Constraints for dendritic cell differentiation : analysis of autocrine inhibitory mechanisms with therapeutic implications

The discovery of dendritic cells (DCs) was followed by an intensive research period aiming at the identification of mechanisms that could induce or inhibit adaptive immune responses through the manipulation of these cells. Only in the recent years the role of metabolic pathways in DC regulation has started to become clear. Metabolic regulators might allow the generation of DCs with prominent immunogenicity or the interference with chronic immune activation accompanying autoimmune responses or HIV-1 infection. Therefore the focus of this thesis is on novel mechanisms that regulate DC function, the relevance of these in generation of DC vaccines and on the delineation of pathways that potentially contribute to the unbalanced immune responses during HIV-1 infection. In paper I, we show that lactate inhibits the differentiation of human inflammatory DCs in a cell culture concentration dependent manner. DCs differentiating in the presence of low lactate concentrations are immune-stimulatory as shown by the production of inflammatory cytokines, the induction of Th1 differentiation and the migration in a trans-well system. In contrast, DCs from dense cultures produce high levels of IL-10 and trans-differentiate into osteoclasts. In paper II, we demonstrate an efficient modulation of DC vaccine immunogenicity by modulating cell culture density during DC development. DCs from sparse cultures migrated more efficiently to draining lymph nodes and induced more robust antigen-specific T cell activation in vivo as compared to dense DC cultures. In addition, DCs developing in sparse cultures exhibited a transcriptional profile associated with increased cholesterol and lipid biosynthesis, suggesting a link between lipid biosynthetic pathways and DC activities. In, paper III we explored the role of DC plasticity in regulating DC/HIV-1 interactions. We showed that DC responses to HIV-1 were largely dependent on the functional characteristics of the cells and strain-specific features of the virus. Suppressed DCs up-regulated production of inflammatory cytokines after HIV-1 exposure, whereas the virus could block cytokine production in the more immunogenic DC types suggesting unique viral pathways induced in the different DC lineages. Finally, in Paper IV we provided evidence that the population of CD4+CD70+ T cells is expanded in lymphopenic HIV-1 infected individuals potentially contributing to B cell abnormalities. In conclusion, the studies presented in this thesis identified new mechanisms and metabolic components that regulate DC immunogenicity and novel immune-modulatory pathways operating during HIV-1 infection

Impaired B cells survival upon production of inflammatory cytokines by HIV-1 exposed follicular dendritic cells

Additional file 3. Activation of B and T cells upon different stimuli. The frequency of activated CD69 + cells among PBMCs (A), B cells (B) and T cells (C) are shown when PBMCs were exposed to different activation stimuli

IL-7 and CD4 T Follicular Helper Cells in HIV-1 Infection

IL-7 was previously shown to upregulate the expression of molecules important for interaction of CD4+ T cells with B cells. It is poorly studied whether IL-7 has a role in the biology of T follicular helper (Tfh) cells and whether IL-7 dysregulates the expression of B-cell costimulatory molecules on Tfh cells. We review the literature and provide arguments in favor of IL-7 being involved in the biology of human Tfh cells. The CD127 IL-7 receptor is expressed on circulating Tfh and non-Tfh cells, and we show that IL-7, but not IL-6 or IL-21, upregulates the expression of CD70 and PD-1 on these cells. We conclude that IL-7, a cytokine whose level is elevated during HIV-1 infection, may have a role in increased expression of B cell costimulatory molecules on Tfh cells and lead to abnormal B cell differentiation

Dendritic cell response to HIV-1 is controlled by differentiation programs in the cells and strain-specific properties of the virus

Dendritic cells (DCs) are potent antigen-presenting cells that might play contradictory roles during HIV-1 infection, contributing not only to antiviral immunity but also to viral dissemination and immune evasion. Although DCs are characterized by enormous functional diversity, it has not been analyzed how differentially programmed DCs interact with HIV-1. We have previously described the reprogramming of DC development by endogenously produced lactic acid that accumulated in a cell culture density-dependent manner and provided a long-lasting anti-inflammatory signal to the cells. By exploiting this mechanism, we generated immunostimulatory DCs characterized by the production of TH1 polarizing and inflammatory mediators or, alternatively, suppressed DCs that produce IL-10 upon activation, and we tested the interaction of these DC types with different HIV-1 strains. Cytokine patterns were monitored in HIV-1-exposed DC cultures. Our results showed that DCs receiving suppressive developmental program strongly upregulated their capacity to produce the TH1 polarizing cytokine IL-12 and the inflammatory chemokines CCL2 and CCL7 upon interaction with HIV-1 strains IIIB and SF162. On the contrary, HIV-1 abolished cytokine production in the more inflammatory DC types. Preincubation of the cells with the HIV-1 proteins gp120 and Nef could inhibit IL-12 production irrespectively of the tested DC types, whereas MyD88- and TRIF-dependent signals stimulated IL-12 production in the suppressed DC type only. Rewiring of DC cytokines did not require DC infections or ligation of the HIV-1 receptor CD209. A third HIV-1 strain, BaL, could not modulate DC cytokines in a similar manner indicating that individual HIV-1 strains can differ in their capacity to influence DCs. Our results demonstrated that HIV-1 could not induce definite and invariable modulatory programs in DCs. Instead, interaction with the virus triggered different responses in different DC types. Thus, the outcome of DC-HIV-1 interactions might be highly variable, shaped by endogenous features of the cells and diversity of the virus

