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

Molecular Imaging of Infections: Advancing the Search for the Hidden Enemy

Even before the coronavirus disease 2019 pandemic, infections were a major threat to human health, as the third leading cause of death and the leading cause of morbidity among all human diseases. Although conventional imaging studies are routinely used for patients with infections, they provide structural or anatomic information only. Molecular imaging technologies enable noninvasive visualization of molecular processes at the cellular level within intact living subjects, including patients, and hold great potential for infections. We hope that this supplement will spur interest in the field and establish new collaborations to develop and translate novel molecular imaging approaches to the clinic.

Computed Tomography Imaging for Monitoring of Marburg Virus Disease: a Nonhuman Primate Proof-Of-Concept Study

Marburg virus (MARV) is a highly virulent zoonotic filovirid that causes Marburg virus disease (MVD) in humans. The pathogenesis of MVD remains poorly understood, partially due to the low number of cases that can be studied, the absence of state-of-the-art medical equipment in areas where cases are reported, and limitations on the number of animals that can be safely used in experimental studies under maximum containment animal biosafety level 4 conditions. Medical imaging modalities, such as whole-body computed tomography (CT), may help to describe disease progression in vivo, potentially replacing ethically contentious and logistically challenging serial euthanasia studies. Towards this vision, we performed a pilot study, during which we acquired whole-body CT images of 6 rhesus monkeys before and 7 to 9 days after intramuscular MARV exposure. We identified imaging abnormalities in the liver, spleen, and axillary lymph nodes that corresponded to clinical, virological, and gross pathological hallmarks of MVD in this animal model. Quantitative image analysis indicated hepatomegaly with a significant reduction in organ density (indicating fatty infiltration of the liver), splenomegaly, and edema that corresponded with gross pathological and histopathological findings. Our results indicated that CT imaging could be used to verify and quantify typical MVD pathogenesis versus altered, diminished, or absent disease severity or progression in the presence of candidate medical countermeasures, thus possibly reducing the number of animals needed and eliminating serial euthanasia. IMPORTANCE Marburg virus (MARV) is a highly virulent zoonotic filovirid that causes Marburg virus disease (MVD) in humans. Much is unknown about disease progression and, thus, prevention and treatment options are limited. Medical imaging modalities, such as whole-body computed tomography (CT), have the potential to improve understanding of MVD pathogenesis. Our study used CT to identify abnormalities in the liver, spleen, and axillary lymph nodes that corresponded to known clinical signs of MVD in this animal model. Our results indicated that CT imaging and analyses could be used to elucidate pathogenesis and possibly assess the efficacy of candidate treatments.

Nipah Virus Aerosol Challenge of Three Distinct Particle Sizes in Nonhuman Primates

Aerosol and inhalational studies of high-consequence pathogens allow researchers to study the disease course and effects of biologicals transmitted through aerosol in a laboratory-controlled environment. Inhalational studies involving Nipah virus with small (1-3 μm), intermediate (6-8 μm), and large particles (10-14 μm) were explored in African green nonhuman primates to determine if the subsequent disease course more closely recapitulated what is observed in Nipah virus human disease. The aerosol procedures outlined describe the different equipment/techniques used to generate the three particle sizes and control the site of particle deposition within this animal model.

Aerosol Test Chambers: Current State and Practice During the COVID-19 Pandemic

Respiratory infectious disease outbreaks such as those caused by coronaviruses and influenza, necessitate the use of specialized aerosol test chambers to study aspects of these causative agents including detection, efficacy of countermeasures, and aerosol survivability. The anthrax attacks from 2001 and earlier biowarfare and biodefense also influenced the study of biological aerosols to learn about how certain pathogens transmit either naturally or through artificial means. Some high containment biological laboratories, which work with Risk Group 3 and 4 agents in biosafety level -3, biosafety level-4 containment, are equipped with aerosol test chambers to enable the study of high-risk organisms in aerosolized form. Consequently, the biomedical, military and environmental sectors have specific applications when studying bioaerosols which may overlap while being different. There are countless aerosol test chambers worldwide and this number along with numerous high containment biological laboratories underscores the need for technical standards, regulatory and dual-use compliance. Here we survey common aerosol test chambers and their history, current use, and practice. Our findings reinforce the importance and need for continued collaboration among the multi-disciplinary fields studying aerobiology and biological aerosols.

