TLR9 and TLR7 agonists mediate distinct type I IFN responses in humans and nonhuman primates in vitro and in vivo

Abstract

Human I-IFNs include IFN-β and 13 independently regulated subtypes of IFN-α (I-IFNs). TLR7 and -9 induce I-IFNs, but it is unknown whether their subtype repertoire is similar. This study used new PCR arrays that selectively amplify individual I-IFN subtype genes of human and nonhuman primates to characterize the TLR7- and -9-mediated IFN response in vitro and in vivo. We show that in human PBMCs, TLR7 agonists induce a rapid burst of I-IFN transcripts, consisting primarily of IFN-α1/13, -α2, and -α14. In contrast, TLR9 agonists, regardless of the type used (CpG C-, B-, or D-ODN), prompted slower but sustained expression of IFN-α1/13, -α2, -α7, -α8, -α10, -α14, -α16, and -α21. These qualitative differences were translated downstream as differences in the pattern of IFN-inducible genes. In macaque PBMCs, imiquimod produced a short burst of IFN mRNA, dominated by IFN-α8, whereas C- or D-ODN induced a greater than tenfold increase in transcripts for all I-IFN subtypes by 12 h of culture. Differences were more evident in vivo, where TLR7 and -9 agonists induced significantly different levels of I-IFN transcripts in skin. Although the rates of gene transcription differed significantly for individual TLR9 agonists, their IFN-α subtype signature was almost identical, indicating that the type of receptor dictates the quality of the I-IFN response in vitro and in vivo. These results may underlie the differential therapeutic effects of TLR7 and -9 agonists and should inform future clinical studies.

CD141+ dendritic cells produce prominent amounts of IFN-α after dsRNA recognition and can be targeted via DEC-205 in humanized mice

“…Reversetranscription and quantitative polymerase chain reactions were performed as described 21 and run on a BIO-RAD iCycler IQ.…”

IFN‐α subtypes: distinct biological activities in anti‐viral therapy

“…Induced Mo et al, 2007 high in poly I : C-stimulated DC Hillyer et al, 2012 High APOBEC3G induction Vazquez et al, 2011 By CpG in PBMC Puig et al, 2012 Intermediate inducer of IFIT1, CXCL10, CXCL11, ISG15 and CCL8 Moll et al, 2011 Less potent against human metapneumovirus Scagnolari et al, 2011 HSV, herpes simplex virus; IDO, indoleamine 2,3-dioxygenase; NDV, Newcastle disease virus; PBMC, peripheral blood mononuclear cells; pDC, plasmacytoid DC; RSV, respiratory syncytial virus. The nomenclature conforms to that used by van Pesch et al (2004).…”

Virus Multiplicity of Infection Affects Type I Interferon Subtype Induction Profiles and Interferon-Stimulated Genes

“…It has been reported extensively that different viruses induce distinct patterns of type I IFN subtype profiles and that this is due mainly to the different combinations of PRRs that are activated when different classes of viruses are present (11,12). In this study, however, we made the novel observation that the same virus could induce distinct type I IFN subtype profiles in the same cell type when different multiplicities of infection (MOIs) were used.…”

“…These sensors then activate different signaling pathways and transcription factors that have different capabilities to bind to the promoter regions of distinct type I IFN subtypes. This idea has been supported by the fact that stimulating human leukocytes with agonists for TLR3, -7, -8, and -9 resulted in different IFN-␣ subtype patterns (11,12). Furthermore, different type I IFN subtype profiles can also be induced in a cell-type-specific manner (26), as different cell types express varying levels of both PRRs and transcription factors that can affect subtype promoter regulation.…”

“…Interestingly, the type I IFN subtypes that we found to be IFNAR independent, which are IFN-␤ and IFN-␣1, -2, and -8, share only 39 to 60% sequence similarity, much less than the IFNAR-dependent subtypes. This may not be surprising, since it has been reported extensively in the literature that the activation of different PRRs induces distinct patterns of type I IFN subtypes, as stimulating human and nonhuman primate leukocytes with agonists for TLR3, -7, -8, and -9 resulted in different IFN-␣ subtype patterns (11,12). Therefore, subtypes that are induced early following PRR stimulation may have distinct sets of transcription factor binding sites for proteins that are activated in the different PRR signaling pathways.…”