Induction of Asymptomatic Nasopharyngeal Carriage and Immune Response by Lyophilized Neisseria lactamica

Overview

Intranasal inoculation with lyophilized Neisseria lactamica (LyoNlac) was safe and induced asymptomatic nasopharyngeal colonization in healthy adults in the UK and Mali. Colonization elicited increased Nlac- and Nmen-specific IgG responses, supporting potential use of LyoNlac to reduce meningococcal carriage and transmission in sub-Saharan Africa.

Background

Neisseria meningitidis (Nmen) causes meningitis outbreaks in the African meningitis belt, with colonization being a prerequisite for disease. Vaccination reduces carriage but is serogroup specific and logistically challenging during outbreaks. Neisseria lactamica (Nlac), a harmless commensal, inversely correlates with Nmen carriage and may inhibit meningococcal acquisition. Prior studies showed experimental Nlac colonization reduces Nmen carriage and induces cross-reactive immunity. A lyophilized Nlac formulation (LyoNlac) was developed for easy deployment without cold chain requirements.

Data Highlights

Key Findings

• Intranasal inoculation with lyophilized Nlac was well tolerated with no significant safety concerns in both UK and Mali cohorts.
• In the UK, a dose of 10⁵ CFU achieved 100% colonization, while in Mali, 10⁷ CFU achieved 65% colonization.
• Colonized participants showed significant increases in Nlac- and Nmen-specific IgG antibodies by day 28 post-challenge.
• No significant seroconversion was observed in non-colonized participants.
• LyoNlac colonization induced immunogenic nasopharyngeal carriage in healthy adults across different geographic and epidemiologic settings.

Clinical Implications

Lyophilized Nlac can safely establish asymptomatic colonization and induce cross-reactive immune responses, suggesting it may be a practical intervention to reduce meningococcal carriage and transmission in the African meningitis belt. Its stability without cold chain requirements facilitates deployment during outbreaks. Further clinical trials are warranted to evaluate its efficacy in preventing meningococcal disease.

Conclusion

LyoNlac is a safe and immunogenic formulation capable of inducing nasopharyngeal colonization in healthy adults, supporting its potential role as a novel strategy to interrupt meningococcal transmission in high-risk regions.

References

1. UK and Mali Controlled Human Infection Studies (2021) -- Induction of Asymptomatic Nasopharyngeal Carriage and Immune Response Following Controlled Infection with Lyophilized Neisseria lactamica