Where HIV genetic information is inserted into host DNA is linked to clonal growth and persistence of infected cells

Persistence of HIV-infected cells in people on combination antiretroviral therapy (cART) is a major barrier for curing HIV infections. HIV inserts a DNA copy of its genetic information into the DNA of cells it infects and insertion sites vary in different infected cells. The site of insertion specifically marks each infected cell and if an infected cell divides, all of the descendants of that cell (called a clone) will also have the viral genetic information inserted at the same place as the parent. Based on an analysis of blood cells from five HIV-infected individuals, NCI researchers have identified more than 2,400 HIV DNA insertion sites. Analysis of these sites showed that there is extensive clonal expansion (growth) of HIV infected cells. In one patient, approximately half of the HIV-infected cells in the blood came from a single clone, and some the infected clones persisted in patients for more than 10 years. The research, by Stephen Hughes, Ph.D., director, HIV Drug Resistance Program, Center for Cancer Research, NCI, and collaborators appeared online in Science June 26, 2014.

The researchers also showed that, in some cases, the clonal expansion of HIV infected cells was associated with the sites at which HIV DNA is inserted into the host genome. The study results show that insertion of HIV DNA in specific regions of two genes, MKL2 and BACH2, was directly involved in clonal expansion of the infected cells. These genes, and several others in which there were multiple independent HIV insertions in clonally expanded cells in patients, are known to play a role in cell growth and human cancers. These findings have important implications for designing and implementing strategies to eliminate persistent HIV infection, for the use of HIV- based vectors as tools to transfer genes into patients, and possibly for the origin of some HIV-related malignancies.