A new international study carried out by researchers from Denmark, Germany and the USA has discovered that the cells of connective tissue are being exploited by HIV to establish the infection in the body. The discovery may lead to new forms of treatment that can prevent HIV infection.

When HIV is sexually transmitted from one person to another, the virus must break through a protective layer of cells that are known as the mucous membrane. If the mucous membrane is damaged, for example during sexual intercourse or via other infections in the tissue, HIV can break through and infect the underlying immune cells.

In the new study, which was published in the journal PLOS Pathogens, the researchers used a model of the mucous membrane and the surrounding tissue to understand how HIV establishes an infection. Using the model, the researchers discovered that the connective tissue cells, which are the most common types of cells in the tissue, actually had a very strong effect on the HIV infection of the immune cells.

"We investigated connective tissue cells from the vagina, uterus, intestine, foreskin and urethra. In all cases, we observed that the connective tissue cells increased the effectiveness of the HIV infection, with up to 100 times greater infection in relation to our models that did not include connective tissue cells," says one of the Danish contributors to the project, Associate Professor Martin Roelsgaard Jakobsen from the Department of Biomedicine, Aarhus University.

The researchers continued working to understand the basic mechanisms of the connective tissue cells and how they could explain why HIV suddenly had an increased ability to infect immune cells.

"We learned that HIV glues itself to the surface of the connective tissue cells without infecting them. Then the connective tissue cells subsequently very effectively transfer HIV on to the immune cells. The scientific name for the process is trans–infection, but it is not previously been proved that any cells are able to do this as well as the connective tissue cells do," says Martin Roelsgaard Jakobsen.

According to the researcher, more knowledge on a molecular level may help to find a new way of fighting HIV infection, and for this reason the collaboration with the researchers from J. Gladstone Institute in San Francisco will also continue.

"If we can find the molecule or molecules which the connective tissue cells use to glue the HIV onto themselves, then it will be possible for us to develop new drugs that can stop this from happening. This can hopefully mean that HIV will not be able to spread in the tissue," explains Martin Roelsgaard Jakobsen.