It rarely happens and still causes a stir: some people are still positive weeks after their corona infection.
Researchers explain why this could be.
Munich - It is one of the riddles that the coronavirus pandemic brought with it: Patients who receive a PCR test with a positive result many weeks after their infection.
Researchers from the Massachusetts Institute of Technology at Cambridge now provided a possible explanation.
The corresponding article was published in the PNAS (Proceedings of the National Academy of Science of the United States of America), a scientific journal.
Covid puzzle: can the genetic material of the virus be inserted into our DNA?
As can be seen from this, parts of the coronavirus genome can be inserted into our DNA.
It was generally said that such a process was not possible because the two genetic information exist in different forms: in humans in the form of DNA, in viruses in the form of RNA.
Cohort-based studies would already indicate that “at least some of these re-positive cases were not caused by reinfection.” This is what the Cambridge researchers around Liguo Zhang wrote.
It was also stated that no virus capable of replicating was detected or spread by these PCR-positive patients.
This ultimately aroused the suspicion that the tests were possibly reacting to Sars-CoV-2 genetic material that had been retained in the patient's genetic material.
Coronavirus: Parts of the genome can be inserted into our DNA
The researchers cite a so-called LINE1 transposon, which is located in our own genetic material, as the cause.
In general, the LINE1 transposon is also called the “jumping gene”.
The research team increased the proportion of these “jumping genes” in human cell cultures.
They then infected the cells with the coronavirus.
Finally, two days later, they examined human cell cultures.
For comparison, the same experiment was carried out with human cell cultures without enrichment by “jumping genes”.
The researchers wrote about their results: "DNA copies of parts of the viral genome were found in almost all human chromosomes." This means that parts of the coronavirus could be detected in the experiment in human cells.
"These results suggest that the Sars-CoV-2 RNA can be transcribed and that the resulting DNA can be integrated into the genome of the host cells," they concluded.
Corona research: what do the results mean for Covid 19 patients?
Finally, the researchers also examined tissue samples and lung fluids from people who had gone through severe Covid-19 disease.
According to the article, it turned out that gene sequences of Sars-CoV-2 were also found in these samples.
However, not much can be said about the frequency of such a process.
It could be that "only a fraction of Covid-19 patients carry Sars-CoV-2 sequences in their DNA".
However, given the high number of people infected with coronavirus around the world, "even an actually rare event could have clinical relevance," the scientists wrote.
According to the researchers, however, it is impossible for new viruses to develop through the built-in DNA parts.
Meanwhile, the corona situation in Germany seems to be calming down. The incidence is falling dramatically. But before the Whitsun vacation, chaos threatens.
(mbr)
