA and PorB p roteins of NMSB in the United States suggests that vaccine strategies not b ased on OMPs should be further investigated.