A bispecific monomeric nanobody induces spike trimer dimers and neutralizes SARS-CoV-2 in vivo

Antibodies binding to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike have therapeutic promise, but emerging variants show the potential for virus escape. This emphasizes the need for therapeutic molecules with distinct and novel neutralization mechanisms. Here we describe the isolation of a nanobody that interacts simultaneously with two RBDs from different spike trimers of SARS-CoV-2, rapidly inducing the formation of spike trimer–dimers leading to the loss of their ability to attach to the host cell receptor, ACE2. We show that this nanobody potently neutralizes SARS-CoV-2, including the beta and delta variants, and cross-neutralizes SARS-CoV. Furthermore, we demonstrate the therapeutic potential of the nanobody against SARS-CoV-2 and the beta variant in a human ACE2 transgenic mouse model. This naturally elicited bispecific monomeric nanobody establishes an uncommon strategy for potent inactivation of viral antigens and represents a promising antiviral against emerging SARS-CoV-2 variants.

TB-3 miR-33a depletion accelerate medulloblastoma generation and invasion

Background and purposes: Lipid metabolism have been shown to be associated with tumorigenicity in various malignancies. The purpose of this study was to investigate the association of miR-33, a key regulator of lipid metabolism, in tumorigenicity and progression of medulloblastoma. Methods: Incidence of medulloblastoma and histopathological findings were compared between ptch1+/- mice and ptch1+/- miR-33a-/- mice. Tumors extracted from these mice were transplanted subcutaneously in nude mice (n=14 for ptch1+/-, n=19 for ptch1+/- miR-33a-/-) and in C57BL/6 mice (n=12 for each). Gene expression profile was compared between tumors from ptch1+/- mice and those from ptch1+/- miR-33a-/- mice. Results: Knockout of miR-33a in ptch1+/- transgenic mouse model increased the incidence of spontaneous generation of medulloblastoma from 34.5% to 84.0% (p< 0.001) at 12 months. Histopathological analysis showed infiltrative tumor borders in ptch1+/- miR-33a-/- tumors as compared with ptch1+/- ones. Tumor formation was observed in 21.4% for ptch1+/- tumors and 68.4% for ptch1+/- miR-33a-/- tumors in nude mice (p= 0.008). It was observed in 0% and 16.7% in immune competent mice. RNA sequencing detected that SCD1 and SREBF1 was upregulated in tumors from miR-33a knockout mice. Discussion: Our results demonstrated that depletion of miR-33a accelerated medulloblastoma generation and invasion. miR-33a may also be important for immune evasion. SCD1, which is reported to play a role in tumor stem cell maintenance and metastasis, can be a potential therapeutic target for medulloblastoma.

Biologic TNF-α inhibitors reduce microgliosis, neuronal loss, and tau phosphorylation in a transgenic mouse model of tauopathy

Background Tumor necrosis factor-α (TNF-α) plays a central role in Alzheimer’s disease (AD) pathology, making biologic TNF-α inhibitors (TNFIs), including etanercept, viable therapeutics for AD. The protective effects of biologic TNFIs on AD hallmark pathology (Aβ deposition and tau pathology) have been demonstrated. However, the effects of biologic TNFIs on Aβ-independent tau pathology have not been reported. Existing biologic TNFIs do not cross the blood–brain barrier (BBB), therefore we engineered a BBB-penetrating biologic TNFI by fusing the extracellular domain of the type-II human TNF-α receptor (TNFR) to a transferrin receptor antibody (TfRMAb) that ferries the TNFR into the brain via receptor-mediated transcytosis. The present study aimed to investigate the effects of TfRMAb-TNFR (BBB-penetrating TNFI) and etanercept (non-BBB-penetrating TNFI) in the PS19 transgenic mouse model of tauopathy. Methods Six-month-old male and female PS19 mice were injected intraperitoneally with saline (n = 12), TfRMAb-TNFR (1.75 mg/kg, n = 10) or etanercept (0.875 mg/kg, equimolar dose of TNFR, n = 10) 3 days/week for 8 weeks. Age-matched littermate wild-type mice served as additional controls. Blood was collected at baseline and 8 weeks for a complete blood count. Locomotion hyperactivity was assessed by the open-field paradigm. Brains were examined for phosphorylated tau lesions (Ser202, Thr205), microgliosis, and neuronal health. The plasma pharmacokinetics were evaluated following a single intraperitoneal injection of 0.875 mg/kg etanercept or 1.75 mg/kg TfRMAb-TNFR or 1.75 mg/kg chronic TfRMAb-TNFR dosing for 4 weeks. Results Etanercept significantly reduced phosphorylated tau and microgliosis in the PS19 mouse brains of both sexes, while TfRMAb-TNFR significantly reduced these parameters in the female PS19 mice. Both TfRMAb-TNFR and etanercept treatment improved neuronal health by significantly increasing PSD95 expression and attenuating hippocampal neuron loss in the PS19 mice. The locomotion hyperactivity in the male PS19 mice was suppressed by chronic etanercept treatment. Equimolar dosing resulted in eightfold lower plasma exposure of the TfRMAb-TNFR compared with etanercept. The hematological profiles remained largely stable following chronic biologic TNFI dosing except for a significant increase in platelets with etanercept. Conclusion Both TfRMAb-TNFR (BBB-penetrating) and non-BBB-penetrating (etanercept) biologic TNFIs showed therapeutic effects in the PS19 mouse model of tauopathy.