Timothy D. Minogue

Monitoring of Ebola virus Makona evolution through establishment of advanced genomic capability in Liberia

The effects of EBOV evolution on diagnostic assays and therapeutic drugs appear to be low.

Evaluation of Inhibitor-Resistant Real-Time PCR Methods for Diagnostics in Clinical and Environmental Samples

Polymerase chain reaction (PCR) is commonly used for pathogen detection in clinical and environmental samples. These sample matrices often contain inhibitors of PCR, which is a primary reason for sample processing; however, the purification process is highly inefficient, becoming unacceptable at lower signature concentrations. One potential solution is direct PCR assessment without sample processing. Here, we evaluated nine inhibitor-resistant PCR reagents for direct detection of Francisella tularensis in seven different clinical and environmental samples using an established real-time PCR assay to assess ability to overcome PCR inhibition. While several of these reagents were designed for standard PCR, the described inhibitor resistant properties (ex. Omni Klentaq can amplify target DNA samples of up to 20% whole blood or soil) led to our evaluation with real-time PCR. A preliminary limit of detection (LOD) was determined for each chemistry in whole blood and buffer, and LODs (20 replicates) were determined for the top five chemistries in each matrix (buffer, whole blood, sputum, stool, swab, soil, and sand). Not surprisingly, no single chemistry performed the best across all of the different matrices evaluated. For instance, Phusion Blood Direct PCR Kit, Phire Hot Start DNA polymerase, and Phire Hot Start DNA polymerase with STR Boost performed best for direct detection in whole blood while Phire Hot Start DNA polymerase with STR Boost were the only reagents to yield an LOD in the femtogram range for soil. Although not the best performer across all matrices, KAPA Blood PCR kit produced the most consistent results among the various conditions assessed. Overall, while these inhibitor resistant reagents show promise for direct amplification of complex samples by real-time PCR, the amount of template required for detection would not be in a clinically relevant range for most matrices.

Development and Evaluation of a Panel of Filovirus Sequence Capture Probes for Pathogen Detection by Next-Generation Sequencing

A detailed understanding of the circulating pathogens in a particular geographic location aids in effectively utilizing targeted, rapid diagnostic assays, thus allowing for appropriate therapeutic and containment procedures. This is especially important in regions prevalent for highly pathogenic viruses co-circulating with other endemic pathogens such as the malaria parasite. The importance of biosurveillance is highlighted by the ongoing Ebola virus disease outbreak in West Africa. For example, a more comprehensive assessment of the regional pathogens could have identified the risk of a filovirus disease outbreak earlier and led to an improved diagnostic and response capacity in the region. In this context, being able to rapidly screen a single sample for multiple pathogens in a single tube reaction could improve both diagnostics as well as pathogen surveillance. Here, probes were designed to capture identifying filovirus sequence for the ebolaviruses Sudan, Ebola, Reston, Taï Forest, and Bundibugyo and the Marburg virus variants Musoke, Ci67, and Angola. These probes were combined into a single probe panel, and the captured filovirus sequence was successfully identified using the MiSeq next-generation sequencing platform. This panel was then used to identify the specific filovirus from nonhuman primates experimentally infected with Ebola virus as well as Bundibugyo virus in human sera samples from the Democratic Republic of the Congo, thus demonstrating the utility for pathogen detection using clinical samples. While not as sensitive and rapid as real-time PCR, this panel, along with incorporating additional sequence capture probe panels, could be used for broad pathogen screening and biosurveillance.

Comparison of Transcriptomic Platforms for Analysis of Whole Blood from Ebola-Infected Cynomolgus Macaques

Ebola virus disease (EVD) is a serious illness with mortality rates of 20–90% in various outbreaks. EVD is characterized by robust virus replication and strong host inflammatory response. Analyzing host immune responses has increasingly involved multimodal approaches including transcriptomics to profile gene expression. We studied cynomolgus macaques exposed to Ebola virus Makona via different routes with the intent of comparing RNA-Seq to a NanoString nCounter codeset targeting 769 non-human primate (NHP) genes. RNA-Seq analysis of serial blood samples showed different routes led to the same overall transcriptional response seen in previously reported EBOV-exposed NHP studies. Both platforms displayed a strong correlation in gene expression patterns, including a strong induction of innate immune response genes at early times post-exposure, and neutrophil-associated genes at later time points. A 41-gene classifier was tested in both platforms for ability to cluster samples by infection status. Both NanoString and RNA-Seq could be used to predict relative abundances of circulating immune cell populations that matched traditional hematology. This demonstrates the complementarity of RNA-Seq and NanoString. Moreover, the development of an NHP-specific NanoString codeset should augment studies of filoviruses and other high containment infectious diseases without the infrastructure requirements of RNA-Seq technology.

