RECOMBINATIONAL REASSORTMENT AMONG OPA GENES FROM ET-37 COMPLEX NEISSERIA-MENINGITIDIS ISOLATES OF DIVERSE GEOGRAPHICAL ORIGINS

Opacity (Opal proteins are a family of antigenically variable outer-me mbrane proteins of Neisseria meningitidis. ET-37 complex meningococci. defined by multilocus enzyme electrophoresis, have been isolated on d ifferent continents. Twenty-six different Opa proteins have been obser ved within strains of the ET-37 complex isolated between the 1960s and the 1980s, although individual strains have only four opa genes per c hromosome. In this work the opa genes of four closely related ST-ST co mplex N. meningitidis strains recently isolated from Mall, West Africa were characterized and compared with the opa genes of strain FAM18, a n ST-ST complex isolate from the USA. DNA sequence analysis and Southe rn blot experiments indicated that recombinational reassortment, inclu ding gene duplication and import by horizontal genetic exchange, has o ccurred in the opa genes within the ET-37 complex, resulting in two pa rtially different Opa repertoires being present in FAM18 and the Mall isolates. Using synthetic peptides derived from the hypervariable (HV) regions of opa genes, the epitopes for nine mAbs were mapped. These b acteria, isolated on different continents, contain both shared and uni que opa HV regions encoding epitopes recognized by mAbs and show evide nce of recombinational reassortment of the HV regions.