Sydney researchers are taking an innovative approach to designing potential COVID-19 vaccines – using a tuberculosis vaccine BCG to deliver components of the SARS-CoV-2 virus. Early results from pre-clinical testing in mice are promising.
Two other separate studies also found the inexpensive and widely-used Bacillus Calmette–Guerin (BCG) vaccine that protects against childhood tuberculosis also prevents severe infection and death from coronavirus disease (Covid-19). One study was conducted in India by researchers at the Jawahar Lal Nehru University and the other was conducted in the US.
Also researchers at the University of Sydney and Centenary Institute are repurposing an existing tuberculosis vaccine to see if it can be used in a new way against COVID-19 to develop a novel vaccine.
The vaccine candidate, which Australian researchers have called BCG:CoVac, combines the vaccine for tuberculosis, Bacille Calmette-Guérin (BCG) with major components of the SARS-CoV-2 virus. The SARS-CoV-2 virus is the pathogen that causes the COVID-19 disease.
The study is part of a collaboration between the University of Sydney and the Centenary Institute to examine the immune response created by new vaccine candidates, including BCG:CoVac.
Lead investigator Professor Jamie Triccas, from the School of Medical Sciences, Faculty of Medicine and Health, and the Charles Perkins Centre said the team was motivated to apply their expertise in studying vaccines to assess the effectiveness of this new formulation.
“We have over two decades of experience in the development and testing of tuberculosis vaccines, which will be applied for the assessment of BCG:CoVac,” said Professor Triccas.
“There have yet to be studies published that combine BCG and components of the SARS-CoV-2 virus as part of a new vaccine design, and we’re excited to test their potential.”
Early results promising
The researchers’ early unpublished results from pre-clinical testing in mice show BCG:CoVac stimulated an immune response aimed to control virus infection in humans.
In mice vaccinated with BCG:CoVac, the vaccine induced high levels of SARS-CoV-2-specific antibodies. The role of these antibodies is to bind the virus and help eliminate it from the body. The vaccine also triggered a strong anti-viral response by T cells (a type of immune cell).
Both these types of immune responses are thought to be important to ensure clearance of the SARS-CoV-2 virus from infected individuals.
The JNU study found the quality of protection depends on the BCG strain used to make the vaccine. The peer-reviewed study was published in Cell Death and Disease part of the Nature group of journals.
The US study published in the Proceedings of the National Academy of Sciences, also linked BCG vaccination with reduced Covid-19 deaths.
In a clear vindication of the theory, the studies found in countries where BCG vaccine is given to general population for Tuberculosis protection, people have been able to fight the virus (COVID-19) with far fewer deaths or far less severe health complications. Researchers believe people with BCG or TB vaccine in childhood have a much better immunity, especially to fight COVID-19 than those countries where this vaccine is not given to general populace.
To the much required relief of Indian authorities, that explains a lot less fatalities number and that of people requiring hospitalization or ICU care.
The good news according to Sydney based researchers is that the preliminary data also showed BCG:CoVac did not create high levels of inflammatory responses, which is a common barrier and concern in vaccine design.
“These initial results are very promising. BCG:CoVac is making the type of immune response that we predict is needed to control SARS-CoV-2 infection in humans,” said Professor Triccas.
“We are currently determining how well the antibodies generated after vaccination can ‘block’ the virus from infecting cells and thus provide protection from disease”, Professor Triccas added.