ABSL-4 aerobiology biosafety and technology at the NIH/NIAID integrated research facility at Fort Detrick

Abstract

The overall threat of a viral pathogen to human populations is largely determined by the modus operandi and velocity of the pathogen that is transmitted among humans. Microorganisms that can spread by aerosol are considered a more challenging enemy than those that require direct body-to-body contact for transmission, due to the potential for infection of numerous people rather than a single individual. Additionally, disease containment is much more difficult to achieve for aerosolized viral pathogens than for pathogens that spread solely via direct person-to-person contact. Thus, aerobiology has become an increasingly necessary component for studying viral pathogens that are naturally or intentionally transmitted by aerosol. The goal of studying aerosol viral pathogens is to improve public health preparedness and medical countermeasure development. Here, we provide a brief overview of the animal biosafety level 4 Aerobiology Core at the NIH/NIAID Integrated Research Facility at Fort Detrick, Maryland, USA.

Figure 1

Schematic presentation of the Class III Biosafety Cabinet setup at the IRF-Frederick. The Class III biosafety cabinet (BSC) is a hermetically sealed stainless steel cabinet containing an ABSL-4 environment under negative pressure (currently in static state for easy viewing) within an ABSL-4 cabinet laboratory. Materials can be introduced into the BSC by staff working in the ABSL-4 cabinet laboratory through an under-cabinet-mounted stainless steel tank containing the disinfectant Micro-Chem Plus^® (commonly referred to as a “dunk tank” in ABSL-4 or BSL-4 settings). Because the BSC is built into the wall separating the cabinet laboratory from an ABSL-4 suit laboratory, materials, animals, and viral pathogens can also be moved into the BSC from the ABSL-4 suit laboratory side using a transport cart and a Rapid Transfer Port (RTP). The contents within the BSC can be manipulated from the outside by researchers wearing various types of synthetic rubber gloves, specifically neoprene/chlorosulphonated polyethylene. Contents, excluding infectious samples, are removed from the BSC after sterilization through a double-door autoclave or disinfection via the dunk tank.

Figure 2

The IRF-Frederick Aerobiology Core Class III BSC laboratory. Shown are the IRF-Frederick Aerobiology Core’s two Class III BSCs within the ABSL-4 cabinet laboratory. One researcher is manipulating the contents of one of the Class III BSCs via synthetic rubber gloves. The other researcher is monitoring the parameters of the experiment electronically.

Figure 3

Class III BSC paraformaldehyde gas decontamination setup. After an experiment, a researcher connects a decontamination machine to the BSC through designated external ports on top of the glove box. From a paraformaldehyde gas generator (Certek, Durham, NC, USA), the gas is pumped into the BSC and decontaminates the BSC after an appropriate contact time (i.e., 6 h). The gas is then neutralized by ammonium bicarbonate for an additional 6 h (12 h total decontamination). Biological indicators are placed throughout the BSC and the results are recorded and analyzed by staff.

Figure 4

The IRF-Frederick Class III BSC laboratory Rapid Transfer Port. (A) View into one of the IRF-Frederick Aerobiology Core Class III BSCs through the Rapid Transfer Port (RTP) connecting the ABSL-4 environment within the BSC to the ABSL-4 suit laboratory. Shown on the left are two researchers in the ABSL-4 cabinet laboratory manipulating the Automated Aerosol Management Platform (AAMP) connected to a whole-body aerosol exposure chamber in the Class III BSC using synthetic rubber gloves; (B) View of the RTP interlocking handle, port door closed; (C) View of RTP door seal, port door open.

Figure 5

ABSL-4 suit laboratory transport carts. Two specialized transport carts within the ABSL-4 suit laboratory are docked to the Class III BSC at the Rapid Transfer Port. Through windows in the wall between the ABSL-4 suit laboratory and the Class III BSC, researchers see into the adjacent ABSL-4 cabinet laboratory containing the Class III BSCs and communicate with staff.

Figure 6

Interlocking double-door autoclave attached to the Class III BSC. Used contents and waste generated during an experiment inside the BSC must be sterilized after use. A researcher is selecting a pre-programmed autoclave cycle to ensure the contents within the autoclave chamber are noninfectious when the outer door is eventually opened. The door located nearest to the researcher cannot be opened until a full sterilization cycle has been completed. Biological indicators inside the autoclave chamber will be analyzed to determine agent inactivation after the sterilization process.

Figure 7

Dunk tank filled with disinfectant attached to the Class III BSC. A liquid barrier created by the appropriate disinfectant protects the researcher by ensuring that contaminants within the BSC are fully contained. Supplies are passed through the dunk tank and into the BSC. A black lid covers the base of the BSC and prevents liquid from splashing into the experimental area.

Figure 8

Schematic presentation of the Automated Aerosol Management Platform. The AAMP is fully contained within the Class III BSC. Compressed air under negative pressure enters the aerosol unit, which is controlled by mass flow controllers and experimental parameters dictated by the researcher on a laptop (not shown). Droplets produced by aerosol generation pass through a mixing tube, are diluted with additional air, and dried. This conditioning of particles ensures that the particles are monodispersed prior to entry into the whole body chamber. Simultaneously, the vacuum pulls air through the whole body chamber ensuring that newly generated particles pass through the chamber while maintaining a dynamic system. A biosampler or cascade impactor and particle sizer are attached to the whole body chamber for collection and analysis. The overall flow of the system is shown by the directional arrows.