HIV persists in infected individuals despite ART. While persistent HIV becomes transcriptionally active in the presence of latency reversing agents, these agents have little effect on the size of the viral reservoir in vivo. Thus, improved killing of infected cells is essential to achieve viral eradication. Towards this goal, we tested whether a TLR9 agonist (MGN1703; lefitolimod) could enhance antiviral immunity in vivo.
Sigmoid biopsies were collected from 11 participants at baseline and 24 hours after the last dose in week 4 of a single-arm phase 1b/2a clinical trial where HIV+ adults received MGN1703 (60 mg s.c.) twice weekly for 4 weeks (NCT02443935). We quantitated IHC signal positive cell profiles (nucleus with associated signal; referred to as cells below) in fixed tissue sections for the antiviral and inflammatory response markers MxA, ISG15, IL-21, CXCL10 or MPO; data were stratified by anatomical location: lamina propria (LP) or epithelium. Remaining biopsy tissue was digested and percoll-enriched intestinal mononuclear cells were obtained for virological and immunological analyses [RNA-seq; HIV DNA/RNA levels (qPCR); CD4/CD8 T cell frequency and activation (flow)]. Plasma viremia quantitation: Cobas Taqman. Data analyses: Wilcoxon signed rank tests, mean fold change (mfc) and Ingenuity Pathway Analysis right-tailed Fisher Exact Test.
RNASeq revealed 248 significantly regulated genes (FDR<0.05) and a potent antiviral response (IPA p=2*10^-14) including many IFN-a stimulated genes. Indeed, MGN1703 dosing increased the number of cells positive for MxA (LP: p=0.001, mfc=8.8; and epithelium: p=0.003, mfc=27.6), ISG15 (LP: p=0.014, mfc=5.6) and IL-21 (LP: p=0.019, mfc=0.5). In contrast, there was no change in the numbers of cells positive for CXCL10 which is IFN-g induced (LP: p=0.97). No cohort-wide changes were observed in: neutrophil infiltration (MPO LP: p=0.97); viral DNA; viral RNA; T cell subset distribution; or T cell activation. However, after stratifying according to MGN1703-induced plasma viremia status, we observed that viremic individuals had a decrease (n=3, mfc=-0.8) in integrated intestinal lymphoid tissue HIV DNA (p=0.042).
MGN1703 induced robust antiviral immune responses in the intestines of HIV+ individuals on ART. In addition, the observed lack of neutrophil infiltration suggests that MGN1703 does not cause destructive tissue inflammation. These data support a prominent role for MGN1703 immunotherapy in HIV eradication strategies.