Scientists spot how HIV infects gut

Researchers have utilized high-resolution electron microscopy to look at HIV infection within the actual tissue of an infected organism, providing perhaps the most detailed characterization yet of HIV infection in the gut.

Lead author Mark Ladinsky, an electron microscope scientist at Caltech worked with Pamela Bjorkman, Max Delbruck Professor of Biology at Caltech, used a technique called electron tomography, in which a tissue sample is embedded in plastic and placed under a high-powered microscope. Then the sample is tilted incrementally through a course of 120 degrees, and pictures are taken of it at one-degree intervals.

All of the images are then very carefully aligned with one another and, through a process called back projection, turned into a 3-D reconstruction that allows different places within the volume to be viewed one pixel at a time.

By procuring such detailed images, researchers were able to confirm several observations of HIV made in prior, in vitro studies, including the structure and behavior of the virus as it buds off of infected cells and moves into the surrounding tissue and structural details of HIV budding from cells within an infected tissue.

The team also described several novel observations, including the existence of "pools" of HIV in between cells, proof that HIV can infect new cells both by direct contact or by free viruses in the same tissue, and that pools of HIV can be found deep in the gut.

The findings have been published in the journal PLOS Pathogens .