Increased Activity of NK Cells and Plasmacytoid Dendritic Cells in HIV-Exposed Seronegative (ESN) Individuals

The mechanisms involved in resistance to HIV-1 infection, especially the role of innate immune response, have not been thoroughly explored in individuals who are repeatedly exposed to HIV-1, but do not get the infection, termed as Exposed sero-negative or ESN. Frequency and activation state of natural killer (NK) cells and plasmacytoid dendritic cells (pDC) in ESNs from North India were compared with those in recently infected HIV positives (RHIV), chronically infected HIV positives (HIV+) and healthy controls (HC). The activation state of NK cells in terms of cytokine response (IFNγ & TNFα) was significantly higher in ESNs compared to the healthy controls, recently infected HIV+ and chronically infected HIV+. Although the number of circulating pDC in different study groups was not significantly different, yet these cells seem to have significantly higher activation state in terms of IFNα production (ex-vivo in response to CpG ODN) in ESNs when compared with other groups. Increased activation status of NK cells and pDC in Exposed but Seronegative individuals indicates their continuous stimulation with HIV antigens due to regular exposure with infected partners and which might be imparting resistance to viral infection in these individuals.