The coronavirus could also slip into our chromosomes

The fact that the coronavirus is able to integrate its genome into the DNA of our chromosomes could explain why some people, even long after recovery, still test positive

(Photo: Qimono / Pixabay) people who recover from Covid-19, in some cases, can remain positive for a long period of time. And this could depend on their immune system, or on a particularly persistent infection. Today, another possible explanation is provided by a new study by researchers at the Massachusetts Institute of Technology (MIT), according to which the coronavirus would hide in a specific place: our chromosomes. In fact, from preliminary analyzes, carried out for now only in the laboratory, it has emerged that the virus could integrate its genome into human chromosomes. A phenomenon already observed for other viruses, such as HIV and some retroviruses, although, the researchers warn, this does not imply that the coronavirus is able to permanently establish itself in human cells to continue proliferating, as HIV does. The results were published in the pre-print bioRxiv journal.

Recall that all viruses insert their genetic material into the cells they infect. But, generally, it remains separate from the cell's DNA. Intrigued by the ever-increasing number of cases of people's positivity, even long after their recovery, the researchers focused on the possibility that the coronavirus, or rather its genome, could integrate into the DNA of chromosomes. To understand this, they added reverse transcriptase (Rt), an enzyme typical of retroviruses and able to use rna as a starting template to synthesize DNA in human cells and cultured the cells engineered with the coronavirus. In particular, in one experiment they added an Rt from HIV and another Rt using human DNA sequences known as Line-1 elements, sequences of ancient retroviral infections that make up about 17% of our genome.

The analyzes showed that the cells that produce both forms of the enzyme caused some fragments of the coronavirus' rna to be converted into DNA and integrated into chromosomes. If the Line-1 sequences, therefore, naturally produced Rt in human cells, the integration of the coronavirus could occur both in people with Covid-19, and with a coronavirus and HIV co-infection. Both situations, the researchers comment, may explain why molecular swabs detect traces of coronavirus genetic material in people who no longer have an active infection for long periods of time.

Some scientists, however, have proved critical and skeptical of these results. For example, in the opinion of David Baltimore, virologist at the California Institute of Technology (Nobel Prize for the discovery of RT), the work is "impressive", even if he points out that the study is incomplete. While John Coffin, a virologist at Tufts University defines the study as "credible". "All in all, I doubt that the phenomenon has much biological relevance," comments the expert to Science. Zandrea Ambrose, a retrovirologist at the University of Pittsburgh, is also of the same opinion: this type of integration would be "extremely rare" if it actually happened, pointing out that Line-1 elements in the human genome rarely remain active. In response, Rudolf Jaenisch, molecular biologist at the Massachusetts Institute of Technology (MIT) and author of the study clarifies that the results clearly demonstrate that integration would not lead to the replication of the coronavirus, therefore to an active infection. “Don't worry”, warns the expert.

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Genetic Coronavirus Health globalData.fldTopic = "Coronavirus, Genetics, Health"

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