Background: An Israeli national taskforce performed a multi-center clinical and analytical validation of seven serology assays to determine their utility and limitations for SARS-CoV-2 diagnosis. Methods: Serology assays from Roche, Abbott, Diasorin, BioMerieux, Beckman-Coulter, Siemens, and Mt.-Sinai ELISA were included. Negative samples from 2391 individuals representative of the Israeli population, and 698 SARS-CoV-2 PCR positive patients, collected between March and May 2020, were analyzed Findings: Immunoassays sensitivities between 81.5%-89.4% and specificities between 97.7%-100% resulted in a profound impact on the expected Positive Predictive Value (PPV) in low (<15%) prevalence scenarios. No meaningful increase was detected in the false positive rate in children compared to adults. A positive correlation between disease severity and antibody titers, and no decrease in antibody titers in the first 8 weeks after PCR positivity was observed. We identified a subgroup of symptomatic SARS-CoV-2 positive patients (~5% of patients), who remained seronegative across a wide range of antigens, isotypes, and technologies. Interpretation: wThe commercially available automated immunoassays exhibit significant differences in performance and expected PPV in low prevalence scenarios. The low false-positivity rate in under 20 0 s suggests that cross-reactive immunity from previous CoV strains is unlikely to explain the milder disease course in children. Finding no decrease in antibody titers in the first 8 weeks is in contrast to some reports of short half-life for SARS-CoV-2 antibodies. The~5% who were seronegative non-responders, using multiple

Epidermal growth factor (EGF) stimulates the growth of various types of cells via its cell surface tyrosine kinase receptor. The EGF receptor (EGF-R) has an oncogenic potential when overexpressed in a wide range of tumor cells. Geldanamycin (GA) and herbimycin (HA), specific inhibitors of the cytosolic chaperone HSP 90 and its endoplasmic reticulum homologue GRP 94, were shown to accelerate degradation of the EGF-R and of its homologue p185 c-erbB-2 . Here we compared the effects of GA and HA on intracellular degradation and maturation of EGF-R. By using an inhibitor of proteasomal degradation, we learned that GA, but not HA, blocks processing of newly synthesized EGF-R. The effects of GA and HA on receptor degradation are mediated by the cytosolic portion of EGF-R and could be conferred to the erythropoietin receptor (EPO-R), by employing the respective chimera. Neither HA nor GA affected stability of newly synthesized EGF-R lacking the cytosolic domain (Ex EGF-R), but GA caused intracellular retention of this mutant. Taken together, our results imply that GA has two distinct targets of action on the EGF-R, one for promoting its degradation and another for mediating its intracellular retention. Apparently, degradation of the EGF-R mediated by GA or HA requires the presence of the EGF-R cytosolic domain, whereas intracellular retention in the presence of GA is coupled to the extracellular domain of the EGF-R.Herbimycin A (HA) 1 and geldanamycin (GA) are benzoquinone ansamycins that specifically inhibit the cytosolic chaperone HSP 90 and its endoplasmic reticulum (ER) homologue GRP 94. These compounds have antiproliferative and antitumor effects as they bind to HSP 90, inhibit the HSP 90-mediated conformational maturation/refolding reaction, and thus promote degradation of HSP 90 substrates (reviewed in Ref. 1). The molecular basis underlying this inhibition is still under intensive investigation (2). GA was shown to accelerate the degradation of cell surface proteins including receptor Tyr kinases (3) and the cystic fibrosis transmembrane conductance regulator (CFTR) protein (4). Enhanced degradation in the presence of GA was also observed for non-membrane proteins including Ser/Thr kinases (5), Tyr kinases (6), and mutated p53 (7).The epidermal growth factor receptor (EGF-R) and its homologue p185 c-erbB-2 are well studied receptor Tyr kinases (8), which are degraded in the presence of GA and HA (9 -11), presumably via the proteasome (3, 12). The cytosolic domain of the EGF-R contains Tyr kinase activity and may also contain determinants that are required for GA-and HA-mediated degradation. This is suggested by evidence that a soluble EGF-R, an EGF-R derivative containing only the extracellular domain of the receptor (11, 13), and p185 c-erbB-2 lacking either the entire cytosolic domain or the kinase domain (10) were not degraded in the presence of HA (11, 13) or GA (10, 13). However, it is not clear whether Tyr kinase activity of the receptor or the presence of the entire kinase domain is required to confer GA...

