Slovenian-developed vaccine produces high immune response in mice
Ljubljana, 31 August - A team of researchers at the Ljubljana-based Chemistry Institute has developed a coronavirus vaccine that has produced a high immune response in mice. Tests have shown that the antibodies neutralise the virus just like with other vaccines and just like the antibodies in patients who have recovered from infection.
The team led by Roman Jerala, biochemist and synthetic biologist, has developed the vaccine based on the plasmid DNA that contains the code for the virus proteins and triggers the production of virus proteins in human cells. These respond by creating anti-bodies and the protective T cells, Jerala told the press today.
He said different coronavirus vaccines based on the plasmid DNA were already being tested in clinical reascend in the US, Japan and South Korea.
The advantages of such vaccines are low costs of production and high stability, also outside freezers, while their downside is that they cannot enter cells as efficiently as viruses.
But Jerala's team has overcome this problem by modifying the virus's proteins into nano parts that are reminiscent of viruses, which improves the response of the immune system.
The team has prepared five varieties of the virus's receptor binding domain (RBD) that is in charge of recognising the cell's receptor.
Tests in mice have shown the best performing variety of the vaccine was the one where a short segment was added to the virus protein to trigger the production of large clusters.
In that case, the response was a hundred times better than that of the monomer protein used in some other vaccines.
The tests have shown that the anti-bodies neutralise the virus's attachment to the human receptor in concentrations that are comparable to other vaccines and the anti-bodies in patients that have recovered from an infection.
Moreover, T cells were produced, which destroy the cells producing virus proteins.
Jerala stressed though that these were only pre-clinical studies, and that the path to the actual use of the vaccine was still long. Comprehensive clinical studies would need to be conducted on humans before it could be used widely, he said, noting that developing the vaccine further would made no sense if another safe and efficient vaccine was made available soon.
Nevertheless, a consortium of researchers from the Veterinary Faculty, Faculty of Pharmacy, the infectious disease clinic of the UKC Ljubljana hospital and the Golnik clinic joined by the company Jafral will continue to work towards preparing the vaccine for clinical studies.
Borut Štrukelj from the Faculty of Pharmacy said this vaccine should definitely be developed further, especially as other vaccines being developed at the moment might not prove to be safe or effective in the long run.
Štrukelj also noted that the vaccine had been developed with ten or hundred times less funds than such projects receive in the US or China.
The article on the preclinical studies is currently available at is https://www.biorxiv.org/content/10.1101/2020.08.28.244269v1. The team will also present its results to the European Medicines Agency.
If the agency responds quickly, clinical studies on humans could start in December, Štrukelj said.
Jerala estimates that enough vaccine for the entire Slovenia could be produced in an industrial fermenter in a week provided that the procedure is optimised.