The transversality of the knowledge and tools available is very important to advance research. It is particularly illustrated with this Covid-19 pandemic for which many discoveries on other viruses allow us to better characterize Sars-Cov-2.
Move like on a network of highways, or send remote signals to the central nervous system like a telecommunications network…
In order to understand the mechanisms behind the long forms of Covid-19, Hervé Bourhy, head of the Lyssavirus, epidemiology and neuropathology unit at the Institut Pasteur, investigated the possible strategies of the SARSCoV-2 virus for use of our neural network for its own purposes.
More than 20% of people who have had Covid-19 suffer from the persistence of certain symptoms following five weeks and for 10% following three months. Severe fatigue, neurological disorders such as anosmia, and anxiety-depressive symptoms, cardiac or respiratory disorders are among the manifestations felt by these people.
Research into the mechanisms of long Covid shows that it might be due to the damage caused by the initial infection, but also by the persistence of the virus and inflammation in certain areas of the human body.
Building on his work on the rabies virus and its use of the network of nerve cells to travel to the brain, Hervé Bourhy and his team, in particular Guilherme Dias de Melo, sought to discover whether SARS CoV-2 infects and also travels along nerve cells.
« The rabies virus circulates and spreads along axons, using the filamentous structure of nerve cells to move through the neural network. We used our knowledge and the tools deployed for the rabies virus to study the SARS-CoV-2 virus “, explains the researcher.
According to a study on anosmia (loss of sense of smell), in which Hervé Bourhy’s team participated, the SARS-CoV-2 virus can be detected within the olfactory epithelium for several months, which might constitute a gateway to the brain and explain certain neurological manifestations of long Covid.
The virus has a destructive effect on the olfactory epithelium and causes inflammation around its neurons. One of the hypotheses is that the inflammation is relayed remotely thanks to the neural network, and leads to the persistence of certain symptoms observed in the long forms.
« To explain the persistence of symptoms linked to Covid, one of the hypotheses being studied is that the virus, even absent, sends signals to the central nervous system. We assume that this virus, like that of rabies, travels via the neural network to certain specific areas of the central nervous system and disrupts certain functions. In vitro models from human and animal cells have demonstrated the neurotropism of the virus, that is to say, its ability to infect and to be conveyed by the neuronal network. “, further details the researcher.
Other research work is carried out in parallel by the team, in particular on rabies. From rabies to Covid, the transfer of knowledge and study tools happened quite naturally with a team accustomed to constantly looking for bridges between pathologies, between animals and humans, between viruses…
Hervé Bourhy inspires this multidisciplinarity and this transversality, which he himself has applied in his professional career. Veterinary doctor, medical microbiologist, he arrived at the Institut Pasteur to take courses in immunology and virology, then to do his doctorate and since then he has developed this research on lyssaviruses (including the rabies virus), qu might transfer to SARS-CoV-2.
