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Plasmacytoid DCs (pDCs) are innate immune cells that are specialized to produce IFN-α and to activate adaptive immune responses. Although IFN-α inhibits HIV-1 replication in vitro, the production of IFN-α by HIV activated pDCs in vivo may contribute more to HIV pathogenesis than to protection. We have now shown that HIV-stimulated human pDCs allow for persistent IFN-α production upon repeated stimulation, express low levels of maturation molecules, and stimulate weak T cell responses. Persistent IFN-α production by HIV-stimulated pDCs correlated with increased levels of IRF7 and was dependent upon the autocrine IFN-α/β receptor feedback loop. Because it has been shown that early endosomal trafficking of TLR9 agonists causes strong activation of the IFN-α pathway but weak activation of the NF-κB pathway, we sought to investigate whether early endosomal trafficking of HIV, a TLR7 agonist, leads to the IFN-α-producing phenotype we observed. We demonstrated that HIV preferentially traffics to the early endosome in human pDCs and therefore skews pDCs toward a partially matured, persistently IFN-α-secreting phenotype., Introduction Plasmacytoid DCs (pDCs) are innate immune cells that circulate in the blood and lymphoid tissues and are specialized to produce copious amounts of type I IFNs (IFN-α/β) in response [...]

Natural nonhuman primate hosts of SIV do not succumb to AIDS despite significant viral replication, a phenomenon attributed to reduced levels of chronic and deleterious 'immune activation.' Two studies in this issue of the JCI, by Bosinger et al. and Jacquelin et al., now show that SIV induces vigorous immune activation and upregulation of IFN-stimulated genes in both natural and susceptible hosts, but strikingly, the responses resolve only in the former (see the related articles beginning on pages 3556 and 3544, respectively). Thus, natural hosts for SIV actively engage mechanisms to abort sustained immune activation and its associated harmful effects., Chronic, generalized immune activation is believed to advance the pathogenesis of progressive HIV and SIV infection (1), (2). The phenomenon, observed in humans and in susceptible strains of monkeys (e.g., [...]

The effects of nelfinavir on the 3T3-F442A adiipocyte cell line are evaluated. The study shows that nelfinavir induces necrosis of adipocytes mediated by a cellular increase of reactive oxygen species.

Objectives: Dendritic cells play a pivotal but still enigmatic role in the control of tumor development. Composed of specialised subsets (cDC1s, cDC2s, pDCs), DCs are critical in triggering and shaping antitumor immune responses. Yet, tumors exploit plasticity of DCs to subvert their functions and escape from immune control. This challenging controversy prompted us to explore the pathophysiological role of cDCs and pDCs in melanoma, where their precise and coordinated involvement remains to be deciphered. Methods: We investigated in melanoma patients the phenotypic and functional features of circulating and tumor‐infiltrating BDCA1+ cDC2s, BDCA2+ pDCs and BDCA3+ cDC1s and assessed their clinical impact. Results: Principal component analyses (PCA) based on phenotypic or functional parameters of DC subsets revealed intra‐group clustering, highlighting specific features of DCs in blood and tumor infiltrate of patients compared to healthy donors. DC subsets exhibited perturbed frequencies in the circulation and actively infiltrated the tumor site, while harbouring a higher activation status. Whereas cDC2s and pDCs displayed an altered functionality in response to TLR triggering, circulating and tumor‐infiltrating cDC1s preserved potent competences associated with improved prognosis. Notably, the proportion of circulating cDC1s predicted the clinical outcome of melanoma patients. Conclusion: Such understanding uncovers critical and distinct impact of each DC subset on clinical outcomes and unveils fine‐tuning of interconnections between DCs in melanoma. Elucidating the mechanisms of DC subversion by tumors could help designing new therapeutic strategies exploiting the potentialities of these powerful immune players and their cross‐talks, while counteracting their skewing by tumors, to achieve immune control and clinical success. [ABSTRACT FROM AUTHOR]

