The emergence of Neisseria meningitidis serogroup X (NmX) in the African meningitis belt has urged understanding of this emergence as well as the development of diagnostic tools and vaccines for this serogroup, especially following the introduction of a conjugate vaccine against N. meningitidis serogroup A (NmA).
We used whole genome sequencing of meningococcal isolates of serogroup X from several countries in the sub-Saharan Africa and from France showed that their emergence in Sub-Saharan Africa is due to the expansion of particular isolates within the clonal complex ST-181. These isolates also showed high virulence in an experimental mice model.
We are also developing and evaluating new rapid diagnostic tests (RDT) for detecting the capsular polysaccharide (cps) antigen of this emerging serogroup. A unique NmX-specific test could be added to the other available set of RDT for the detection of meningococcal meningitis in Africa as a major tool to reinforce epidemiological surveillance after the introduction of the NmA conjugate vaccine.
We also showed that the new vaccine, 4CMenB, is composed of surface proteins of N. meningitidis is able to cover these emerging NmX isolates.
We are currently studying the mergence of meningococci serogroup C in Niger