You don’t know exactly where and how it happened, but the genetic information of the new Sars-CoV-2 coronavirus suggests that the pathogen comes from the animal kingdom. “The virus is closely related to the corona viruses in bats,” says Thomas Mettenleiter, President of the Friedrich Loeffler Institute, the central institution of the Federal Republic for animal health.
For this reason alone, research is interested in how the viruses behave in different animals. The Friedrich Loeffler Institute (FLI) is researching this in its high-security laboratories on the Baltic island of Riems. And the scientists also want to know: in which animals is the disease similar to that in humans? Such animals should then help to find vaccines and medicines for Covid-19 and thus end the corona crisis.
Vector vaccines: experiments with ferrets
Animal models have so far been indispensable for one question: how effective is the protective effect of a particular vaccine? How much is the viral load reduced in vaccinated versus non-vaccinated animals? “Animal experiments are well suited to establishing such protective correlates,” says Mettenleiter. His own institute is currently testing a so-called vector vaccine on ferrets. A harmless virus is modified so that infected human cells produce a corona antigen, which the immune system then responds to. The first results of this research will be presented soon.
Ferrets are researched because it is known that they can become infected and transmit the virus. Farm animals like pigs and chickens cannot do this, as the experiments at the FLI show. The Syrian golden hamsters are even better suited as animal models. These rodents even get a mild pneumonia and thus have a similar course of the disease as humans. However, animals have so far not been suspected of being potential carriers of corona. Although it is known that cats can transmit corona, proven cases in which an animal has caused infections in humans have so far not been known, says Mettenleiter.
Hamsters show symptoms similar to humans
Before a new active ingredient can be tested on humans – researchers speak of “first-in-men” trials – its basic safety must be established. Scientists are using animals to test whether the substance causes damage to the organs. How is a substance distributed in the body and what reactions does it cause? “Hamsters are the model of choice here because they show symptoms similar to those of humans,” says Paul Cichutek, President of the Paul Ehrlich Institute (PEI), which is responsible for the approval of new drugs in Germany. Certain species of monkeys can also serve as animal models. However, the absolutely suitable animal model for corona research has not yet been found, says Cichutek.
There are basically two approaches to vaccine research worldwide, says the PEI boss. On the one hand, specific vaccines against Sars-CoV-2 would be developed, on the other hand non-specific ones that stimulate the immune system so that it can also ward off corona. In addition, research is being carried out on various medications that are intended to ward off or neutralize the virus in the body. This includes therapy with the blood plasma of previously recovered corona patients. Other companies develop monoclonal antibodies, on the one hand to neutralize the virus, and on the other hand to interrupt an excessive reaction of the immune system. In all of these cases, substances would first have to be tested on animals to protect people, says Cichutek.
The way to the replacement of animal experiments is lengthy
In the long run, some animal experiments could be replaced by tests in cell cultures. But the way there is long, says Cichutek. The effectiveness of these replacement tests has to be tried and proven before they can be included in the official approval process.