Open access Protocol BMJ Open: first published as 10.1136/bmjopen-2018-026544 on 1 May 2019. Downloaded from Protocol for a controlled human infection with genetically modified Neisseria lactamica expressing the meningococcal vaccine antigen NadA: a potent new technique for experimental medicine Diane Gbesemete,1,2 Jay Robert Laver,3 Hans de Graaf,1,2 Muktar Ibrahim,3 Andrew Vaughan,3 Saul Faust,1 Andrew Gorringe,4 Robert Charles Read 3,5 To cite: Gbesemete D, Laver JR, ABSTRACT Strengths and limitations of this study de Graaf H, et al. Protocol for Introduction Neisseria lactamica is a commensal a controlled human infection organism found in the human nasopharynx and is closely with genetically modified ► This human challenge study using a genetically related to the pathogen N. meningitidis (meningococcus). Neisseria lactamica expressing modified organism will provide insight into the role Carriage of N. lactamica is associated with reduced the meningococcal vaccine of a specific bacterial antigen in nasopharyngeal meningococcal carriage and disease. We summarise an antigen NadA: a potent new carriage and immunity, and provide a novel means ethically approved protocol for an experimental human technique for experimental to test the herd-immunity potential of vaccines. medicine. challenge study using a genetically modified strain of BMJ Open ► Safety is the first priority and has been considered at 2019;9:e026544. doi:10.1136/ N. lactamica that expresses the meningococcal antigen all points of the study design with extensive preclin- bmjopen-2018-026544 NadA. We aim to develop a model to study the role of ical testing, a period of admission for close obser- specific bacterial antigens in nasopharyngeal carriage ► Prepublication history and vation following inoculation and stringent infection and immunity, to evaluate vaccines for their efficacy in additional material for this control rules throughout the study. preventing colonisation and to provide a proof of principle http://bmjopen.bmj.com/ paper are available online. To ► The use of environmental sampling and regular con- for the development of bacterial medicines. view these files, please visit tact volunteer sampling will provide new information Methods and analysis Healthy adult volunteers aged the journal online (http:// dx. doi. regarding the shedding and transmission of respira- org/ 10. 1136/ bmjopen- 2018- 18–45 years will receive an intranasal inoculation of tory tract organisms. 026544). either the NadA containing strain of N. lactamica or a ► The planned inoculum dose is based on previous genetically modified, but wild-type equivalent control studies with wild-type N. lactamica and may not be Received 12 September 2018 strain. These challenge volunteers will be admitted for Revised 18 January 2019 the optimal dose to achieve colonisation with the 4.5 days observation following inoculation and will then Accepted 6 March 2019 genetically modified strains. be discharged with strict infection control rules. Bedroom ► The low number of participants may be insufficient contacts of the challenge volunteers will also be enrolled on September 27, 2021 by guest. Protected copyright. to prove an effect of the expression of NadA on colo- as contact volunteers. Safety, colonisation, shedding, nisation so further research may be required. transmission and immunogenicity will be assessed over 90 days after which carriage will be terminated with antibiotic eradication therapy. the modified organisms expressing the gene Ethics and dissemination This study has been approved of interest. Volunteers, colonised with the by the Department for Environment, Food and Rural Affairs and South Central Oxford A Research Ethics Committee strain harboured in the nasopharynx, will (reference: 18/SC/0133). Findings will be published in be allowed to leave the Clinical Research peer-reviewed open-access journals as soon as possible. Facility (CRF) after a 4.5-day period of obser- Trial registration number NCT03630250; Pre-results. vation. This implies deliberate release of a genetically modified organism (GMO) so the © Author(s) (or their employer(s)) 2019. Re-use protocol has been reviewed and approved by permitted under CC BY. INTRODUCTIon the UK Department for Environment, Food Published by BMJ. A controlled human infection experiment and Rural Affairs (DEFRA).1 For numbered affiliations see with a genetically modified (GM) Neisseria N. lactamica and N. meningitidis are end of article. lactamica strain is currently underway. In Gram-negative diplococci which both Correspondence to the protocol presented here, organisms are colonise the human nasopharynx. N. Dr Diane Gbesemete; inoculated into the nasopharynx of healthy lactamica is non-pathogenic, non-encap- D. Gbesemete@ soton. ac. uk volunteers to study the immune response to sulated and lactose fermenting and is Gbesemete D, et al. BMJ Open 2019;9:e026544. doi:10.1136/bmjopen-2018-026544 1 Open access BMJ Open: first published as 10.1136/bmjopen-2018-026544 on 1 May 2019. Downloaded from a common commensal, particularly in young chil- Meningococcal vaccines dren.2 3 In contrast, N. meningitidis expresses poly- Glycoconjugate vaccines directed against capsular anti- saccharide capsule and although it usually colonises gens for serogroups C, A, W-135 and Y have been in use asymptomatically, it can in a minority of colonised globally for several years. These have had dramatic effects individuals cause invasive disease.4 5 Due to recombi- on disease incidence, which is probably mostly due to nation events, the organism exists in multiple clonal herd protection conferred by vaccine-induced modifica- forms, with specific clonal complexes being charac- tion of colonisation reducing interhost transmission.14 15 teristically associated with invasive disease.6 Invasive Recent vaccine developments include a new subcapsular meningococcal disease remains a significant global vaccine, 4CMenB (Bexsero), which induces bactericidal cause of morbidity and mortality with sporadic disease antibodies against a range of strains, including serogroup and small outbreaks throughout the world and signifi- B, and protects vaccinated infants against disease.16 In cant epidemics occurring in the meningococcal belt of view of the importance of carriage reduction for herd sub-Saharan Africa.7 immunity, a large prospective randomised study was done to measure this, but the effect of Bexsero on carriage of N. Carriage of N. lactamica and N. meningitidis meningitidis was found to be relatively modest and delayed 17 Of note, N. lactamica appears to provide commensal-re- until 3 months after vaccination, with no evidence of an lated protection against meningococcal disease. Age-spe- effect on carriage of the serogroup B organisms carried cific rates of N. meningitidis carriage and disease are by the participants. inversely proportional to carriage of N. lactamica.8–10 The More rapidly effective and longer lasting vaccines highest rate of natural carriage of N. lactamica occurs in are required, particularly to halt transmission during infants. This then wanes in toddlers and older children and epidemics in the meningitis belt of sub-Saharan Africa. by adolescence carriage is approximately 1%.2 8 Carriage Successful future vaccines should maximise herd immu- of N. meningitidis is low in infants, increasing gradually nity by targeting carriage and transmission. The develop- throughout childhood and peaking in adolescence with ment of such vaccines requires a greater understanding the highest rates of carriage seen in teenagers and univer- of mucosal immune mechanisms and the specific anti- sity students.11 gens involved in colonisation. The mechanism of this epidemiological relationship is as yet undetermined. It is probably not due to cross-pro- The meningococcal antigen NadA tective antibody production; the early years of life associ- In this human challenge study volunteers will receive ated with high rates of N. lactamica carriage predate the intranasal inoculation with a GM strain of N. lactamica development of natural bactericidal meningococcal anti- expressing the meningococcal antigen NadA. This http://bmjopen.bmj.com/ bodies.4 Other postulated mechanisms include microbial antigen is being used because it is well defined, and competition, innate immune responses triggered by N. one of the four strongly immunogenic components of lactamica colonisation and cross-reactive non-humoral the Bexsero vaccine. Bexsero has been demonstrated acquired immunity.12 13 to be immunogenic in terms of generating serum bactericidal antibodies (SBA) against N. meningitidis 18 Human challenge with N. lactamica strains that express NadA and moderately effective in A controlled human infection model of N. lactamica reducing acquisition of nasopharyngeal carriage of N. meningitidis over the course of 12 months after vacci- colonisation has been used to investigate the mecha- on September 27, 2021 by guest. Protected copyright. 17 nism of this natural effect. Previous studies have shown nation. NadA expression by N. lactamica may induce that human challenge with wild-type N. lactamica is systemic and mucosal immunity to NadA. When studied safe and can induce long-standing colonisation. Over alongside a control strain, use of a GMO N. lactamica 350 healthy adult volunteers have been experimen- expressing NadA could permit advanced study of tally nasally inoculated with wild-type N. lactamica the mechanisms underlying mucosal immunity and in previous studies. The colonisation fraction (the