The extent of SARS-CoV-2 infection throughout the United States population is currently unknown. High quality serology is key to avoiding medically costly diagnostic errors, as well as to assuring ...properly informed public health decisions. Here, we present an optimized ELISA-based serology protocol, from antigen production to data analyses, that helps define thresholds for IgG and IgM seropositivity with high specificities. Validation of this protocol is performed using traditionally collected serum as well as dried blood on mail-in blood sampling kits. Archival (pre-2019) samples are used as negative controls, and convalescent, PCR-diagnosed COVID-19 patient samples serve as positive controls. Using this protocol, minimal cross-reactivity is observed for the spike proteins of MERS, SARS1, OC43 and HKU1 viruses, and no cross reactivity is observed with anti-influenza A H1N1 HAI. Our protocol may thus help provide standardized, population-based data on the extent of SARS-CoV-2 seropositivity, immunity and infection.
The SARS-CoV-2 spike trimer is the primary antigen for several serology assays critical to determining the extent of SARS-CoV-2 exposure in the population. Until stable cell lines are developed to ...increase the titer of this secreted protein in mammalian cell culture, the low yield of spike protein produced from transient transfection of HEK293 cells will be a limiting factor for these assays. To improve the yield of spike protein and support the high demand for antigens in serology assays, we investigated several recombinant protein expression variables by altering the incubation temperature, harvest time, chromatography strategy, and final protein manipulation. Through this investigation, we developed a simplified and robust purification strategy that consistently yields 5 mg of protein per liter of expression culture for two commonly used forms of the SARS-CoV-2 spike protein. We show that these proteins form well-behaved stable trimers and are consistently functional in serology assays across multiple protein production lots.
•Improved yields of SARS-CoV-2 spike protein through modification of expression and purification parameters.•Yields of greater than 5 mg/l obtained for VRC spike under optimal conditions.•Spike protein quality was validated by QC methods to ensure utility in serology assays.
Previous work employing five SARS-CoV-2 spike protein receptor-binding domain (RBD) constructs, comprising versions originally developed by Mt. Sinai or the Ragon Institute and later optimized ...in-house, revealed potential heterogeneity which led to questions regarding variable seropositivity assay performance. Each construct was subjected to N-deglycosylation and subsequent intact mass analysis, revealing significant deviations from predicted theoretical mass for all five proteins. Complementary tandem MS/MS analysis revealed the presence of an additional pyroGlu residue on the N-termini of the two Mt. Sinai RBD constructs, as well as on the N-terminus of the full-length spike protein from which they were derived, thus explaining the observed mass shift and definitively establishing the spike protein N-terminal sequence. Moreover, the observed mass additions for the three Ragon Institute RBD constructs were identified as variable N-terminal cleavage points within the signal peptide sequence employed for recombinant expression. To resolve this issue and minimize heterogeneity for further seropositivity assay development, the best-performing RBD construct was further optimized to exhibit complete homogeneity, as determined by both intact mass and tandem MS/MS analysis. This new RBD construct has been validated for seropositivity assay performance, is available to the greater scientific community, and is recommended for use in future assay development.
Reports of adverse effects associated with proton pump inhibitors (PPIs) are concerning because of high usage and over-the-counter availability. We sought to determine the awareness of PPI adverse ...effects among our patient population, which is medically underserved, low-income, and racially diverse. A 21-item survey was administered to gastroenterology-clinic outpatients. It collected information about age, gender, education, race, specialty of the prescriber, specific PPI, indication, knowledge of dose, adherence, duration of use and awareness of any risks. Medical records were reviewed to verify survey responses pertaining to indication, dosing, and adherence. A vast majority (96%) of 101 participants were not aware of PPI adverse effects. In total, 63% of the patients completed a high school education or less, which was associated with a higher risk of long-term PPI use than completion of at least an undergraduate degree (
= 0.05). In contrast to other studies, the shockingly low patient awareness about PPI adverse effects in our patient population is particularly concerning, especially as it is tied to their demographic attributes. This may lead to long-term and high-dose PPI use. Our study highlights the need for effective provider-driven education regarding medication risks, especially in the communities with significant health disparities.
derived cell lines are commonly used to enable recombinant protein expression via baculovirus infection to generate materials approved for clinical use and in clinical trials. In order to develop ...systems biology and genome engineering tools to improve protein expression in this host, we performed de novo genome assembly of the
-derived cell line Tni-FNL.
