HIV is a virus that can lead to AIDS, a disease that breaks down the immune system and allows for entry of life-threatening secondary infections. HIV is transmitted through the exchange of bodily fluids, primarily through sexual intercourse. Using ART treatments, people with HIV have been able to delay HIV replication and immune system deterioration and to improve quality of life. Data from the Strategies for Management of Antiretroviral Therapy (SMART) study indicate that episodic use of ART is associated with a higher risk of CVD than is continuous use of ART. The reasons behind this increased risk of CVD in the presence of HIV are not well understood. This study will determine mechanisms underlying the increased CVD risk among people infected with HIV and, specifically, in those who receive episodic ART.