The genetic structure of Neisseria meningitidis populations in Cuba before and after the introduction of a serogroup BC vaccine

We investigated the population genetics in collections of meningococci sampled in Cuba during the period 1983-2005, thereby covering a period before and after the introduction of an antimeningococcal B-C vaccine. A total of 163 case isolates and 210 isolates from healthy carriers were characterized by multilocus sequence typing (MLST) and sequence determination of porA, porB and fetA genes. A total of 56 sequence types (STs) including 28 new STs were identified among these isolates. The analysis of surface antigens revealed variants 3-1 and 3-8 to be prevalent for porB; variant F5-1 was the most common FetA epitope, and variants 19 and 15 corresponded to the prevalent variable regions 1 (VR1) and VR2 PorA epitopes, respectively. The strongest associations between specific surface protein variants and clonal complexes were detected in lineages ST-32 and ST-53. All ST-32 complex isolates possessed porB3 alleles, and the most frequent antigen combination among ST-32 complex isolates was P1.19,15;F5-1. Variants PorB3-64 at PorB and P1.30 at PorA VR2, in combination with the PorA VR1 variants P1.12-1, P1.7 and P1.7-2 as well as the FetA variants F1-2 and F1-7, dominated the ST-53 complex organisms. Furthermore, we observed a statistically significant association between the most frequent porA, porB and fetA alleles and strain invasiveness. Finally, this study showed that the application of VA-MENGOC-BC((R)), the Cuban antimeningococcal vaccine, reduced the number and frequency of the hypervirulent Clonal Complexes ST-32 and ST-41/44, and also impacted on other lineages. The vaccine also affected the genetic composition of the carrier-associated meningococcal isolates. The number of carrier isolates belonging to hypervirulent lineages decreased significantly after vaccination, and ST-53, a sequence type common in carriers, became the predominant ST.