The following images show a few ways in which cutting-edge research tools are giving us clearer views of viruses—and possible ways to disarm them. The examples, which highlight work involving HIV and the coronavirus, were funded in part by our Biomedical Technology Research Resources program.
Uncloaking HIV’s Camouflage
To sneak past our immune defenses and infect human cells, HIV uses a time-honored strategy—disguise. The virus’ genome is enclosed in a protein shell called a capsid (on left) that’s easily recognized and destroyed by the human immune system. To evade this fate, the chrysalis-shaped capsid cloaks itself with a human protein known as cyclophilin A (in red, on right). Camouflaged as human, the virus gains safe passage into and through a human cell to deposit its genetic material in the nucleus and start taking control of cellular machinery.
Biomedical and technical experts teamed up to generate these HIV models at near-atomic resolution. First, structural biologists at the Pittsburgh Center for HIV Protein Interactions used a technique called cryo-electron microscopy (cryo-EM) to get information on the shape of an HIV capsid as well as the capsid-forming proteins’ connections to each other and to cyclophilin A. Then experts at the Resource for Macromolecular Modeling and Bioinformatics fed the cryo-EM data into their visualization and simulation programs to computationally model the physical interactions among every single atom of the capsid and the cyclophilin A protein. The work revealed a previously unknown site where cyclophilin A binds to the capsid, offering new insights on the biology of HIV infection. Continue reading