Nanovaccines Displaying the Influenza Virus Hemagglutinin in an Inverted Orientation Elicit an Enhanced Stalk-Directed Antibody Response.

Despite the availability of licensed vaccines, influenza causes considerable morbidity and mortality worldwide. Current influenza vaccines elicit an immune response that primarily targets the head domain of the viral glycoprotein hemagglutinin (HA). Influenza viruses, however, readily evade this response by acquiring mutations in the head domain. While vaccines that target the more conserved HA stalk may circumvent this problem, low levels of antistalk antibodies are elicited by vaccination, possibly due to the poor accessibility of the stalk domain to B cell receptors. In this work, it is demonstrated that nanoparticles presenting HA in an inverted orientation generate tenfold higher antistalk antibody titers after a prime immunization and fivefold higher antistalk titers after a boost than nanoparticles displaying HA in its regular orientation. Moreover, nanoparticles presenting HA in an inverted orientation elicit a broader antistalk response that reduces mouse weight loss and improves survival after challenge to a greater extent than nanoparticles displaying HA in a regular orientation. Refocusing the antibody response toward conserved epitopes by controlling antigen orientation may enable the design of broadly protective nanovaccines targeting influenza viruses and other pathogens with pandemic potential.

Multivalent S2-based vaccines provide broad protection against SARS-CoV-2 variants of concern and pangolin coronaviruses.

BACKGROUND: The COVID-19 pandemic continues to cause morbidity and mortality worldwide. Most approved COVID-19 vaccines generate a neutralizing antibody response that primarily targets the highly variable receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein. SARS-CoV-2 "variants of concern" have acquired mutations in this domain allowing them to evade vaccine-induced humoral immunity. Recent approaches to improve the breadth of protection beyond SARS-CoV-2 have required the use of mixtures of RBD antigens from different sarbecoviruses. It may therefore be beneficial to develop a vaccine in which the protective immune response targets a more conserved region of the S protein. METHODS: Here we have developed a vaccine based on the conserved S2 subunit of the S protein and optimized the adjuvant and immunization regimen in Syrian hamsters and BALB/c mice. We have characterized the efficacy of the vaccine against SARS-CoV-2 variants and other coronaviruses. FINDINGS: Immunization with S2-based constructs elicited a broadly cross-reactive IgG antibody response that recognized the spike proteins of not only SARS-CoV-2 variants, but also SARS-CoV-1, and the four endemic human coronaviruses. Importantly, immunization reduced virus titers in respiratory tissues in vaccinated animals challenged with SARS-CoV-2 variants B.1.351 (beta), B.1.617.2 (delta), and BA.1 (omicron) as well as a pangolin coronavirus. INTERPRETATION: These results suggest that S2-based constructs can elicit a broadly cross-reactive antibody response resulting in limited virus replication, thus providing a framework for designing vaccines that elicit broad protection against coronaviruses. FUNDING: NIH, Japan Agency for Medical Research and Development, Garry Betty/ V Foundation Chair Fund, and NSF.

Potent neutralization of SARS-CoV-2 including variants of concern by vaccines presenting the receptor-binding domain multivalently from nanoscaffolds.

The persistence of the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has brought to the forefront the need for safe and effective vaccination strategies. In particular, the emergence of several variants with greater infectivity and resistance to current vaccines has motivated the development of a vaccine that elicits a broadly neutralizing immune response against all variants. In this study, we used a nanoparticle-based vaccine platform for the multivalent display of the receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein, the primary target of neutralizing antibodies. Multiple copies of RBD were conjugated to the SpyCatcher-mi3 protein nanoparticle to produce a highly immunogenic nanoparticle-based vaccine. RBD-SpyCatcher-mi3 vaccines elicited broadly cross-reactive antibodies that recognized the spike proteins of not just an early isolate of SARS-CoV-2, but also three SARS-CoV-2 variants of concern as well as SARS-CoV-1. Moreover, immunization elicited high neutralizing antibody titers against an early isolate of SARS-CoV-2 as well as four variants of concern, including the delta variant. These results reveal the potential of RBD-SpyCatcher-mi3 as a broadly protective vaccination strategy.

Multivalent nanoparticle-based vaccines protect hamsters against SARS-CoV-2 after a single immunization.

The COVID-19 pandemic continues to wreak havoc as worldwide SARS-CoV-2 infection, hospitalization, and death rates climb unabated. Effective vaccines remain the most promising approach to counter SARS-CoV-2. Yet, while promising results are emerging from COVID-19 vaccine trials, the need for multiple doses and the challenges associated with the widespread distribution and administration of vaccines remain concerns. Here, we engineered the coat protein of the MS2 bacteriophage and generated nanoparticles displaying multiple copies of the SARS-CoV-2 spike (S) protein. The use of these nanoparticles as vaccines generated high neutralizing antibody titers and protected Syrian hamsters from a challenge with SARS-CoV-2 after a single immunization with no infectious virus detected in the lungs. This nanoparticle-based vaccine platform thus provides protection after a single immunization and may be broadly applicable for protecting against SARS-CoV-2 and future pathogens with pandemic potential.

The Design of Vaccines Based on the Shielding of Antigenic Site Ø of a Respiratory Syncytial Virus Fusion Protein Immunogen.

Respiratory syncytial virus (RSV), for which there is currently no licensed vaccine, displays a fusion (F) protein that is considered a vaccine target. This protein has an antigenic site called site Ø, which has been shown to elicit potent, neutralizing antibodies and has therefore been considered important in the formulation of RSV vaccines. However, this site is also the least conserved region on the F protein across RSV subtypes. Therefore, directing the immune response away from site Ø and refocusing it toward more conserved parts of the RSV F protein might serve to better elicit broadly neutralizing antibodies. To demonstrate that directing the immune response away from site Ø is a viable approach, a prefusion F-based vaccine based on an F protein with a shielded site Ø is generated. Sera from mice immunized with multivalent scaffolds presenting this immunogen is capable of neutralizing RSV of both subtypes. This result may have application in the development of an effective and broadly protective RSV vaccine.