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Pooled Human Serum Off The Clot from Innovative Research was used in the following study:
Abraham J. Qavi, Krista Meserve, M. Javad Aman, Hong Vu, Larry Zeitlin, John M. Dye, Jeffrey W. Froude, Daisy W. Leung, Lan Yang, Frederick W. Holtsberg,, Ryan C. Bailey, and Gaya K. Amarasinghe
June 20, 2022
RNA viruses are particularly effective at causing diseases in human populations, partially because of their ability to rapidly mutate. One of the deadliest types of RNA viruses, Filoviruses, are single-stranded, negative-sense RNA viruses; an example of a particularly deadly Filovirus is the Ebola virus (EBOV), which causes EBOV disease (EVD).
Historic EBOV outbreaks have illustrated the need for rapid diagnostics to be available for accurate disease testing. The current standard for EBOV testing relies on PCR-based techniques, ELISAs, or lateral flow assays; they typically rely on targeting the glycoprotein (GP) of EBOV or rely on nucleic acid-based testing. Unfortunately, there is a limited viable window to perform these tests, and the different assays all vary in their rates of success and come with other unique limitations. Thus, the need for a rapid, accurate, and low maintenance method for EBOV diagnosis is apparent.
EBOV GP is expressed as two different transcriptional proteins that are expressed through site-specific editing of the GP gene. Since most other transcripts are unedited, sGP is the dominant product of GP gene transcription and translation. The sGP is dimerized by cysteine bridges and released from cells infected with EBOV. The full-length GP is only expressed after editing of the GP gene, where an additional uridine residue is added to the genomic RNA. This adds another adenosine residue in the transcript, resulting in an extended window for diagnostic testing to occur.
sGP appears to play several roles in EBOV pathogenesis; one theory proposes that sGP expression and secretion allows EBOV to evade the host immune response, thus increasing virulence. Further observations have shown that sGP has immune modulatory functions; namely, it inhibits pro-inflammatory cytokine production, limits macrophage migration, and reduces CD16b receptors on human neutrophils. It also activates the MAP signaling pathway, possibly increasing the uptake of EBOV virions.
Here, researchers adapted a silicon photon microring resonator platform to detect EBOV sGP. Microring resonators are a subclass of whispering gallery mode (WGM) devices, which rely on a system where light circulating within the microring interacts with molecule deposits on the ring surface, shifting the ring’s resonant wavelength proportionally to the amount of surface materials that are absorbed.
In this study, the researchers first used an ELISA assay to detect secreted sGP in EBOV-positive samples of both treated and untreated NHPs. sGP levels were observed increasing earlier or at the same time as RT-PCR values in all samples. Further, regardless of treatment status, all hosts with EBOV levels over 1,000ng/mL succumbed to the disease.
The researchers then used a silicon photonic microring resonator platform to detect sGP. As changes occurred in the local refractive index (RI) in the sensing region, the resonant wavelength shifts were observed and measured. When compared to blind controls using common immunoassays, their detection method proved to be effective in providing a diagnosis in under 40 minutes. Further, compared to the traditional methods, their microring method operated in a wider dynamic range and was more sensitive to changes in sGP concentrations. Their research suggests that microrings are a promising area of interest in terms of EBOV detection, and that sGP is in fact a promising biomarker in terms of early detection of EBOV.
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