African and Asian Zika Virus Isolates Display Phenotypic Differences Both In Vitro and In Vivo

Zika virus (ZIKV) is a mosquito-borne member of the genus Flavivirus that has emerged since 2007 to cause outbreaks in Africa, Asia, Oceania, and most recently, in the Americas. Here, we used an isolate history as well as genetic and phylogenetic analyses to characterize three low-passage isolates representing African (ArD 41525) and Asian (CPC-0740, SV0127-14) lineages to investigate the potential phenotypic differences in vitro and in vivo. The African isolate displayed a large plaque phenotype (∼3-4 mm) on Vero and HEK-293 cells, whereas the Asian isolates either exhibited a small plaque phenotype (∼1-2 mm) or did not produce any plaques. In multistep replication kinetics in nine different vertebrate and insect cell lines, the African isolate consistently displayed faster replication kinetics and yielded ∼10- to 10,000-fold higher peak virus titers (infectious or RNA copies) compared with the Asian isolates. Oral exposure of Aedes aegypti mosquitoes with the African isolate yielded higher infection and dissemination rates compared with the Asian isolates. Infection of Ifnar1-/- mice with the African isolate produced a uniformly fatal disease, whereas infection with the Asian isolates produced either a delay in time-to-death or a significantly lower mortality rate. Last, the African isolate was > 10,000-fold more virulent than the Asian isolates in an interferon type I antibody blockade mouse model. These data demonstrate substantial phenotypic differences between low-passage African and Asian isolates both in vitro and in vivo and warrant further investigation. They also highlight the need for basic characterization of ZIKV isolates, as the utilization of the uncharacterized isolates could have consequences for animal model and therapeutic/vaccine development.

DETEQT: Algorithms for Adjudicating Targeted Infectious Disease Next-Generation Sequencing Panels

Next-generation sequencing (NGS) for infectious disease diagnostics is a relatively new and underdeveloped concept. If this technology is to become a regulatory-grade clinical diagnostic, standardization in the form of locked-down assays and firmly established underlying processes is necessary. Targeted sequencing, specifically by amplification of genomic signatures, has the potential to bridge the gap between PCR- and NGS-based diagnostics; however, existing NGS assay panels lack validated analytical techniques to adjudicate high background and error-prone NGS data. Herein, we present the Diagnostic targETEd seQuencing adjudicaTion (DETEQT) software, consisting of an intuitive bioinformatics pipeline entailing a set of algorithms to translate raw sequencing data into positive, negative, and indeterminate diagnostic determinations. After basic read filtering and mapping, the software compares abundance and quality metrics against heuristic and fixed thresholds. A novel generalized quality function provides an amalgamated quality score for the match between sequence reads of an assay and panel targets, rather than considering each component factor independently. When evaluated against numerous assay samples and parameters (mock clinical, human, and nonhuman primate clinical data sets; diverse amplification strategies; downstream applications; and sequence platforms), DETEQT demonstrated improved rejection of false positives and accuracies >95%. Finally, DETEQT was implemented in the user-friendly Empowering the Development of Genomics Expertise (EDGE) bioinformatics platform, providing a complete, end-to-end solution that can be operated by nonexperts in a clinical laboratory setting.

A conserved transcriptional response to intranasal Ebola virus exposure in nonhuman primates prior to onset of fever