Applications of minimally invasive multimodal telemetry for continuous monitoring of brain function and intracranial pressure in macaques with acute viral encephalitis

Alphaviruses such as Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) are arboviruses that can cause severe zoonotic disease in humans. Both VEEV and EEEV are highly infectious when aerosolized and can be used as biological weapons. Vaccines and therapeutics are urgently needed, but efficacy determination requires animal models. The cynomolgus macaque (Macaca fascicularis) provides a relevant model of human disease, but questions remain whether vaccines or therapeutics can mitigate CNS infection or disease in this model. The documentation of alphavirus encephalitis in animals relies on traditional physiological biomarkers and behavioral/neurological observations by veterinary staff; quantitative measurements such as electroencephalography (EEG) and intracranial pressure (ICP) can recapitulate underlying encephalitic processes. We detail a telemetry implantation method suitable for continuous monitoring of both EEG and ICP in awake macaques, as well as methods for collection and analysis of such data. We sought to evaluate whether changes in EEG/ICP suggestive of CNS penetration by virus would be seen after aerosol exposure of naïve macaques to VEEV IC INH9813 or EEEV V105 strains compared to mock-infection in a cohort of twelve adult cynomolgus macaques. Data collection ran continuously from at least four days preceding aerosol exposure and up to 50 days thereafter. EEG signals were processed into frequency spectrum bands (delta: [0.4 - 4Hz); theta: [4 - 8Hz); alpha: [8-12Hz); beta: [12-30] Hz) and assessed for viral encephalitis-associated changes against robust background circadian variation while ICP data was assessed for signal fidelity, circadian variability, and for meaningful differences during encephalitis. Results indicated differences in delta, alpha, and beta band magnitude in infected macaques, disrupted circadian rhythm, and proportional increases in ICP in response to alphavirus infection. This novel enhancement of the cynomolgus macaque model offers utility for timely determination of onset, severity, and resolution of encephalitic disease and for the evaluation of vaccine and therapeutic candidates.

Electrocardiography Abnormalities in Macaques after Infection with Encephalitic Alphaviruses

Eastern (EEEV) and Venezuelan (VEEV) equine encephalitis viruses (EEVs) are related, (+) ssRNA arboviruses that can cause severe, sometimes fatal, encephalitis in humans. EEVs are highly infectious when aerosolized, raising concerns for potential use as biological weapons. No licensed medical countermeasures exist; given the severity/rarity of natural EEV infections, efficacy studies require animal models. Cynomolgus macaques exposed to EEV aerosols develop fever, encephalitis, and other clinical signs similar to humans. Fever is nonspecific for encephalitis in macaques. Electrocardiography (ECG) metrics may predict onset, severity, or outcome of EEV-attributable disease. Macaques were implanted with thermometry/ECG radiotransmitters and exposed to aerosolized EEV. Data was collected continuously, and repeated-measures ANOVA and frequency-spectrum analyses identified differences between courses of illness and between pre-exposure and post-exposure states. EEEV-infected macaques manifested widened QRS-intervals in severely ill subjects post-exposure. Moreover, QT-intervals and RR-intervals decreased during the febrile period. VEEV-infected macaques suffered decreased QT-intervals and RR-intervals with fever onset. Frequency-spectrum analyses revealed differences in the fundamental frequencies of multiple metrics in the post-exposure and febrile periods compared to baseline and confirmed circadian dysfunction. Heart rate variability (HRV) analyses revealed diminished variability post-exposure. These analyses support using ECG data alongside fever and clinical laboratory findings for evaluating medical countermeasure efficacy.

