Challenge of the Nasopharynx With Neisseria Lactamica Expressing the Meningococcal Protein Neisseria Adhesin A (NadA)

This study is part of a research programme that aims to improve ways of protecting people from serious illnesses such as meningitis and sepsis caused by a bacterium called Neisseria meningitidis (N. meningitidis), using a closely related but harmless bacterium called Neisseria lactamica (N. lactamica). Investigators have previously given nose drops containing N. lactamica to over 350 volunteers - this is known as inoculation. In these studies the investigators have shown that they can cause colonisation of many inoculated volunteers (35-60%) with N. lactamica. Colonisation is when bacteria survive on or in a person without causing any illness or disease. N. lactamica specifically colonises the nose and throat. Investigators have also shown that colonisation with N. lactamica results in an immune (antibody) response. In this study investigators will be using a genetically modified version of N. lactamica which contains a single gene from N. meningitides. It is anticipated that the presence of this gene will change the number of people who are colonised and how long people remain colonised for, as well as causing them to produce an immune response to N. meningitides. The purpose of this study are to prove that inoculation with this modified N. lactamica does not cause any symptoms or illness, and to analyse the immune response produced in healthy volunteers.