A Study Assessing Colonisation & Immunogenicity After Nasal Inoculation With N. Lactamica and Eradication on Day 4 or 14

N. lactamica (Nlac) has been shown to be safe to use in human challenge experiments. Even at a very low dose of 10,000 colony forming units (cfu) long lasting colonisation with Nlac is easily induced in 35-65% of volunteers. The investigators have previously showed that increasing the inoculum to 100,000 cfu increased the subsequent carriage of Nlac to 50%. In 80-90% of those volunteers successfully colonised, this is detectable by 1-2 weeks. Data regarding earlier detection of colonisation is currently lacking. Colonisation has a clear effect on the volunteers nasal mucosal microbiome, in that meningococcal acquisition is effectively inhibited in volunteers who carry the organism. Colonisation is immunogenic, with an increase in specific serum IgG by 2 weeks and specific salivary IgA by 4 weeks. No antibiotic eradication therapy has previously been given following experimental inoculation but Ciprofloxacin has been shown to be effective in the eradication of N. meningitidis. To design future planned studies using Nlac nasal inoculation and colonisation in order to prevent invasive N. meningitidis disease, it is necessary to further evaluate the colonisation kinetics and efficacy of the eradication following antibiotic treatment. In previous challenges the investigators inoculated volunteers with Nlac and followed those volunteers for prolonged periods of time (over 6 months). This study will compare the effect of short (4 days) versus longer (14 days) periods of nasal carriage of Nlac in volunteers on immunogenicity, and confirm the efficacy of antibiotic eradication therapy with ciprofloxacin. Healthy adult volunteers will receive a nasal inoculation of Nlac with an antibiotic given on day 4 or 14. This information will be used to inform the design of future research into the colonisation and immunogenicity of related organisms. Before designing future protocols the study investigators need to know whether a short containment of the volunteers will be sufficient for immunogenicity, and how quickly the volunteers can be discharged after antibiotic treatment. A wild-type strain of Nlac (Y92-100) will be used for this study, selected because the investigators have previously used it safely in experimental challenge of over 340 human volunteers. The same strain will be the parent strain for any future GMO work.