The Role of Inflammation and Aging in HIV-Associated Cardiovascular Risk

Inclusion Criteria: * HIV controllers: positive for HIV by standard antibody serological determinations with undetectable HIV RNA level (\< 75 copies RNA/mL) in absence of therapy * HIV non-controllers: detectable HIV RNA levels in absence of therapy * Highly active anti-retroviral therapy responders (HAART responders): on combination antiretroviral therapy with undetectable HIV RNA levels. * HIV-seronegative participants will also be studied. Exclusion Criteria: * Treated individuals that changed antiretroviral regimen within 12 weeks prior to study enrollment. * Individuals who have started or stopped antihypertensive medication or lipid lowering medication or changed doses of these drugs within 12 weeks of the study will be excluded. * As nitroglycerin is administered to assess endothelium-independent vasodilation, we also plan to exclude patients who have taken sildenafil, vardenafil, or tadalafil within 72 hours of the endothelial function study, or who are hypotensive (systolic BP \<100).