Retroviruses, such as HIV, are viruses whose genetic material is coded by RNA rather than DNA. They reproduce by first infecting a host cell, reverse transcribing their RNA into DNA and then integrating this DNA into the host cell’s genome.

So far treatments for retroviral infections like HIV consist of suppressing the virus’s life cycle, but do not actually eliminate the integrated virus’s genetic material from the infected cells.

The June 19 issue of Science has a paper by a group in Germany at the Max-Planck Institute who have found a way to actually cut the genetic material from HIV-1 out of infected cells.

They engineered a recombinase enzyme to recognize and cut out the DNA from HIV-1 using a method called substrate-linked protein evolution. Recombinases are enzymes that recognize a specific DNA segment, delete it and then rejoin the two remaining ends. Cre is a recombinase that recognizes a segment called loxP which is 50% similar to the segments called long terminal repeats (LTR) in HIV-1. Cre doesn’t recognize these LTR’s however. The Max-Planck group, as mentioned above, used a technique to create a modified Cre they called Tre that does recognize and remove DNA between HIV-1’s LTR’s.

They were able to express Tre in cultured human cells that were infected with HIV-1 - and it succeessfully deleted the HIV-1 DNA from the cells.

It is still too far away to be used in people with HIV - safe and efficient ways to deliver it to target cells in the body without causing any harm still need to be developed - but it has the potential to be useful in treating HIV and other retroviral infections among other things at some point in the future.