Defense against SARS-CoV-2 21 Aug 2024 By Bettina Reckter Reading time: approx. 2 minutes
A team at the Helmholtz Centre for Infection Research has developed a vaccine that protects against Covid-19 for longer than previously established active ingredients. It uses a mouse virus as a vehicle for the spike protein.
Constant vaccination against corona? Not necessary with a new active ingredient that German researchers have developed. It works longer than the usual vaccines.
Photo: PantherMedia / Arne Trautmann
There are now several vaccines against Covid-19, a disease transmitted by coronaviruses. However, the protective effect of most vaccines decreases over time. Then a new vaccination with a booster is necessary. Now a team at the Helmholtz Centre for Infection Research (HZI) has developed a vector vaccine that shows a significantly longer-lasting immune response after only a single dose. The team led by Luka Cicin-Sain reported on the promising vector vaccine in 2022. The vaccine has confirmed its effectiveness in animal experiments with mice.
Vector vaccine based on animal virus
It is also based on a vector that cannot be dangerous to humans. In medicine, a vector is the vehicle used to introduce a substance into the body. In this case, it is an animal cytomegalovirus (MCMV) that transports the information for the coronavirus’s spike protein. This is completely harmless to humans because cytomegaloviruses are highly host-selective. This means that the MCMV infects mice, but cannot multiply in humans, as two of the lead authors, Kristin Metzdorf and Henning Jacobsen, confirm.
The immune system pursues two strategies
In order to keep the pathogens at bay, the immune system takes a two-pronged approach: Firstly, highly specific antibodies are formed that are directed against certain structures of the attacker and render it harmless. Secondly, specific immune cells are mobilized that recognize the pathogen in infected cells and actively fight it. So-called CD8+ T cells play a central role here. After a vaccination, both the freely circulating antibodies in the blood are permanently increased and the CD8+ T cells directed against the coronavirus are permanently ready for use.
Why the vaccine effect lasts so long is still being investigated
The researchers are now investigating why the MCMV vaccine has a comparatively long protective effect. One assumption is that cytomegaloviruses hide in the host and remain in a kind of dormant mode. Only when the immune system weakens do they switch to active mode and can then cause symptoms of illness. The MCMV vector viruses probably also try to nest in the human organism. But because humans are not the right host for them, reactivation does not work. The human immune system does not allow mouse viruses to reappear in the blood and attacks them as soon as they form proteins and before infectious particles are formed. In this way, according to the theory, the immune system is repeatedly stimulated and the vaccination effect is maintained.
