Innate immune cell responses in non pathogenic versus pathogenic SIV infections

• Six types of innate immune cells at least are modulated during HIV/SIV infections.
• Natural hosts resolve inflammation and restore innate immune cells to normal levels.
• The control of inflammation and the immune restoration in natural hosts is very rapid.
• NK cells are the most activated in natural hosts and develop a cytotoxic phenotype.
• The study of control in natural hosts could help defining HIV remission strategies.

HIV-1/SIVmac infections deeply disturb innate host responses. Most studies have focused on the impact on dendritic cells and NK cells. A few but insufficient data are available on other innate immune cell types, such as neutrophils. It has been shown that innate lymphoid cells are depleted early and irreversibly during SIVmac/HIV-1 infections. Studies in natural hosts of SIV have contributed to pinpoint that early control of inflammation is crucial. In natural hosts, plasmacytoid dendritic cells, myeloid dendritic cells and NK cells are depleted during acute infection but return to normal levels by the end of acute infection. We summarize here the similarities and differences of various types of innate immune responses in natural hosts compared to pathogenic HIV/SIV mac infections.