RESUMO
The novel SARS-CoV-2 variant, Omicron (B.1.1.529) contains an unusually high number of mutations (>30) in the spike protein, raising concerns of escape from vaccines, convalescent sera and therapeutic drugs. Here we analyze the alteration of neutralizing titer with Omicron pseudovirus. Sera obtained 3 months after double BNT162b2 vaccination exhibit approximately 18-fold lower neutralization titers against Omicron than parental virus. Convalescent sera from Alpha and Delta patients allow similar levels of breakthrough by Omicron. Domain-wise analysis using chimeric spike revealed that this efficient evasion was primarily achieved by mutations clustered in the receptor-binding domain, but that multiple mutations in the N-terminal domain contributed as well. Omicron escapes a therapeutic cocktail of imdevimab and casirivimab, whereas sotrovimab, which targets a conserved region to avoid viral mutation, remains effective. The ACE2 decoy is another virus-neutralizing drug modality that is free, at least in theory, from complete escape. Deep mutational analysis demonstrated that, indeed, engineered ACE2 prevented escape for each single-residue mutation in the receptor-binding domain, similar to immunized sera. Engineered ACE2 neutralized Omicron comparable to Wuhan and also showed a therapeutic effect against Omicron infection in hamsters and human ACE2 transgenic mice. Like previous SARS-CoV-2 variants, some sarbecoviruses showed high sensitivity against engineered ACE2, confirming the therapeutic value against diverse variants, including those that are yet to emerge. One Sentence SummaryOmicron, carrying [~]30 mutations in the spike, exhibits effective immune evasion but remains highly susceptible to blockade by engineered ACE2.
RESUMO
The novel SARS-CoV-2 variant, Omicron (B.1.1.529) contains about 30 mutations in the spike protein and the numerous mutations raise the concern of escape from vaccine, convalescent sera and therapeutic drugs. Here we analyze the alteration of their neutralizing titer with Omicron pseudovirus. Sera of 3 months after double BNT162b2 vaccination exhibite [~]27-fold lower neutralization titers against Omicron than D614G mutation. Neutralization titer is also reduced in convalescent sera from Alpha and Delta patients. However, some Delta patients have relatively preserved neutralization activity up to the level of 3-month double BNT162b2 vaccination. Omicron escapes from the cocktail of imdevimab and casirivimab, whereas sotrovimab that targets the conserved region to prevent viral escape is effective to Omicron similarly to the original SARS-CoV-2. The ACE2 decoy is another modality that neutralize the virus independently of mutational escape and Omicron is also sensitive to the engineered ACE2.
RESUMO
The SARS-CoV-2 spike protein binds to the human angiotensin-converting enzyme 2 (ACE2) receptor via receptor binding domain (RBD) to enter into the cell and inhibiting this interaction is a main approach to inhibit SARS-CoV-2 infection. We engineered ACE2 to enhance the affinity with directed evolution in 293T cells. Three cycles of random mutation and cell sorting achieved 100-fold higher affinity to RBD than wild-type ACE2. The extracellular domain of modified ACE2 fused to the human IgG1-Fc region had stable structure and neutralized SARS-CoV-2 without the emergence of mutational escape. Therapeutic administration protected hamsters from SARS-CoV-2 infection, decreasing lung virus titers and pathology. Engineering ACE2 decoy receptors with human cell-based directed evolution is a promising approach to develop a SARS-CoV-2 neutralizing drug that has affinity comparable to monoclonal antibodies yet displaying resistance to escape mutations of virus. One Sentence SummaryEngineered ACE2 decoy receptor has a therapeutic potential against COVID-19 without viral escape mutation.
