Using dual-photon in-vivo imaging, we previously showed significantly lower concentrations of tenofovir (TFV) in rat lymph nodes (LN) compared to peripheral blood (PB). This finding was later confirmed for intracellular active drug-metabolite (IADM) levels of nucleos(t)ide reverse transcriptase inhibitors (NRTIs) in antiretroviral (ARV) therapy (ART) of HIV/SIV. Understanding factors that regulate penetration of NRTIs across the blood-lymphatic barrier can assist the development of new formulations (e.g. lipid-based nanoparticles) optimized for HIV treatment and prevention.
We retrospectively analyzed ARV levels in 21 Indian rhesus macaques (RMs) infected with SIVmac239nefstop and treated with daily ART (20mg/kg,SQ,TFV, 30mg/kg,SQ,emtricitabine (FTC), and 100mg,P.O.,integrase inhibitor L-870812) starting at week 5 post-infection (M0) for 3 months (Di Mascio et al., Science 2019). We quantified TFV and FTC in plasma and their IADMs (TFV-diphosphate, TFV-dp; FTC-triphosphate, FTC-tp) in PBMC and LN mononuclear cells (LNMC) by HPLC-MS/MS at month 1 (M1) and month 3 (M3) post-ART initiation. Collagen type-1 in LN at M0 was measured. Viral load in plasma, LN and rectal tissue (SIV-RNA copies/10?6 cell eq.), and %Ki67+ in PB CD4T, CD8T, and CD20B cells were measured.
TFVdp and FTCtp concentrations were significantly lower in the LNMC compared to PBMC (median;M1: 3 and 12-fold, M3: 2 and 7-fold, respectively;p?0.005). Between M1 and M3, viral RNA decreased in LN, and IADM levels increased in both LNMC (2-3-fold, p?0.001) and PBMC (1.4-1.5-fold, p?0.01). LNMC IADM levels at M1 were inversely correlated with plasma viremia (TFVdp: p=0.003, FTCtp: p=0.07), LN (TFVdp: p=0.06, FTCtp: p<0.05) and rectal tissue (p<0.05) viral load at ART initiation, but not collagen deposition or PB %Ki67+. Yet, LNMC IADM levels at M1 were not predictive of viral decay rates during ART. A larger reduction in PB %Ki67+ in CD4T cells during M1 was associated with higher LNMC IADM levels at M1 (p<0.05).
NRTI IADM levels were consistently lower in LNMC vs. PBMC of SIV-infected and ART-treated RMs. Viral clearance during the first 3 months of ART corresponded with increasing IADM levels in LNMC and to a lesser extent in PBMC. Given the human and macaque models showing the IADM loading phase of ~1 week in PBMC and rectal tissue, these data suggest a link between viral dissemination/viral-induced generalized immune activation and drug penetration in LNs, a major reservoir of viral replication.