Genetic Diversity of Meningococcal Serogroup B Vaccine Antigens among Carriage Isolates Collected from Students at Three Universities in the United States, 2015-2016

Carriage evaluations were conducted during 2015 to 2016 at two U.S. universities in conjunction with the response to disease outbreaks caused by Neisseria meningitidis serogroup B and at a university where outbreak and response activities had not occurred. All eligible students at the two universities received the serogroup B meningococcal factor H binding protein vaccine (MenB-FHbp); 5.2% of students (181/3,509) at one university received MenB-4C. A total of 1,514 meningococcal carriage isolates were obtained from 8,905 oropharyngeal swabs from 7,001 unique participants. Whole-genome sequencing data were analyzed to understand MenB-FHbp's impact on carriage and antigen genetic diversity and distribution. Of 1,422 isolates from carriers with known vaccination status (726 [51.0%] from MenB-FHbp-vaccinated, 42 [3.0%] from MenB-4C-vaccinated, and 654 [46.0%] from unvaccinated participants), 1,406 (98.9%) had intact fHbp alleles (716 from MenB-FHbp-vaccinated participants). Of 726 isolates from MenB-FHbp-vaccinated participants, 250 (34.4%) harbored FHbp peptides that may be covered by MenB-FHbp. Genogroup B was detected in 122/1,422 (8.6%) and 112/1,422 (7.9%) isolates from MenB-FHbp-vaccinated and unvaccinated participants, respectively. FHbp subfamily and peptide distributions between MenBFHbp-vaccinated and unvaccinated participants were not statistically different. Eighteen of 161 MenB-FHbp-vaccinated repeat carriers (11.2%) acquired a new strain containing one or more new vaccine antigen peptides during multiple rounds of sample collection, which was not statistically different (P= 0.3176) from the unvaccinated repeat carriers (1/ 30; 3.3%). Our findings suggest that lack of MenB vaccine impact on carriage was not due to missing the intact fHbp gene; MenB-FHbp did not affect antigen genetic diversity and distribution during the study period. IMPORTANCE The impact of serogroup B meningococcal (MenB) vaccines on carriage is not completely understood. Using whole-genome sequencing data, we assessed the diversity and distribution of MenB vaccine antigens (particularly FHbp) among 1,514 meningococcal carriage isolates recovered from vaccinated and unvaccinated students at three U.S. universities, two of which underwent MenB-FHbp mass vaccination campaigns following meningococcal disease outbreaks. The majority of carriage isolates recovered from participants harbored intact fHbp genes, about half of which were recovered from MenB-FHbp-vaccinated participants. The distribution of vaccine antigen peptides was similar among carriage isolates recovered from vaccinated and unvaccinated participants, and almost all strains recovered from repeat carriers retained the same vaccine antigen profile, suggesting insignificant vaccine selective pressure on the carriage population in these universities.

Automated summary

The MenB-FHbp vaccine did not impact carriage of Neisseria meningitidis serogroup B strains in university students, regardless of vaccination status. The distribution of vaccine antigen peptides was similar between vaccinated and unvaccinated participants, indicating insignificant vaccine selective pressure on the carriage population. The majority of carriage isolates harbored intact fHbp genes, and strains recovered from repeat carriers retained the same vaccine antigen profile.