Assays for the Evaluation of the Immune Response to Marburg and Ebola Sudan Vaccination-Filovirus Animal Nonclinical Group Anti-Marburg Virus Glycoprotein Immunoglobulin G Enzyme-Linked Immunosorbent Assay and a Pseudovirion Neutralization Assay.

Since the discovery of the Marburg virus (MARV) in 1967 and Ebola virus (EBOV) in 1976, there have been over 40 reported outbreaks of filovirus disease with case fatality rates greater than 50%. This underscores the need for efficacious vaccines against these highly pathogenic filoviruses. Due to the sporadic and unpredictable nature of filovirus outbreaks, such a vaccine would likely need to be vetted through the U.S. Food and Drug Administration (FDA), following the Animal Rule or similar European Medicines Agency (EMA) regulatory pathway. Under the FDA Animal Rule, vaccine-induced immune responses correlating with survival of non-human primates (NHPs), or another well-characterized animal model, following lethal challenge, will need to be bridged for human immune response distributions in clinical trials. A correlate of protection has not yet been identified for the filovirus disease, but antibodies, specifically anti-glycoprotein (GP) antibodies, are believed to be critical in providing protection against the filovirus disease following vaccination and are thus a strong candidate for a correlate of protection. Thus, species-neutral methods capable of the detection and bridging of these antibody immune responses, such as methods to quantify anti-GP immunoglobulin G (IgG)-binding antibodies and neutralizing antibodies, are needed. Reported here is the development and qualification of two Filovirus Animal Nonclinical Group (FANG) anti-GP IgG Enzyme-Linked Immunosorbent Assays (ELISAs) to quantify anti-MARV and anti-Sudan virus (SUDV) IgG antibodies in human and NHP serum samples, as well as the development of pseudovirion neutralization assays (PsVNAs) to quantify MARV- and SUDV-neutralizing antibodies in human and NHP serum samples.

Characterization of Cholinesterases From Multiple Large Animal Species for Medical Countermeasure Development Against Chemical Warfare Nerve Agents.

Organophosphorus (OP) compounds, which include insecticides and chemical warfare nerve agents (CWNAs) such as sarin (GB) and VX, continue to be a global threat to both civilian and military populations. It is widely accepted that cholinesterase inhibition is the primary mechanism for acute OP toxicity. Disruption of cholinergic function through the inhibition of acetylcholinesterase (AChE) leads to the accumulation of the neurotransmitter acetylcholine. Excess acetylcholine at the synapse results in an overstimulation of cholinergic neurons which manifests in the common signs and symptoms of OP intoxication (miosis, increased secretions, seizures, convulsions, and respiratory failure). The primary therapeutic strategy employed in the United States to treat OP intoxication includes reactivation of inhibited AChE with the oxime pralidoxime (2-PAM) along with the muscarinic acetylcholine receptor antagonist atropine and the benzodiazepine, diazepam. CWNAs are also known to inhibit butyrylcholinesterase (BChE) without any apparent toxic effects. Therefore, BChE may be viewed as a "bioscavenger" that stoichiometrically binds CWNAs and removes them from circulation. The degree of inhibition of AChE and BChE and the effectiveness of 2-PAM are known to vary among species. Animal models are imperative for evaluating the efficacy of CWNA medical countermeasures, and a thorough characterization of available animal models is important for translating results to humans. Thus, the objective of this study was to compare the circulating levels of each of the cholinesterases as well as multiple kinetic properties (inhibition, reactivation, and aging rates) of both AChE and BChE derived from humans to AChE and BChE derived from commonly used large animal models.

A Novel, Modified Human Butyrylcholinesterase Catalytically Degrades the Chemical Warfare Nerve Agent, Sarin.

Chemical warfare nerve agents (CWNAs) present a global threat to both military and civilian populations. The acute toxicity of CWNAs stems from their ability to effectively inhibit acetylcholinesterase (AChE). This inhibition can lead to uncontrolled cholinergic cellular signaling, resulting in cholinergic crisis and, ultimately, death. Although the current FDA-approved standard of care is moderately effective when administered early, development of novel treatment strategies is necessary. Butyrylcholinesterase (BChE) is an enzyme which displays a high degree of structural homology to AChE. Unlike AChE, the roles of BChE are uncertain and possibilities are still being explored. However, BChE appears to primarily serve as a bioscavenger of toxic esters due to its ability to accommodate a wide variety of substrates within its active site. Like AChE, BChE is also readily inhibited by CWNAs. Due to its high affinity for binding CWNAs, and that null-BChE yields no apparent health effects, exogenous BChE has been explored as a candidate therapeutic for CWNA intoxication. Despite years of research, minimal strides have been made to develop a catalytic bioscavenger. Furthermore, BChE is only in early clinical trials as a stoichiometric bioscavenger of CWNAs, and large quantities must be administered to treat CWNA toxicity. Here, we describe previously unidentified mutations to residues within and adjacent to the acyl binding pocket (positions 282-285 were mutagenized from YGTP to NHML) of BChE that confer catalytic degradation of the CWNA, sarin. These mutations, along with corresponding future efforts, may finally lead to a novel therapeutic to combat CWNA intoxication.