By integration of PacBio single-molecule sequencing, Bionano optical mapping, and 10X Genomics linked-reads data, we have produced a draft genome assembly of Tni-FNL.
Our assembly contains 280 scaffolds, with a N50 scaffold size of 2.3 Mb and a total length of 359 Mb. Annotation of the Tni-FNL genome resulted in 14,101 predicted genes and 93.2% of the predicted proteome contained recognizable protein domains. Ortholog searches within the superorder
provided further evidence of high accuracy and completeness of the Tni-FNL genome assembly.
This first draft Tni-FNL genome assembly was enabled by complementary long-read technologies and represents a high-quality, well-annotated genome that provides novel insight into the complexity of this insect cell line and can serve as a reference for future large-scale genome engineering work in this and other similar recombinant protein production hosts.
In order to properly understand the spread of SARS-CoV-2 infection and development of humoral immunity, researchers have evaluated the presence of serum antibodies of people worldwide experiencing ...the pandemic. These studies rely on the use of recombinant proteins from the viral genome in order to identify serum antibodies that recognize SARS-CoV-2 epitopes. Here, we discuss the cross-reactivity potential of SARS-CoV-2 antibodies with the full spike proteins of four other betacoronaviruses that cause disease in humans, MERS-CoV, SARS-CoV, HCoV-OC43, and HCoV-HKU1. Using enzyme-linked immunosorbent assays (ELISAs), we detected the potential cross-reactivity of antibodies against SARS-CoV-2 towards the four other coronaviruses, with the strongest cross-recognition between SARS-CoV-2 and SARS /MERS-CoV antibodies, as expected based on sequence homology of their respective spike proteins. Further analysis of cross-reactivity could provide informative data that could lead to intelligently designed pan-coronavirus therapeutics or vaccines.
While subglacial hydrology is known to play a role in glacial dynamics on sub-annual to decadal scales, it remains unclear whether subglacial hydrology plays a critical role in ice sheet evolution on ...centennial or longer timescales. Furthermore, several drainage systems have been inferred, but it is unclear which is most applicable at the continental/glacial scale. More fundamentally, it is even unclear if the structural choice of subglacial hydrology truly matters for this context.
The SHOC2-MRAS-PPP1CA (SMP) complex is a holoenzyme that plays a vital role in the MAP kinase signaling pathway. Previous attempts to produce this challenging three-protein complex have relied on ...co-infection with multiple viruses and the use of affinity tags to attempt to isolate functional recombinant protein complexes. Leucine-rich repeat containing proteins have been historically challenging to express, and we hypothesized that co-expression of appropriate chaperones may be necessary for optimal production. We describe here how the SUGT1 chaperone can, in conjunction with polycistronic protein expression in baculovirus-infected insect cells, dramatically enhance production yield and quality of recombinant SHOC2, the SMP complex, and other leucine-rich repeat proteins.
•Improved yields and purity of LRR proteins and multiprotein complexes through polycistronic chaperone co-expression.•Over 300-fold yield increase of SMP protein complex from 0.1 mg/L to 32.6 mg/L.•SUGT1 co-expression is a highly effective technique for recombinant LRR protein expression and purification.•Polycistronic baculovirus infection is ideal for production of multiprotein complexes.
Abstract
Emergence of a new spike protein variant (D614G) with increased infectivity has prompted many to analyze its role in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ...pandemic. There is concern regarding whether an individual exposed to one variant of a virus will have cross-reactive memory to the second variant. Accordingly, we analyzed the serologic reactivity of both variants, and we found that antibodies from 88 donors from a high-incidence population reacted toward both the original spike and the D614 spike variant. These data suggest that patients who are exposed to either variant have cross-responsive humoral immunity. This represents an important finding both for SARS-CoV-2 disease biology and for therapeutics.
As the D614G spike variant emerged as the main severe acute respiratory syndrome coronavirus 2 variant in the United States, concerns arose regarding possible differences in antibody binding and serologic assay performance. We show that antibodies cross-react with both variants.
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