Immunobiology of dendritic cells and the influence of HIV infection

Impairment of endocytosis-related factors FNBP1L, ARHGAP24, and ATP6V1B1 increases HIV-1 entry into dendritic cells

HIV-1 infects several types of CD4+ cells. Among these, dendritic cells (DCs) are considered one of the first to encounter the virus upon sexual transmission. Expression of several restriction factors, of which SAMHD1 is well known, limits productive infection. Still, DCs are essential players in shaping adaptive immune responses that contribute heavily to the pathogenesis of HIV. Here, we set out to identify other factors that potentially contribute to the resistance of dendritic cells to HIV infection. Since endocytosis and the cytoskeleton impact HIV infection, we have put special emphasis on proteins implied in these pathways. In a selective, shRNA-mediated knockdown screen in primary monocyte-derived dendritic cells (MDDCs) infected with HIV in the presence of SAMHD1-disactivating Vpx containing virus-like particles, three proteins hampering HIV-1 infection were identified: FNBP1L, ARHGAP24, and ATP6V1B1. Findings of our research indicate that upon blocking of factors involved in endocytosis, increased viral entry is observed providing supportive evidence for endocytosis mostly being a dead-end entry pathway for HIV infection of MDDCs. Additional experiments show that changes in the cytoskeleton and endosomal pH that lead to impaired fluid-phase endocytosis and phagocytosis are responsible for these shifts in the phenotype observed.IMPORTANCEUnderstanding how HIV-1 interacts with dendritic cells (DCs) is pivotal in deciphering early viral transmission and immune evasion but is subject to a long-standing controversy in HIV virology. Therefore, the identification of endocytosis-related host factors as barriers to productive infection in DCs emphasizes the role of endocytosis as a restrictive pathway for viral entry. By disrupting these processes, we highlight a shift in the cellular environment that could influence viral entry and transmission. These findings challenge existing models of HIV-1 entry into DCs. New insights into how cellular pathways limit viral spread have implications for the development of strategies aimed to curb viral dissemination and reservoir formation. Whether the knockdown of the proteins described simply augments the efficiency of infection via existing pathways or opens additional routes for HIV-1 entry remains to be investigated.

Human Dendritic Cells: Ontogeny and Their Subsets in Health and Disease

Dendritic cells (DCs) are a type of cells derived from bone marrow that represent 1% or less of the total hematopoietic cells of any lymphoid organ or of the total cell count of the blood or epithelia. Dendritic cells comprise a heterogeneous population of cells localized in different tissues where they act as sentinels continuously capturing antigens to present them to T cells. Dendritic cells are uniquely capable of attracting and activating naïve CD4⁺ and CD8⁺ T cells to initiate and modulate primary immune responses. They have the ability to coordinate tolerance or immunity depending on their activation status, which is why they are also considered as the orchestrating cells of the immune response. The purpose of this review is to provide a general overview of the current knowledge on ontogeny and subsets of human dendritic cells as well as their function and different biological roles.

Immune Enhancing Activity of β-(1,3)-Glucan Isolated from Genus Agrobacterium in Bone-Marrow Derived Macrophages and Mice Splenocytes

An effective method for activating macrophages and deriving a Th1 immune response could be used to improve the defenses of hosts. In this study, we investigated the immunomodulation effect and the related signaling mechanism of [Formula: see text]-(1,3)-glucan, isolated from the Agrobacterium species. Here, we found that [Formula: see text]-(1,3)-glucan predominantly induced the tumor necrosis factor (TNF)-[Formula: see text], interleukin (IL)-1[Formula: see text], IL-6, IL-12p70, and nitric oxide, which was dependent on mitogen-activated protein kinases (MAPK) and nuclear factor (NF)-[Formula: see text]B signaling. Additionally, [Formula: see text]-(1,3)-glucan treatment significantly up-regulated the expression of the co-stimulatory molecules CD80 and CD86, and also significantly increased the expression of iNOS and Dectin-1, which is a transmembrane protein that binds [Formula: see text]-glucan and associates with macrophage activation. Importantly, the splenic T cells co-cultured with [Formula: see text]-(1,3)-glucan-treated macrophages produced the a Th1 cytokine profile that includes high levels of IFN-[Formula: see text], but not IL-4 (Th2 cytokine), indicating that [Formula: see text]-(1,3)-glucan contributes to Th1 polarization of the immune response. Taken together, our results suggest that [Formula: see text]-(1,3)-glucan isolated from Agrobacterium species can induce macrophage activation through the MAPK and NF-[Formula: see text]B signaling pathway, as well as Th1 polarization.

Phenotypic and functional analysis of CD1a+ dendritic cells from cats chronically infected with feline immunodeficiency virus

Numerous studies suggest dendritic cell (DC) dysfunction is central to the dysregulated immune response during HIV infection; however, in vivo studies are lacking. In the present study we used feline immunodeficiency virus (FIV) infection of cats as a model for HIV-1 infection to assess the maturation and function of dendritic cells, in vivo and in vitro. We compared CD1a+ DC migration, surface phenotype, endocytosis, mixed leukocyte reaction (MLR) and regulatory T cell (Treg) phenotype induction by CD1a+ cells isolated from lymph nodes of FIV-infected and control cats. Results showed that resident CD1a+ DC in lymph nodes of chronically FIV-infected cats are phenotypically mature, can stimulate normal primary T cell proliferation, override Treg suppression and do not skew toward Treg induction. In contrast, FIV infection had deleterious effects on antigen presentation and migratory capacity of CD1a+ cells in tissues.

