A Common Path to Innate Immunity to HIV-1 Induced by Toll-Like Receptor Ligands in Primary Human Macrophages

Abstract

Toll-like receptors (TLR) represent the best characterized receptor family transducing innate immune responses, the first line of defense against microbial invaders. This study was designed to investigate whether responses through TLR inhibit HIV-1 replication in its primary target cells. Primary human macrophages and lymphocytes from several different donors and HIV-1 infection in tissue culture were used exclusively in this work. We report that ligands of three different TLR: LPS, R848, and double stranded RNA, induce a common antiviral response in macrophages as assayed by measurement of HIV-1 p24 protein, gag DNA, and entry into cells. HIV-1 infection is arrested after efficient entry but prior to reverse transcription. TLR-ligand activated cells secrete antiviral factors that induce a similar restriction. HIV-1 infection of lymphocytes is not affected by exposure to TLR ligands or to antiviral factors secreted by activated macrophages. TBK1, but neither NF-κB nor JAK-STAT activity, is required in macrophages to mount this antiviral response; the combination of p38 MAPK and JNK are partially required for induction of antiviral activity. Based on transcriptional induction and inhibition, the TLR-linked antiviral activity is different from APOBEC3 A or G, interferon-β, NAMPT, or p21Cip1. The cell-type specificity, site of action, and requirement for signaling intermediates suggest that the TLR-linked antiviral activity is novel.

TLR7/8 agonist induces a post-entry SAMHD1-independent block to HIV-1 infection of monocytes

“…In both cases, the block was to infection of stimulated PBMCs where the major target cells targeted for HIV-1 infection are activated T cells. We and Wang et al [8] find that TLR7/8 agonist treatment of activated T cells has no effect on HIV-1. Thus, the R848-induced restriction in stimulated PBMC is mediated by a soluble factor such as type-I IFN released by MDMs, monocytes or pDC, while the post-entry block in a single-cycle infection is due to an intrinsic restriction and not a soluble factor.…”

“…The TLR7/8 agonist R848 has been found to induce a block to HIV-1 replication in monocytes and MDMs [7, 8, 10]. To further investigate the mechanism by which the drug interferes with HIV-1 replication we used a VSV-G-pseudotyped reporter virus engineered to package the SIVmac accessory protein Vpx [36].…”

“…A previous study by Wang et al [8] showed that LPS, R848 and double-stranded RNA induced a post-entry block to HIV reverse transcription in MDMs but not activated T cells. Here, we measured single-cycle reporter gene expression rather than released p24 and used undifferentiated monocytes rather than MDMs.…”

“…Several TLR agonists inhibit the replication of HIV-1 in lymphocytes, monocytes and monocyte-derived macrophages (MDM). The imidazoquinoline TLR7/8 agonists R848 (resiquimod) and gardiquimod were found to inhibit HIV-1 replication in MDMs by inducing soluble antiviral factors and in the case of gardiquimod, by acting as a nucleoside reverse transcriptase inhibitor [7, 8]. In monocytes isolated from HIV-infected individuals, R848-treatment reduced viral RNA in the culture supernatants [9].…”

Porphyromonas gingivalis-mediated signaling through TLR4 mediates persistent HIV infection of primary macrophages

“…E. coli LPS has been suggested to interfere with HIV replication at multiple steps of the HIV replication cycle in macrophages including interference of efficient viral entry (Franchin et al, 2000; Herbein et al, 1995; Herbein and Varin, 2010; Mikulak et al, 2009; Verani et al, 1997; Verani et al, 2002) and a restriction after entry but before proviral integration (Devadas et al, 2010; Donninelli et al, 2016; Pushkarsky et al, 2001; Schlaepfer et al, 2014; Wang et al, 2011). Our data suggests that a step post-proviral integration and transcription are targeted in MDMs when infected with HIV in the presence of P. gingivalis .…”