Modeling SIV kinetics supports that cytotoxic response drives natural control and unravels heterogeneous populations of infected cells

SIVmac251-infected Mauritius cynomolgus macaques presenting a M6 MHC haplotype or challenged with a low inoculum dose by mucosal route are models for natural HIV control. Here we characterized by modeling the dynamics of plasma SIV-RNA and of SIV-DNA in blood cells of 16 macaques of the ANRS SIC study. SIV-RNA kinetics was best fitted using a model where the cytotoxic immune response progressively mounted up and reduced actively infected cells half-life (t1/2) from 5.5 days early on to about 0.3 days. The model predicted that the control was achieved in animals able to mount an effective immune response within three months, and this was corroborated by the longitudinal analysis of the CD8+ T-cell antiviral activity measured ex vivo. The control of SIV-RNA was accompanied in parallel by a slow and biphasic decline of SIV-DNA. This unravels the presence of at least two compartments of non-actively infected cells that are not rapidly eliminated by the immune system, one with a rapid turnover rate (t1/2=5.1 days) and predominant as long as SIV-RNA levels are still large, and one with a slow turnover (t1/2=118 days) consistent with the half-life of memory T-cells, and only visible when control is achieved. In summary, our analysis suggests that the establishment of an efficient CD8+ T-cell response in the first three months of the infection, and that progressively increases overtime is key to achieve SIV-RNA control in this model. Frequent SIV-DNA quantifications allowed identifying that most cells infected after viral peak have a short t1/2 but do not contribute significantly to viral production. One sentence summaryModeling viral dynamics in SIV natural controller macaques predicts that viral control is primarily driven by the capability to establish an efficient cytotoxic response and the viral decline during control unravels distinct compartments of infected cells.