TLR9 Expression and Function Is Abolished by the Cervical Cancer-Associated Human Papillomavirus Type 16

Abstract

Cervical cancer development is linked to the persistent infection by high-risk mucosal human papillomaviruses (HPVs) types. The E6 and E7 major oncoproteins from this dsDNA virus play a key role in the deregulation of the cell cycle, apoptosis, and adaptive immune surveillance. In this study, we show for the first time that HPV type 16 (HPV16), the most carcinogenic type among the high-risk subgroup, interferes with innate immunity by affecting the expression of TLRs. Infection of human primary keratinocytes with HPV16 E6 and E7 recombinant retroviruses inhibits TLR9 transcription and hence functional loss of TLR9-regulated pathways. Similar findings were achieved in HPV16-positive cancer-derived cell lines and primary cervical cancers, demonstrating that this event occurs also in an in vivo context. Interestingly, E6 and E7 from the low-risk HPV type 6 are unable to down-regulate the TLR9 promoter. In addition, E6 and E7 from the high-risk HPV type 18, which are known to persist less competently in the host than HPV16, have reduced efficiency compared with HPV16 in inhibiting TLR9 transcription. Furthermore, a CpG motif derived from the HPV16 E6 DNA sequence activated TLR9, indicating this virus is able to initiate innate responses via the receptor it later down-regulates. This study reveals a novel mechanism used by HPV16 to suppress the host immune response by deregulating the TLR9 transcript, providing evidence that abolishing innate responses may be a crucial step involved in the carcinogenic events mediated by HPVs.

C/EBPδ and STAT-1 Are Required for TLR8 Transcriptional Activity

“…THP-1 cells were transfected with the Ϫ3496 TLR8 promoter cloned in front of the luciferase (Luc) reporter gene. Cells were harvested as described previously (19). The data are the mean of three independent experiments.…”

“…Monocytes were purified from peripheral blood mononuclear cells using CD14-positive selection (Miltenyi) and cultured as described previously (18). Huh-7 cells (kindly provided by Alex Weber, Deutsches Krebsforschungszentrum) and HEK293 were grown in the same conditions as described previously (19). Fig.…”

“…Transient Transfection and Luciferase Assay-Transient transfections were performed in duplicate using FuGENE 6 (Roche Applied Science) as described previously (19).…”

CD56-positive lymphocyte infiltration in relation to human papillomavirus association and prognostic significance in oropharyngeal squamous cell carcinoma

“…[40][41][42] HPV 16 E5 interacts with HLA I heavy chain preventing transport of the major histocompatibility class I (MHC I in mice; HLA class I in humans) to the cell surface. 43 The E5 expression was accompanied by a decreased expression of HLA-A2 and had a functional impact on recognition of E5 expressing cells by HPV specific CD81 T cells.…”

TLR9 Expression in Uterine Cervical Lesions of Uyghur Women Correlate with Cervical Cancer Progression and Selective Silencing of Human Papillomavirus 16 E6 and E7 Oncoproteins in Vitro

“…The E6 and E7 oncoproteins exert their functions by inducing the degradation of two important tumor suppressors, p53 and retino-blastoma (pRb), respectively, and cooperates with each other to immortalize primary keratinocytes (Stanley et al, 2007). However, Hasan UA (Hasan et al, 2007) found that TLR9 expression and function also was abolished by the cervical cancer-associated human papillomavirus type 16.…”