Summary: Matrix metalloproteinase-2 (MMP-2) is a proteolytic enzyme degrading the extracellular matrix and overexpressed by many tumors. Here, we documented the presence of MMP-2-specific CD4+ T cells in tumor-infiltrating lymphocytes (TILs) from melanoma patients. Strikingly, MMP-2-specific CD4+ T cells displayed an inflammatory TH2 profile, i.e., mainly secreting TNF-α, IL-4, and IL-13 and expressing GATA-3. Furthermore, MMP-2-conditioned dendritic cells (DCs) primed naïve CD4+ T cells to differentiate into an inflammatory TH2 phenotype through OX40L expression and inhibition of IL-12p70 production. MMP-2 degrades the type I IFN receptor, thereby preventing STAT1 phosphorylation, which is necessary for IL-12p35 production. Active MMP-2, therefore, acts as an endogenous type 2 “conditioner” and may play a role in the observed prevalence of detrimental type 2 responses in melanoma. [ABSTRACT FROM AUTHOR]

Virus-like particles (VLPs) are versatile protein-based platforms that can be used as a vaccine platform mainly in infectiology. In the present work, we compared a previously designed, non-infectious, adenovirus-inspired 60-mer dodecahedric VLP to display short epitopes or a large tumor model antigen. To validate these two kinds of platforms as a potential immuno-stimulating approach, we evaluated their ability to control melanoma B16-ovalbumin (OVA) growth in mice. A set of adjuvants was screened, showing that polyinosinic-polycytidylic acid (poly(I:C)) was well suited to generate a homogeneous cellular and humoral response against the desired epitopes. In a prophylactic setting, vaccination with the VLP displaying these epitopes resulted in total inhibition of tumor growth 1 month after vaccination. A therapeutic vaccination strategy showed a delay in grafted tumor growth or its total rejection. If the "simple" epitope display on the VLP is sufficient to prevent tumor growth, then an improved engineered platform enabling display of a large antigen is a tool to overcome the barrier of immune allele restriction, broadening the immune response, and paving the way for its potential utilization in humans as an off-the-shelf vaccine., Competing Interests: The authors declare no competing interests., (© 2022 The Author(s).)

Objectives: Dendritic cells play a pivotal but still enigmatic role in the control of tumor development. Composed of specialised subsets (cDC1s, cDC2s, pDCs), DCs are critical in triggering and shaping antitumor immune responses. Yet, tumors exploit plasticity of DCs to subvert their functions and escape from immune control. This challenging controversy prompted us to explore the pathophysiological role of cDCs and pDCs in melanoma, where their precise and coordinated involvement remains to be deciphered., Methods: We investigated in melanoma patients the phenotypic and functional features of circulating and tumor-infiltrating BDCA1 + cDC2s, BDCA2 + pDCs and BDCA3 + cDC1s and assessed their clinical impact., Results: Principal component analyses (PCA) based on phenotypic or functional parameters of DC subsets revealed intra-group clustering, highlighting specific features of DCs in blood and tumor infiltrate of patients compared to healthy donors. DC subsets exhibited perturbed frequencies in the circulation and actively infiltrated the tumor site, while harbouring a higher activation status. Whereas cDC2s and pDCs displayed an altered functionality in response to TLR triggering, circulating and tumor-infiltrating cDC1s preserved potent competences associated with improved prognosis. Notably, the proportion of circulating cDC1s predicted the clinical outcome of melanoma patients., Conclusion: Such understanding uncovers critical and distinct impact of each DC subset on clinical outcomes and unveils fine-tuning of interconnections between DCs in melanoma. Elucidating the mechanisms of DC subversion by tumors could help designing new therapeutic strategies exploiting the potentialities of these powerful immune players and their cross-talks, while counteracting their skewing by tumors, to achieve immune control and clinical success., Competing Interests: The authors declare no conflict of interest., (© 2020 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Plasmacytoid dendritic cells (pDC) are innate immune cells that sense viral nucleic acids through endosomal Toll-like receptor (TLR) 7/9 to produce type I interferon (IFN) and to differentiate into potent antigen presenting cells (APC). Engagement of TLR7/9 in early endosomes appears to trigger the IRF7 pathway for IFN production whereas engagement in lysosomes seems to trigger the NF-κB pathway for maturation into APC. We showed previously that HIV-1 (HIV) localizes predominantly to early endosomes, not lysosomes, and mainly stimulate IRF7 rather than NF-κB signaling pathways in pDC. This divergent signaling may contribute to disease progression through production of pro-apoptotic and pro-inflammatory IFN and inadequate maturation of pDCs. We now demonstrate that HIV virions may be re-directed to lysosomes for NF-κB signaling by either pseudotyping HIV with influenza hemagglutinin envelope or modification of CD4 mediated-intracellular trafficking. These data suggest that HIV envelope-CD4 receptor interactions drive pDC activation toward an immature IFN producing phenotype rather than differentiation into a mature dendritic cell phenotype.

