CD4 and infection: HIV/SIV both replicate in macrophages and CD4+ T cells in the oral mucosa, regardless of the route of infection (Cutler and Jotwani, 2006; Moutsopoulos et al., 2006; Lu and Jacobson, 2007) and virus replication seems to activate toll-like receptors (TLR) that are found at high densities throughout the oral cavity (Challacombe and Naglik, 2006).