HIV-infected individuals on antiretroviral therapy (ART) are at increased risk for cardiovascular disease (CVD), likely due to chronically increased inflammation. Low-dose methotrexate (LDMTX) may reduce CVD risk in people with rheumatoid arthritis, who like those with HIV, have increased levels of inflammation. The NHLBI is funding a clinical trial targeting the excess inflammation in HIV. That "Parent Study" is a randomized, double-blind, placebo-controlled trial that will assess whether 24-week treatment with LDMTX: i) is safe, ii) reduces circulating inflammatory biomarkers and levels of immune cell activation and iii) improves brachial artery reactivity. However, neither the biomarkers nor endothelial function tests measured as part of the parent study will report on atherosclerotic inflammation, (the desired pathobiological target of LDMTX therapy in HIV). As such, the direct evaluation of arterial inflammation would substantially enhance the scientific value of the trial. In this imaging sub-study, the overall goal is to determine if treating virologically suppressed, HIV-infected individuals with LDMTX will reduce inflammation within the arterial wall.