An animal model of Ebola virus infection with variable disease onset identifies host markers of infection that precede symptoms by 4 days. An enlightening Ebola model Using large doses of highly pathogenic agents in animal models can ensure consistent and fully penetrant infection but does not recapitulate human exposure and possibly immune responses. Speranza and colleagues intranasally infected cynomolgus macaques with a small dose of Ebola virus, which led to various disease presentation and allowed for detection of early immunity. Regardless of the timing of symptoms, analysis of the host response revealed a conserved interferon signature that preceded fever by several days. These results shed light on the host response to Ebola virus and established a model that could be used for future studies of pathogenesis, treatment, or prevention. Ebola virus disease (EVD), caused by Ebola virus (EBOV), is a severe illness characterized by case fatality rates of up to 90%. The sporadic nature of outbreaks in resource-limited areas has hindered the ability to characterize the pathogenesis of EVD at all stages of infection but particularly early host responses. Pathogenesis is often studied in nonhuman primate (NHP) models of disease that replicate major aspects of human EVD. Typically, NHP models use a large infectious dose, are carried out through intramuscular or aerosol exposure, and have a fairly uniform disease course. By contrast, we report our analysis of the host response to EBOV after intranasal exposure. Twelve cynomolgus macaques were infected with 100 plaque-forming units of EBOV/Makona through intranasal exposure and presented with varying times to onset of EVD. We used RNA sequencing and a newly developed NanoString CodeSet to monitor the host response via changes in RNA transcripts over time. When individual animal gene expression data were phased based on the onset of sustained fever, the first clinical sign of severe disease, mathematical models indicated that interferon-stimulated genes appeared as early as 4 days before fever onset. This demonstrates that lethal EVD has a uniform and predictable response to infection regardless of time to onset. Furthermore, expression of a subset of genes could predict disease development before other host-based indications of infection such as fever.

Next-Generation Sequencing for Biodefense: Biothreat Detection, Forensics, and the Clinic

BACKGROUND Next-generation sequencing (NGS) is revolutionizing a variety of molecular biology fields including bioforensics, biosurveillance, and infectious disease diagnostics. For pathogen detection, the ability to sequence all nucleic acids in a sample allows near limitless multiplexability, free from a priori knowledge regarding an etiologic agent as is typically required for targeted molecular assays such as real-time PCR. Furthermore, sequencing capabilities can generate in depth genomic information, allowing detailed molecular epidemiological studies and bioforensics analysis, which is critical for source agent identification in a biothreat outbreak. However, lack of analytical specificity, inherent to NGS, presents challenges for regulated applications such as clinical diagnostics and molecular attribution. CONTENT Here, we discuss NGS applications in the context of preparedness and biothreat readiness. Specifically, we investigate current and future applications of NGS technologies to affect the fields of biosurveillance, bioforensics, and clinical diagnostics with specific focus on biodefense. SUMMARY Overall, there are many advantages to the implementation of NGS for preparedness and readiness against biowarfare agents, from forensics to diagnostics. However, appropriate caveats must be associated with any technology. This includes NGS. While NGS is not the panacea replacing all molecular techniques, it will greatly enhance the ability to detect, characterize, and diagnose biowarfare agents, thus providing an excellent addition to the biodefense toolbox of biosurveillance, bioforensics, and biothreat diagnosis.

Sequence Optimized Real-Time Reverse Transcription Polymerase Chain Reaction Assay for Detection of Crimean-Congo Hemorrhagic Fever Virus

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus of the genus Nairovirus within the family Bunyaviridae. Infection can result in general myalgia, fever, and headache with some patients developing hemorrhagic fever with mortality rates ranging from 5% to 30%. CCHFV has a wide geographic range that includes Africa, Asia, the Middle East, and Europe with nucleotide sequence variation approaching 20% across the three negative-sense RNA genome segments. While phylogenetic clustering generally aligns with geographic origin of individual strains, distribution can be wide due to tick/CCHFV dispersion via migrating birds. This sequence diversity negatively impacts existing molecular diagnostic assays, leading to false negative diagnostic results. Here, we updated a previously developed CCHFV real-time reverse transcription polymerase chain reaction (RT-PCR) assay to include strains not detected using that original assay. Deep sequencing of eight different CCHFV strains, including three that were not detectable using the original assay, identified sequence variants within this assay target region. New primers and probe based on the sequencing results and newly deposited sequences in GenBank greatly improved assay sensitivity and inclusivity with the exception of the genetically diverse strain AP92. For example, we observed a four log improvement in IbAr10200 detection with a new limit of detection of 256 PFU/mL. Subsequent comparison of this assay to another commonly used CCHFV real-time RT-PCR assay targeting a different region of the viral genome showed improved detection, and both assays could be used to mitigate CCHFV diversity for diagnostics. Overall, this work demonstrated the importance of continued viral sequencing efforts for robust diagnostic assay development.

Development of real-time PCR assays for the detection of Moraxella macacae associated with bloody nose syndrome in rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) macaques

Moraxella macacae is a recently described bacterial pathogen that causes epistaxis or so‐called bloody nose syndrome in captive macaques. The aim of this study was to develop specific molecular diagnostic assays for M. macacae and to determine their performance characteristics.