Design and Preclinical Evaluation of a Nanoparticle Vaccine against Respiratory Syncytial Virus Based on the Attachment Protein G.

Human respiratory syncytial virus (RSV) poses a significant human health threat, particularly to infants and the elderly. While efficacious vaccines based on the F protein have recently received market authorization, uncertainties remain regarding the future need for vaccine updates to counteract potential viral drift. The attachment protein G has long been ignored as a vaccine target due to perceived non-essentiality and ineffective neutralization on immortalized cells. Here, we show strong G-based neutralization in fully differentiated human airway epithelial cell (hAEC) cultures that is comparable to F-based neutralization. Next, we designed an RSV vaccine component based on the central conserved domain (CCD) of G fused to self-assembling lumazine synthase (LS) nanoparticles from the thermophile Aquifex aeolicus as a multivalent antigen presentation scaffold. These nanoparticles, characterized by high particle expression and assembly through the introduction of N-linked glycans, showed exceptional thermal and storage stability and elicited potent RSV neutralizing antibodies in a mouse model. In conclusion, our results emphasize the pivotal role of RSV G in the viral lifecycle and culminate in a promising next-generation RSV vaccine candidate characterized by excellent manufacturability and immunogenic properties. This candidate could function independently or synergistically with current F-based vaccines.

Immunogenicity and efficacy of one and two doses of Ad26.COV2.S COVID vaccine in adult and aged NHP.

Safe and effective coronavirus disease-19 (COVID-19) vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one- and two-dose regimens of the Ad26.COV2.S vaccine candidate in adult and aged nonhuman primates (NHPs). A two-dose Ad26.COV2.S regimen induced higher peak binding and neutralizing antibody responses compared with a single dose. In one-dose regimens, neutralizing antibody responses were stable for at least 14 wk, providing an early indication of durability. Ad26.COV2.S induced humoral immunity and T helper cell (Th cell) 1-skewed cellular responses in aged NHPs that were comparable to those in adult animals. Aged Ad26.COV2.S-vaccinated animals challenged 3 mo after dose 1 with a SARS-CoV-2 spike G614 variant showed near complete lower and substantial upper respiratory tract protection for both regimens. Neutralization of variants of concern by NHP sera was reduced for B.1.351 lineages while maintained for the B.1.1.7 lineage independent of Ad26.COV2.S vaccine regimen.

Restrained expansion of the recall germinal center response as biomarker of protection for influenza vaccination in mice.

Correlates of protection (CoP) are invaluable for iterative vaccine design studies, especially in pursuit of complex vaccines such as a universal influenza vaccine (UFV) where a single antigen is optimized to elicit broad protection against many viral antigenic variants. Since broadly protective antibodies against influenza virus often exhibit mutational evidence of prolonged diversification, we studied germinal center (GC) kinetics in hemagglutinin (HA) immunized mice. Here we report that as early as 4 days after secondary immunization, the expansion of HA-specific GC B cells inversely correlated to protection against influenza virus challenge, induced by the antigen. In contrast, follicular T helper (TFH) cells did not expand differently after boost vaccination, suggestive of a B-cell intrinsic difference in activation and differentiation inferred by protective antigen properties. Importantly, differences in antigen dose only affected GC B-cell frequencies after primary immunization. The absence of accompanying differences in total anti-HA or epitope-specific antibody levels induced by vaccines of different efficacy suggests that the GC B-cell response upon revaccination represents an early and unique marker of protection that may significantly accelerate the pre-clinical phase of vaccine development.

Maternal antibodies protect offspring from severe influenza infection and do not lead to detectable interference with subsequent offspring immunization.

BACKGROUND: Various studies have shown that infants under the age of 6 months are especially vulnerable for complications due to influenza. Currently there are no vaccines licensed for use in this age group. Vaccination of pregnant women during the last trimester, recommended by the WHO as protective measure for this vulnerable female population, may provide protection of newborns at this early age. Although it has been observed that maternal vaccination can passively transfer protection, maternal antibodies could possibly also interfere with subsequent active vaccination of the offspring. METHODS: Using a mouse model, we evaluated in depth the ability of maternal influenza vaccination to protect offspring and the effect of maternal immunization on the subsequent influenza vaccination of the offspring. By varying the regimen of maternal immunization we explored the impact of different levels of maternal antibodies on the longevity of these antibodies in their progeny. We subsequently assessed to what extent maternal antibodies can mediate direct protection against influenza in their offspring, and whether these antibodies interfere with protection induced by active vaccination of the offspring. RESULTS: The number of immunizations of pregnant mice correlates to the level and longevity of maternal antibodies in the offspring. When these antibodies are present at time of influenza challenge they protect offspring against lethal influenza challenge, even in the absence of detectable HAI titers. Moreover, no detectable interference of passively-transferred maternal antibodies on the subsequent vaccination of the offspring was observed. CONCLUSION: In the absence of a licensed influenza vaccine for young children, vaccination of pregnant women is a promising measure to provide protection of young infants against severe influenza infection.

Protection against H5N1 by multiple immunizations with seasonal influenza vaccine in mice is correlated with H5 cross-reactive antibodies.

BACKGROUND: Current seasonal influenza vaccines are believed to confer protection against a narrow range of virus strains. However, their protective ability is commonly estimated based on an in vitro correlate of protection that only considers a subset of anti-influenza antibodies that are typically strain specific, i.e., hemagglutination inhibiting antibodies. Here, we evaluate the breadth of protection induced with a seasonal trivalent influenza vaccine (composition H1N1 A/California/07/09, H3N2 A/Victoria/210/08, B/Brisbane/60/08) against influenza challenge in mice. METHODS: Balb/c mice were immunized once, twice, or three times with seasonal influenza vaccine to assess protection against heterosubtypic H5N1 influenza challenge, or homologous H1N1 influenza virus as a control. Passive transfer of immune serum was used to determine the contribution of humoral immunity to protection. RESULTS: Multiple immunizations with seasonal influenza vaccine induced up to 80% protection against heterosubtypic H5N1 influenza challenge in mice without eliciting detectable H5N1 neutralizing antibodies. Comparable levels of protection were reached by passive transfer of immune serum, and protection was correlated with the titer of vaccine-induced, H5 cross-reactive, non-neutralizing antibodies that are at least in part directed against conserved HA epitopes. CONCLUSIONS: Here, we demonstrate that seasonal vaccine has the ability to induce broad serum-mediated protection, and that the mechanism of this protection is different from the vaccine-induced homologous protection.

IgG-mediated anaphylaxis to a synthetic long peptide vaccine containing a B cell epitope can be avoided by slow-release formulation.

Synthetic long peptides (SLP) are a promising vaccine modality to induce therapeutic T cell responses in patients with chronic infections and tumors. We studied different vaccine formulations in mice using SLP derived from carcinoembryonic Ag. We discovered that one of the SLP contains a linear Ab epitope in combination with a CD4 epitope. Repeated vaccination with this carcinoembryonic Ag SLP in mice shows improved T cell responses and simultaneously induced high titers of peptide-specific Abs. These Abs resulted in unexpected anaphylaxis after a third or subsequent vaccinations with the SLP when formulated in saline. Administration of low SLP doses in the slow-release vehicle IFA prevented the anaphylaxis after repeated vaccination. This study underscores both the immunogenicity of SLP vaccination, for inducing T cell as well as B cell responses, and the necessity of safe administration routes.