Tonsils May Play a Role in HIV Transmission
July 26, 2007
Researchers have long considered our tonsils to serve as reservoirs for the replication of the human immunodeficiency virus. However, they have never clearly established whether the tonsils also can serve as a conduit for person to person HIV transmission. In the August issue of The American Journal of Pathology, NIDCR scientists and colleagues add an important new layer of evidence that tonsils may play a role. The scientists extracted epithelial cells from the tonsil and broadly profiled the levels at which various genes were expressed. This allowed them to compare the genetic profile of the tonsil epithelium with a genetic read out of gingival epithelial cells. Among the variations in the two profiles was significantly higher expression in the tonsil epithelium of the CXCR4 gene, which encodes a surface protein that HIV often uses to anchor itself to cells before entering them. They confirmed this finding in followup laboratory work using antibodies that detected CXCR4 on the epithelial cells. The scientists also discovered increased gene expression in the tonsil epithelium of potentially HIV-binding molecules FcRγIII, complement receptor 2, and various immune-signaling complement components. Interestingly, they also noted a trend toward lower levels of gene expression in the tonsil epithelium for innate immune molecules with possible anti-HIV activity such as SLPI, β-defensins, and thrombospondin. As the authors concluded, “Collectively, our data suggest that increased expression of molecules associated with HIV binding and entry coupled with decreased innate antiviral factors may render the tonsil a potential site for oral transmission.”