A recent article published in the bioRxiv * prepress server identified numerous effective antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from convalescent patients with SARS-CoV-2.
Study: Fc-modified SARS-CoV-2 neutralizing antibodies with therapeutic effects in two animal models. Image credit: NIAID
Fund
The SARS-CoV-2 pandemic continues through consecutive emerging viral variants. Several 2019 coronavirus disease vaccines (COVID-19) have been established focusing on the initial strains of Wuhan SARS-CoV-2. Fortunately, they have been effective against viral strains aroused later.
The number of SARS-CoV-2 infections declined in certain nations, perhaps as a result of the effectiveness of vaccination. However, the global pandemic of COVID-19 has not yet been contained.
Antiviral therapy is effective during the SARS-CoV-2 replication stage, which occurs in the early stages of infection. Similarly, the use of therapeutic neutralizing antibodies against COVID-19 has been significantly effective. Unfortunately, there are few beneficial antibodies to combat the evolution of SARS-CoV-2 strains.
About the study
In the present research, the scientists developed multiple monoclonal antibodies from convalescent patients with SARS-CoV-2. Since the onset of the SARS-CoV-2 epidemic in March 2020 in Japan, the authors have collected peripheral blood samples from patients with recovering COVID-19, which have been used to generate neutralizing antibodies.
The researchers obtained blood samples from patients with SARS-CoV-2 discharged from Keio University Hospital. The SARS-CoV-2 cell-based angiotensin-converting enzyme 2 (ACE2) enzyme was used to evaluate the neutralizing capacity of the sera. The team selected 12 patients who exhibited outstanding neutralizing concentrations for antibody generation.
The authors profiled patient-derived antibodies by 1) evaluating S-ACE2 inhibition and 2) associating the ability of these antibodies to adhere to S-expressing cells and their potential. to hinder ACE2 adhesion to S-expressing cells. To further analyze these antibodies, they also investigated the neutralizing potential using a cell fusion experiment. The researchers performed a final microneutralization screening to verify that the chosen antibodies could neutralize the true SARS-CoV-2.
To identify more potential antibodies, the scientists evaluated the affinity for the SARS-CoV-2 receptor binding domain (RBD) antigen and analyzed the overlap of epitopes. They chose five antibodies and used a pseudovirus that housed the S protein from the original SARS-CoV-2 Wuhan sequence and four significant variants to conduct a neutralization experiment before worrying variants (VOCs) emerged. After the appearance of VOCs, they tested the ability of antibodies to neutralize the original WK-521 virus and its variants, including Beta, Alpha, Gamma, Kappa, Delta, and Omicron BA.2 and BA.1.
The team performed cryoelectron microscopy (cryo-MS) research to obtain a structural understanding of the SARS-CoV-2 antibody and S protein. The discovered antibodies currently used in the in vivo investigation possessed the N297A mutation in the crystallizable region of the G1 (IgG1) (Fc) immunoglobulin fragment to prevent antibody-dependent enhancement (ADE). In addition, the N297A mutation decreases adhesion to the Fc receptor. The researchers then examined the effects of these antibodies on two animal models (a cynomolgus macaque model and a hamster model) to see the impact of these antibodies in in vivo environments.
Cryo-MS structure of neutralizing antibodies (A) The structures of RBD and Ab159, Ab188, Ab326, Ab354, Ab445 and Ab496 are shown. Only the variable domains of the antibodies are modeled and drawn as a cartoon tube (individual color) on the RBD surface (gray), and the epitope of each antibody has the same color as each antibody. The red area of central RBD is the ACE2 binding residue (7A94) (Benton et al., 2020), which shows the relationship between antibody binding sites, which are roughly divided into three groups. Key amino acid positions are indicated by black arrows. (B) Spike residues 400-506 are shown.
Results
The researchers found 494 antibodies from people recovered from COVID-19, most showing a SARS-CoV-2 neutralizing ability identical to the antibodies used clinically in the neutralization assessment. Initially, antigen-specific memory B cells and non-antigen-specific plasma cells were used to create antibodies. However, the former harbored superior antibodies, emphasizing the importance of choosing B cells for antigen. Data from the authentic endpoint viral neutralization assay confirmed the findings of the S-ACE2 inhibition and cell fusion assays that detected neutralizing antibodies.
Cryo-EM inhibition experiments and S-ACE2 cell-based mutants identified S protein epitopes as antibodies were selected by competing with ACE2, classifying antibody adhesion to S as a class. 1/2. Insertion of N297 into IgG1-Fc was one of the characteristics of the antibodies discovered in this study. This mutation almost eradicated adhesion to Fc receptors. In fact, it stopped the Fc-facilitated absorption of the virus into Raji cells.
The selected antibodies were comparable or better than imdevimab, a COVID-19 therapeutic agent, in the Wuhan strain neutralization tests and VOCs using authentic viruses and pseudoviruses. As for the in vivo activity of these antibodies, they showed potency for therapeutic use in macaque and hamster models. At doses between 5 and 7 mg / kg, current antibodies showed therapeutic efficacy in hamsters and macaques without causing an increase in viral uptake by ADE.
Conclusions
Overall, in the current study, the authors generated many antibodies from the B cells of convalescent patients with COVID-19 infected with the SARS-CoV-2 D614G mutant or Wuhan strain. In addition, they identified numerous neutralizing antibodies with potent neutralizing properties of anti-SARS-CoV-2 variant strains.
These Fc-modified neutralizing antibodies from individuals recovered by SARS-CoV-2 had neutralizing properties comparable to the clinical antibodies to COVID-19. The efficacy of these antibodies was illustrated by investigating infections with macaque and hamster models in vivo and authentic virus and pseudovirus neutralization assays in vitro. These findings demonstrated that the antibodies currently discovered had adequate antiviral activity to serve as COVID-19 treatment options.
* Important news
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and therefore should not be considered conclusive, guided by clinical practice / health-related behavior, or treated as established information.
Magazine reference:
- Fc-modified SARS-CoV-2 neutralizing antibodies with therapeutic effects in two animal models; Masaru Takeshita, Hidehiro Fukuyama, Katsuhiko Kamada, Takehisa Matsumoto, Chieko Makino-Okamura, Tomomi Uchikubo-Kamo, Yuri Tomabechi, Kazuharu Hanada, Saya Moriyama Takahashi, Hirohito Ishigaki, Misako Nakayama, Cong Thanh Yguus Im, Ih Mas , Tadashi Maemura, Yuri Furusawa, Hiroshi Ueki, Kiyoko Iwatsuki-Horimoto, Mutsumi Ito, Seiya Yamayoshi Yoshirouki, Seiya Yamayoshi,, Yasushi Kondo, Yuko Kaneko, Katsuya Suzuki, Koichi Fukunaga, Tsutomu Takeuchi BioRxI DO: