ABSTRACT
Dendritic cells (DCs) link innate and adaptive immunity by sensing pathogens or vaccinogens and signaling a variety of defense responses. Since human papillomavirus type 16 L1 virus-like particles (HPV16 VLPs) induce a potent, protective immune response after vaccination, we examined their recognition by DCs. HPV16 VLPs cause phenotypic maturation of murine bone marrow-derived DCs (BMDCs), and immunization of mice with HPV16 VLP-loaded BMDCs or HPV16 VLPs alone induced T helper 1 (Th1)-biased immune responses. Analysis of transcriptional responses of murine BMDCs by microarray suggested that alpha/beta interferon (IFN-α/β) transcripts and numerous proinflammatory cytokines and chemokines are up regulated in response to HPV16 VLPs. Indeed, the induction of IFN-α, IFN-γ, and interleukin-12 (IL-12) production by BMDCs after stimulation with HPV16 VLPs was demonstrated by quantitative enzyme-linked immunosorbent assay. Many microbial products that induce proinflammatory responses are recognized via Toll-like receptor (TLR) signaling through the key adaptor protein MyD88 and activation of NF-κB, nuclear factor of activated T cells (NF-AT), and activating protein 1 (AP-1). Reporter assays indicated that HPV16 VLPs activated NF-κB-, NF-AT-, and AP-1-dependent transcription in the RAW264.7 macrophage cell line. Knockdown of MyD88 transcripts by small interfering RNA in the RAW264.7 macrophage cell line inhibited the activation of NF-κB-, NF-AT- and AP-1-dependent transcription by HPV16 VLP. Furthermore, MyD88−/− BMDCs failed to up regulate IL-12 and IFN-α and -γ in response to HPV16 VLPs. Finally, Th1-biased immune responses to HPV16 VLPs are dramatically impaired in MyD88 and IFN-α/β receptor-deficient mice. This implicates TLR recognition as central to immune recognition of HPV16 L1 VLPs.
Soyasaponin A1 inhibits the lipid raft recruitment and dimerization of TLR4, MyD88, and TRIF by maintaining cholesterol homeostasis in palmitic acid-stimulated inflammatory Raw264.7 macrophage cell line
