RESUMEN
Accumulating mutations in the SARS-CoV-2 Spike (S) protein can increase the possibility of immune escape, challenging the present COVID-19 prophylaxis and clinical interventions. Here, 3 receptor binding domain (RBD) specific monoclonal antibodies (mAbs), 58G6, 510A5 and 13G9, with high neutralizing potency blocking authentic SARS-CoV-2 virus displayed remarkable efficacy against authentic B.1.351 virus. Each of these 3 mAbs in combination with one neutralizing Ab recognizing non-competing epitope exhibited synergistic effect against authentic SARS-CoV-2 virus. Surprisingly, structural analysis revealed that 58G6 and 13G9, encoded by the IGHV1-58 and the IGKV3-20 germline genes, both recognized the steric region S470-495 on the RBD, overlapping the E484K mutation presented in B.1.351. Also, 58G6 directly bound to another region S450-458 in the RBD. Significantly, 58G6 and 510A5 both demonstrated prophylactic efficacy against authentic SARS-CoV-2 and B.1.351 viruses in the transgenic mice expressing human ACE2 (hACE2), protecting weight loss and reducing virus loads. These 2 ultrapotent neutralizing Abs can be promising candidates to fulfill the urgent needs for the prolonged COVID-19 pandemic.
RESUMEN
The spread of SARS-CoV-2 confers a serious threat to the public health without effective intervention strategies1-3. Its variant carrying mutated Spike (S) protein D614G (SD614G) has become the most prevalent form in the current global pandemic4,5. We have identified a large panel of potential neutralizing antibodies (NAbs) targeting the receptor-binding domain (RBD) of SARS-CoV-2 S6. Here, we focused on the top 20 potential NAbs for the mechanism study. Of them, the top 4 NAbs could individually neutralize both authentic SARS-CoV-2 and SD614G pseudovirus efficiently. Our epitope mapping revealed that 16/20 potent NAbs overlapped the same steric epitope. Excitingly, we found that one of these potent NAbs (58G6) exclusively bound to a linear epitope on S-RBD (termed as 58G6e), and the interaction of 58G6e and the recombinant ACE2 could be blocked by 58G6. We confirmed that 58G6e represented a key site of vulnerability on S-RBD and it could positively react with COVID-19 convalescent patients plasma. We are the first, as far as we know, to provide direct evidences of a linear epitope that can be recognized by a potent NAb against SARS-CoV-2 S-RBD. This study paves the way for the applications of these NAbs and the potential safe and effective vaccine design.
RESUMEN
Neutralizing antibodies (Abs) have been considered as promising therapeutics for the prevention and treatment of pathogens. After the outbreak of COVID-19, potent neutralizing Abs to SARS-CoV-2 were promptly developed, and a few of those neutralizing Abs are being tested in clinical studies. However, there were few methodologies detailly reported on how to rapidly and efficiently generate neutralizing Abs of interest. Here, we present a strategically optimized method for precisive screening of neutralizing monoclonal antibodies (mAbs), which enabled us to identify SARS-CoV-2 receptor-binding domain (RBD) specific Abs within 4 days, followed by another 2 days for neutralization activity evaluation. By applying the screening system, we obtained 198 Abs against the RBD of SARS-CoV-2. Excitingly, we found that approximately 50% (96/198) of them were candidate neutralizing Abs in a preliminary screening of SARS-CoV-2 pseudovirus and 20 of these 96 neutralizing Abs were confirmed with high potency. Furthermore, 2 mAbs with the highest neutralizing potency were identified to block authentic SARS-CoV-2 with the half-maximal inhibitory concentration (IC50) at concentrations of 9.88 ng/ml and 11.13 ng/ml. In this report, we demonstrated that the optimized neutralizing Abs screening system is useful for the rapid and efficient discovery of potent neutralizing Abs against SARS-CoV-2. Our study provides a methodology for the generation of preventive and therapeutic antibody drugs for emerging infectious diseases.
RESUMEN
Objective@#To construct the recombinant adenoviral containing fructose 1, 6-biphosphatase 1 (FBP1), and to investigate whether FBP1 has effect on autophagy and proliferation in liver cancer cells (HepG2).@*Methods@#FBP1 cDNA sequence was amplified by PCR and cloned in adenovirus vector pAdTrack-TO4, and then recombinant adenovirus plasmid pAdTrack-FBP1 was constructed. The recombinant adenovirus plasmid was transfected into HEK293 cells by Lipofectamine 3000. High-titer of recombinant adenovirus AdFBP1 was obtained by packaging and amplification. HepG2 cells were infected with recombinant adenovirus AdFBP1, and the Mock and AdGFP group were set at the same time. Western blot and confocal laser scanning microscopy were used to observe the effect of FBP1 on the level of autophagy in hepatocellular carcinoma cells, and the effect of FBP1on the proliferation was observed by MTS and colony formation assay. A t-test and one-way ANOVA were used to compare the mean between group.@*Results@#A high-titer recombinant adenovirus FBP1 was successfully constructed. Western blot and confocal laser scanning microscopy showed that the level of autophagy in AdFBP1 group was significantly lower than that in AdGFP group. Western blot results showed that LC3-II protein expression level in AdGFP was 1.10 ± 0.10 and 0.30 ± 0.01 in AdFBP1 group, F = 90.36, P < 0.01. Confocal laser scanning microscopy analysis showed that the average number of autophages in AdGFP was 28.33 ± 1.53 and 12.33 ± 1.53 in AdFBP1group, F = 97.40, P < 0.01. In addition, the results of colony formation assay and MTS assay showed that the proliferation of liver cancer cells in the AdFBP1 group was significantly inhibited compared with the AdGFP group. The results of colony formation showed that the cell clones in the AdGFP group was 65.66 ± 2.57 and 34.00 ± 2.00 in AdFBP1 group, F = 141.50, P < 0.01. MTS results showed that the absorbance of AdGFP group at 96h was 39.13 ± 2.21 and 30.61 ± 3.33 in AdFBP1 group, F = 7.80, P < 0.05.@*Conclusion@#FBP1 inhibited the autophagy and proliferation in liver cancer cells (HepG2).