To Test the Protective Efficacy of Whole-Inactivated SARS-CoV-2 Vaccine in Syrian Hamsters

At a Glance

When this project began, the COVID-19 pandemic required the development of vaccines to mitigate the impact of this virus. Whole inactivated vaccines are easy to produce and have been shown to be effective for several viruses including corona, influenza, and Ebola. Thus, the research team proposed to generate a whole inactivated SARS-CoV-2 vaccine virus and test its ability to protect against COVID-19 in an animal model of Syrian hamsters.

The research team determined that the inactivated vaccine virus elicited a protective immune response in a hamster model of SARS-CoV-2 infection. The vaccine alone without Quil-A® gave protection two weeks after a second vaccination, even against emerging variants. Although the durability of this inactivated vaccine is currently unknown, the addition of an immune response enhancing substance like Quil-A may extend its protective efficacy.

The Challenge

There is a need for vaccines that protect not only against current circulating variants of SARS-CoV-2, but new and emerging ones in the future. Thus, additional research must be done and efforts made to produce vaccines that can protect people from the mutating virus.

Project Goals

The goal of this project was to test a novel approach for developing a potential vaccine for COVID-19 using Syrian hamsters as an animal model for coronavirus research.

Results

The research group determined that Syrian hamsters are highly susceptible to SARS-CoV-2 infection and show similar infection symptoms to those of infected humans, making these hamsters an ideal animal model to evaluate vaccine candidates. When immunized with the vaccine virus, hamsters that received one vaccine only and hamsters that received one vaccine combined with Quil-A (a substance that enhances immune response), showed high levels of antibodies. The hamsters that received a saline injection instead of the vaccine virus did not show any levels of antibodies against SARS-CoV-2.

When tested for protective efficacy, hamsters that were immunized with the vaccine only or the vaccine combined with Quil-A showed no signs of weight loss and complete protection of the lungs from the virus with decreased antibodies detected in this region. However, hamsters in the control groups that were immunized with saline or only Quil-A showed weight loss and high amounts of viral infection in the lungs.

From these results, the research team determined that the inactivated vaccine virus elicited a protective immune response in a hamster model of SARS-CoV-2 infection. The vaccine alone without the Quil-A gave protection two weeks after a second vaccination, even against emerging variants. Although the durability of this inactivated vaccine is currently unknown, the addition of an immune response enhancing substance like Quil-A may extend its protective efficacy.

Lasting Impact

The results of the project inform future mitigation efforts, research, and production of potential vaccines for emerging SARS-CoV-2 variants.