Spreading the load: Antigen transfer between migratory and lymph node-resident dendritic cells promotes T-cell priming

Integrative transcriptomic and metabolomic analysis in mice reveals the mechanism by which ginseng stem-leaf saponins enhance mucosal immunity induced by a porcine epidemic diarrhea virus vaccination

Porcine epidemic diarrhea virus (PEDV) is a main cause of severe enteric disease in piglets, leading to millions of dollars lost annually in the global pig industry. Parenteral vaccination is limited in generating sufficient mucosal immunity, which is crucial for early defense against PEDV. Here, we orally administered ginseng stem-leaf saponins (GSLS) to mice before parenteral vaccination and found that GSLS significantly enhanced the phagocytosis of dendritic cells, promoted the activities of CD4+ T cells and increased PEDV-specific IgA antibodies in the intestinal mucosa. Transcriptomic results showed that the altered genes following GSLS treatment were mostly related to the immune response and metabolism. In addition, integrated analysis of the transcriptome and metabolome revealed that the mechanism by which GSLS enhances mucosal immunity may be associated with progesterone-related pathways. Further studies are needed to explore the detailed molecular mechanisms.

Cotransfer of antigen and contextual information harmonizes peripheral and lymph node conventional dendritic cell activation

T cell responses against infections and cancer are directed by conventional dendritic cells (cDCs) in lymph nodes distant from the site of challenge. Migratory cDCs, which travel from the tissue to the lymph node, not only drive initial T cell activation but also transfer antigen to lymph node-resident cDCs. These resident cells have essential roles defining the character of the resulting T cell response; however, it is unknown how they can appropriately process and present antigens to suitably direct responses given their spatial separation. Here, using a novel strain of influenza A and a modified melanoma model, we show that tissue and lymph node cDC activation is harmonized and that this is driven by cotransfer of contextual cues. In the tumor, incomplete cDC activation in the tumor microenvironment is mirrored by lymph node-resident cDCs, whereas during influenza infection, pathogen-associated molecular patterns cotransferred with antigen drive TLR signaling in resident cDCs and their subsequent robust activation. This cotransfer mechanism explains how individual antigens can be handled distinctly by resident cDCs and how signals driving poor tumoral cDC activation further impact the lymph node. Our findings clarify how tissue context dictates antigenic and, consequently, T cell fate in the lymph node.

Tumor-targeted superantigens produce curative tumor immunity with induction of memory and demonstrated antigen spreading

BACKGROUND

Despite remarkable progress, the immunotherapies currently used in the clinic, such as immune checkpoint blockade (ICB) therapy, still have limited efficacy against many types of solid tumors. One major barrier to effective treatment is the lack of a durable long-term response. Tumor-targeted superantigen (TTS) therapy may overcome this barrier to enhance therapeutic efficacy. TTS proteins, such as the clinical-stage molecule naptumomab estafenatox (NAP), increase tumor recognition and killing by both coating tumor cells with bacterial-derived superantigens (SAgs) and selectively expanding T-cell lineages that can recognize them. The present study investigated the efficacy and mechanism of action of repeated TTS (C215Fab-SEA) treatments leading to a long-term antitumor immune response as monotherapy or in combination with PD-1/PD-L1 inhibitors in murine tumor models.

METHODS

We used syngeneic murine tumor models expressing the human EpCAM target (C215 antigen) to assess the efficacy and mechanism of action of repeated treatment with TTS C215Fab-SEA alone or with anti-PD-1/PD-L1 monoclonal antibodies. Tumor draining lymph nodes (TDLNs) and tumor tissues were processed and analyzed by immunophenotyping and immunohistochemistry. Isolated RNA from tumors was used to analyze gene expression and the TCR repertoire. Tumor rechallenge and T-cell transfer studies were conducted to test the long-term antitumor memory response.

RESULTS

TTS therapy inhibited tumor growth and achieved complete tumor rejection, leading to a T-cell-dependent long-term memory response against the tumor. The antitumor effect was derived from inflammatory responses converting the immunosuppressive TME into a proinflammatory state with an increase in T-cell infiltration, activation and high T-cell diversity. The combination of TTS with ICB therapy was significantly more effective than the monotherapies and resulted in higher tumor-free rates.

