Neutralizing antibodies have been designed to specifically target and bind to the receptor binding domain (RBD) of spike (S) protein to block severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus from attaching to angiotensin converting enzyme 2 (ACE2). This study reports a distinctive nanobody, designated as VHH21, that directly catalyzes the S-trimer into an irreversible transition state through postfusion conformational changes. Derived from camels immunized with multiple antigens, a set of nanobodies with high affinity for the S1 protein displays abilities to neutralize pseudovirion infections with a broad resistance to variants of concern of SARS-CoV-2, including SARS-CoV and BatRaTG13. Importantly, a super-resolution screening and analysis platform based on visual fluorescence probes was designed and applied to monitor single proteins and protein subunits. A spontaneously occurring dimeric form of VHH21 was obtained to rapidly destroy the S-trimer. Structural analysis via cryogenic electron microscopy revealed that VHH21 targets specific conserved epitopes on the S protein, distinct from the ACE2 binding site on the RBD, which destabilizes the fusion process. This research highlights the potential of VHH21 as an abzyme-like nanobody (nanoabzyme) possessing broad-spectrum binding capabilities and highly effective anti-viral properties and offers a promising strategy for combating coronavirus outbreaks.
Single-Domain Antibodies/immunology* ; Spike Glycoprotein, Coronavirus/metabolism* ; SARS-CoV-2/immunology* ; Animals ; Humans ; Antibodies, Neutralizing/immunology* ; Camelus ; COVID-19/immunology* ; Antibodies, Viral/immunology* ; Angiotensin-Converting Enzyme 2

In order to study the effects and the possible mechanisms of Daxx overexpressed in HepG2 to hydrogen peroxide treatment, and to search new targets for cancer chemotherapy, HepG2cells were transfected using lipofectamine 2000, and selected by treatment with G418. Stable cell lines were confirmed by reverse transeriptase polymerase chain reaction (RT-PCR) targeting vector gene. Experiments include the following groups: (1) control group (non-transfected cells); (2) transfected with empty vector (HepG2/GFP cells); and (3) transfected with pEGFP-C1-Daxx (HepG2/GFP-Daxx cells). After incubation with hydrogen peroxide (H2O2) for 24 h, cellular viability was analyzed by MTT, and cellular apoptosis was measured by flow cytometric analysis. Gene expression at protein level was detected by Western blot. The RT-PCR results showed that Daxx RNA in cells transfected with pEGFP-C1-Daxx was increased significantly compared with that in the HepG2/GFP cells. Fluorescence microscopy revealed that Daxx protein was localized in the nuclei. Hydrogen peroxide was used to induce apoptosis of HepG2 cells and observed that the hydrogen peroxide decreased the viability of HepG2 cells in concentration-dependent pattern. The IC50 values in three groups (Normal cells, HepG2/GFP cells and HepG2/GFP-Daxx cells) were 0.72, 0.76, and 0.49 mmol/L respectively. The apoptotic ratio was significantly higher in HepG2/GFP-Daxx cells as compared to the other two groups. HepG2/GFP-Daxx cell incubated with hydrogen peroxide, showed a significant increase in the activation of caspase-3 and JNK as compare with the other groups. Over-expression of Daxx facilitated HepG2 cells apoptosis induced by hydrogen peroxide. Furthermore, there may be a synergetic relation with apoptosis and increase of JNK activity.

AIM: To determine the effect of promoting cellular cholesterol efflux on the apoptosis of foam cells derived from monocytes. METHODS: RAW264.7 cells were incubated with 50 mg/L ox-LDL as a foam cell mode. The apoptosis rate of RAW264.7 cells was assayed by flow cytometry. Cellular lipid droplet was assayed by oil red staining. The rate of cellular cholesterol efflux was assayed with [~3H] label cholesterol, and the content of cellular cholesterol were assayed by high performance liquid chromatography. RESULTS: After incubation with 50 mg/L ox-LDL for 48 h, the content of cellular cholesterol ester increased from (6.8?3.6) mg/g to (101.7?4.5) mg/g (P