A Vibrating Mesh Nebulizer as an Alternative to the Collison Three-Jet Nebulizer for Infectious Disease Aerobiology

Experimental infection of animals with aerosols containing pathogenic agents is essential for an understanding of the natural history and pathogenesis of infectious disease as well as evaluation of potential treatments. We evaluated whether the Aeroneb nebulizer, a vibrating mesh nebulizer, would serve as an alternative to the Collison nebulizer, the "gold standard" for generating infectious bioaerosols. While the Collison possesses desirable properties that have contributed to its longevity in infectious disease aerobiology, concerns have lingered about the liquid volume and concentration of the infectious agent required to cause disease and the damage that jet nebulization causes to the agent. Fluorescein salt was added to the nebulizer contents to assess pathogen loss during aerosolization. Relative to fluorescein salt, loss of influenza virus during aerosolization was worse with the Collison than with the Aeroneb. Four other viruses also had superior aerosol performance with the Aeroneb. The Aeroneb did not improve the aerosol performance for a vegetative bacterium, Francisella tularensis Environmental parameters collected during the aerosol challenges indicated that the Aeroneb generated a higher relative humidity in exposure chambers while not affecting other environmental parameters. The aerosol mass median aerodynamic diameter (MMAD) was generally larger and more disperse for aerosols generated by the Aeroneb than what is seen with the Collison, but ≥80% of particles were within the range that would reach the lower respiratory tract and alveolar regions. The improved aerosol performance and generated particle size range suggest that for viral pathogens, the Aeroneb is a suitable alternative to the Collison three-jet nebulizer for use in experimental infection of animals.IMPORTANCE Respiratory infection by pathogens via aerosol remains a major concern for both natural disease transmission as well as intentional release of biological weapons. Critical to understanding the disease course and pathogenesis of inhaled pathogens are studies in animal models conducted under tightly controlled experimental settings, including the inhaled dose. The route of administration, particle size, and dose can affect disease progression and outcome. Damage to or loss of pathogens during aerosolization could increase the dose required to cause disease and could stimulate innate immune responses, altering outcome. Aerosol generators that reduce pathogen loss would be ideal. This study compares two aerosol generators to determine which is superior for animal studies. Aerosol research methods and equipment need to be well characterized to optimize the development of animal models for respiratory pathogens, including bioterrorism agents. This information will be critical for pivotal efficacy studies in animals to evaluate potential vaccines or treatments against these agents.

The Promise of Molecular Imaging in the Study and Treatment of Infectious Diseases

Infectious diseases are a major threat to humanity, and it is imperative that we develop imaging tools that aid in their study, facilitate diagnosis, and guide treatment. The alarming rise of highly virulent and multi-drug-resistant pathogens, their rapid spread leading to frequent global pandemics, fears of bioterrorism, and continued life-threatening nosocomial infections in hospitals remain as major challenges to health care in the USA and worldwide. Early diagnosis and rapid monitoring are essential for appropriate management and control of infections. Tomographic molecular imaging enables rapid, noninvasive visualization, localization, and monitoring of molecular processes deep within the body and offers several advantages over traditional tools used for the study of infectious diseases. Noninvasive, longitudinal assessments could streamline animal studies, allow unique insights into disease pathogenesis, and expedite clinical translation of new therapeutics. Since molecular imaging is already in common use in the clinic, it could also become a valuable tool for clinical studies, for patient care, for public health, and for enabling precision medicine for infectious diseases.

Introduction

Infectious diseases are a major cause of morbidity and mortality worldwide and in the USA. Overall costs and morbidity are expected to continue to rise due to increasing rates of drug-resistant pathogens, use of invasive techniques such as implants, as well as immunosuppressive and cancer therapies. Tomographic molecular imaging techniques enable rapid visualization and monitoring of molecular processes noninvasively and promise unparalleled opportunities for field of infectious diseases. These technologies are an emerging field of research, overcome several fundamental limitations of current tools, and could have a broad impact on both basic research and patient care. Beyond diagnosis and monitoring disease, these technologies could also provide a uniform cross-species platform for animal studies, allow unique insights into understanding disease pathogenesis, and expedite bench-to-bedside translation of new therapeutics. Finally, since molecular imaging is readily available for humans, validated tracers could also become valuable tools for clinical applications and for enabling personalized medicine for infectious diseases.