CONCLUSIONS

These new results indicate that TTSs not only can turn a "cold" tumor into a "hot" tumor but also can enable epitope spreading and memory response, which makes TTSs ideal candidates for combination with ICB agents and other anticancer agents.

Nanoparticle vaccines can be designed to induce pDC support of mDCs for increased antigen display

Cancer vaccine immunotherapy facilitates the immune system's recognition of tumor-associated antigens, and the biomolecular design of these vaccines using nanoparticles is one important approach towards obtaining strong anti-tumor responses. Following activation of dendritic cells (DCs), a robust CD8+ T cell-mediated adaptive immune response is critical for tumor elimination. While the role of efficient antigen-presenting myeloid DCs (mDCs) is conventionally attributed towards vaccine efficacy, participation by highly cytokine-producing plasmacytoid DCs (pDCs) is less understood and is often overlooked. We examined vaccines based on the E2 protein nanoparticle platform that delivered encapsulated TLR9 agonist bacterial-like DNA (CpG1826 or CpG1018) or TLR7 agonist viral ssRNA to determine their efficacy over free agonists in activating both mDCs and pDCs for antigen presentation. Although mDCs were only activated by nanoparticle-encapsulated TLR9 agonists, pDCs were activated by all the individually tested constructs, and CpG1826 was shown to induce pDC cytokine production. Transfer of secreted factors from pDCs that were stimulated with a vaccine formulation comprising peptide antigen and CpG1826 enhanced mDC display of the antigen, particularly when delivered in nanoparticles. Only when treated with nanoparticle-conjugated vaccine could pDCs secrete factors to induce antigen display on naïve mDCs. These results reveal that pDCs can aid mDCs, highlighting the importance of activating both pDCs and mDCs in designing effective cancer vaccines, and demonstrate the advantage of using nanoparticle-based vaccine delivery.

Immune Enhancement of Nanoparticle-Encapsulated Ginseng Stem-Leaf Saponins on Porcine Epidemic Diarrhea Virus Vaccine in Mice

Porcine epidemic diarrhea virus (PEDV) causes severe enteric disease in pigs, particularly neonatal piglets. Current vaccines do not provide complete protection against PEDV. Ginseng stem-leaf saponins (GSLS), a promising oral adjuvant candidate, can improve intestinal immune responses in poultry and mice. However, its low stability limits further use. Poly lactic-co-glycolic acid (PLGA), a biocompatible and biodegradable nanoparticle, has been widely used in biomedicine for stable and targeted drug delivery. In this study, we developed GSLS-PLGA nanoparticles (GSLS-NPs) and evaluated the mucosal adjuvant efficacy in vitro and in vivo. GSLS-NPs significantly enhanced antigen internalization and pro-inflammatory cytokine secretion by DC2.4 cells. Mice orally administered GSLS-NPs before intramuscular inoculation generated CD11b+CD8α- and CD11b-CD103+ dendritic cells in the spleen and draining mesenteric lymph nodes, respectively, which are the types mainly responsible for antigen presentation. Additionally, enhanced neutralizing and non-neutralizing antibody responses and expanded activities of specific effector and memory CD4+ and CD8+ T cells were also observed in mice immunized with PEDV vaccines plus GSLS-NPs compared to mice receiving the vaccines alone. Furthermore, GSLS-NPs showed a good safety profile and presented great advantages over GSLS aqueous solution. Collectively, our results highlight the potential of GSLS-NPs as a mucosal adjuvant and provide an attractive vaccination strategy for combatting PEDV. Further study is required to evaluate the efficacy of this mucosal adjuvant in swine.

