Universal Dengue Vaccine Elicits Neutralizing Antibodies against Strains from All Four Dengue Virus Serotypes.

Any potential dengue virus (DENV) vaccine needs to elicit protective immunity against strains from all four serotypes to avoid potential antibody-dependent enhancement (ADE). In this study, four independent DENV envelope (E) glycoproteins were generated using wild-type E sequences from viruses isolated between 1943 and 2006 using computationally optimized broadly reactive antigen (COBRA) methodology. COBRA and wild-type E antigens were expressed on the surface of subvirion viral particles (SVPs). Four separate wild-type E antigens were used for each serotype. Mice vaccinated with wild-type DENV SVPs had anti-E IgG antibodies that neutralized serotype-specific viruses. COBRA DENV SVPs elicited a broader breadth of antibodies that neutralized strains across all four serotypes. Two COBRA DENV vaccine candidates that elicited the broadest breadth of neutralizing antibodies in mice were used to vaccinate rhesus macaques (Macaca mulatta) that either were immunologically naive to any DENV serotype or had preexisting antibodies to DENV. Antibodies elicited by COBRA DENV E immunogens neutralized all 12 strains of DENV in vitro, which was comparable to antibodies elicited by a tetravalent wild-type E SVP vaccination mixture. Therefore, using a single DENV COBRA E protein can elicit neutralizing antibodies against strains representing all four serotypes of DENV in both naive and dengue virus-preimmune populations.IMPORTANCE Dengue virus infects millions of people living in tropical areas of the world. Dengue virus-induced diseases can range from mild to severe with death. An effective vaccine will need to neutralize viruses from all four serotypes of dengue virus without inducing enhanced disease. A dengue virus E vaccine candidate generated by computationally optimized broadly reactive antigen algorithms elicits broadly neutralizing protection for currently circulating strains from all four serotypes regardless of immune status. Most dengue vaccines in development formulate four separate components based on prM-E from a wild-type strain representing each serotype. Designing a monovalent vaccine that elicits protective immunity against all four serotypes is an effective and economical strategy.

Multivalent next generation influenza virus vaccines protect against seasonal and pre-pandemic viruses.

Each year, new influenza virus vaccine formulations are generated to keep up with continuously circulating and mutating viral variants. A next-generation influenza virus vaccine would provide long-lasting, broadly-reactive immune protection against current and future influenza virus strains for both seasonal and pre-pandemic viruses. Next generation immunogens were designed using computationally optimized broadly reactive antigen (COBRA) methodology to protect against a broad range of strains over numerous seasons. Novel HA and NA amino acid sequences were derived from multilayered consensus sequence alignment for multiple subtypes of influenza. This multivalent formulation was hypothesized to elicit broadly protective immune responses against both seasonal and pre-pandemic influenza viruses. Mice were vaccinated with multivalent mixtures of HA and NA (H1, H2, H3, H5, H7, N1, N2) proteins. Multivalent COBRA vaccinations elicited antibodies that recognized a broad panel of strains and vaccinated mice were protected against viruses representing multiple subtypes. This is a promising candidate for a universal influenza vaccine that elicits protective immune responses against seasonal and pre-pandemic strains over multiple seasons.

Discovery and Characterization of a Pan-betacoronavirus S2-binding antibody.

Three coronaviruses have spilled over from animal reservoirs into the human population and caused deadly epidemics or pandemics. The continued emergence of coronaviruses highlights the need for pan-coronavirus interventions for effective pandemic preparedness. Here, using LIBRA-seq, we report a panel of 50 coronavirus antibodies isolated from human B cells. Of these antibodies, 54043-5 was shown to bind the S2 subunit of spike proteins from alpha-, beta-, and deltacoronaviruses. A cryo-EM structure of 54043-5 bound to the pre-fusion S2 subunit of the SARS-CoV-2 spike defined an epitope at the apex of S2 that is highly conserved among betacoronaviruses. Although non-neutralizing, 54043-5 induced Fc-dependent antiviral responses, including ADCC and ADCP. In murine SARS-CoV-2 challenge studies, protection against disease was observed after introduction of Leu234Ala, Leu235Ala, and Pro329Gly (LALA-PG) substitutions in the Fc region of 54043-5. Together, these data provide new insights into the protective mechanisms of non-neutralizing antibodies and define a broadly conserved epitope within the S2 subunit.

Putting the pieces together: Chimeric virus strategy decode Dengue virus 3 antibody responses.

In this issue of Cell Host & Microbe, Munt et al. shed light on variability in human immune responses after natural infection compared to vaccination by using a recombinant virus platform that expresses chimeric Dengue virus type 1 and type 3 envelope proteins to identify and characterize type-specific neutralizing antibodies.

Formulation of dry powders of vaccines containing MF59 or AddaVax by Thin-Film Freeze-Drying: Towards a dry powder universal flu vaccine.

MF59® is an oil-in-water (O/W) nanoemulsion-based vaccine adjuvant that is often used in seasonal and pandemic influenza vaccines. We explored the feasibility of developing dry powders of vaccines adjuvanted with MF59 or AddaVax™, a preclinical grade equivalent of MF59 with the same composition and droplet size as MF59, by thin-film freeze-drying (TFFD). Liquid AddaVax alone was successfully converted to a dry powder by TFFD using trehalose as a stabilizing agent while maintaining the droplet size distribution of AddaVax after it was reconstituted. TFFD was then applied to convert liquid AddaVax-adjuvanted vaccines containing either a model antigen (e.g., ovalbumin) or mono-, bi-, and tri-valent recombinant hemagglutinin (rHA) protein-based H1 and/or H3 (universal) influenza vaccine candidates, as well as the MF59-containing Fluad® Quadrivalent influenza vaccine to dry powders. Both antigens and stabilizing agents affected the physical properties of the vaccines (e.g., mean particle size and particle size distribution) after the vaccines were subjected to TFFD. Importantly, the integrity and hemagglutination activity of the rHA antigens did not significantly change and the immunogenicity of reconstituted influenza vaccine candidates was maintained when evaluated in a mouse model. The vaccine dry powder was not sensitive to repeated freezing-and-thawing, in contrast to its liquid counterpart. It is concluded that TFFD can be applied to convert liquid vaccines containing MF59 or AddaVax to dry powders while maintaining the immunogenicity of the vaccines. Ultimately, TFFD technology may be used to prepare dry powders of multivalent universal influenza vaccines.

Dengue virus and the host innate immune response.

Dengue virus (DENV) is a mosquito-borne Flavivirus that is endemic in many tropical and sub-tropical countries where the transmission vectors Aedes spp. mosquitoes resides. There are four serotypes of the virus. Each serotype is antigenically different, meaning they elicit heterologous antibodies. Infection with one serotype will create neutralizing antibodies to the serotype. Cross-protection from other serotypes is not long term, instead heterotypic infection can cause severe disease. This review will focus on the innate immune response to DENV infection and the virus evasion of the innate immune system by escaping recognition or inhibiting the production of an antiviral state. Activated innate immune pathways includes type I interferon, complement, apoptosis, and autophagy, which the virus can evade or exploit to exacerbate disease. It is important to understand out how the immune system reacts to infection and how the virus evades immune response in order to develop effective antivirals and vaccines.