The basement is filled with lungs in Berlin and the telescope looks into the past

At the end of the year, Sébastien Calvignac-Spencer alone goes down to the basement of a medical history museum in Berlin, a basement that holds so many old medical specimens, so much so that every organ in the body has them. It must have a separate storage room, which contains creepy art collections.

In the dark, Calvignac-Spencer headed for the room containing the lungs. He and his colleagues surveyed more than 400 nearly 500 specimens brought down here for decades. And finally, they found what they were looking for.

It was the lungs of a girl who died in 1912. The 2-year-old had pneumonia as a complication of measles. The lungs have been embalmed in the chemical ever since, preserving valuable clues about the source of the disease.

Intention of Calvignac-Spencer? He will unearth the corpses of viruses more than 100 years old, sequencing their genes to compare with current generations of measles grandchildren.

The final difference will give us a telescope to look back thousands of years, from the first day the measles virus was formed and spread the terrible disease of our species.

Calvignac-Spencer is a virologist working at the Robert Koch Institute, Germany. For over a year, he led a project to decode the genome of ancient measles viruses. "For viruses, we can't get their fossils," Calvignac-Spencer said.

Therefore, the only way to study ancient viruses is to search for collections of specimens that are scattered around the world. Then, by comparing the genomes of old viruses and modern viruses, scientists can create a mathematical model to estimate the evolution and create what they call "plant growth." "the genotype of the virus."

Next, this evolution will be pulled back into the past, becoming a telescope that helps us look at the time thousands of years before the advent of the virus.

In the basement of the Berlin Medical History Museum in Charité, Calvignac-Spencer found a girl's lungs that died in 1912 from a measles complication. The virus samples included in it were successfully decoded by his team and became the oldest measles genome ever assembled.

The mathematical simulation of the genetically engineered tree has since estimated that the measles virus was infected in humans as early as, around 400 BC, 1,500 years earlier than the previous genetic estimate.

This was a groundbreaking discovery, and only made possible thanks to the excellent storage conditions of the patient samples. If the mathematical model is considered to be the body of a telescope, modern measles viruses will be eyepieces, while the specimen containing the 1912 measles virus is the objective.

We can easily find transparent and good quality "objectives" at the present time. But with the specimen from centuries ago, it needs to be extremely well preserved to limit the "aberrations" for the "objective" to look into the past.

In fact, all specimens stored at the Berlin Medical History Museum are preserved with formalin, a liquid chemical that can prevent decomposition by suspending all biological process. However, formalin also causes a phenomenon that interferes with the viral gene's decoding, which causes the viral RNA to clump and bind to other molecules.

To extract the measles virus's RNA, the team will have to break its bonds with other molecules. The easiest way is to use the temperature. "You can boil the sample," Calvignac-Spencer explained. Exactly, you are boiling a part of the lungs of a girl who died in 1912, sounds scary.

But precisely by doing so, boiling the lung tissue sample to 98 degrees Celsius for 15 minutes, Calvignac-Spencer and his colleagues were able to extract RNA from the measles virus and reconstruct their genome.

Of course, biologists don't need only a single lens to look into history. Calvignac-Spencer and his colleagues needed to find as many virus samples as possible to sequence their genes for more lenses.

In a laboratory they collaborated with in Czechoslovakia, a 1960s measles virus sample was also excavated and sequenced. In addition, the Calvignac-Spencer team also used up to 127 genomes of modern measles virus strains to add to its time-telescope system.

To calibrate that massive lens, they compared the entire genomes of the measles virus received, to their close cousins: One is the rinderpest, a virus strain from the past that infected and killed. the number of cattle but has been eradicated. The other is peste des petits reminants, a virus that still infects sheep and goats.

From there, the gene-generating tree was erected, along with the telescope that allowed us to look into the past.

From his lens system, Calvignac-Spencer simulated the evolution of the measles virus. Measles and rinderpest have thus branched off from the same ancestral virus some 2,400 years ago. Rinderpest continues to infect animals, while measles has taken a while longer to move from animals to humans.

The spread of measles in human populations probably coincides with the time when our major cities began to appear. Because of the specificity of the disease, anyone who survives measles is immune to the disease.

Measles is only circulating in small communities, it will either cause death for those who are ill, or make them immune to life. As a result, the virus finally disappeared.

Only when circulating in a city large enough to be densely populated with susceptible children is constantly born, measles can maintain its transmission chain, epidemiologist Ottar Bjornstad, from Pennsylvania State University, said.

Scientists estimate that, for measles to survive and circulate, a city must have a scale of more than 250,000 to half a million people. And that was around 2,300 years ago, when cities in North Africa, India, China and Europe reached that scale.

It could also be the time when measles turns to infect humans, Calvignac-Spencer and the team conclude.

With a mathematical model that uses the genetic data of past virus samples, "you can really give yourself a glimpse into history," says Sophie Gryseels, a virologist at KU University. Leuven, Belgium said.

Previously, Gryseels also used similar techniques to study the evolutionary history of HIV, starting with an isolated virus sample in 1966.

In this technique, the older the virus samples are found, the more accurate we will look at the past. Before Calvignac-Spencer and his team found the measles virus sample in 1921, scientists had only three genomes of the measles virus sample over 30 years old. The oldest virus sample they acquired was in 1954, the same virus used to make the measles vaccine.

Using this old "lens system," a team of Japanese scientists predicted that measles did not appear or at least had not spread to humans until before the Middle Ages, specifically around the century. 11-12 AD.

So far, however, Calvignac-Spencer's work has shown that that milestone was marked more than 1,500 years ago, namely in 345 BC.

However, the possibility that the virus first appeared on humans, then jumped to animals and returned to humans in the Middle Ages has not been ruled out. Calvignac-Spencer and his team are therefore still looking for new "lenses" for themselves to keep finding the truth.

In the basement of the Berlin Medical History Museum in Charité, they are continuing to stick orange sticky notes on the sample boxes they are planning to study. "It's a treasure," Calvignac-Spencer said. "[That cellar] is the window into the past that we have in this age."

Reference Science, Atlantic