Immune State Conversion of the Mesenteric Lymph Node in a Mouse Breast Cancer Model

Secondary lymphoid tissues, such as the spleen and lymph nodes (LNs), contribute to breast cancer development and metastasis in both anti- and pro-tumoral directions. Although secondary lymphoid tissues have been extensively studied, very little is known about the immune conversion in mesenteric LNs (mLNs) during breast cancer development. Here, we demonstrate inflammatory immune conversion of mLNs in a metastatic 4T1 breast cancer model. Splenic T cells were significantly decreased and continuously suppressed IFN-γ production during tumor development, while myeloid-derived suppressor cells (MDSCs) were dramatically enriched. However, T cell numbers in the mLN did not decrease, and the MDSCs only moderately increased. T cells in the mLN exhibited conversion from a pro-inflammatory state with high IFN-γ expression to an anti-inflammatory state with high expression of IL-4 and IL-10 in early- to late-stages of breast cancer development. Interestingly, increased migration of CD103+CD11b+ dendritic cells (DCs) into the mLN, along with increased (1→3)-β-D-glucan levels in serum, was observed even in late-stage breast cancer. This suggests that CD103+CD11b+ DCs could prime cancer-reactive T cells. Together, the data indicate that the mLN is an important lymphoid tissue contributing to breast cancer development.

Dendritic Cell Vaccines: A Promising Approach in the Fight against Ovarian Cancer

Simple Summary

With an overall 5-year survival of only 20% for advanced-stage ovarian cancer patients, enduring and effective therapies are a highly unmet clinical need. Current standard-of-care therapies are able to improve progression-free survival; however, patients still relapse. Moreover, immunotherapy has not resulted in clear patient benefits so far. In this situation, dendritic cell vaccines can serve as a potential therapeutic addition against ovarian cancer. In the current review, we provide an overview of the different dendritic cell subsets and the roles they play in ovarian cancer. We focus on the advancements in dendritic cell vaccination against ovarian cancer and highlight the key outcomes and pitfalls associated with currently used strategies. Finally, we address future directions that could be taken to improve the dendritic cell vaccination outcomes in ovarian cancer.

Abstract

Ovarian cancer (OC) is the deadliest gynecological malignancy in developed countries and is the seventh-highest cause of death in women diagnosed with cancer worldwide. Currently, several therapies are in use against OC, including debulking surgery, chemotherapy, as well as targeted therapies. Even though the current standard-of-care therapies improve survival, a vast majority of OC patients relapse. Additionally, immunotherapies have only resulted in meager patient outcomes, potentially owing to the intricate immunosuppressive nexus within the tumor microenvironment. In this scenario, dendritic cell (DC) vaccination could serve as a potential addition to the therapeutic options available against OC. In this review, we provide an overview of current therapies in OC, focusing on immunotherapies. Next, we highlight the potential of using DC vaccines in OC by underscoring the different DC subsets and their functions in OC. Finally, we provide an overview of the advances and pitfalls of current DC vaccine strategies in OC while providing future perspectives that could improve patient outcomes.

Gold-Nanostar-Chitosan-Mediated Delivery of SARS-CoV-2 DNA Vaccine for Respiratory Mucosal Immunization: Development and Proof-of-Principle

The COVID-19 pandemic is caused by the coronavirus SARS-CoV-2 (SC2). A variety of anti-SC2 vaccines have been approved for human applications, including those using messenger RNA (mRNA), adenoviruses expressing SC2 spike (S) protein, and inactivated virus. The protective periods of immunization afforded by these intramuscularly administered vaccines are currently unknown. An alternative self-administrable vaccine capable of mounting long-lasting immunity via sterilizing neutralizing antibodies would be hugely advantageous in tackling emerging mutant SC2 variants. This could also diminish the possibility of vaccinated individuals acting as passive carriers of COVID-19. Here, we investigate the potential of an intranasal (IN)-delivered DNA vaccine encoding the S protein of SC2 in BALB/c and C57BL/6J immunocompetent mouse models. The immune response to IN delivery of this SC2-spike DNA vaccine transported on a modified gold-chitosan nanocarrier shows a strong and consistent surge in antibodies (IgG, IgA, and IgM) and effective neutralization of pseudoviruses expressing S proteins of different SC2 variants (Wuhan, beta, and D614G). Immunophenotyping and histological analyses reveal chronological events involved in the recognition of SC2 S antigen by resident dendritic cells and alveolar macrophages, which prime the draining lymph nodes and spleen for peak SC2-specific cellular and humoral immune responses. The attainable high levels of anti-SC2 IgA in lung mucosa and tissue-resident memory T cells can efficiently inhibit SC2 and its variants at the site of entry and also provide long-lasting immunity.

