Design of universal Ebola virus vaccine candidates via immunofocusing

Ebola virus vaccination elicits Ebola virus-specific immune responses without substantial cross-reactivity to other filoviruses

The Janssen Ebola virus (EBOV) vaccine consists of the adenovirus type 26 vector encoding the EBOV glycoprotein (GP) (Ad26.ZEBOV) and the modified vaccinia Ankara (MVA) vector encoding GP from EBOV, Sudan virus, and Marburg virus and nucleoprotein from Tai Forest virus (MVA-BN-Filo) administered 8 weeks later. We conducted a systems immunology analysis of antibody-mediated and cellular immune responses induced after two immunizations with either vaccine used first. The response to vaccination was EBOV GP specific and defined by high antibody binding, Fc effector, and neutralizing responses with CD4 T cell responses also contributing. The vaccine-induced antibody profile did not distinguish people living with or without HIV-1. Samples from 48 survivors and 121 contacts from the 2007 Ugandan Bundibugyo virus epidemic also showed minimal cross-reactivity to other filovirus proteins after infection and exposure. The lack of cross-reactivity suggests that different multivalent vaccine candidates are required to provide broad protection across filoviruses.

Rational design of next-generation filovirus vaccines with glycoprotein stabilization, nanoparticle display, and glycan modification

Filoviruses pose a significant threat to human health with frequent outbreaks and high mortality. Although two vector-based vaccines are available for Ebola virus, a broadly protective filovirus vaccine remains elusive. In this study, we evaluate a general strategy for stabilizing glycoprotein (GP) structures of Ebola, Sudan, and Bundibugyo ebolaviruses and Ravn marburgvirus. A 3.2 Å-resolution crystal structure provides atomic details for the redesigned Ebola virus GP, and cryo-electron microscopy reveals how a pan-ebolavirus neutralizing antibody targets a conserved site on the Sudan virus GP (3.13 Å-resolution), in addition to a low-resolution model of antibody-bound Ravn virus GP. A self-assembling protein nanoparticle (SApNP), I3-01v9, is redesigned at the N-terminus to allow the optimal surface display of filovirus GP trimers. Following detailed in vitro characterization, the lymph node dynamics of Sudan virus GP and GP-presenting SApNPs are investigated in a mouse model. Compared with soluble GP trimer, SApNPs show ~112 times longer retention in lymph node follicles, up-to-28 times greater presentation on follicular dendritic cell dendrites, and up-to-3 times stronger germinal center reactions. Functional antibody responses induced by filovirus GP trimers and SApNPs bearing wildtype and modified glycans are assessed in mice. Our study provides a foundation for next-generation filovirus vaccine development.

Prokaryote- and Eukaryote-Based Expression Systems: Advances in Post-Pandemic Viral Antigen Production for Vaccines

This review addresses the ongoing global challenge posed by emerging and evolving viral diseases, underscoring the need for innovative vaccine development strategies. It focuses on the modern approaches to creating vaccines based on recombinant proteins produced in different expression systems, including bacteria, yeast, plants, insects, and mammals. This review analyses the advantages, limitations, and applications of these expression systems for producing vaccine antigens, as well as strategies for designing safer, more effective, and potentially 'universal' antigens. The review discusses the development of vaccines for a range of viral diseases, excluding SARS-CoV-2, which has already been extensively studied. The authors present these findings with the aim of contributing to ongoing research and advancing the development of antiviral vaccines.

Engineered protein subunit COVID19 vaccine is as immunogenic as nanoparticles in mouse and hamster models

Initial studies on the immunogenicity of SARS-CoV-2 (CoV-2) S glycoprotein ("spike") as a protein subunit vaccine suggested sub-optimal efficacy in mammals. Although protein engineering efforts have produced CoV-2 spike protein sequences with greatly improved immunogenicity, additional strategies for improving the immunogenicity of CoV-2 protein subunit vaccines are scaffolding and the use of adjuvants. Comparisons of the effectiveness of engineered protein-only and engineered protein-nanoparticles vaccines have been rare. To explore this knowledge gap, we inoculated mice with two doses of either sequence-optimized trimeric spike protein or one of several sequence-optimized spike nanoparticles. We measured their immune response up to two months after the first dose. We also measured the immune response and protection against live virus in hamsters inoculated with either sequence-optimized trimeric spike protein or a liposome-based sequence-optimized spike nanoparticle. We found that in the presence of adjuvant, the antibody and neutralization titers elicited by spike-nanoparticles were not significantly greater than those elicited by spike-only in mice, even at doses as low as 0.1 µg/animal. Hamsters vaccinated with spike-only or spike-nanoparticles were equally protected from live virus one month after their first inoculation. These results suggest that sequence-optimized protein subunit vaccines in the form of individual prefusion-stabilized trimers can be as effective in improving immunogenicity as scaffolded forms.

Ferritin Vaccine Platform for Animal and Zoonotic Viruses

Viral infections in animals continue to pose a significant challenge, affecting livestock health, welfare, and food safety, and, in the case of zoonotic viruses, threatening global public health. The control of viral diseases currently relies on conventional approaches such as inactivated or attenuated vaccines produced via platforms with inherent limitations. Self-assembling ferritin nanocages represent a novel vaccine platform that has been utilized for several viruses, some of which are currently undergoing human clinical trials. Experimental evidence also supports the potential of this platform for developing commercial vaccines for veterinary viruses. In addition to improved stability and immunogenicity, ferritin-based vaccines are safe and DIVA-compatible, and can be rapidly deployed in response to emerging epidemics or pandemics. This review discusses the structural and functional properties of ferritin proteins, followed by an overview of the design and production of ferritin-based vaccines, the mechanisms of immune responses, and their applications in developing vaccines against animal and zoonotic viruses.