Acquisition of gonococcal denitrification apparatus in the Neisseria meningitidis urethritis clade

Project Summary Neisseria meningitidis is carried in the nasopharynx asymptomatically by up to 5-10% of the human population and remains a leading cause of meningitis and rapidly fatal sepsis, usually in otherwise healthy individuals. Historically, N. meningitidis has not been a significant sexually transmitted pathogen.

However, since 2015 recent outbreaks of sexually transmitted meningococcal urethritis have occurred, primarily, in heterosexual males in over thirteen US states, the UK, and Vietnam.

Unlike previous sporadic cases of meningococcal urethritis, these urethritis cases are all caused by a capsule-defective meningococcal clade belonging to the hyper-invasive cc11.2 lineage.

This clade of N. meningitidis, like N. gonorrhoeae, causes male urethritis in unprecedented numbers in communities, can also be isolated from the pharynx and rectal tract, and can cause meningococcemia and meningitis, as well as other mucosal infections (neonatal conjunctivitis).

Whereas isolated cases of urogenital colonization and urethritis caused by a range of meningococcal genotypes are reported, no other genotype has caused widespread urethritis outbreaks.

These urethritis outbreaks suggest that this 11.2 lineage clade has acquired novel genetic and, thus, phenotypic changes that allow it to effectively colonize the urogenital tract, to adapt to local innate immune responses, and to cause urogenital tract disease.

In support of this hypothesis, we discovered that all isolates of N. meningitidis urethritis clade, from multiple states and globally, but not sporadic meningococcal urethritis isolates, have the distinct N. gonorrhoeae denitrification apparatus - the gonococcal nitrite reductase, AniA, and the gonococcal nitric oxide (NO) reductase, NorB.

This precise chromosomal gene conversion event has also endowed the clade with the gonococcal regulatory region that separates the divergent transcripts encoding aniA and norB.

This aniA-norB conversion appears to provide a major adaptation to N. meningitidis for the oxygen-limited microaerobic/anaerobic urogenital environment and allowing emergence of this urethrotropic meningococcal clade.

In two Specific Aims, we seek to define the unique regulatory and physiological traits conferred to this meningococcal clade through the gonococcal aniA-norB gene conversion event.

In Aim 1, the unique hybrid transcriptional regulatory network, consisting of multiple meningococcal regulators controlling the divergently transcribed gonococcal aniA and norB promoters, will be examined in detail to define, new and critical, cis and trans regulatory elements in this clade. Global transcription profiles affected by the gene conversion in the clade will be examined using RNA-seq.

In Aim 2, we will determine the impact of the gonococcal denitrification conversion on phenotypes important in urogenital pathogenesis: microaerobic growth, NO susceptibility and utilization, and defense against NO-mediated immune responses.

Successful completion of these proposed studies will provide valuable insights into the continuing evolution of urethrotropic N. meningitidis and address two NIAID key priority areas, emerging infections and STIs.