Researchers at the State University of Campinas (Unicamp) confirmed, through experiments with cell culture, that the new coronavirus (Sars-CoV-2) is capable of infecting human neurons.
The infection and the increase in viral load in nerve cells were confirmed by the real-time PCR technique, the same used in the diagnosis of Covid-19 in reference laboratories. The group coordinated by the professor of the Institute of Biology Daniel Martins-de-Souza also confirmed that neurons express the protein ACE-2 (angiotensin-converting enzyme 2), a molecule to which the virus connects to invade cells human.
In the coming days, the team plans to investigate how the functioning of these nerve cells is altered by the infection.
The research is being conducted as part of a project approved by Fapesp in the so-called “Supplements for Rapid Implementation against Covid-19”, as part of task force created by Unicamp.
“We are going to compare the proteins and other metabolites present in cell cultures before and after infection. The idea is to observe how the pattern of the molecules changes and, based on this information, try to tell the story of how the virus acts on the central nervous system ”, explains Martins-de-Souza to Agência Fapesp.
In the experiment, carried out by postdoctoral fellow Fernanda Crunfli, a human brain cell line was used, as well as human neurons obtained from induced pluripotent stem cells (IPS).
The method initially consists of reprogramming adult cells – which may come from the skin or other easily accessible tissue – to make them assume a pluripotency stage similar to that of embryonic stem cells. This first part was carried out in the laboratory of the professor at the Federal University of Rio de Janeiro (UFRJ) Stevens Rehen, at the DOR Institute of Research and Teaching. Then, Martins-de-Souza’s team induced, through chemical stimuli, IPS cells to differentiate into neural stem cells – a type of progenitor cell that can give rise to several brain cells, such as neurons, astrocytes and oligodendrocytes.
“We are also starting tests with human astrocytes and, soon, we will know if the virus infects these cells, which support the functioning of neurons and are the most abundant in the central nervous system”, says Martins-de-Souza.
Effects on the brain
As Martins-de Souza explains, studies in other countries suggest that Sars-CoV-2 has tropism for the central nervous system, that is, a certain propensity to infect nerve cells. “But we still don’t know if the virus really can cross the blood-brain barrier [estrutura que protege o cérebro de substâncias tóxicas e patógenos presentes na circulação sanguínea] and, if you can, what kind of impact it can have on nerve tissue. We will try to look for clues that help to clarify these doubts ”, says the researcher.
The in vitro experiments with viral isolates are being carried out at the Laboratory for Emerging Virus Studies (Leve) of the Unicamp Institute of Biology, which has level 3 of biosafety (on a scale of up to 4) and is coordinated by the researcher José Luiz Proença Modena.
The graduate students Gabriela Fabiano de Souza and Stéfanie Primon Muraro, supervised by Modena, and Ana Campos Codo and Gustavo Gastão Davanzo, under the guidance of professor Pedro Moraes Vieira, participate in the tests.
The metabolomics and proteomics tests will be conducted at the Neuroproteomics Laboratory, coordinated by Martins-de-Souza, by postdoctoral students Victor Corasolla Carregari and Pedro Henrique Vendramini. For this, a mass spectrometer will be used, equipment capable of discriminating different substances present in a solution based on the molecular weight of each one.
“In addition to investigating whether the amount of a given protein in the sample increases or decreases after infection, we also intend to assess how the level of phosphorylation and glycosylation of the molecules is. These two biochemical mechanisms are used by the cell to quickly activate or deactivate the function performed by proteins. This will give us clues about the metabolic pathways that are altered in neurons in response to the new coronavirus ”, says Martins-de-Souza.
In a video published on the Unicamp website, neurologist Li Li Min comments on the neurological manifestations already observed in patients with COVID-19, including loss of smell and taste, mental confusion, stroke and muscle pain (unrelated to any muscle injury ).
According to the researcher, it is estimated that up to 30% of those infected with the new coronavirus may have some neurological symptom. Min is coordinator of Education and Dissemination of Knowledge at the Research Institute on Neuroscience and Neurotechnology (Brainn), a Research, Innovation and Dissemination Center (Cepid) supported by Fapesp.