HIV's Hidden Loop: Yale Discovers Circular RNA That Helps the Virus Copy Itself

A Surprise Hidden in Plain Sight

For decades, scientists assumed that HIV, like other retroviruses, produced only straight, linear strands of RNA. A team at Yale University has now overturned that assumption with the discovery that HIV generates circular RNA molecules, loop-shaped genetic structures that help the virus replicate more efficiently.

The most abundant of these loops, which the researchers have named circHIV, was found in blood plasma from eighteen people living with HIV, as well as in infected immune cells grown in the laboratory.

How It Works

CircHIV works by latching onto a viral protein called Tat, short for Trans-Activator of Transcription. Tat is already known to be essential for switching on HIV's genes. By binding to Tat, circHIV effectively supercharges the virus's gene-reading machinery, leading to increased production of viral components.

When the researchers reduced circHIV levels in infected cells, viral activity dropped. When they added extra circHIV, infection rates climbed. The team also found that circHIV and another RNA element called TAR bind to Tat at different sites, suggesting the protein has a previously unknown binding domain specifically for circular RNA.

Why It Matters

Circular RNAs lack the exposed ends that make linear RNA easy for cellular enzymes to break down, which means they persist much longer inside cells. This stability makes circHIV both a promising biomarker for monitoring infection and a potential drug target.

Because circHIV operates through a completely different mechanism from existing antiretroviral drugs, which typically block viral enzymes, therapies aimed at this molecule could sidestep current drug resistance problems and work alongside established treatments.

The study, published in Nature Microbiology, was led by immunologist Grace Chen and represents a significant new chapter in understanding how HIV manipulates its host.