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The emergence and global spread of the SARS-CoV-2 Omicron variants, which carry an unprecedented number of mutations, raise serious concerns due to the reduced efficacy of current vaccines and resistance to therapeutic antibodies. Here, we report the generation and characterization of two potent human monoclonal antibodies, NA8 and NE12, against the receptor-binding domain of the SARS-CoV-2 spike protein. NA8 interacts with a highly conserved region and has a breadth of neutralization with picomolar potency against the Beta variant and the Omicron BA.1 and BA.2 sublineages and nanomolar potency against BA.2.12.1 and BA.4. Combination of NA8 and NE12 retains potent neutralizing activity against the major SARS-CoV-2 variants of concern. Cryo-EM analysis provides the structural basis for the broad and complementary neutralizing activity of these two antibodies. We confirm the in vivo protective and therapeutic efficacies of NA8 and NE12 in the hamster model. These results show that broad and potent human antibodies can overcome the continuous immune escape of evolving SARS-CoV-2 variants. [Display omitted] • Monoclonal antibodies are isolated from COVID-19 convalescent patients • NA8 and NE12 potently neutralize newly emerging SARS-CoV-2 variants of concern • Structural analysis reveals a unique conserved binding epitope for NA8 • NA8 and NE12 show prophylactic and therapeutic efficacy in the Syrian hamster model The emergence of new SARS-CoV-2 variants that escape neutralization can jeopardize the efficacy of vaccines and therapeutic antibodies. Chen et al. report the isolation of potent human antibodies that neutralize emerging variants of concern, including various Omicron sublineages. These antibodies show prophylactic and therapeutic efficacy in the hamster model. [ABSTRACT FROM AUTHOR]

Abstract: Infection of rabbits with aerosolized rabbitpox virus (RPXV) produces a disease similar to monkeypox and smallpox in humans and provides a valuable, informative model system to test medical countermeasures against orthopoxviruses. Due to the eradication of smallpox, the evaluation of the efficacy of new-generation smallpox vaccines depends on relevant well-developed animal studies for vaccine licensure. In this study, we tested the efficacy of IMVAMUNE® [modified vaccinia Ankara-Bavarian Nordic (MVA-BN®)] for protecting rabbits against aerosolized RPXV. Rabbits were vaccinated with either phosphate-buffered saline (PBS), Dryvax®, a single low dose of IMVAMUNE®, a single high dose of IMVAMUNE®, or twice with a high dose of IMVAMUNE®. Aerosol challenge with a lethal dose of RPXV was performed 4 weeks after the last vaccination. All PBS control animals succumbed to the disease or were euthanized because of the disease within 7 days postexposure. The rabbits vaccinated with Dryvax®, a low dose of IMVAMUNE®, or a single high dose of IMVAMUNE® showed minimal to moderate clinical signs of the disease, but all survived the challenge. The only clinical sign displayed by rabbits that had been vaccinated twice with a high dose of IMVAMUNE® was mild transient anorexia in just two out of eight rabbits. This study shows that IMVAMUNE® can be a very effective vaccine against aerosolized RPXV. [Copyright &y& Elsevier]

Abstract: There is little known concerning the disease caused by Zaire ebolavirus (ZEBOV) when inhaled, the likely route of exposure in a biological attack. Cynomolgus macaques, rhesus macaques, and African green monkeys were exposed to aerosolized ZEBOV to determine which species might be the most relevant model of the human disease. A petechial rash was noted on cynomolgus and rhesus macaques after fever onset but not on African green monkeys. Fever duration was shortest in rhesus macaques (62.7±16.3 h) and longest in cynomolgus macaques (82.7±22.3h) and African green monkeys (88.4±16.7h). Virus was first detectable in the blood 3 days after challenge; the level of viremia was comparable among all three species. Hematological changes were noted in all three species, including decreases in lymphocyte and platelet counts. Increased blood coagulation times were most pronounced in African green monkeys. Clinical signs and time to death in all three species were comparable to what has been reported previously for each species after parenteral inoculation with ZEBOV. These data will be useful in selection of an animal model for efficacy studies. [Copyright &y& Elsevier]