Longitudinal kinetics of RBD+ antibodies in COVID-19 recovered patients over 14 months.

We describe the longitudinal kinetics of the serological response in COVID-19 recovered patients over a period of 14 months. The antibody kinetics in a cohort of 192 recovered patients, including 66 patients for whom follow-up serum samples were obtained at two to four clinic visits, revealed that RBD-specific antibodies decayed over the 14 months following the onset of symptoms. The decay rate was associated with the robustness of the response in that antibody levels that were initially highly elevated after the onset of symptoms subsequently decayed more rapidly. An exploration of the differences in the longitudinal kinetics between recovered patients and naïve vaccinees who had received two doses of the BNT162b2 vaccine showed a significantly faster decay in the naïve vaccinees, indicating that serological memory following natural infection is more robust than that following to vaccination. Our data highlighting the differences between serological memory induced by natural infection vs. vaccination contributed to the decision-making process in Israel regarding the necessity for a third vaccination dose.

Immunosuppressive Drugs Alter α1-Antitrypsin Production in Hepatocytes: Implications for Epithelial Gap Repair.

Immunosuppressive drugs are an inherent component of hematopoietic stem cell transplantation (HSCT) for the prevention of acute graft-versus-host disease (GVHD). Circulating α1-antitrypsin (AAT), a serine-protease inhibitor produced predominantly by hepatocytes that rises during acute phase responses, is lost in patient's stool due to gastrointestinal GVHD, and its augmentation has been found to attenuate GVHD. Here we explored the effect of immunosuppressive drugs on hepatocyte production of AAT and intestinal epithelial gap repair. The effect of commonly used immunosuppressants on AAT production was examined in vitro using HepG2 cells and primary mouse hepatocytes, and their impact on human intestinal epithelial cell line gap repair was evaluated. Sera from 12 allogeneic HSCT recipients, obtained at 14 days post-transplantation, predating the diagnosis of GVHD (n = 6), were examined for reepithelialization, with added clinical-grade AAT. Rapamycin compromised AAT production under inflammatory conditions. Mycophenolate mofetil and cyclosporine A (CSA) inhibited reepithelialization; AAT minimized the effect of CSA. Patient sera displayed superior gap repair with exogenous AAT. Functional insufficiency in circulating AAT may be the result of drug toxicities leading to ineffective gut reepithelization and compromised gut lining. Taken together, our data strengthen the rationale for incorporating AAT augmentation therapy into immunosuppressive treatment protocols.

Antibody-Mediated Inhibition of Insulin-Degrading Enzyme Improves Insulin Activity in a Diabetic Mouse Model.

Diabetes is a metabolic disease that may lead to different life-threatening complications. While insulin constitutes a beneficial treatment, its use may be limited due to increased degradation and an increase in side effects such as weight gain and hypoglycemia. Small molecule inhibitors to insulin-degrading enzyme (IDE) have been previously suggested as a potential treatment for diabetes through their ability to reduce insulin degradation and thus increase insulin activity. Nevertheless, their tendency to bind to the zinc ion in the catalytic site of IDE may affect other important metalloproteases and limit their clinical use. Here, we describe the isolation of an IDE-specific antibody that specifically inhibits insulin degradation by IDE. Using phage display, we generated a human IDE-specific antibody that binds human and mouse IDE with high affinity and specificity and can differentiate between active IDE to a mutated IDE with reduced catalytic activity in the range of 30 nM. We further assessed the ability of that IDE-inhibiting antibody to improve insulin activity in vivo in an STZ-induced diabetes mouse model. Since human antibodies may stimulate the mouse immune response to generate anti-human antibodies, we reformatted our inhibitory antibody to a "reverse chimeric" antibody that maintained the ability to inhibit IDE in vitro, but consisted of mouse constant regions, for reduced immunogenicity. We discovered that one intraperitoneal (IP) administration of the IDE-specific antibody in STZ-induced diabetic mice improved insulin activity in an insulin tolerance test (ITT) assay and reduced blood glucose levels. Our results suggest that antibody-mediated inhibition of IDE may be beneficial on improving insulin activity in a diabetic environment.