Screening for novel anti-infectives targeting either the pathogen (up to BSL-3) or the host

The HZI is a specialist screening site focused on infectious diseases, i.e. screening campaigns can be run in BSL 1-3 laboratories using pathogenic microorganisms and viruses. The screening system is fully automated and integrated allowing the production of assay-ready plates by acoustic dispensing technologies and the performance of assays of even high complexities in 96 well and 384 well plates with quantification of absorbance, fluorescence or luminescence.

HZI has laboratories (BSL 1-3) fully equipped for work with pathogenic microorganisms and viruses as well as with mammalian cell cultures. Assay-ready plates can be prepared using the Echo® 550 liquid handler, which allows deposition of volumes of compound solutions as low as 2.5 nL. Usually assays are run in 96 or 384 well plates. The screening system in the BSL-2 - laboratories allows the automation of even complex assay protocols, including the addition of various reagents at selected time-points, flexible incubation at room temperature or 37°C, washing steps and intermittent data recording, as the screening system comprises an automated liquid handler (Biomek i7 from Beckman Coulter) and an integrated cell culture incubator. Routinely a fully integrated multi-mode microtiter plate reader is used as detector, but an automated microscope is also available as “add-on” detector. The ImageXpress microscope (Molecular Devices) is a high content screening system and allows quantitative microscopic analysis of cell cultures even in 384 well plates.

The HZI is a specialist screening site for infectious diseases. The assays may target directly viability or proliferation of the pathogen under appropriate conditions, the activity of virulence factors or the interaction of the pathogen with the host. Some examples are mentioned in the following: antibiotic activities of compounds are detected by analyzing the effects of the compounds on growth or viability of bacteria. Depending on the cultivation conditions and on the properties of the test organism the identified active compounds could be for example broad- or narrow-spectrum antibiotics or inhibitors of resistance mechanisms. The assays are usually based on (semi-) continuously monitoring turbidity at 600 nm (OD600), or on viability assays based on the quantification of ATP (luminescence assay), or on the turnover of resazurin (fluorescence measurement) or of tetrazolium salts (determination of optical density). The same system also allows evaluation of the formation / disruption of biofilms, one of the important bacterial virulence traits. Also, more complex assays can be performed comprising both host cells and pathogens. Using respective assay protocols and appropriate assay components, such as reporter strains, the adsorption of bacteria on host cells or the internalization of bacteria, but also the entry and replication of viruses in host cells can be detected and quantified. Even immunological responses, such as the production of cytokines by host cells in response to the presence of pathogens, are suitable parameters.

Number of compounds screened

100,000 (full commercial set) of the EU-OPENSCREEN ERIC compound library

Time frame for screen up to validated hits

2 - 6 months, depending on the development stage of the assay, the compatibility of the original assay protocol with the screening system and the complexity and schedule of the assay

• Integrated compound management system comprising the acoustic dispenser Echo® 550 and the automated work station Biomek i5: Preparation of assay-ready plates.
• Integrated system for assay automation under BSL-2 conditions comprising the automated work station Biomek i7, an automated incubator, a multi-mode microtiter plate reader, and a multidrop™.
• Automated screening system under BSL-3 conditions.
• Automated microscope: ImageXpress Micro XLS.
• Infrastructure (clean benches, centrifuges, incubators, microscopes) required for microbiological and mammalian cell culture workflows.
• Infrastructure required for molecular biological projects (PCR, gel electrophoresis, Western Blots).
• Data management using the platform from grit42, allowing the integration of chemical and biological data.

• Adaptation of the assay protocol provided by the applicant to the automated screening system (Screening system).
• Miniaturization of the assay into 384-well plates (if applicable) (Compound management and Screening system).
• Pilot screen using 5,000 compounds from the EU-OS compound library (Compound management system, Screening system, microbiological and cell culture infrastructure).
• Analysis of pilot screen data (data management system (grit42)).
• Full screen with the remaining 95,000 compounds of the EU-OS compound library (Compound management system, Screening system, microbiological and cell culture infrastructure).
• Data analysis and subsequent selection of primary hits (data management (grit 42)).
• Hit picking of primary hits for hit validation (Compound management).
• Hit validation by variation of the compound concentration (determinations of IC50- or comparable parameters); eventually performance of relevant counter screens (e.g., effects on reporter proteins).

Please note that this project includes the possibility of re-screening during potential chemical optimization under the medicinal chemistry call starting in 2021 (tentative date).

The prerequisite starting point to qualify for access is the availability of an established bioassay and associated key bespoke reagents, developed at lab-scale by the successful applicant. The assay format is compatible with the performance in microtiter plates allowing the quantitative determination of an optical parameter (e.g. absorbance, fluorescence, luminescence).

Positive and negative controls are identified, and the resultant quantitative assay data are sufficiently different to allow unambiguous distinction. The target of the assay is related to infectious diseases, preferably caused by microorganisms or viruses.

As specifics of the assay transfer procedure may vary between partner sites, the applicant and the individual sites will agree on the appropriate steps and logistics together.

Apply now

Topics / Keywords:

drug discovery, small molecules, high-throughput screening, cell-based assays

Open Time:

Start date:
June-01-2019 (20:00 CET)

Closing date:
September-30-2019 (20:00 CET)

Contacts:

Scientific/technical/machine/methods contact:

Ursula.bilitewski@helmholtz-hzi.de