Challenge of the Nasopharynx With Neisseria Lactamica Expressing the Meningococcal Protein Neisseria Adhesin A (NadA) — NadA-Lac4  

Meningitis, Bacterial Clinical Trial

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

Status Completed

Clinical Trial Summary

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.

Clinical Trial Description

The NadA protein is one of the 4 strongly immunogenic components of the 4CMenB vaccine against serogroup B meningococcal disease (Bexsero) and has been demonstrated to be immunogenic in terms of generating serum bactericidal antibodies against N. meningitides strains that express the cognate NadA. Furthermore, University students vaccinated with Bexsero exhibit moderately reduced acquisition of nasopharyngeal carriage of N. meningitidis over the course of 12 months after vaccination. These studies imply that NadA expression by N. meningitidis may induce systemic and mucosal immunity to NadA during carriage, and that immunity directed against NadA may protect against colonisation by N. meningitidis. A greater understanding of the mucosal immune mechanisms of protection against pathobionts is essential for design of more effective and long lasting vaccines in the future. Then direct way to do this would be experimental human challenge with N. meningitidis but this carries potential hazard. As N. lactamica human challenge has shown to be safe, an alternative technique to investigate mucosal immunity to meningococcal antigens such as NadA will utilise Genetically Modified Organisms (GMOs) such as the one described here. Two strains of genetically modified N. lactamica will be used in this study, both of which have been derived from a beta-D-galactosidase (lacZ)-deficient mutant strain of N. lactamica Y92-1009 (△lacZ). This mutant can be differentiated from wild type bacteria when grown on the chromogenic substrate, X-gal. Both Genetically modified (GM) strains have demonstrated to remain acutely susceptible to killing by normal human serum and retain sensitivity to the front-line antibiotics used clinically to treat meningococcal disease (rifampicin, ciprofloxacin and ceftriaxone). The efficacy of ciprofloxacin to clear N. lactamica carriage is likely to similar as for N. meningitidis, as the organism is extremely sensitive to this antibiotic. Ciprofloxacin has been effective in clearing N. lactamica carriage within 24 hours in 100% of 4 individuals experimentally colonised in an ongoing human challenge study with wild type N. lactamica (unpublished data). ;

Related Conditions & MeSH terms

• Meningitis
• Meningitis, Bacterial
• Neisseria Infection

• NCT number: NCT03630250
• Study type: Interventional
• Source: University of Southampton
• Status: Completed
• Phase: Early Phase 1
• Start date: October 18, 2018
• Completion date: September 1, 2019