Comparison of respiratory inductive plethysmography versus head-out plethysmography for anesthetized nonhuman primates in an animal biosafety level 4 facility

For inhalational studies and aerosol exposures to viruses, head-out plethysmography acquisition has been traditionally used for the determination of estimated inhaled dose in anesthetized nonhuman primates prior to or during an aerosol exposure. A pressure drop across a pneumotachograph is measured within a sealed chamber during inspiration/exhalation of the nonhuman primate, generating respiratory values and breathing frequencies. Due to the fluctuation of depth of anesthesia, pre-exposure respiratory values can be variable, leading to less precise and accurate dosing calculations downstream. Although an anesthesia infusion pump may help stabilize the depth of sedation, pumps are difficult to use within a sealed head-out plethysmography chamber. Real-time, head-out plethysmography acquisition could increase precision and accuracy of the measurements, but the bulky equipment needed for head-out plethysmography precludes real-time use inside a Class III biological safety cabinet, where most aerosol exposures occur. However, the respiratory inductive plethysmography (RIP) acquisition method measures the same respiratory parameters by detecting movement of the chest and abdomen during breathing using two elastic bands within the Class III biological safety cabinet. As respiratory values are relayed to a computer for software integration and analysis real-time, adjustment of aerosol exposure duration is based on the depth of sedation of the animal. The objective of this study was to compare values obtained using two methodologies (pre-exposure head-out plethysmography and real-time RIP). Transitioning to RIP technology with real-time acquisition provides more consistent, precise, and accurate aerosol dosing by reducing reported errors in respiratory values from anesthesia variability when using pre-exposure head-out plethysmography acquisition.

Safety Precautions and Operating Procedures in an (A)BSL-4 Laboratory: 3. Aerobiology

Aerosol or inhalational studies of high-consequence pathogens have recently been increasing in number due to the perceived threat of intentional aerosol releases or unexpected natural aerosol transmission. Specific laboratories designed to perform these experiments require tremendous engineering controls to provide a safe and secure working environment and constant systems maintenance to sustain functionality. Class III biosafety cabinets, also referred to as gloveboxes, are gas-tight enclosures with non-opening windows. These cabinets are maintained under negative pressure by double high-efficiency-particulate-air (HEPA)-filtered exhaust systems and are the ideal primary containment for housing aerosolization equipment. A well planned workflow between staff members within high containment from, for instance, an animal biosafety level-4 (ABSL-4) suit laboratory to the ABSL-4 cabinet laboratory is a crucial component for successful experimentation. For smooth study execution, establishing a communication network, moving equipment and subjects, and setting up and placing equipment, requires staff members to meticulously plan procedures prior to study initiation. Here, we provide an overview and a visual representation of how aerobiology research is conducted at the National Institutes of Health, National Institute of Allergy and Infectious Diseases Integrated Research Facility at Fort Detrick, Maryland, USA, within an ABSL-4 environment.

Claire M, Johnson RF, Bollinger L, Lackemeyer MG, Hensley LE, Kindrachuk J, Kuhn JH. The NIAID Integrated Research Facility at Frederick, Maryland: a unique international resource to facilitate medical countermeasure development for BSL-4 pathogens

Scientists at the National Institute of Allergy and Infectious Diseases Integrated Research Facility at Fort Detrick, Frederick, Maryland, coordinate and facilitate preclinical research on infectious diseases to develop medical countermeasures for high-consequence pathogens. This facility is unique in that it is the only maximum containment laboratory in the world where conventional and molecular medical imaging equipments are incorporated into the design of the facility. This capability provides investigators with unique tools to dissect disease pathogenesis, evaluate the ability of animal models to recapitulate human disease, and test candidate countermeasures. Importantly, advanced molecular imaging has the potential to provide alternative endpoints to lethality. Using these alternative endpoints, investigators can reduce the number of animals used in experiments and evaluate countermeasures in sublethal models. With the incorporation of medical imaging modalities, a clinical laboratory modeled after those existing in hospitals, and a highly trained veterinary medicine team, IRF-Frederick is uniquely suited to advance our understanding of emerging infectious diseases and to facilitate the development of medical countermeasures and clinical care paradigms previously considered impossible.