Demonstration of the Pre-Emergency Use Authorization Path Using 3 Minor Groove Binder-Hydrolysis Probe Assays to Detect Escherichia coli O104:H4.

BACKGROUND: The Department of Defense (DoD) and the Food and Drug Administration (FDA) have collaboratively worked on a pre-Emergency Use Authorization (pre-EUA) process for in vitro diagnostic (IVD) devices, using FDA's regulatory flexibilities under the EUA authorities. The pre-EUA process enables FDA review of data in anticipation of a request for an EUA, advancing US government public health emergency preparedness efforts. METHODS: The IVD device developed to detect Escherichia coli O104:H4, for which an EUA has not been issued, serves as an example to illustrate that process. Specifically, DoD designed real-time PCR assays to target the virulent E. coli strain O104:H4 (etiological agent of the 2011 German outbreak) including: fliC (flagellin), Agg3C (AAF), and rfb (wbwC) on the basis of the published sequences. RESULTS: After development and optimization of these 3 specific assays, a defined protocol was followed to determine and document the sensitivity and specificity of each assay analytically. CONCLUSIONS: FDA reviewed these data and returned commentary on additional required experiments to complete the pre-EUA process and expedite the use of the device should there be an emergency need for an IVD device to detect this virulent E. coli strain before such a test is cleared by FDA.

Evaluation of ViroCyt® Virus Counter for rapid filovirus quantitation.

Development and evaluation of medical countermeasures for diagnostics, vaccines, and therapeutics requires production of standardized, reproducible, and well characterized virus preparations. For filoviruses this includes plaque assay for quantitation of infectious virus, transmission electron microscopy (TEM) for morphology and quantitation of virus particles, and real-time reverse transcription PCR for quantitation of viral RNA (qRT-PCR). The ViroCyt® Virus Counter (VC) 2100 (ViroCyt, Boulder, CO, USA) is a flow-based instrument capable of quantifying virus particles in solution. Using a proprietary combination of fluorescent dyes that stain both nucleic acid and protein in a single 30 min step, rapid, reproducible, and cost-effective quantification of filovirus particles was demonstrated. Using a seed stock of Ebola virus variant Kikwit, the linear range of the instrument was determined to be 2.8E+06 to 1.0E+09 virus particles per mL with coefficient of variation ranging from 9.4% to 31.5% for samples tested in triplicate. VC particle counts for various filovirus stocks were within one log of TEM particle counts. A linear relationship was established between the plaque assay, qRT-PCR, and the VC. VC results significantly correlated with both plaque assay and qRT-PCR. These results demonstrated that the VC is an easy, fast, and consistent method to quantify filoviruses in stock preparations.

Therapeutic intervention of Ebola virus infection in rhesus macaques with the MB-003 monoclonal antibody cocktail.

Ebola virus (EBOV) remains one of the most lethal transmissible infections and is responsible for high fatality rates and substantial morbidity during sporadic outbreaks. With increasing human incursions into endemic regions and the reported possibility of airborne transmission, EBOV is a high-priority public health threat for which no preventive or therapeutic options are currently available. Recent studies have demonstrated that cocktails of monoclonal antibodies are effective at preventing morbidity and mortality in nonhuman primates (NHPs) when administered as a post-exposure prophylactic within 1 or 2 days of challenge. To test whether one of these cocktails (MB-003) demonstrates efficacy as a therapeutic (after the onset of symptoms), we challenged NHPs with EBOV and initiated treatment upon confirmation of infection according to a diagnostic protocol for U.S. Food and Drug Administration Emergency Use Authorization and observation of a documented fever. Of the treated animals, 43% survived challenge, whereas both the controls and all historical controls with the same challenge stock succumbed to infection. These results represent successful therapy of EBOV infection in NHPs.

Drs2p-dependent formation of exocytic clathrin-coated vesicles in vivo.

The small GTP binding protein ARF has been implicated in budding clathrin-coated vesicles (CCVs) from Golgi and endosomal membranes. An arf1 synthetic lethal screen identified DRS2/SWA3 along with a clathrin heavy-chain conditional allele (chc1-5/swa5-1) and SWA2, encoding the yeast auxilin-like protein involved in uncoating CCVs. Drs2p/Swa3p is a P-type ATPase and a potential aminophospholipid translocase that localizes to the trans-Golgi network (TGN) in yeast. Genetic and phenotypic analyses of drs2Delta mutants suggested that Drs2p was required for clathrin function. To address a potential role for Drs2p in CCV formation from the TGN in vivo, we have performed epistasis analyses between drs2 and mutations that cause accumulation of distinct populations of post-Golgi vesicles. We find that Drs2p is required to form a specific class of secretory vesicles that accumulate when the actin cytoskeleton is disrupted. Accumulation of these vesicles also requires clathrin and is perturbed by mutation of AP-1, but not AP-2, AP-3, or GGA adaptins. Most of the accumulated vesicles are uncoated; however, clathrin coats can be partially stabilized on these vesicles by deletion of SWA2. These data provide the first in vivo evidence for an integral membrane protein requirement in forming CCVs.