Israel experienced a new wave of coronavirus disease during June 2021, six months after implementing a national vaccination campaign. We conducted 3 discrete analyses using data from a large health maintenance organization in Israel to determine whether IgG levels of fully vaccinated persons decrease over time, describe the relationship between IgG titer and subsequent PCR-confirmed infection, and compare PCR-confirmed infection rates by period of vaccination. Mean IgG levels steadily decreased over the 6-month period in the total tested population and in all age groups. An inverse relationship was found between IgG titer and subsequent PCR-positive infection. Persons vaccinated during the first 2 months of the campaign were more likely to become infected than those subsequently vaccinated. The vaccinated group > 60 years of age had lower initial IgG levels and were at greater risk for infection. The findings support the decision to add a booster vaccine for persons > 60 years of age.

Erythropoietin (EPO) promotes the viability, proliferation and differentiation of mammalian erythroid progenitor cells via its specific cell surface receptor. The EPO receptor (EPO-R) is a member of the cytokine receptor superfamily and is comprised of one identified subunit which homodimerizes upon ligand binding. To study the role of the intracellular domain of the EPO-R in the endocytosis of EPO, we compared the rate and extent of IPS I-EPO endocytosis by wild type (wt) EPO-R and five cytoplasmically truncated EPO-Rs: 1^251 EPO-R, 1^257 EPO-R, 1^267 EPO-R, 1^276 EPO-R and 1^306 EPO-R which contain 4, 10, 20, 29 or 59 amino acids of the cytoplasmic domain, respectively. We also studied an EPO-R mutant (PB) which lacks amino acid residues 281^300 of the cytoplasmic domain. The experiments were conducted in COS 7 cells transfected with the EPO-R cDNAs and in Ba/F3 cells stably expressing the wt EPO-R, 1^251 or 1^257 EPO-R. Cells expressing wt EPO-R, PB EPO-R (v v281^300), 1^276 EPO-R or 1^306 EPO-R internalized approximately 50% of IPS I-EPO bound to the cell surface, while cells expressing 1^251, 1^257 or 1^267 EPO-R internalized only 25% of the bound IPS I-EPO. The steady-state expression levels of these latter receptors on the cell surface were typically 2^5-fold higher than wt EPO-R. Our data indicate that amino acid residues 267^276 (FEGLFTTHK) of the EPO-R cytoplasmic domain may have a role in receptor internalization. Metabolic labeling experiments suggest that in transiently transfected COS 7 cells most of the wt EPO-R and 1^257 EPO-Rs do not exit the ER and may be degraded there. The half-life of both receptors was essentially similar and was in the range of 1 h. In Ba/F3 cells the mature Golgi processed 1^257 EPO-R was more stable than the corresponding form of the wt EPO-R, possibly contributing to its higher cell surface expression.z 1998 Federation of European Biochemical Societies.

Deployment of the BNT162b2 mRNA Covid-19 Vaccine in Israel began in December 2020. This is a retrospective analysis of serological data, showing SARS-CoV-2 anti-S IgG kinetics in 116 Israeli health care workers receiving BNT162b2. Sero-conversion occurred in 14 days in all study participants, with IgG levels peaking approximately 30 days after initiation of the vaccination series. A statistically significant difference was observed in IgG levels between subjects younger than 50 years and older participants, although in all cases, IgG levels were well above the level considered reactive by the test's manufacturer. The importance of this difference needs to be studied further, but a potential difference in vaccine efficacy and vaccine effect length could possibly be present between these two groups.