SPIRFISH -simultaneous protein and RNA analysis in single extracellular vesicles, including viruses

Detecting HIV (human immunodeficiency virus) accurately is a huge challenge because the virus hides among other particles that look very similar. When an HIV-infected cell releases virus particles, it also releases tiny structures called extracellular vesicles (EVs). These EVs are not viruses, but they can carry a mix of viral and host material, making it hard to distinguish between actual HIV particles and these look-alikes. To complicate things further, both EVs and HIV particles are about the same size and have a similar structure, which makes them even harder to tell apart under normal analysis techniques.

The main feature that sets infectious HIV particles apart from EVs is the presence of HIV genomic RNA (gRNA). This RNA is essential for the virus to replicate and spread the infection. While some advanced methods exist to look at individual particles (single-particle analysis), they usually focus on detecting proteins and often miss the critical RNA that would identify infectious HIV particles from the mix.

Introducing SPIRFISH

Scientists at Johns Hopkins University School of Medicine have developed a new technique called SPIRFISH (Single Particle Interferometric Reflectance Imaging Sensor with Fluorescence in Situ Hybridization), which could be an answer for this problem. This method is able to look at both the viral proteins and the RNA inside individual particles, which means it can tell the difference between infectious HIV particles and other non-infectious particles like EVs.

Using SPIRFISH, researchers can detect specific proteins found in HIV, such as the envelope protein gp120, alongside the HIV genomic RNA inside the virus. This combination gives a much clearer picture of what’s a real HIV particle and what’s just a harmless EV or a non-infectious virus particle that can’t replicate.

Why This is Important

SPIRFISH isn’t just helpful for detecting HIV. It can also be used to look at EVs themselves, which are becoming a big focus in medical research, especially for their potential to deliver therapeutic RNA. Being able to analyze individual EVs for specific RNAs could open new doors for using them in treatments, like delivering RNA to target specific diseases.

In summary, SPIRFISH offers a new, more accurate way to analyze and differentiate between HIV particles and EVs, solving a long-standing problem in viral detection. It has the potential to advance HIV research, improve diagnostic methods, and even impact the growing field of EV-based therapeutics.