The human herpesvirus 6 (HHV-6) – the causative agent of “sixth disease”, a usually benign infantile pox disease – infects almost 100 per cent of people from early childhood, staying in the body permanently. But now a team of researchers at the University of South Florida, directed by Peter Medveczky found that in a small percentage of people can integrate their DNA into human chromosomes. The finding is somewhat surprising since, as several other herpesvirus infection can cause permanent, the mechanism is different: their DNA is enclosed to the rim and stays in the cell nucleus in this way, without adding in the chromosomes. During the study, described in an article published on Proceedings of the National Academy of SciencesThe researchers also confirmed the suspicion, advanced years ago after further research, that the HHV-6 is able to infect sperm and egg cells. Consequently, about one per cent of the population (the estimate has been conducted on the U.S. population) is born with the virus DNA present in all cells of the body. Indeed HHV-6 is the first virus that has proved capable of transmitting in a functional way through the human germ line. The study found that the site of entry of the virus within the telomeres, structures at the ends of chromosomes that play a central role in regulating cell division and therefore the processes of aging and the development of tumors. Finally, the researchers found that the viral genome integrated into the chromosome can be reactivated in its infectious form. Normally the reactivation of the virus – which can lead to encephalitis, hepatitis, myocarditis and pneumonia, occurs only in severely immunocompromised persons, but have found, though very rarely, even cases in healthy people. “Now we find out whether the location of integration has an impact on disease. And although there are medications that may cause the reactivation in patients who are carriers of the virus in every cell. In this case it would be important for these patients avoid those drugs “said Medveczky. But the problem is even larger, the researchers note: people who have inherited the virus are more prone to disease? In these people the viral proteins present at birth are recognized as foreign by the immune system of the subject or not? And if not, it is an advantage or a disadvantage for the health of the person? And yet, given that the viral insertion occurs at the telomeres, this trend has an impact on cellular aging or degenerating into a form of cancer?

Source:lescienze.espresso.repubblica.it