Researchers have long considered the tonsils to serve as reservoirs for the replication of the human immunodeficiency virus (HIV). However, they have never clearly established whether the tonsils also can serve as a conduit for person-to-person HIV transmission. In the American Journal of Pathology (August 2007), NIDCR scientists and colleagues added 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 readout of gingival epithelial cells. Among the variations in the 2 profiles was a 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 follow-up laboratory work using antibodies that detected CX-CR4 on the epithelial cells. The scientists also discovered increased gene expression in the tonsil epithelium of potentially HIV-binding molecules FcRgIII, 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, beta-defensins, and thrombo-spondin. 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.”
(Source: NIDCR, Science News in Brief, July 26, 2007)
