The presence of particular combinations of HLA and KIR genes impacts the rate of HIV-1 disease progression.4–6 In particular, the combination of KIR3DS1 with HLA-Bw4 molecules possessing isoleucine at position 80 (Bw4-80I)

is linked with a delayed progression to AIDS.4 More recently, our group has published data indicating that the presence of KIR3DS1 alone may be sufficient to affect NK cell function in HIV-1 infection.6 The issue is further complicated by data suggesting that find more the presence of alleles of KIR3DL1 encoding proteins expressed at high levels on the cell surface of NK cells in combination with HLA-Bw4-80I is strongly associated with delayed HIV-1 disease progression.5 Previous studies have suggested that the presence of alleles for KIR3DS1 or KIR3DL1 may also lead to delayed HIV-1 disease progression. KIR3DS1 is expressed at the cell surface, ICG-001 and can be discriminated from KIR3DL1 by flow cytometry with the use of two KIR-specific antibodies (i.e. DX9 and Z27).31 As we do not know the KIR genotype of this cohort of Brazilian subjects, and certain alleles of KIR3DL1 that are expressed in low amounts (similar to KIR3DS1) can be misassigned as KIR3DS1, we have used nomenclature to reflect the relative levels of binding of the DX9 and Z27 antibodies. In previous studies in which the KIR genotype

was known, NK cells that were DX9-negative and Z27-low were defined as KIR3DS1+ cells, whereas NK cells positive for DX9 only, or both DX9 and Z27, were defined as KIR3DL1+. Although this is probably correct, we have chosen to define our populations as KIR3D-positive to reflect either DX9 and/or Z27 binding, and segregated this group into populations that are KIR3Dhigh or KIR3Dlow based on Z27 staining characteristics (Fig. 4a). No significant differences were seen in the number or frequency of KIR3D+ NK cells among seronegative, HIV-1 mono-infected, and HIV-1 and HSV-2 co-infected subjects (Fig. 4b). However, we then correlated the number of KIR3D+ NK cells with HIV-1 viral

load and noted an inverse correlation (Fig. 4c). The number of KIR3D+ NK many cells correlated inversely with HIV-1 viral load in all HIV-positive subjects combined, and this correlation became significant when the HIV-1 mono-infected subjects were segregated as a group (P = 0·029). However, this correlation was lost in the HSV-2 co-infected group (P = 0·634). When KIR3D+ NK cells were segregated into KIR3Dhigh and KIR3Dlow expression groups, a stronger inverse correlation with viral load was observed in the KIR3Dlow population (P = 0·043 and P < 0·1 for all groups and HIV-1 mono-infected individuals, respectively), and this correlation was again lost in the HSV-2 co-infected group (P = 0·969).