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Genetic interrogation of virulence in Candida albicans, the major fungal pathogen of humans

Project details

First supervisor: Dr Jonathan Paul Richardson

Second supervisor: Professor Gordon Proctor

Sponsor: (joint) Guy's and St Thomas' Biomedical Research Centre and King's College London Faculty of Dentistry, Oral & Craniofacial Sciences

Funding available: MRC rate stipend & £5k per annum bench fee

Duration of award: 3 years

Mode of study: Full time

Eligibility: Home/EU

Start date:  1 October 2020

Application deadline:  14 February 2020

Reference number:  2020/DOCS/03

Project description

Candida albicans is an opportunistic fungal pathogen that causes superficial and life-threatening infections in humans. During mucosal infection, C. albicans undergoes a morphological transition from yeast (commensal) to invasive filamentous hyphae (pathogen) that damage host tissue. Current research demonstrates that the invasive hyphae of C. albicans use multiple virulence factors to cause disease in the human host. Among these, adherence to the mucosal surface, production of a cytolytic toxin and enzymatic degradation of host proteins are major pathogenic attributes that facilitate disease progression.

The major hyphal adhesin of C. albicans is Als3p, which mediates attachment to host tissue through its interaction with the epidermal growth factor receptor (EGFR). Als3p is also a major fungal invasin that drives receptor-induced endocytosis of hyphae into host tissue. The hyphae of C. albicans can damage a range of host cell types by secreting candidalysin, a peptide toxin encoded by the gene ECE1, while secreted aspartyl proteinases (SAPs), particularly Sap2p are involved in the degradation of host proteins.

While studies demonstrate that C. albicans mutants unable to produce either Als3p, candidalysin or Sap2p exhibit diminished pathogenicity, we hypothesise that removal of all three factors may render C. albicans avirulent during both mucosal and systemic infection.

This proposal will investigate the combined role of C. albicans Als3p, candidalysin and Sap2p during fungal infection of human epithelial cells.

 The goals of this PhD project are to:

1. Construct an als3/ece1/sap2 triple null mutant in C. albicans.

2. Characterise the C. albicans mutant phenotype using human oral epithelial cells in vitro.

3. Determine the pathogenicity of the C. albicans triple mutant using human in vitro and murine in vivo models.

The als3/ece1/sap2 triple null mutant will be created using established CRISPR technology optimised for use in C. albicans and validated by whole genome sequencing. Successful deletion of each target gene will be confirmed using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Characterisation of mutant phenotypes will comprise analysis of microbial growth and hyphal development, quantification of adhesion to human oral epithelial cells and receptor-induced endocytosis.

The host response to wild type and mutated C. albicans will be investigated using a combination of cellular damage assays, analysis of intracellular signal transduction responses (EGFR phosphorylation, p38 MAPK signalling) and analysis of cytokine secretion from epithelial cells. The pathogenicity of the als3/ece1/sap2 triple null mutant will be evaluated using primary 3-D models of reconstituted human epithelium and established murine models of mucosal and systemic infection.

The findings of this research will contribute greatly to our understanding of the mechanisms that underpin C. albicans pathogenesis during mucosal and systemic infection.

Person specification

 

Candidates must possess, or be expected to achieve a 1st or upper 2nd class degree in a relevant subject including the biosciences, chemistry, physics, computer science or mathematics, and be enthusiastic about combining their expertise with other disciplines in the field of healthcare. The full fellowship is open to EU/Home students only 

Research training

Two codon optimised CRISPR systems for use in C. albicans.

ClarioStar multimode plate reader (cellular damage assays).

Bioplex system (multiplexed quantification of cytokine secretion).

LiCor Odyssey platform (quantitative analysis of signal transduction by western blot).

BSU facilities.

Students will also have access to a wide range of short courses provided through the KCL Health Sciences Doctoral Training Centre (https://www.kcl.ac.uk/study/doctoral-studies/health-sciences-doctoral-training-centre/workshop-and-course-listings)

To view entry requirements and further general information, see Dental and Health Sciences Research MPhil/PhD prospectus page.

Next steps

Please apply online at apply.kcl.ac.uk following these steps:

  1. Register a new account/login
  2. Once logged in, select Create a new application
  3. Enter ‘Dental and Health Sciences Research MPhil/PhD (Full-time)/(Part-time)' under Choose a programme. Please ensure you select the correct mode of study
  4. Select 1 October 2020 as the start date
  5. Please note: Applicants must include the project reference number (2020/DOCS/03) in the 'Research proposal' and 'Funding (point 5)' sections of the application.

Applications must be received by the deadline specified in this listing.

Applicants are strongly encouraged to discuss projects with the first supervisor prior to submitting an application. 

Contact for further information

Dr Jonathan Paul Richardson

Email: jonathan.richardson@kcl.ac.uk

Related Centre: https://www.kcl.ac.uk/dentistry/research/centre-for-host-microbiome-interactions

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