Accelerating the development of effective vaccines for protection against Mycobacterium tuberculosis

Lead Research Organisation: London Sch of Hygiene and Trop Medicine
Department Name: Infectious and Tropical Diseases

Abstract

The aim of this project is to accelerate and improve the preclinical development of effective vaccines for protection against tuberculosis (TB). TB is a primarily airborne infection caused by members of the Mycobacterium tuberculosis complex (MTBC). The BCG vaccine is the only clinically approved vaccine against TB. However, it has variations in protection (0-80%) globally [2]. In addition, variations in protection against different TB strains (representative of different lineages of MTBC) have been reported in animal models [3]. Increasing our understanding of these variations may have important implications on vaccine design and testing. An important step involves inclusion of TB strains when preclinically validating vaccines. During preclinical vaccine development, specific biological indictors are analysed to help find candidates that induce a strong immune response. Within the TB field, indicators of a strong immune response (which may indicate protection) remain unknown.
The mycobacterial growth inhibition assay (MGIA) is able to quantify mycobacteria, based on the principle that a reduction of bacterial growth will be observed following co-culture of mycobacteria with cells from immunised individuals versus unimmunised. In this project, the MGIA is used as a read-out of the ability of cells from mice to inhibit MTB growth. Since initial bacterial input is the same, the bacterial growth inhibitory effect of cells isolated from vaccinated mice is compared with unvaccinated, as a potential surrogate of vaccine efficacy. Further, this assay is being utlilised to investigate variations in the ability of BCG-vaccinated mice to inhibit growth of different TB strains, with the later aim to set up a system in which novel vaccines can also be investigated. To date, an MGIA has been established in mouse spleen and lung cells. Growth inhibition of an MTB laboratory strain has been shown in lung and spleen cells from mice vaccinated with BCG, as well as a novel TB vaccine, compared with unvaccinated mice. In order to understand the differences in the ability of cells from vaccinated and unvaccinated animals to control bacterial growth, RNA seq was performed to determine changes in gene expression which may account for these variations. Flow cytometric analysis was also performed to determine changes in cell populations over the assay culture period. A further RNA seq experiment has been performed to understand variations observed in the ability of cells from vaccinated animals to control growth of different lineages of the MTBC.
To carry out this analysis, I have obtained a Home Office licence (whole organ/organism physiology). I have attended two quantitative immunology courses in preparation for transcriptomic analysis (quantitative). I completed a placement at SATVI (Cape Town, South Africa) focusing on host signatures and machine learning (quantitative). I am taking part in an industrial placement in Seattle in January 2020 where I will be involved in mouse MTB challenge studies (whole organ/organism physiology) and performing bioinformatic analysis on samples obtained from the challenge study (quantitative). During the studentship I expect to increase my understanding of vaccine research and development, and the molecular mechanisms of MTB infection and disease progression. I hope to gain skills in experimentation in animal models, bacterial culture and quantitative analysis of transcription.

1. Sharma A, Bloss E, Heilig CM, Click ES. Tuberculosis caused by Mycobacterium africanum, United States, 2004-2013. Emerg Infect Dis 2016:22,396-403.
2. Colditz GA, Brewer TF, Berkey CS et al. Efficacy of BCG vaccine in the prevention of tuberculosis. Metaanalysis of the published literature. JAMA 1994;271:698-702.
3. Henao-Tamayo M et al. The efficacy of the BCG vaccine against newly emerging clinical strains of mycobacterium tuberculosis. PLoS One 2015:10,1-15.

Publications

10 25 50
 
Description MRC National Productivity Investment Fund
Amount £9,376 (GBP)
Organisation Medical Research Council (MRC) 
Sector Academic/University
Country United Kingdom
Start 01/2020 
End 03/2020
 
Title Lung mycobacterial growth inhibition assay 
Description The splenocyte mycobacterial growth inhibition assay (MGIA) [1] has been optimised and adapted for use in murine lung as a potential 'in vitro challenge model' to analyse tuberculosis (TB) vaccine efficacy in mice. The MGIA has been developed as a tool to enable existing and preclinical tuberculosis vaccine to be evaluated in animals models in tandem with TB challenge studies. 1. Zelmer, A. et al. Ex vivo mycobacterial growth inhibition assay (MGIA) for tuberculosis vaccine testing - a protocol for mouse splenocytes. bioRxiv 1-10 (2015). doi:http://dx.doi.org/10.1101/020560 
Type Of Material Technology assay or reagent 
Year Produced 2018 
Provided To Others? No  
Impact The assay does not require the animals to be challenged with Mycobacterium tuberculosis, reducing both the length of study and severity level assigned to it. In addition, since multiple cell inputs for the assay can be harvested from a single animal, less animals are required to design a experiment with sufficient power. The assay incorporates both the refinement and reduction principles of the 3Rs of animals in research.