A vaccine containing a protein key to HIV replication has been found to improve the effectiveness of antiretrovirals (ARVs). Researchers injected 168 HIV-positive study members with a vaccine that contained either 7.5 or 30 micrograms of Tat, a protein that fuels the virus’s life cycle. The participants, who were all on ARVs, were given the vaccine once a month for either three or five months. The vaccine prompted participants’ immune systems to develop antibodies to the protein. The study members also experienced rising CD4 levels as well as higher levels of T, B and other immune cells. These effects lasted for the entire three-year study. The larger dose of the vaccine, when given over a three-month period, led to the greatest effect. The vaccine was also linked to a drop in HIV proviral DNA, which is an indication of a diminished viral reservoir.