No abstract

CD38, an ectoenzyme and a signaling receptor, is a novel marker of human mature monocyte-derived dendritic cells (MDDCs). The working hypothesis is that CD38 is not only a marker but also contributes to functions specifically gained by MDDCs with maturation. This was tested by assessing the role(s) of CD38 after signaling with agonistic anti-CD38 monoclonal antibodies or by blocking the interactions taking place between CD38 and CD31, its counterreceptor. IntroductionCD38 is a pleiotropic cell surface molecule acting as an ectoenzyme and a receptor. The enzymatic activity ends in the synthesis of Ca 2ϩ -mobilizing metabolites (ie, ADP-ribose [ADPR], nicotinic acid adenine dinucleotide phosphate [NAADP], and cyclic ADP-ribose [cADPR]) involved in the regulation of calcium-dependent calcium release. 1,2 CD38 has a unique pattern of surface expression among cells of the human immune system, being present on lymphoid and myeloid progenitors, lost during differentiation, and re-expressed at high density in activated T, B, and natural killer (NK) cells. 3,4 The molecule shows a broad distribution in different tissues. 5 CD38 ligation in immune cells delivers activation signals and induces cytokine production and secretion by T, 6 B, 7 and NK cells 8 and monocytes. 9 CD38 also regulates cell viability by preventing human germinal center B cells from undergoing apoptosis 10 and contributing to increased survival of B-cell chronic lymphocytic leukemia (B-CLL) cells. 11 This panoply of different functional roles may be explained considering some nonconventional features of CD38 as a receptor. The intrinsic ineptitude of CD38 to transduce signals is overcome by working in physical and functional associations with specialized signaling molecules, such as T-cell receptor on T cells, 12-14 B-cell receptor on B cells, 15,16 and CD16 on NK cells. 17 CD38 can sustain adhesion and rolling of CD38 ϩ lymphocytes on endothelial cells through interaction with CD31 (identified as a specific counterreceptor 18 ), suggesting its possible role in lymphocyte trafficking. 19 All the signals mediated by monoclonal antibody (mAb) ligation of CD38 can be reproduced by its interaction with CD31.In murine models, CD38 is involved in chemotaxis and transendothelial migration of both polymorphonuclear leukocytes (PMNs) and dendritic cells (DCs) and this function requires its enzymatic activities. 20,21 Consequently, CD38 knockout mice have impaired capacity to respond to infections. 20 The evaluation of the expression of the molecule also has applications in clinical diagnosis, such as in AIDS (where CD38 is one of the earliest indicators of infection 22 ) and B-CLL (where the expression is generally associated with poor prognosis 15 ). Autoantibodies specific for CD38 are found in diabetes and thyroid disorders. [23][24][25][26] The agonistic properties of these autoantibodies envisage pathogenic role(s) in these diseases.We recently reported a pulsatile pattern of surface CD38 expression in human monocyte-derived dendritic cells (MDDCs). 27 ...

Dendritic cell (DC) maturation is characterized by the gain or loss of immunological functions and by expression of distinctive surface receptors. CD38 is an ectoenzyme that catalyzes the synthesis of cyclic ADP ribose (a potent second messenger for Ca 2+ release), as well as a receptor that initiates transmembrane signaling upon engagement with its counterreceptor CD31 or with agonistic monoclonal antibodies. Since CD38 is expressed by resting monocytes, we aimed to monitor CD38 expression during the differentiation of human monocyte-derived DC (MDDC) and to investigate the possibility that CD38 plays a functional role during DC maturation. CD38 is down-modulated during differentiation into immature MDDC and expressed again upon maturation. The extent of CD38 expression is dependent on the stimulus adopted (LPS G IFN-+ G CD40 cross-linking). Although weak, IFN-+ consistently induces DC maturation. De novo-synthesized CD38 is enzymatically active, and its expression in mature (m) MDDC is dependent on NF-‹ B activity. However, CD38 is not merely a maturation marker but also mediates signaling in mMDDC, where it maintains its functions as a receptor. Activation via agonistic anti-CD38 mAb induces up-regulation of CD83 expression and IL-12 secretion, whereas disruption of CD38/CD31 interaction inhibits CD83 expression, IL-12 secretion and MDDC-induced allogeneic T cell proliferation.

