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The world is entering a new era of the COVID-19 pandemic in which there is an increasing call for reliable antibody testing. To support decision making on the deployment of serology for either population screening or diagnostics, we present a detailed comparison of serological COVID-19 assays. We show that among the selected assays there is a wide diversity in assay performance in different scenarios and when correlated to virus neutralizing antibodies. The Wantai ELISA detecting total immunoglobulins against the receptor binding domain of SARS CoV-2, has the best overall characteristics to detect functional antibodies in different stages and severity of disease, including the potential to set a cut-off indicating the presence of protective antibodies. The large variety of available serological assays requires proper assay validation before deciding on deployment of assays for specific applications., SARS-CoV-2 is causing a global pandemic in which the implementation of serology can support decision making in different scenarios. Here, the authors compare the outcome of eight commercially available assays to virus neutralization and discuss their use in diagnostics and exposure assessment of SARS-CoV-2.

Background Performance of the SD Biosensor saliva antigen rapid test was evaluated at a large designated testing site in non-hospitalized patients, with or without symptoms. Method All eligible people over 18 years of age presenting for a booked appointment at the designated SARS-CoV-2 testing site were approached for inclusion and enrolled following verbal informed consent. One nasopharyngeal swab was taken to carry out the default antigen rapid test from which the results were reported back to the patient and one saliva sample was self-taken according to verbal instruction on site. This was used for the saliva antigen rapid test, the RT-PCR and for virus culture. Sensitivity of the saliva antigen rapid test was analyzed in two ways: i, compared to saliva RT-PCR; and ii, compared to virus culture of the saliva samples. Study participants were also asked to fill in a short questionnaire stating age, sex, date of symptom onset. Recommended time of ≥30mins since last meal, drink or cigarette if applicable was also recorded. The study was carried out in February-March 2021 for 4 weeks. Results We could include 789 people with complete records and results. Compared to saliva RT-PCR, overall sensitivity and specificity of the saliva antigen rapid test was 66.1% and 99.6% which increased to 88.6% with Ct ≤30 cutoff. Analysis by days post onset did not result in higher sensitivities because the large majority of people were in the very early phase of disease ie Conclusion Overall, the potential benefits of saliva antigen rapid test, could outweigh the lower sensitivity compared to nasopharyngeal antigen rapid test in a comprehensive testing strategy, especially for home/self-testing and in vulnerable populations like elderly, disabled or children where in intrusive testing is either not possible or causes unnecessary stress.

Highlights • Commercial SARS-CoV-2 RT-PCR analytical performance comparison. • Analytical sensitivity of 13 SARS-CoV-2 RT-PCRs varied between 3.3–330 RNA copies. • All but 1 assay had sensitivity within one order of magnitude of the reference assay. • Only 1 assay cross reacted with another coronavirus (MERS)., The emergence of a new coronavirus in Wuhan China has triggered a global need for accurate diagnostic assays. Initially, mostly laboratory developed molecular tests were available but shortly thereafter different commercial assays started to appear and are still increasing in number. Although independent performance evaluations are ongoing, available data is still scarce. Here we provide a direct comparison of key performance characteristics of 13 commercial RT-PCR assays. Thirteen RT-PCR assays were selected based on the criteria that they can be used following generic RNA extraction protocols, on common PCR platforms and availability. Using a 10-fold and 2-fold dilution series of a quantified SARS-CoV-2 cell-cultured virus stock, performance was assessed compared to our in house validated assay. Specificity was tested by using RNA extracted from cultured common human coronaviruses. All RT-PCR kits included in this study exhibited PCR efficiencies > 90%, except for the Sentinel Diagnostics B E-gene RUO assay (80%). Analytical sensitivity varied between 3.3 RNA copies to 330 RNA copies. Only one assay cross reacted with another human coronavirus (MERS). This study provides a technical baseline of 13 different commercial PCR assays for SARS-CoV-2 detection that can be used by laboratories interested in purchasing any of these for further full clinical validation.

Background: Oxidative stress is a key event in the determination of host cell fate. Results: The hepatitis C virus NS5A protein binds to the MLK3 kinase, blocking both oxidative stress induced apoptosis and activation of the potassium channel Kv2.1. Conclusion: NS5A blocks host cell apoptosis and potassium efflux. Significance: Interference with the host stress response could facilitate viral persistence., Hepatitis C virus (HCV) infection results in the activation of numerous stress responses including oxidative stress, with the potential to induce an apoptotic state. Previously we have shown that HCV attenuates the stress-induced, p38MAPK-mediated up-regulation of the K+ channel Kv2.1, to maintain the survival of infected cells in the face of cellular stress. We demonstrated that this effect was mediated by HCV non-structural 5A (NS5A) protein, which impaired p38MAPK activity through a polyproline motif-dependent interaction, resulting in reduction of phosphorylation activation of Kv2.1. In this study, we investigated the host cell proteins targeted by NS5A to mediate Kv2.1 inhibition. We screened a phage-display library expressing the entire complement of human SH3 domains for novel NS5A-host cell interactions. This analysis identified mixed lineage kinase 3 (MLK3) as a putative NS5A interacting partner. MLK3 is a serine/threonine protein kinase that is a member of the MAPK kinase kinase (MAP3K) family and activates p38MAPK. An NS5A-MLK3 interaction was confirmed by co-immunoprecipitation and Western blot analysis. We further demonstrate a novel role of MLK3 in the modulation of Kv2.1 activity, whereby MLK3 overexpression leads to the up-regulation of channel activity. Accordingly, coexpression of NS5A suppressed this stimulation. Additionally we demonstrate that overexpression of MLK3 induced apoptosis, which was also counteracted by NS5A. We conclude that NS5A targets MLK3 with multiple downstream consequences for both apoptosis and K+ homeostasis.

Hepatitis C virus (HCV) establishes a persistent infection that in many cases leads to cirrhosis and hepatocellular carcinoma. The non-structural 5A protein (NS5A) has been implicated in this process as it contains a C-terminal polyproline motif (termed P2) that binds to Src homology 3 (SH3) domains to regulate cellular signalling and trafficking pathways. We have shown previously that NS5A impaired epidermal growth factor (EGF) receptor (EGFR) endocytosis, thereby inhibiting EGF-stimulated EGFR degradation by a mechanism that remained unclear. As EGFR has been implicated in HCV cell entry and trafficking of the receptor involves several SH3-domain containing proteins, we investigated in more detail the mechanisms by which NS5A perturbs EGFR trafficking. We demonstrated that the P2 motif was required for the NS5A-mediated disruption to EGFR trafficking. We further demonstrated that the P2 motif was required for an interaction between NS5A and CMS, a homologue of CIN85 that has previously been implicated in EGFR endocytosis. We provided evidence that CMS was involved in the NS5A-mediated perturbation of EGFR trafficking. We also showed that NS5A effected a loss of EGFR ubiquitination in a P2-motif-dependent fashion. These data provide clues to the mechanism by which NS5A regulates the trafficking of a key cellular receptor and demonstrate for the first time the ability of NS5A to regulate host cell ubiquitination pathways.