Atack Group

Supervisor: John Atack

Non-typeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae (Spn) both colonise the human nasopharynx asymptomatically. Transition to other niches in the body results in a variety of diseases, such as middle ear infection (otitis media, OM) in young children, exacerbations in chronic obstructive pulmonary disease (COPD) in the elderly, pneumonia across all age-groups, and serious invasive diseases, such as sepsis and meningitis. Co-infections involving the two species are common, but the molecular basis for their interactions is poorly understood.

There are current vaccines available to protect against Spn, but these are only effective against a limited number of serotypes. No current vaccine exists to protect against NTHi. A major hurdle to vaccine development against both species is the random and reversible switching of gene expression in both pathogens. Both species encode randomly switching epigenetic regulators called phasevarions, which control multiple virulence traits that trigger infection. We will investigate if specific alleles and expression states of these systems are under selection pressure by undertaking detailed in-vitro studies using model strains. This will also allow identification of other factors required for interactions between these two species. Additionally, we will use the ORChID collection, samples from a 4-year birth cohort study of children in SE QLD over their first 2-years of life for an epidemiological determination of the role of co-colonisation events on disease incidence, severity, and burden.

Our studies will examine if certain gene(s) are required for NTHi-pneumococcal interactions. We will determine the role phasevarions play in this interaction, and if specific genes/alleles of each methyltransferase provide an advantage to either species during interaction. Detailed analysis of chronological samples from the ORChID collection will determine if co-colonisation events precede disease, and if particular strains/serotypes are more associated with colonisation and/or disease. This information will allow development of better vaccines and treatments for two pathogens of major importance to human health.

Supervisors: Dr John Atack and Prof Michael Jennings

Many host-adapted bacterial pathogens contain phase variable methyltransferases, which control expression of multiple genes, and known as phasevarions (phase variable regulons).

Our studies will investigate the specificity, and the mode of gene regulation through differential methylation by these phase-variable methyltransferases. We will clone and over-express newly identified methyltransferases to determine their recognition sequences. We have identified a number of genes in both human and animal pathogens that are differentially expressed in several phasevarions: we will investigate how methylation alters regulation of these genes. We will investigate if these genes are regulated directly or indirectly, and determine the effect of removing any recognition sequences from the promoters of these genes. This project will use protein over-expression and purification methods to allow us to study these methyltransferases in vitro. Surface plasmon resonance will be used to conduct kinetic measurements, and gel-shift assays (EMSA) will be used to study binding affinity and ability.  Reporter constructs will be made to observe the effect of methyltransferase phase-variation on the level of expression from individual promoters.

Supervisors: Dr John Atack, Prof Michael Jennings

Non-typeable Haemophilus influenzae is a major human adapted pathogen and causes a number of acute and chronic diseases of the human respiratory tract, including middle ear disease, otitis media (OM) in children, exacerbations in chronic obstructive pulmonary disease (COPD) in the elderly, and pneumoniae. Invasive disease (meningitis and septicaemia) caused by NTHi is increasing annually and is a particular problem in infants under 1 year of age, where the mortality is close to 20%. Antibiotic resistance is increasing each year, resulting in NTHi being on the World Health Organisations list of priority pathogens. There is no currently licensed vaccine available for NTHi. Vaccine design is a problem for NTHi as individual strains show high genetic diversity, and many antigenic proteins are phase-variable – their expression is randomly and reversibly switched on or off. If a vaccine target is able to randomly turn off, the vaccine would lose effectiveness.

This project will: 1) determine the best possible combination of conserved protein antigens to include in a universal NTHi vaccine from both current and putative vaccine candidates; 2) study the role and regulation of a number of uncharacterised NTHi proteins that show high sequence and strain conservation; and 3) determine if know proteins that have been discounted from use in vaccines as they are phase-variable can be used in vaccines as their expression is critical for certain disease stages or colonisation of particular host niches.

Supervisor: Dr John Atack

Acinetobacter baumannii is classified by the WHO as a critical top priority pathogen andis resistant to almost all current antibiotics. This is particularly problematic as there are very few new antibiotics currently in development. The rate at which A. baumannii acquires resistance to antibiotics means A. baumannii infections may soon become impossible to treat. A. baumannii is a particular problem in hospitals and aged care units due to its ability to survive harsh environments and cleaning procedures. It is crucial to develop novel treatment methods and therapeutics due to the lack of current new antibiotics in development. Although much is known about A. baumannii virulence factors, little is known about the exact host factors A. baumannii interacts with during colonisation and disease. Many human adapted pathogens use host glycans (sugars) as to bind to host surfaces and cells. This project will determine which glycans A. baumannii interacts with in the human host, i.e., we will define the A. baumannii glycointeractome, by leveraging the innovation of glycan array technology and biophysical approaches to precisely determine the glycans A. baumannii interacts with. We will utilize multiple in vitro and in vivo models to determine the ability of these glycans and novel compounds to serve as blocking agents for the treatment of MDR A. baumannii infections. This will aid in the development of new treatment strategies and lay the groundwork to develop novel agents to serve as an alternative to, or act in synergy with, existing antibiotics.