Dendritic cells in hepatitis C virus infection: key players in the IFNL3-genotype response

Recently, single nucleotide polymorphisms, in the vicinity of the interferon lambda 3 (IFNL3) gene have been identified as the strongest predictor of spontaneous and treatment induced clearance of hepatitis C virus (HCV) infection. Since then, increasing evidence has implicated the innate immune response in mediating the IFNL3 genotype effect. Dendritic cells (DCs) are key to the host immune response in HCV infection and their vital role in the IFNL3 genotype effect is emerging. Reports have identified subclasses of DCs, particularly myeloid DC2s and potentially plasmacytoid DCs as the major producers of IFNL3 in the setting of HCV infection. Given the complexities of dendritic cell biology and the conflicting current available data, this review aims to summarize what is currently known regarding the role of dendritic cells in HCV infection and to place it into context of what is know about lambda interferons and dendritic cells in general.

Antioxidant and anti-inflammatory activities of extracts from Cassia alata, Eleusine indica, Eremomastax speciosa, Carica papaya and Polyscias fulva medicinal plants collected in Cameroon

BACKGROUND

The vast majority of the population around the world has always used medicinal plants as first source of health care to fight infectious and non infectious diseases. Most of these medicinal plants may have scientific evidence to be considered in general practice.

OBJECTIVE

The aim of this work was to investigate the antioxidant capacities and anti-inflammatory activities of ethanol extracts of leaves of Cassia alata, Eleusine indica, Carica papaya, Eremomastax speciosa and the stem bark of Polyscias fulva, collected in Cameroon.

METHODS

Chemiluminescence was used to analyze the antioxidant activities of plant extracts against hydrogen peroxide or superoxide anion. Comet assays were used to analyze the protection against antioxidant-induced DNA damage induced in white blood cells after treating with hydrogen peroxide. Flow cytometry was used to measure γδ T cells proliferation and anti-inflammatory activity of γδ T cells and of immature dendritic cells (imDC) in the presence of different concentrations of plant extracts.

RESULTS

Ethanol extracts showed strong antioxidant properties against both hydrogen peroxide and superoxide anion. Cassia alata showed the highest antioxidant activity. The effect of plant extracts on γδ T cells and imDC was evidenced by the dose dependent reduction in TNF-α production in the presence of Cassia alata, Carica papaya, Eremomastax speciosa Eleusine indica, and Polyscias fulva. γδ T cells proliferation was affected to the greatest extent by Polyscias fulva.

CONCLUSION

These results clearly show the antioxidant capacity and anti-inflammatory activities of plant extracts collected in Cameroon. These properties of leaves and stem bark extracts may contribute to the value for these plants in traditional medicine and in general medical practice.

In vivo administration of a JAK3 inhibitor during acute SIV infection leads to significant increases in viral load during chronic infection

The studies reported herein are the first to document the effect of the in vivo administration of a JAK3 inhibitor for defining the potential role of NK cells during acute SIV infection of a group of 15 rhesus macaques (RM). An additional group of 16 MHC/KIR typed RM was included as controls. The previously optimized in vivo dose regimen (20 mg/kg daily for 35 days) led to a marked depletion of each of the major NK cell subsets both in the blood and gastro-intestinal tissues (GIT) during acute infection. While such depletion had no detectable effects on plasma viral loads during acute infection, there was a significant sustained increase in plasma viral loads during chronic infection. While the potential mechanisms that lead to such increased plasma viral loads during chronic infection remain unclear, several correlates were documented. Thus, during acute infection, the administration of the JAK3 inhibitor besides depleting all NK cell subsets also decreased some CD8⁺ T cells and inhibited the mobilization of the plasmacytoid dendritic cells in the blood and their localization to the GIT. Of interest is the finding that the administration of the JAK3 inhibitor during acute infection also resulted in the sustained maintenance during chronic infection of a high number of naïve and central memory CD4⁺ T cells, increases in B cells in the blood, but decreases in the frequencies and function of NKG2a⁺ NK cells within the GIT and blood, respectively. These data identify a unique role for JAK3 inhibitor sensitive cells, that includes NK cells during acute infection that in concert lead to high viral loads in SIV infected RM during chronic infection without affecting detectable changes in antiviral humoral/cellular responses. Identifying the precise mechanisms by which JAK3 sensitive cells exert their influence is critical with important implications for vaccine design against lentiviruses.

In efforts to define the potential role of innate immune effector mechanisms in influencing the course of SIV infection during the acute infection period, our lab utilized the in vivo daily administration of 20 mg/kg orally of a compound called Tofacitinib (a Janus kinase 3 inhibitor) to a group of 15 rhesus macaques starting at day −6 and until day 28 post intravenous SIVmac239 infection. An additional group of 16 similarly SIV infected rhesus macaques served as a placebo control. This drug targets the JAK/STAT pathway that is utilized by cells including the NK cell lineage, a major cell of the innate immune system. The dosage utilized was based on extensive previous PK studies that resulted in a marked depletion of the NK cells. Of interest while such drug administration had no effect on plasma viral loads during acute infection, such drug administration led to significant increases in plasma and gastro-intestinal tissues (GIT) viral loads during chronic infection. A series of phenotypic/functional studies were performed to determine the mechanisms for this delayed effect and the correlates identified. These data are the first to document the effect of JAK-3 inhibitor during acute SIV infection with implications for HIV vaccine design.

4th Australasian vaccines and immunotherapeutic development meeting

This report describes advances in the understanding of how we might intervene in destructive processes, such as autoimmunity, infectious disease and cancer, through the development of innovative vaccines and immunotherapeutics.