Lipids in HIV’s Envelope Help the Virus to Spread
Dendritic cells (DCs) are a type of immune cell that patrol tissues, on the lookout for microbial invaders. When DCs encounter a pathogen, they chop it up into tiny pieces and then carry samples of it to local lymph nodes. There, they display their finds to another kind of immune cell, the T cell, which then mounts a full-fledged immune response against the invader.
Unfortunately, HIV, the virus that causes AIDS, can exploit the DC surveillance network to its own advantage: HIV is picked up by DCs that patrol mucosal tissues, but avoids being killed by them, and instead hitches a ride to lymph nodes. There, the virus transfers into its favorite host cell type, the T cell. Until now, it wasn’t clear how DCs recognize HIV for uptake—a mystery that’s now been solved thanks to a joint effort by Spanish and German research groups. The groups, headed by Nuria Izquierdo-Useros and Javier Martinez-Picado in Spain, and Maier Lorizate and Hans-Georg Kräusslich in Germany, uncover the culprit in this month’s issue of PLoS Biology.
It’s no mystery how DCs detect many pathogens: the microbes betray themselves by displaying certain pathogen-specific compounds on their surfaces, which DCs recognize using dedicated receptors. HIV also displays a few viral proteins on its surface (it hides the rest away under a lipid bilayer envelope that it acquires from the plasma membrane of infected cells). However, previous studies indicated that viral proteins displayed on the surface may not be essential for DC capture. Instead, prior work from Martinez-Picado’s group led the authors to theorize that host cell glycosphingolipids incorporated into the virus envelope could be critical in triggering DC recognition.