MRI scans help spot persistent HIV in brain

Dr Lewis Haddow, senior clinical research associate and Ravindra Gupta, Professor of infection and immunity,  talk about how a new study by Central and North West London (CNWL) NHS Foundation Trust and University College London (UCL), has helped confirm cognitive problems in HIV patients using MRI scans

The UK is on its way to achieving the United Nations AIDS target of 90% of people diagnosed with HIV on antiretroviral treatment and 90% of those who receive antiretrovirals being virally suppressed. But concerns remain around persistent reservoirs of HIV infection in organs such as the brain.1 These reservoirs are a major barrier to finding a cure for HIV, and in some people the virus can “escape”, showing evidence of replication in particular cells and body fluids. We recently brought together clinicians and academics from two NHS Trusts (Central and North West London [CNWL] and University College London Hospitals [UCLH]) and University College London to produce an important study of viral escape in the central nervous system (CNS) of people living with HIV (PLWH).2

We had noticed that a proportion of HIV positive patients undergoing lumbar punctures had detectable virus in their cerebrospinal fluid (CSF). Given that in an untreated patient, the number of copies of HIV RNA is typically ten-fold lower than the plasma titre, detecting virus in the CSF of patients with an undetectable plasma viral load (less than 50 copies per millilitre) was a significant finding. Furthermore, a number of patients with quantifiable levels of virus in their plasma had CSF levels that were higher than in the blood. PLWH may have a lumbar puncture to exclude serious causes of neurological symptoms, but in recent years we were requesting more lumbar punctures in those with milder symptoms to look for viral escape. The phenomenon of viral escape or “discordance” between CSF and plasma had been described before, notably by researchers in France and Sweden,3,4 but there was still little way of predicting which patients would have this anomaly. By understanding the phenomenon better, we could potentially avoid or delay an invasive procedure in some HIV positive patients, while prioritising the investigation for those most likely to benefit.