Antiretroviral therapy (ART) has enabled most people living with HIV to live long and healthy lives. However, a small portion of people experience detectable traces of the virus, known as nonsuppressible viremia (NSV), despite strict adherence to long-term treatment regimens and the absence of symptoms. The results of a study headed by researchers at Johns Hopkins University School of Medicine now suggest that most cases of NSV are explained by defective and noninfectious copies of the virus. The study, which involved more than 50 people, found that while traces of HIV-1 RNA can persist in blood after optimal therapy, cases of non-suppressible viremia are driven by HIV-1 RNA with defects in a piece of the RNA known as 5’-leader. The team developed a digital PCR (dPCR) assay, CLAWS (Capturing 5′ Leader Anomalies Without Sequencing), that distinguishes intact from defective 5′L RNA. “From a clinical perspective, this is important because people with HIV are taught that the absolute goal of their medication is to achieve undetectable viral load, and they worry,” said Francesco R. Simonetti, MBChBD, PhD, an assistant professor of medicine in the Division of Infectious Diseases at Johns Hopkins University School of Medicine. The new findings, said Simonetti and his team, should provide relief to many people living with HIV who fear a viral rebound or who are concerned about transmitting the virus to partners despite taking effective treatment. Simonetti is senior and corresponding author of the team’s report in Nature Communications (“5′ leader defects drive persistent HIV-1 viremia…