In a new study, researchers found that a candidate COVID-19 vaccine raised neutralizing antibodies that robustly protected non-human primates (NHPs) against SARS-CoV-2, the virus that causes COVID-19.
In addition, the optimal vaccine-elicited robust immune response and may prevent severe clinical disease—including weight loss, pneumonia, and death.
The research was conducted by a team at Beth Israel Deaconess Medical Center (BIDMC).
Most people with COVID-19 have relatively mild disease, but a subset of people develop severe pneumonia and respiratory failure, potentially leading to death.
The Ad26-based SARS-CoV-2 vaccine uses a common cold virus, called adenovirus serotype 26 (Ad26), to deliver the SARS-CoV-2 spike protein into host cells, where it stimulates the body to raise immune responses against the coronavirus.
The team developed a series of vaccine candidates designed to express different variants of the SARS-CoV-2 spike protein, which is the major target for neutralizing antibodies.
In the current study, the researchers immunized Syrian golden hamsters with a single injection of the Ad26-based SARS-CoV-2 vaccine, which induced neutralizing antibodies in all animals.
Four weeks later, the animals were exposed to a high dose of SARS-CoV-2.
Vaccinated animals lost less weight and had less virus in their lungs and other organs than unvaccinated control animals. They also showed lower mortality.
Moreover, the researchers found that neutralizing antibody responses were inversely correlated with weight loss and viral loads in respiratory tissues.
The Ad26.COV2.S vaccine is currently being evaluated in clinical studies to establish the performance of the vaccine candidate in humans.
Pending clinical trial outcomes, the Ad26.COV2.S vaccine is on track to start a phase 3 efficacy trial in up to 60,000 participants in September 2020.
One author of the study is immunologist Dan H. Barouch, MD, Ph.D.
The study is published in Nature.
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