KIR3DS1 represents the only activating receptor with three extracellular domains and several studies have identified this gene to be associated with the outcome of various diseases, including viral infection like HIV-1 (slower progression to AIDS and lower viral load in individuals carrying KIR3DS1 and HLA-B Bw4 I80) [22], HBV (increased rate of spontaneous recovery) [94] and HCV (viral clearance and sustained virological response) [95]. This evidence concerns the gene HLA-B and viral infectious disease.