For therapies to be effective, drugs have to be able to reach their target. But what if you don’t know exactly where that target is? The human immunodeficiency virus (HIV), which causes AIDS, is extremely small; about 1 million HIV particles could fit on the head of a pin. So only a powerful electron microscope can reveal its whereabouts in the body. HIV is known to infect and destroy immune cells. An image taken with an electron microscope reveals HIV particles, digitally colored blue, lurking in the deep layers of the intestinal tissue of an infected mouse—a tissue that houses many immune cells. Here the HIV particles are found in the spaces between the gut cells, where they can essentially “hide” from antiviral drugs in the blood. Ordinarily, HIV does not infect mice, so this mouse was implanted with human immune cells to make the infection possible. Scientists can then monitor the virus at different stages of infection.
Mice were implanted with human immune cells and then infected with HIV. After the infection, different mouse organs were preserved and prepared for electron tomography, which produces 3-dimensional views of structures that are even smaller than viruses.
Image courtesy of Mark Ladinsky PhD and HHMI investigator Pamela Bjorkman PhD, California Instutute of Technology