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The active vitamin A metabolite, all‐trans‐retinoic acid (RA), primes precursor dendritic cells (DCs) into a mucosal phenotype with tolerogenic properties characterized by the expression of integrin CD103. CD103+ DCs can counteract pathogenic Th1 and Th17 in inflammatory bowel disease (IBD) or celiac disease (CD). Tolerogenic manipulation of DCs using nanoparticles carrying tolerogenic adjuvants and disease‐specific antigens is a valuable treatment strategy to induce antigen‐specific mucosal tolerance in vivo. Here, we investigated the effects of RA‐loaded liposomes on human DC phenotype and function, including DC‐driven T‐cell development, both during the generation of monocyte‐derived DCs (moDCs) as well as by priming immature moDCs. RA liposomes drove CD103+ DC differentiation as well as ALDH1A2 expression in DCs. Neutrophil‐dependent Th17 cell development was reduced by RA‐liposome‐differentiated and RA‐liposome‐primed DCs. Moreover, RA liposome treatment shifted T‐cell development toward a Th2 cell profile. Importantly, RA liposomes induced the development of IL‐10‐producing and FoxP3+ regulatory T cells (Tregs) of various Treg subsets, including ICOS+ Tregs, that were potent inhibitors of bystander memory T‐cell proliferation. Taken together, RA‐loaded liposomes could be a novel treatment avenue for IBD or CD patients. [ABSTRACT FROM AUTHOR]

This article discusses the use of plant-produced bioparticles to deliver allergens for immunotherapy. The researchers compared the allergenic and immunogenic potency of soluble and particulate allergen presentation. They found that the bioparticles were hypoallergenic and induced immunomodulatory responses in dendritic cells, regardless of the allergic background. The study suggests that these bioparticles could be used to redirect the immune response towards a more balanced Th1/Treg response, improving the safety and efficacy of allergen immunotherapy. [Extracted from the article]

Neutrophils are important players in COVID‐19, contributing to tissue damage by release of inflammatory mediators, including ROS and neutrophil elastase. Longitudinal studies on the effects of COVID‐19 on neutrophil phenotype and function are scarce. Here, we longitudinally investigated the phenotype and degranulation of neutrophils in COVID‐19 patients (28 nonhospitalized and 35 hospitalized patients) compared with 17 healthy donors (HDs). We assessed phenotype, degranulation, CXCL8 (IL‐8) release, and ROS generation within 8 days, at one or 6 month(s) after COVID‐19 diagnosis. For degranulation and ROS production, we stimulated neutrophils, either with ssRNA and TNF or granulocyte‐macrophage colony‐stimulating factor and N‐Formylmethionyl‐leucyl‐phenylalanine. During active COVID‐19, neutrophils from hospitalized patients were more immature than from HDs and were impaired in degranulation and ROS generation, while neutrophils from nonhospitalized patients only demonstrated reduced CD66b+ granule release and ROS production. Baseline CD63 expression, indicative of primary granule release, and CXCL8 production by neutrophils from hospitalized patients were elevated for up to 6 months. These findings show that patients hospitalized due to COVID‐19, but not nonhospitalized patients, demonstrated an aberrant neutrophil phenotype, degranulation, CXCL8 release, and ROS generation that partially persists up to 6 months after infection. [ABSTRACT FROM AUTHOR]

Human immunodeficiency virus type 1 (HIV-1) is able to infect a variety of cell types with differences in entry efficiency and replication kinetics determined by the host cell type or the viral phenotype. The phenotype of the virus produced from these various cell types, including infectivity, co-receptor usage and neutralisation sensitivity, may also be affected by the characteristics of the producing cell. This can be due to incorporation of variant cell-specific molecules or differences in post-translational modifications of the gp41/120 envelope. In this study we produced genetically identical virus strains from macrophages, CD4-enriched lymphocytes as well as Th1 and Th2 CD4+ cell lines and compared each different virus stock for their infectivity in various cell types and sensitivity to neutralisation. In order to study the effect of the producer host cell on the virus phenotype, virus stocks were normalised on infectivity and were sequenced to confirm env gene homogeneity. Virus production by Th1 or Th2 cells did not compromise infectivity of the variant cell types tested. We observed no difference in sensitivity to co-receptor blocking agents upon viral passage through Th1 and Th2 CD4+ cell lineages nor did this affect DC-SIGNmediated viral capture as measured in a transfer assay to CD4+ lymphocytes. Virus produced by macrophages was comparably sensitive to CC-chemokine inhibition as was virus generated from the array of CD4+ lymphocytes. We identified that virus produced from macrophages was fourteen times more resistant to 2G12 neutralisation than virus produced from CD4+ lymphocytes. Macrophage-produced dual-tropic (R5/X4) virus was six times more efficiently transmitted to CD4+ cells than lymphocyte-derived HIV-1 (p<0.0001) after DCSIGN capture. These results provide further insights to what extent the host cell influences viral phenotype and thereby various aspects of HIV-1 pathogenesis but suggest that viruses generated from Th1 versus Th2 cells are consistent in phenotype. [ABSTRACT FROM AUTHOR]

Introduction: Nanomedicine provides a promising platform for manipulating dendritic cells (DCs) and the ensuing adaptive immune response. For the induction of regulatory responses, DCs can be targeted in vivo with nanoparticles incorporating tolerogenic adjuvants and auto-antigens or allergens. Methods: Here, we investigated the tolerogenic effect of different liposome formulations loaded with vitamin D3 (VD3). We extensively phenotyped monocyte-derived DCs (moDCs) and skin DCs and assessed DC-induced regulatory CD4+ T cells in coculture. Results: Liposomal VD3 primed-moDCs induced the development of regulatory CD4+ T cells (Tregs) that inhibited bystander memory T cell proliferation. Induced Tregs were of the FoxP3+ CD127low phenotype, also expressing TIGIT. Additionally, liposome-VD3 primed moDCs inhibited the development of T helper 1 (Th1) and T helper 17 (Th17) cells. Skin injection of VD3 liposomes selectively stimulated the migration of CD14+ skin DCs. Discussion: These results suggest that nanoparticulate VD3 is a tolerogenic tool for DC-mediated induction of regulatory T cell responses. [ABSTRACT FROM AUTHOR]