Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2022

Novel small molecules that increase the susceptibility of Neisseria gonorrhoeae to cationic antimicrobial peptides by inhibiting lipid A phosphoethanolamine transferase (82837)

Christopher A Mullally 1 , Keith A Stubbs 2 , Anandhi Anandan 2 , Stephanie Bartley 1 , Martin J Scanlon 3 , Gary A Jarvis 4 , Constance John 4 , Katherine Lim 1 , Courtney M Sullivan 1 , Mitali Sarkar-Tyson 1 , Alice Vrielink 2 , Charlene Kahler 1
  1. School of Biomedical Sciences, University Of Western Australia, CRAWLEY, WA, Australia
  2. School of Molecular Sciences, University of Western Australia, CRAWLEY, Western Australia, Australia
  3. Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria, Australia
  4. Center for Immunochemistry, Veterans Affairs Medical Center, San Francisco, California, USA

Objectives:

Neisseria gonorrhoeae is an exclusively human pathogen that commonly infects the urogenital tract resulting in gonorrhoea. Empirical treatment of gonorrhoea with antibiotics has led to multi-drug resistance (MDR) and the need for new therapeutics. Inactivation of lipooligosaccharide phosphoethanolamine transferase A (EptA), which attaches phosphoethanolamine (PEA) to lipid A, results in attenuation of the pathogen in infection models. Small molecules that inhibit EptA are predicted to enhance natural clearance of gonococci via the human innate immune response.

Methods:

A library of small fragment compounds was tested for the ability to enhance sensitivity of the reference strain N. gonorrhoeae FA1090 to polymyxin B (PxB). The effect of these compounds on lipid A synthesis and viability in models of infection were tested.

Results:

Three compounds, 135, 136, 137, enhanced sensitivity of strain FA1090 to PxB by 4-fold. Pre-treatment of bacterial cells with all three compounds resulted in enhanced killing by macrophages. Only lipid A from bacterial cells exposed to compound 137 showed a 17% reduction in the level of decoration of lipid A with PEA by MALDI-TOF mass spectrometry (MS) analysis and reduced stimulation of cytokine responses in THP-1 cells. Binding of 137 occurred with higher affinity to purified EptA than the starting material as determined by 1D-STD NMR. Treatment of eight MDR-strains with 137 increased susceptibility to PxB in all cases.

Conclusions:

Small molecules have been designed that bind to EptA, inhibit addition of phosphoethanolamine to lipid A and can sensitise N. gonorrhoeae to killing by macrophages.

Outcomes:

We describe a program for the development of narrow spectrum compounds for use as a prophylactic to reduce the risk of gonorrhoea and pelvic inflammatory disease in women.