Summary paragraph Influenza vaccines that confer broad and durable protection against diverse virus strains would have a major impact on global health 1 . Here we show that computationally designed, two-component nanoparticle immunogens 2 induce potently neutralizing and broadly protective antibody responses against a wide variety of influenza viruses. The nanoparticle immunogens display 20 hemagglutinin (HA) trimers in an ordered array, and their assembly in vitro enables precisely controlled co-display of multiple distinct HAs in defined ratios. Nanoparticle immunogens co-displaying the four HAs of licensed quadrivalent influenza vaccines (QIV) elicited antibody responses against vaccine-matched strains that were equivalent or superior to commercial QIV, and simultaneously induced broadly protective antibody responses to heterologous viruses by targeting the subdominant yet conserved HA stem. The combination of potent receptor-blocking and cross-reactive stem-directed antibodies induced by the nanoparticle immunogens make them attractive candidates for a supraseasonal influenza vaccine candidates with potential to replace conventional seasonal vaccines 3 .

Humoral immunity to SARS-CoV-2 can be supplemented with polyclonal sera from convalescent donors or an engineered monoclonal antibody (mAb) product. While pentameric IgM antibodies are responsible for much of convalescent sera’s neutralizing capacity, all available mAbs are based on the monomeric IgG antibody subtype. We now show that IgM mAbs derived from immune memory B cell receptors are potent neutralizers of SARS-CoV-2. IgM mAbs outperformed clonally identical IgG antibodies across a range of affinities and SARS-CoV-2 receptor-binding domain epitopes. Strikingly, efficacy against SARS-CoV-2 viral variants was retained for IgM but not for clonally identical IgG. To investigate the biological role for IgM memory in SARS-CoV-2, we also generated IgM mAbs from antigen-experienced IgM+ memory B cells in convalescent donors, identifying a potent neutralizing antibody. Our results highlight the therapeutic potential of IgM mAbs and inform our understanding of the role for IgM memory against a rapidly mutating pathogen.

Influenza vaccines that confer broad and durable protection against diverse virus strains would have a major impact on global health. However, next-generation vaccine design efforts have been complicated by challenges including the genetic plasticity of the virus and the immunodominance of certain epitopes in its glycoprotein antigens. Here we show that computationally designed, two-component nanoparticle immunogens induce potently neutralizing and broadly protective antibody responses against a wide variety of influenza viruses. The nanoparticle immunogens display 20 hemagglutinin (HA) trimers in a highly immunogenic array, and their assembly in vitro enables precisely controlled co-display of multiple distinct HAs in defined ratios. Nanoparticle immunogens displaying the four HAs of licensed quadrivalent influenza vaccines (QIV) elicited hemagglutination inhibition and neutralizing antibody responses to vaccine-matched strains that were equivalent or superior to commercial QIV in mice, ferrets, and nonhuman primates. The nanoparticle immunogens—but not QIV—simultaneously induced broadly protective antibody responses to heterologous viruses, including H5N1 and H7N9, by targeting the subdominant yet conserved HA stem. Unlike previously reported influenza vaccine candidates, our nanoparticle immunogens can alter the intrinsic immunodominance hierarchy of HA to induce both potent receptor-blocking and broadly cross-reactive stem-directed antibody responses and are attractive candidates for a next-generation influenza vaccine that could replace current seasonal vaccines.One Sentence SummaryNanoparticle immunogens displaying four seasonal influenza hemagglutinins elicit neutralizing antibodies directed at both the immunodominant head and the conserved stem and confer broad protective immunity.

Hydrogen/deuterium exchange with mass spectrometry (HDX-MS) is capable of providing unique insight into complex biological systems that are difficult to study by other techniques. Due to arduous sample handling requirements, automating HDX experimentation for higher throughput requires specialized equipment. While recent advances have enabled automation of sample preparation and analysis, several proteins of interest and types of HDX experiments remain incompatible with automated workflows and require manual sample preparation that greatly limits experimental throughput. To expand throughput and increase the precision of HDX-MS for systems requiring manual preparation, we have developed an inexpensive autosampler capable of thawing and injecting frozen HDX-MS samples in a highly reproducible manner.