Figure 6

Long ssDNA comprising the 5′-terminal HIV-1 (−)-strand sequence is highly immunostimulatory, and the recognition of endogenous retroelement-derived ssDNA depends on unpaired guanosines. (a) ELISA of IFN-α in supernatants of monocyte-derived macrophages 36 h after treatment with medium alone (Med) or transfection of genomic DNA, G₃-YSD or ssDNA species of various lengths (116 nucleotides (ss-116; this is SL2 plus SL3 as in Fig. 1c), 180 nucleotides (ss-180) or 381 nucleotides (ss-381)); results are presented relative to those of cells transfected with G₃-YSD, set as 100%. (b) IFN-α in supernatants of chloroquine-treated PBMCs 24 h after treatment with medium alone (Med) or transfection of wild-type (WT) or mutant (ΔG) HERV-E or ERV3.1 (right), and mFOLD-derived models of the secondary structures of HERV-E or ERV3.1 (left); circles indicate mutation of guanosine (black, G to C; gray: G to A). *P ≤ 0.05 (one-way ANOVA followed by Tukey’s post-hoc test). Data are pooled from two experiments with one or two biological replicates in each (mean and s.e.m. of n = 3 donors (a) or n = 4 donors (b)).