Advanced single cell imaging and genomic technologies to fight SARS-CoV-2
Over the last few months the COVID-19 pandemic has reached more than 180 countries and caused over 150,000 deaths. The scientific community has been deploying all weapons - economic, technological and intellectual - at its disposal to better understand the virus and rapidly develop prophylactic and therapeutic strategies as soon as possible.
To join this international effort, IRCCS Ospedale San Raffaele will adopt a unique approach: a biosafety level (BSL) 3 laboratory for animal models that is fully equipped with cutting-edge single cell imaging and genomic technologies such as the intravital microscopy, which allows to visualize the interaction between SARS-Cov-2 (the causative agent of COVID-19) and the immune system in real time, and transcriptomic and epigenomic systems, which allow to assess how individual host cells change after their encounter with the virus.
The facility usually hosts animal studies on hepatitis B virus (HBV) and hemorrhagic fever viruses that are performed by the groups of Luca Guidotti, deputy scientific director of Ospedale San Raffaele and full professor at Vita-Salute San Raffaele University, and Matteo Iannacone, head of the Dynamic Immune Response Unit of the same institute.
San Raffaele will repurpose a section of the lab and purchase the necessary equipment thanks to the support of the Same Deutz Fahr group, which donated 700.000 € to this ambitious project, and the contribution of Fondazione Prossimo Mio along with other private donors.
When the SARS epidemic (caused by SARS-CoV-1) began at the end of 2002, US top experts on coronaviruses immediately set out to study the pathogen with the goal of developing new therapies. Among the first objectives achieved was the engineering of an animal model of the disease.
Both SARS-CoV-1 and the current SARS-CoV-2 enter human cells through a receptor called ACE2 that is expressed in the lungs and other organs of the body. Mice have a similar receptor. It differs from ours, in the parts that contact the virus, by less than 1%: still enough to make mice relatively resistant to these human coronaviruses. This is why researchers in the past engineered a transgenic mouse model of SARS in which susceptible cells express the human ACE2 in addition to the endogenous counterpart. As the epidemic ended on mid 2003, however, the research on the virus significantly contracted and the SARS mouse model was put into cryopreservation at the Jackson Laboratory in Maine.
Research on the new coronavirus
With the first outbreak of COVID-19 in China the Jackson Laboratory reactivated the transgenic lineage and now many labs around the world are waiting on line to receive it.
"When a virus enters the body, it penetrates all cells in varying tissues and organs that express the 'right' receptor. We can think of it as a lock for which that particular virus has the key,” explains Luca Guidotti. “This is why the systemic consequences of a viral infection – which results from the dysfunction of all these cells as well as the response from the immune system – cannot be reproduced in vitro: it takes the complexity of an entire organism”.
As the mice originally engineered to study SARS-CoV-1 may not be entirely suited to study SARS-CoV-2, we are already taking advantage of CRISPR-Cas9 technology to selectively modify the mouse's ACE2 receptor and make it identical to the human receptor," continues Guidotti.
Doing animal research on SARS-CoV-2 is not an easy task: it requires a special laboratory that guarantees the safety of researchers and prevents the virus from escaping into the environment.
"Studying infectious diseases in animal models is far more dangerous than performing experiments in vitro, and the risk of contagion for researchers is higher. It entails more resources and a great deal of experience," explains Guidotti. An experience that his research team, together with the one led by his former postdoc and now collaborator Matteo Iannacone, has built up over decades of research on hepatitis B and hemorrhagic fever viruses.
A unique research facility for animal models of infectious diseases
Thanks to the support of several Italian private donors, San Raffaele is remodeling its BSL-3 animal facility to accommodate the use of advanced single cell technologies in mouse models of SAR-CoV-2 infection. Visualizing and analyzing the in vivo the interactions between the infected cells and the immune system, which vary greatly among different infectious diseases, may hides the secret for the development of new therapies and vaccines against SARS-Cov-2.
"This was the case of HBV and hopefully it will be the case of this or new coronaviruses that may emerge in the future. The challenge is not only to defeat SARS-Cov-2 and overcome this crisis, but also to prepare ourselves for the next one. To prevent what happened with SARS research in 2003 from happening again. We could not afford it then, much less we can afford it today,” Guidotti concludes.