Cycle threshold responses in SARS-COV2 PCR tests depend on the method by which the samples were obtained and require strict global standardization

Purpose

Since 2020, a SARS-COV2 epidemic has been raging worldwide. The cycle of the PCR test in which the virus is detected is called cycle threshold (CT). The method of obtaining the sample is not detailed in any published study and is based on general guidelines of the CDC. Our contention is that the manner in which the sample is obtained has a dramatic effect on CT values.

Methods

For each person suspected of having Covid-19 who arrives at the emergency room, two swabs are taken in succession, one according to CDC guidelines and the other according to “Ziv” guidelines. The Ziv method sample collection guidelines determine the depth of penetration, the number of rotations of the swab, and their direction. Each double sample was sent for analysis.

Results

Analysis of the CT results of the sample to results methods and of the Seegene platform clearly found (p = 0.003 and p = 0.001, respectively) that more rigorous sample collection yielded lower CT values.

Conclusion

The method of obtaining the samples had a dramatic effect on CT results. Any publication that includes CT results, and certainly studies that discuss CT kinetics, must describe in detail the method by which the samples were obtained. In places where it is also important to detect the onset of illness (airports, hospitals, schools, etc.), it is important to use the Ziv method to reduce the risk of false negatives.

An efficient chemical screening method for structure-based inhibitors to nucleic acid enzymes targeting the DNA repair-replication interface and SARS CoV-2

We present a Chemistry and Structure Screen Integrated Efficiently (CASSIE) approach (named for Greek prophet Cassandra) to design inhibitors for cancer biology and pathogenesis. CASSIE provides an effective path to target master keys to control the repair-replication interface for cancer cells and SARS CoV-2 pathogenesis as exemplified here by specific targeting of Poly(ADP-ribose) glycohydrolase (PARG) and ADP-ribose glycohydrolase ARH3 macrodomains plus SARS CoV-2 nonstructural protein 3 (Nsp3) Macrodomain 1 (Mac1) and Nsp15 nuclease. As opposed to the classical massive effort employing libraries with large numbers of compounds against single proteins, we make inhibitor design for multiple targets efficient. Our compact, chemically diverse, 5000 compound Goldilocks (GL) library has an intermediate number of compounds sized between fragments and drugs with predicted favorable ADME (absorption, distribution, metabolism, and excretion) and toxicological profiles. Amalgamating our core GL library with an approved drug (AD) library, we employ a combined GLAD library virtual screen, enabling an effective and efficient design cycle of ranked computer docking, top hit biophysical and cell validations, and defined bound structures using human proteins or their avatars. As new drug design is increasingly pathway directed as well as molecular and mechanism based, our CASSIE approach facilitates testing multiple related targets by efficiently turning a set of interacting drug discovery problems into a tractable medicinal chemistry engineering problem of optimizing affinity and ADME properties based upon early co-crystal structures. Optimization efforts are made efficient by a computationally-focused iterative chemistry and structure screen. Thus, we herein describe and apply CASSIE to define prototypic, specific inhibitors for PARG vs distinct inhibitors for the related macrodomains of ARH3 and SARS CoV-2 Nsp3 plus the SARS CoV-2 Nsp15 RNA nuclease.