MRI Dye Technique Could Detect HIV Dementia

A new magnetic resonant imaging (MRI) contrast dye could be used to target specific white blood cells (WBCs) believed to play a key role in the development of HIV-associated neurocognitive disorders (HAND).

Researchers at the University of Hawaii (Honolulu, USA) are conducting studies to examine the use of ferumoxytol—an ultra-small iron oxide MRI contrast agent—to identify and quantitate monocyte/macrophage (M/MΦ)-mediated inflammation in the brain of HIV-infected people. M/MΦs are believed to play a critical role in the pathogenesis of HAND, but neuroimaging HIV research has not as yet focused on assessing M/MΦ-mediated inflammation in the brain, since no modality exists that can define inflammation extent as a diagnostic tool, or assist in defining objective improvement in clinical trials addressing HAND.

The researchers hypothesized that imaging based on ferumoxytol, which is avidly taken up by circulating M/MΦs, could identify ongoing inflammation resulting from the perivascular M/MΦ, a key pathologic correlate of HAND. The neurocognitive disorders in HIV continue to be prevalent, despite effective combination antiretroviral therapy (cART), and are responsible for a significant impact on morbidity and quality of life. The researchers believe that once M/MΦs have switched on to battle HIV, an unintended consequence is the production of toxic chemicals in the brain that cause uncontrolled inflammation and ultimately cognitive impairment.

“Four HIV-infected subjects with undetectable HIV RNA levels on antiretroviral therapy and cognitive impairment underwent ferumoxtyol-enhanced brain MRI,” wrote lead investigator Neurologist Beau Nakamoto, MD, PhD, in a 2013 study. “On post-ferumoxytol susceptibility-weighted images, all HIV-infected subjects demonstrated a diffuse “tram track” appearance in the perivascular regions of cortical and deep white matter vessels, suggesting ferumoxytol uptake in monocytes/macrophages. This finding was not present in a HIV-seronegative control.”

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