Neuroimaging Correlates of Monocyte/Macrophage Infiltration in HIV-infected Individuals: A Cross-sectional Pilot Study Using IV Ferumoxytol

The continued existence of cognitive dysfunction in HIV infected individuals in the era of effective antiretroviral therapy may be, in part, secondary to the failure of current antiretroviral regimens to eradicate the pool of HIV-infected and activated monocytes within the bloodstream. Trafficking of such HIV infected and activated blood monocytes into the brain parenchyma is believed to introduce HIV into the brain and precipitate immune activation and inflammation, ultimately leading to neuronal degeneration. Ferumoxytol is an ultrasmall superparamagnetic iron-oxide (USPIO), which is FDA-approved for intravenous iron-replacement therapy in anemic patients with chronic kidney disease. The paramagnetic properties of ferumoxytol also allow it to be used as a MRI contrast agent. Ferumoxytol is avidly taken up by circulating monocytes and reactive astrocytes, microglia, and dendritic cells within the brain, making it potentially a novel biomarker for HIV-associated cognitive impairment given the role of monocytes in its pathogenesis. This proposal intends to investigate the possible use of ferumoxytol (a new MRI contrast agent) as a biomarker for HIV-associated cognitive impairment and to assess the safety and tolerability of ferumoxytol in HIV-infected individuals. Hypotheses to be tested: HIV-infected subjects with undetectable plasma HIV RNA levels and detectable levels of HIV DNA in CD14+ peripheral blood mononuclear cells (PBMCs) and impairment on neurocognitive testing will demonstrate ferumoxytol contrast enhancement in the perivascular regions of the brain consistent with monocyte/macrophage infiltration in these regions. Ferumoxytol can be safely administered to HIV-infected subjects.