MALT1 inhibition suppresses antigen-specific T cell responses

The aim of this study was to assess the potential use of a selective small molecule MALT1 inhibitor in solid tumor treatment as an immunotherapy targeting regulatory T-cells (Tregs). In vitro, MALT1 inhibition suppressed the proteolytic cleavage of the MALT1-substrate HOIL1 and blocked IL-2 secretion in Jurkat cells. It selectively suppressed the proliferation of PBMC-derived Tregs, with no effect on conventional CD4+ T-cells. In vivo, however, no evident anti-tumor effect was achieved by MALT1 inhibition monotherapy or in combination with anti-CTLA4 in the MB49 cancer model. Despite decreased Treg-frequencies in lymph nodes of tumor-bearing animals, intratumoral Treg depletion was not observed. We also showed that MALT1-inhibition caused a reduction of antigen-specific CD8+ T-cells in an adoptive T-cell transfer model. Thus, selective targeting of Tregs would be required to improve the immunotherapeutic effect of MALT1-inhibition. Also, various dosing schedules and combination therapy strategies should be carefully designed and evaluated further

Reactive oxygen species as an initiator of toxic innate immune responses in retort to SARS-CoV-2 in an ageing population, consider N-acetylcysteine as early therapeutic intervention

During the current COVID-19 pandemic, a need for evaluation of already available drugs for treatment of the disease is crucial. Hereby, based on literature review from the current pandemic and previous outbreaks with corona viruses we analyze the impact of the virus infection on cell stress responses and redox balance. High levels of mortality are noticed in elderly individuals infected with SARS-CoV2 and during the previous SARS-CoV1 outbreak. Elderly individuals maintain a chronic low level of inflammation which is associated with oxidative stress and inflammatory cytokine production, a condition that increases the severity of viral infections in this population. Coronavirus infections can lead to alterations of redox balance in infected cells through modulation of NAD + biosynthesis, PARP function along with altering proteasome and mitochondrial function in the cell thereby leading to enhanced cell stress responses which further exacerbate inflammation. ROS production can increase IL-6 production and lipid peroxidation resulting in cell damage. Therefore, early treatment with anti-oxidants such as NAC during COVID-19 can be a way to bypass the excessive inflammation and cell damage that lead to severe infection, thus early NAC as intervention should be evaluated in a clinical trial setting.Title manuscript: Commentary Proteasome and reactive oxygen species dysfunction as risk factors for SARS-CoV-2 infection; consider N-acetylcystein as therapeutic intervention</p

Dysfunctional phenotypes of CD4+ and CD8+ T cells are comparable in patients initiating ART during early or chronic HIV-1 infection

11sinoneEarly initiation of antiretroviral therapy (ART) is becoming a common clinical practice according to current guidelines recommending treatment to all HIV-1-infected patients. However, it is not known whether ART initiated during the early phase of infection prevents the establishment of abnormal phenotypic features previously reported in CD4+ and CD8+T cells during chronic HIV-1 infection. In this cross-sectional study, blood specimens were obtained from 17 HIV-1-infected patients who began ART treatment shortly after infection (early ART [EA]), 17 age-matched HIV-1-infected patients who started ART during chronic phase of infection (late ART [LA]), and 25 age-matched non-HIV-1-infected controls. At collection of specimens, patients in EA and LA groups had received ART for comparable periods of time. Total HIV-1 DNA was measured in white blood cells by quantitative PCR. The concentration of 9 inflammatory parameters and 1 marker of fibrosis, including sCD14 and b-2 microglobulin, was measured in plasma. Furthermore, expression of markers of abnormal immune activation (human leukocyte antigen-antigen D related [HLA-DR] and CD38), exhaustion (programmed death 1, CD28, CD57) and terminal differentiation (CD127) was measured on CD4+ and CD8+T cells. T-cell proliferation was measured through Ki67 expression. The copies of total HIV-1 DNA in blood were significantly lower (P=0.009) in EA compared with that in LA group. Only the expression of HLA-DR on naïve CD4+ T cells distinguished EA from LA, whereas expression of 3 surface markers distinguished T-cell populations of HIV-1-infected patients from controls. These included HLA-DR distinguishing CD4+ T cells from EA compared with controls, and also CD38 and CD127 on CD4+ and CD8+ T cells, respectively, distinguishing both groups of patients from controls. The sCD14 levels were significantly higher in EA patients, and b-2 microglobulin levels were higher in LA group compared with that in controls. Our results demonstrate an equivalent abnormal expression of activation (HLA-DR and CD38 on CD4+ T cells) and terminal differentiation (CD127 on CD8+ T cells) markers in T cells from both EA and LA patients. The size of total HIV-1 DNA copies in blood of EA was lower compared with LA patients. These findings suggest that some abnormalities taking place in the T-cell compartment during primary HIV-1 infection may not be corrected by early ART.openAmu, Sylvie; Graham, Rebecka Lantto; Bekele, Yonas; Nasi, Aikaterini; Bengtsson, Carina; Rethi, Bence; Sorial, Sam; Meini, Genny; Zazzi, Maurizio; Hejdeman, Bo; Chiodi, FrancescaAmu, Sylvie; Graham, Rebecka Lantto; Bekele, Yonas; Nasi, Aikaterini; Bengtsson, Carina; Rethi, Bence; Sorial, Sam; Meini, Genny; Zazzi, Maurizio; Hejdeman, Bo; Chiodi, Francesc