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Hamburg and Oxford: While there is an urgent search for an effective vaccine against the novel SARS-CoV-2 coronavirus, two vaccine candidates for the related MERS-CoV have been shown to be safe in phase 1 studies. Infectious diseases of the lancet (2020; DOI: 10.1016 / S1473-3099 (20) 30248-6 and 30160-2) The published results also document an immune response against the virus.
Of the 3 corona viruses that can cause fatal infections, MERS-CoV is the most dangerous. Of the 2,519 diseases known to date, 866 died fatally, resulting in a case fatality rate of 34.3%. Most diseases occur in Saudi Arabia, where dromedaries are the natural reservoir. However, the 2014 outbreak in South Korea, where 186 people became ill, of which 38 died, shows that MERS has the potential for a pandemic.
The current situation with COVID-19 shows the importance of a vaccine that could be rapidly manufactured in an emergency. Two research teams have completed the first clinical trials on two MERS vaccines.
Both vaccines use a harmless virus as a vehicle. Sarah Gilbert’s group at Oxford University is involved in the ChAdOx1 variant of an adenovirus circulating in chimpanzees that cannot replicate. It was equipped with the MERS-CoV spike protein.
The team led by Marylyn Addo of the University of Hamburg-Eppendorf Medical Center (UKE) uses a vaccine based on the modified Vaccinia Ankara virus (MVA), which was originally developed as a smallpox vaccine. To convert it into a MERS vaccine, it was also equipped with the MERS-CoV peak protein.
Both viruses in the vaccine are known to be safe. The two phase 1 studies examined whether this is still the case after the spike protein has been added. At Oxford, 24 healthy subjects received a single vaccine, and increasing doses were tested. 26 healthy volunteers were vaccinated in Hamburg, so 2 vaccinations were planned. Here, too, the vaccine dose was slowly increased over the course of the study to explore possible limits of tolerability.
Both vaccines have passed the safety test. Both have had an immune response. It is not yet clear if it is enough to protect people from infection. The ChAdOx1-MERS vaccine achieved an antibody response that was still detectable after 18 days in 18 of 24 patients (75%). On day 364, 13 of the 29 participants were still protected. The MVA-MERS vaccine appears to be somewhat weaker. Only 3 of 22 subjects (14%) still had detectable antibody titers after 180 days.
Both groups want to continue developing their vaccine. It probably would not be effective against SARS-CoV-2. Both viruses enter cells through different receptors. MERS-CoV uses the DPP4 receiver, while SARS-CoV-2 pairs with the ACE2 receiver. © © rme / aerzteblatt.de
