Researchers from Imperial College in London and Harvard University in Boston have grown a crystal that shows the structure of the integrase enzyme. The HIV virus uses integrase to copy itself into an infected person’s DNA, paving the way for the virus to spread.

Now that there is a model of the integrase structure available to researchers, it is now possible to understand how existing integrase blocking medications work, how to improve such medications, and how to stop the virus from resisting the medication.

The crystal was made public in a study published January 30 in the journal Nature. This has been hailed as a major step in the fight against HIV. Scientists have attempted numerous times over the last 20 years to understand integrase and how related medications work.

Dr. Peter Cherepanov, the lead author of the study from the Department of Medicine at Imperial College, said in a statement: “When we started out, we knew that the project was very difficult, and that many tricks had already been tried and given up by others long ago. Therefore, we went back to square one and started by looking for a better model of HIV integrase, which could be more amenable for crystallization. Despite initially painstakingly slow progress and very many failed attempts, we did not give up and our effort was finally rewarded.”

The study was funded by the U.K. Medical Research Council and the U.S. National Institute of Health. The news was first reported by ScienceDaily.