A study by Vall d'Hebron Research Institute (VHIR) has succeeded in determining that the HIV virus is transcribed into a subpopulation of cells, known as T CD4+ effector memory, long-lived memory cells that persist in patients for years even if they have been for a period in antiretroviral treatment. And it has done so using a new technique called RNA FISH-flow which is the first time it is used in HIV to determine RNA (ribonucleic acid) in cellular populations. "Until now, one of the great unknowns had been to find out where the reservoir was and specifically what kind of cells it was that was supporting the replication of the virus in patients receiving antiretroviral treatment," explains Dr. María José Buzón, Head of Translational Research on HIV at the http://bit.ly/2ppDTrb Infectious Diseases Research Group at VHIR. This study, published in the journal http://bit.ly/2u96Mdr mBio (American Society for Microbiology) has used a new technology that allows to visualize viral RNA in individual cells in a simpler way. "The RNA FISH-flow, which is the name of this technology, allows to obtain by flow cytometry a greater volume of information and in a smaller sample compared to the conventional technique of PCR (polymerase chain reaction), adds Dr. Buzón, coordinator of the research. "One of the great advantages of RNA FISH-flow is that it allows to make surface markings to phenotype the cells with which it is working and to identify their nature", emphasizes Judith Grau, a predoctoral student of the group, and first author of the research work. This is how they have come to identify the CD4+ effector memory T cell subpopulation as the reservoir of virus that is transcribed in patients on antiretroviral therapy. And they have been able to do so from a very small number of cells.Next stepsAnother advantage of this technique is that it facilitates both the identification of other cell types by surface markers and the subsequent verification of whether or not they are transcribing the HIV virus to design therapies directed to these cells in order to eliminate the viral reservoir. The group is currently working on a project to evaluate how different drugs and combinations of drugs are capable of awakening the latent virus. That is, to be able to measure the transcription of the virus in each cell subpopulation when a certain drug is added.