A leading candidate of the Covid-19 vaccine developed by global healthcare company Johnson & Johnson (J&J) prevented the severe illness — including weight loss, pneumonia, and death in a small group of Syrian golden hamsters.
The vaccine — developed through a collaboration between Beth Israel Deaconess Medical Center (BIDMC) and J&J — 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.
BIDMC immunologist Dan H Barouch and J&J 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.
“We recently reported that an Ad26-based SARS-CoV-2 vaccine provided robust protection in rhesus macaques, and this vaccine is currently being evaluated in humans,” said Barouch.
“However, nonhuman primates typically don’t get the severe clinical disease, and thus it was important to study whether this vaccine could prevent severe pneumonia and death due to SARS-CoV-2 in hamsters, which are more susceptible to clinical disease,” Barouch added.
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. Vaccinated animals also demonstrated 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.
“This hamster model of severe Covid-19 disease should prove useful to complement current non-human primate models in the evaluation of candidate vaccines and therapeutics,” said Barouch.
In July, J&J experimental vaccine raised neutralizing antibodies and robustly protected monkeys against SARS-CoV-2, the virus that causes Covid-19.
“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,” the team wrote.
