Two new Australian-made COVID ‘super vaccines’ are about to enter clinical trials that researchers say may greatly improve immunity to the Omicron strain.
Recruiting is underway for clinical trials of two new COVID vaccines developed by research teams in Melbourne.
The vaccines differ from those currently in use because they focus the immune response on the very tip of the virus spike protein, called the receptor binding domain (RBD). The RBD enables the virus to enter and infect cells in the body.
The first is known as an RBD protein vaccine and uses part of the COVID virus protein to illicit an immune response. The second is an RBD mRNA vaccine and uses the genetic sequence for the tip of the spike protein to illicit the production of RBD protein, which triggers the immune response.
The two vaccine candidates were developed by the University of Melbourne’s Doherty Institute and the Monash Institute of Pharmaceutical Science (MIPS).
The researchers are looking for 114 healthy adults aged between 18 and 70 for the phase one trial, which will be conducted by the Doherty Institute.
“This trial will assess the safety and efficacy of a single dose of these vaccines as a fourth dose of a COVID-19 vaccine, therefore participants must have had their third dose at least three months prior to the study commencing,” says Professor Terry Nolan, head of the institute’s Vaccine and Immunisation Research Group.
“People who have been infected with COVID-19 are also eligible, provided they had their infection at least three months prior and have had their third vaccine dose.”
It’s hoped these new vaccines will provide longer-lasting immunity to a greater variety of COVID variants.
The RBD protein vaccine performed well in pre-clinical trials in mice, inducing high levels of neutralising antibodies after two doses.
“Immunity induced by the RBD protein vaccine protects against virus challenge in a mouse model of SARS-CoV-2 infection, even 100 days following the boost,” says Dr Georgia Deliyannis, who performed most of the RBD protein vaccine experiments.
“It also retains its potential to neutralise the original ancestral strain, and preliminary in-lab studies have demonstrated neutralising activity against other variants including Delta and Omicron.”
The RBD mRNA vaccine, developed primarily at MIPS, was designed in a similar way to other mRNA vaccines such as the Pfizer and Moderna vaccines but tweaked sightly to focus specifically on the tip of the virus spike protein.
“In common with the RBD protein vaccine, the RBD mRNA vaccine induced high levels of RBD-specific antibodies and protected against virus challenge in the mouse model,” says Professor Colin Pouton of MIPS.
“We have good reason to think that both vaccines will perform well in the clinic.”
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