Genomic and functional approaches to identify novel antibiotics that block virulence

Transcription

1 Genomic and functional approaches to identify novel antibiotics that block virulence New principle for antimicrobials. Disarm the Invader Bacterial multiplication not affected May prevent development of resistance

2 Introduction Many obligate human bacterial pathogens have small genomes, <1 Mb They likely evolved from bacteria with larger genomes. Correlation between parasitic life styles and condensed genomes. Essential genes for survival in the host have been mantained. A subgroup of these genes may be essential to support the growth (multiplication-clearing) of the pathogen in the host These genes are not essential for growth outside the host.

3 Background >100 complete microbial genome sequences If distantly related human pathogens are compared, genes that are conserved throughout evolution can be identified The genes found might be required for growth in the human host

4 Aims Identify conserved genes with unknown function in human specific pathogens. Knock-out these genes in Yersinia pseudotuberculosis. (good animal model) Check for attenuation of virulence in a mouse model Study the interesting proteins further

5 Strategy Start with the genome of Treponema pallidum Why? Human specific pathogen Condensed genome about 1000 genes Look only at ORFs with unknown or hypothetical function in order to identify new and unknown virulence associated genes (Vag) Compare to other human specific pathogens having different virulence strategies.

6 Compare the ORFs of Treponema pallidum assigned to the functional classes conserved hypothetical (176) and unknown function (35) to Yersinia pestis on amino acid level (blastp) The Yersinia pestis homologous sequences (73) was then put into another round of comparisons to four other bacterial genomes: Neisseria gonorrhoeae Helicobacter pylori Streptococcus pneumoniae Borrelia burgdorferi The ORFs with homologues in all six species (17) were knocked-out in Yersinia pseudotuberculosis Virulence of the mutants were evaluated in an oral mouse model of infection.

7 Results Construction of single crossover mutants in Yersinia pseudotuberculosis Creates polar insertion mutants 3 impossible to obtain, probably lethal mutations 14 succesfully constructed Growth in rich and minimal media Minimal media: M9 + glucose, MgSO 4 and KCl Rich media: LB Virulence evaluated in mice Oral infections

8 Name Predicted function Yop secretion Cytotoxicity (HeLa cells) Growth, 26 /37 Virulence vaga GTPase /+++ Attenuated vagb Methyltransferase /+++ Attenuated vagc RNA mod. enzyme /+++ Attenuated vagd Cell cycle protein /+++ Attenuated vage Celldivision protein * +++/+ Attenuated vagf RNA mod. enzyme /+++ Attenuated vagg DNA transfer /+++ Attenuated vagh Methyltransferase + +++* +++/+++ Attenuated vagi Unknown + +++* +++/+++ Attenuated vagk Chorismate met /+++ Virulent vagl Nucleotidyltransf /+++ Virulent vagm Methyltrans /+++ Virulent vagn Metal dep. hydrolase /+++ Virulent vago GTPase /+++ Virulent vagp Methyltransf. ND ND ND ND vagq Pyrophosphate synt. ND ND ND ND vagr GTPase ND ND ND ND *Delayed Virulence Associated Genes

9 Attenuated vag-mutants in Yersinia VagA: Putative GTPase VagC: Pseudouridylate synthase VagG: Involved in DNA transfer VagH: Protein methyl transferase VagI: Unknown

10 vag-mutants in Streptococcus pneumoniae (TIGR 4) Knockout mutants in pneumococcal vaga,vagc, vagg, vagh and vagi were tested for virulence in a murine intranasal invasive disease model.

11 1.2 Survival of vag mutants Survival vaga vagc vagg vagh vagi T Time (days)

12 Conclusions Novel genes required for bacterial growth in the host can be identified by bioinformatics. These genes will uncover novel traits for in vivo growth. The corresponding gene-products may constitute novel targets for antibacterial treatment. Of the five vag-genes required for Yersinia virulence, three (vaga, vagh, and vagh) are also needed for pneumococcal invasive disease.

13 Ongoing activities Screen for inhibitors of the protein methyl transferase activity of VagH. VagH is required for invasive disease caused by the gastrointestinal pathogen Yersinia and the respiratory pathogen S. pneumoniae

14 Type III Secretion Inhibitors Disarming the Intruder

15 Microinjection Animal/Human Pathogens Yersinia Salmonella Shigella E.coli Chlamydia Bordetella Pseudomonas Plant Pathogens Erwinia Xanthomonas Rhizobia

16 TYPE-III Secretion Systems

17 Requirements for Efficient Type III Secretion by Yersinia Protein Secretion through the Bacterial Envelope Environmental sensing coupled to Positive and Negative Regulatory Control Loops Translocated Anti-host Effectors Cell associated Yersinia Pore formation and Effector Translocation Target cell

18 Contact-Dependent Yop Production yope luxab LuxAB FMNH 2 + RCHO + O 2 FMN + RCO 2 H + H 2 O + Light

19 Screening Readout 37 C, no Ca 2+ Yop E Inhibition Luciferase Inhibitor yope LuxAB yop E LuxAB 37 C, 2.5 mm Ca 2+ Yop E LcrQ Inhibition Activator Luciferase yope LuxAB yope LuxAB

20 TypeIII inhibitors

21 Inhibition of Yop Secretion 0 2, µm Secretion inhibitor Western blot, Type III secreted Yersinia proteins

22 Zooming in on the Target % Inhibition yope-lux yera-lux Concentration, µm

23 Inhibition of motility

24 Inp0007 blocks YopH translocation

25 INP0007 blocks inhibition of uptake of Y.pseudotuberculosis into HeLa cells

26 INP0007 inhibits ExoS secretion in Pseudomonas aeruginosa (and Salmonella)

27 Ongoing Activities Optimization of inhibitors In vitro and in vivo evaluation Target identification

28 Acknowledgements Hans Wolf-Watz and his team, Umeå University Mikael Elofsson, INNATE Pharmaceuticals, Umeå Birgitta Henriques Normark and her team, Swedish Institute for Infectious Disease Control, Stockholm Mikael Rhen and his team, Karolinska Institutet