A genome-wide approach to understand the interplay between bacterial virulence genes and host immune responses
Lead Research Organisation:
University of Cambridge
Department Name: Veterinary Medicine
Abstract
Salmonella causes serious infections in humans and animals worldwide. Current measures for controlling Salmonella infections are far from ideal. Antibiotics are widely used, but an increasing number of Salmonella isolates are resistant to these drugs. Vaccines can potentially be an effective method to prevent some forms of Salmonella disease. Unfortunately, most of the currently used vaccines are only moderately effective and are based on old technology. There are currently no vaccines against septicaemic salmonellosis that is an emerging form of the disease especially in Africa in young children and immunocompromised individuals. The use of live vaccines can be potentially dangerous, especially in those areas where immunodeficiencies are prevalent. People who may have a latent (as yet undiscovered) immunodeficiency syndrome (e.g. HIV infected individuals or people with subclinical malaria) may be at serious risk if they receive a live vaccine that can potentially revert to virulence when the host immune system is not fully competent.
Here we propose to use a cost effective, global and modern approach to identify bacterial genes that are responsible for the increased virulence of Salmonella in individuals with common forms of immunodeficiencies that can be encountered in the geographical areas where Salmonella is endemic. Deletion of appropriate combinations of such genes, would make live vaccines safe also in those individuals with an impaired immune system.
Here we propose to use a cost effective, global and modern approach to identify bacterial genes that are responsible for the increased virulence of Salmonella in individuals with common forms of immunodeficiencies that can be encountered in the geographical areas where Salmonella is endemic. Deletion of appropriate combinations of such genes, would make live vaccines safe also in those individuals with an impaired immune system.
Technical Summary
The main aim of the research is to understand which genes in Salmonella enterica are required for fitness and virulence in models of immunodeficiencies known to pre-dispose to salmonellosis in humans.
We will use a cost effective, global approach to screen libraries of Tn5 and Mu transposon mutants of S. enterica for their ability to infect gene-targeted immunodeficient mice and grow in their tissues (gp91-/-, IFN-gamma-/- and T-cell deficient mice). These bacterial mutants will be analysed using Transposon Directed Insertion-site Sequencing (TraDIS), which uses Illumina deep-sequencing to assess the genotypes and relative fitnesses of individuals within complex pools of bacterial transposon mutants. The work will give a quantitative measure of the extent to which individual mutants in the pools are negatively or positively selected during infection, with those mutants that are lost during infection being indicators of the genes required to colonise the particular mouse knock-out strain being used as host. The work will allow us to identify candidates for development into live attenuated vaccines that would be safer to use in situations and or/geographical areas where these immunodeficiences might be prevalent and in many cases latent or undiagnosed.
We will use a cost effective, global approach to screen libraries of Tn5 and Mu transposon mutants of S. enterica for their ability to infect gene-targeted immunodeficient mice and grow in their tissues (gp91-/-, IFN-gamma-/- and T-cell deficient mice). These bacterial mutants will be analysed using Transposon Directed Insertion-site Sequencing (TraDIS), which uses Illumina deep-sequencing to assess the genotypes and relative fitnesses of individuals within complex pools of bacterial transposon mutants. The work will give a quantitative measure of the extent to which individual mutants in the pools are negatively or positively selected during infection, with those mutants that are lost during infection being indicators of the genes required to colonise the particular mouse knock-out strain being used as host. The work will allow us to identify candidates for development into live attenuated vaccines that would be safer to use in situations and or/geographical areas where these immunodeficiences might be prevalent and in many cases latent or undiagnosed.
