A nurse tests a blood sample during a free HIV test at a blood tests party, part of a campaign to prevent HIV infection among male same-sex couples, in Bangkok in this September 20, 2014 file photo.
New research that sheds light on the methods and machinery used by HIV to infect cells provides insight into the tricky virus that potentially could guide the development of a vaccine against the virus that causes AIDS, according to U.S. government and other scientists. REUTERS/Athit Perawongmetha/Files (THAILAND – Tags: HEALTH SCIENCE TECHNOLOGY)