Bordetella pertussis and B. parapertussis are the etiological agents of pertussis, yet the former has a higher incidence and is the cause of a more severe disease, in part due to pertussis toxin. To identify other factors contributing to the different pathogenicity of the two species, we analyzed the capacity of structurally different lipooligosaccharide (LOS) from B. pertussis and LPS from B. parapertussis to influence immune functions regulated by dendritic cells. Either B. pertussis LOS and B. parapertussis LPS triggered TLR4 signaling and induced phenotypic maturation and IL-10, IL-12p40, IL-23, IL-6, and IL-1β production in human monocyte-derived dendritic cells (MDDC). B. parapertussis LPS was a stronger inducer of all these activities as compared with B. pertussis LOS, with the notable exception of IL-1β, which was equally produced. Only B. parapertussis LPS was able to induce IL-27 expression. In addition, although MDDC activation induced by B. parapertussis LPS was greatly dependent on soluble CD14, B. pertussis LOS activity was CD14-independent. The analysis of the intracellular pathways showed that B. parapertussis LPS and B. pertussis LOS equally induced IκBα and p38 MAPK phosphorylation, but B. pertussis LOS triggered ERK1/2 phosphorylation more rapidly and at higher levels than B. parapertussis LPS. Furthermore, B. pertussis LOS was unable to induce MyD88-independent gene induction, which was instead activated by B. parapertussis LPS, witnessed by STAT1 phosphorylation and induction of the IFN-dependent genes, IFN regulatory factor-1 and IFN-inducible protein-10. These differences resulted in a divergent regulation of Th cell responses, B. pertussis LOS MDDC driving a predominant Th17 polarization. Overall, the data observed reflect the different structure of the two LPS and the higher Th17 response induced by B. pertussis LOS may contribute to the severity of pertussis in humans.

The capacity of pertussis toxin (PT) to induce maturation and functional activities of human monocyte-derived dendritic cells (DCs) was investigated. Both native PT (nPT) and genetically detoxified PT (dPT) efficiently promoted expression on DCs of CD80, CD86, human leukocyte antigen-DR, and CD83 markers, alloreactive antigen presentation, and cytokine production, primarily interferon (IFN)-gamma. Although they did not affect interleukin (IL)-10 production by lipopolysaccharide (LPS)-stimulated DCs, both nPT and dPT strongly synergized with LPS for IL-12 production. PTs plus LPS-stimulated DCs secreted soluble factors fostering IFN-gamma but not IL-4 and IL-5 production by naive T cells. T helper type 1 (Th1) polarization was, as alloreactive antigen presentation, inhibited by anti-IL-12 monoclonal antibody. These findings support the notion that nPT, in addition to inducing specific immune response, is a potent Th1 adjuvant and that dPT fully preserves this adjuvanticity. The synergic interaction between PT and LPS in IL-12 production might be relevant for the mechanisms of vaccine-induced protection.

Dendritic cells (DCs) are central players in immunity and are used in immune-adoptive vaccine protocols in humans. IFN-γ, mandatory in Th-1 polarization and endowed with regulatory properties, is currently used to condition monocyte-derived DCs (MDDC) in cancer therapy and in clinical trials to treat chronic infectious diseases. We therefore performed a wide analysis of IFN-γ signaling consequences on MDDC multiple effector functions. IFN-γ itself induced IL-27p28 expression and survival but did not promote relevant CCR7-driven migration or activated Th-1 cell recruitment capacity in MDDC. Administered in association with classical maturation stimuli such as CD40 or TLR-4 stimulation, IFN-γ up-regulated IL-27 and IL-12 production, CCR7-driven migration, and activated Th-1 cell recruitment, whereas it decreased IL-10 production and STAT3 phosphorylation. CD38 signaling, which orchestrates migration, survival, and Th-1 polarizing ability of mature MDDC, was involved in IFN-γ-mediated effects. Thus, IFN-γ is a modulator of multiple DC effector functions that can be helpful in MDDC-based vaccination protocols. These data also help understand the dual role exerted by this cytokine as both an inducer and a regulator of inflammation and immune response.

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Objectives A seroprevalence study of SARS-CoV-2 was conducted in a high-incidence area located in North-eastern Italy. Methods All citizens above ten years of age resident in 5 municipalities of the Autonomous Province of Trento, with the highest incidence of COVID-19 cases, were invited to participate in the study. Overall, among 6098 participants, 6075 sera and a standardized questionnaire administered face-to-face were collected between May 5 and 15, 2020 and examined. Symptomatic individuals and their family contacts were tested by RT-PCR. Anti-SARS-CoV-2 antibodies were detected using an Abbott SARS-CoV-2 IgG assay which was performed on the Abbott Architect i2000SR automated analyzer. Seroprevalence was calculated as the proportion of positive people on the total number of tested. A multivariable logistic regression model was performed to assess the relationship between seropositive versus seronegative individuals for a set of explanatory variables. Results A total of 1402 participants were positives for IgG antibodies against SARS-CoV-2, with a prevalence of 23.1% (1402/6075). The highest prevalence was found in the age class 40-49 years. Overall, 34.4% (2096/6098) of the participants reported at least 1 symptom. The ratio between reported cases identified by molecular test and those resulting seropositive was 1:3, with a maximum ratio of about 1:7 in the age group <20 years and a minimum around 1:1 in those >70 years old. The infection fatality rate was 2.5% (35/1402). Among the symptoms, anosmia and ageusia were strongly associated with seropositivity. Conclusions The estimated seroprevalence of 23% was 3-fold higher than the number of cases reported in the COVID-19 Integrated Surveillance data in the study area. This may be explained in part by a relatively high number of individuals presenting mild or no illness, especially of younger age, and/or who did not seek medical care or testing, but who may contribute to virus transmission in the community.