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Tuesday, March 31, 2009

Video of HIV Infection

This is remarkable. Scientists have captured video of an HIV-infected T cell transferring the virus directly into a healthy T-Cell through a virological synapse -- basically a tunnel from the interior of one cell into the interior of another. This is a huge development, because it shows that once the virus has infected a host, it can spread without ever leaving its host cells, and this means that the immune system's antibodies, which float around outside the cells, are never given a chance to recognize and attack the virus as it spreads.

This suggests part of why and AIDS vaccine has been so difficult to develop; not only does the virus change the proteins on its surface in order to prevent an effective immune response, it looks like any vaccine targeted at the virus itself can only function as a first line of defense -- attempting to recognize and destroy the virus before it infects any cells. This is a huge problem, especially because the immune system requires some spool-up time, even after vaccination to ramp up antibody production once an invading wave of viruses has been recognized. The lag in "secondary response" combined with the virus' ability to hide in host cells means that, by the time the immune system is up to speed, it's probably too late.

Of course, there are other avenues of treatment; it should now be possible to target the specific proteins which infected cells coat themselves with in order to capture healthy cells and create the virological synapses (in the video below, you can see how the healthy cell becomes stuck and is unable to separate, while other healthy cells bounce off each other). By recognizing those proteins, the immune system can target and destroy infected cells. And this approach, if we work it out, should be vastly more effective than attempting to catch the virus before it infects any cells.

Still, it's a lesson in how much we still have to learn about the mechanics of basic microbiology. We have a tendency to see viruses as stripped-down machines, little boxes of infectious badness that float around and overwhelm us with their lethal efficiency and sheer numbers. But this sometimes overlooks how active and innovative viruses are. It's stunning what HIV can do with only a handful of genes. And it's amazing that after two decades of research into HIV we are only now starting to unravel its mechanisms of transmission.

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