Objective: Myeloid dendritic cell (mDC) dysfunction during HIV infection may hinder the formation of both innate and adaptive immune responses and contribute to pathogenesis. Our objective was to determine whether circulating factors during chronic HIV infection impair mDC function with respect to secretion of IL-12, a pro-Th1 cytokine, and T-cell stimulatory capacity. Particular focus was placed on the effect of combination antiretroviral therapy (cART) and the role of HIV itself on mDC function., Methods: Monocyte-derived DC (moDC) from uninfected donors were exposed to plasma from HIV-infected individuals before Toll-like receptor (TLR) stimulation. Cytokine secretion was measured via cytokine bead arrays, and T-cell proliferation and IFNγ secretion was evaluated after coculture with naive CD4 T cells. Expression of genes central to TLR-mediated signal transduction was analyzed via quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) arrays and western blot., Results: Exposure of monocyte-derived DC to plasma from untreated HIV-infected donors suppressed secretion of IL-12, and impaired Th1-skewing of CD4 T cells. The suppressive effect was less by plasma donors receiving cART. Removal of virus from plasma did not relieve suppression nor was IL-12 secretion decreased on addition of HIV to control plasma. On a transcriptional level, decreased expression of IKKβ, a key regulator in the TLR/NF-kappaB signaling pathway, corresponded to suppressed cytokine secretion., Conclusions: Plasma factors during chronic HIV infection impair mDC function in a manner that likely impacts the formation of immune responses to HIV, opportunistic pathogens, and vaccines. Despite partial alleviation by cART, this suppression was not directly mediated by HIV.

Background and Objectives: The residual tumor cells remaining after completion of standard chemotherapy and radiation treatment in B lymphoma patients, may be eradicated by active immunotherapy that stimulates tumor-specific T lymphocytes. Irradiated autologous lymphoma cells expressing tumor-associated antigens (TAA) may serve as a potential tumor vaccine, provided that they are effectively targeted to the antigen-presenting cells (APC). We propose exploiting the natural anti-Gal antibody in order to target vaccinating tumor cells to APC. Anti-Gal constitutes 1% of IgG in human serum and interacts specifically with the alpha-gal epitope (Galalpha1-3Galphalbeta1-4GlcNAc-R)., Design and Methods: Alpha-gal epitopes were synthesized in vitro on the membrane of primary lymphoma cells by using the recombinant glycosylation enzyme alpha1,3galactosyltransferase (alpha1,3GT). Processed tumor cells were opsonized by purified anti-Gal antibodies and studied for uptake (phagocytosis) by APC including monocyte-derived macrophages and dendritic cells. Cross-presentation of tumor antigens after phagocytosis of processed MHC-I negative lymphoma cells was measured by activation of a tumor-specific CD8+ T-cell line., Results: We demonstrate synthesis of alpha-gal epitopes on freshly isolated B lymphoma cells of various types following the use of the recombinant enzyme alpha1,3GT. The subsequent binding of anti-Gal to the de novo synthesized alphagal epitopes opsonizes these tumor cells for effective uptake by macrophages and dendritic cells, through phagocytosis mediated by FcgammaR1 (CD64). Moreover, anti-Gal-mediated phagocytosis resulted in cross-presentation of TAA by dendritic cells., Interpretation and Conclusions: This study suggests that immunization with irradiated autologous lymphoma cells processed to express alpha-gal epitopes will result in anti-Gal-mediated, in vivo targeting of the autologous tumor vaccine to APC.