Squalene-Based Influenza Vaccine Adjuvants and Their Impact on the Hemagglutinin-Specific B Cell Response

Influenza infections continue to cause significant annual morbidity and mortality despite ongoing influenza vaccine research. Adjuvants are administered in conjunction with influenza vaccines to enhance the immune response and strengthen protection against disease. Squalene-based emulsion adjuvants including MF59, AS03, and AF03, are registered for administration with influenza vaccines and are widely used in many countries. Squalene-based emulsion adjuvants induce a strong innate immune response, enhancing antigen presentation both quantitively and qualitatively to generate strong B cell responses and antibody production. They also diversify the reactivity profiles and strengthen the affinities of antibodies against the influenza hemagglutinin, increasing protection across virus clades. In this review, we consider the mechanisms of the enhancement of innate and adaptive immune responses by squalene-based emulsionSE adjuvants and the resulting increase in magnitude and breadth of hemagglutinin-specific B cell responses. We relate observed effects of SE adjuvants and current mechanistic understandings to events in responding lymph nodes. These insights will guide the rational design and optimization of influenza vaccines to provide broad and effective protection.

Severe Acute Respiratory Syndrome Coronavirus 2: The Role of the Main Components of the Innate Immune System

At the end of December 2019, the COVID-19 pandemic began in Wuhan of China. COVID-19 affects different people with a wide spectrum of clinical manifestations, ranging from asymptomatic with recovery without hospitalization up to a severe acute respiratory syndrome (SARS). The innate and adaptive immunity appears responsible for the defense against the virus and recovery from the disease. The innate immune system, as the first line of defense, is essential for the detection of virus and subsequent activation of acquired immunity. The innate immune response is carried out by sentinel cells such as monocytes/macrophages and dendritic cells and by receptors known as pattern recognition receptors (PRR). These receptors can recognize various components of the virus, which lead to intracellular signaling and subsequently the synthesis of various cytokines. These cytokines then recruit other immune cells, activate adaptive immune responses, and inhibit viral spreading. The most common receptors include Toll-like receptors, C-type lectin receptors, and RIG-I like receptors. This review describes the current knowledge about the interplay between innate immune responses and SARS-CoV-2 with a focus on the innate immune cells and the role of their receptors in viral RNA recognition, as well as their mechanisms for recognizing SARS-CoV-2.

The Innate Immune Cell Profile of the Cornea Predicts the Onset of Ocular Surface Inflammatory Disorders

Ocular surface inflammatory disorder (OSID) is a spectrum of disorders that have features of several etiologies whilst displaying similar phenotypic signs of ocular inflammation. They are complicated disorders with underlying mechanisms related to several autoimmune disorders, such as rheumatoid arthritis (RA), Sjögren’s syndrome, and systemic lupus erythematosus (SLE). Current literature shows the involvement of both innate and adaptive arms of the immune system in ocular surface inflammation. The ocular surface contains distinct components of the immune system in the conjunctiva and the cornea. The normal conjunctiva epithelium and sub-epithelial stroma contains resident immune cells, such as T cells, B cells (adaptive), dendritic cells, and macrophages (innate). The relative sterile environment of the cornea is achieved by the tolerogenic properties of dendritic cells in the conjunctiva, the presence of regulatory lymphocytes, and the existence of soluble immunosuppressive factors, such as the transforming growth factor (TGF)-β and macrophage migration inhibitory factors. With the presence of both innate and adaptive immune system components, it is intriguing to investigate the most important leukocyte population in the ocular surface, which is involved in immune surveillance. Our meta-analysis investigates into this with a focus on both infectious (contact lens wear, corneal graft rejection, Cytomegalovirus, keratitis, scleritis, ocular surgery) and non-infectious (dry eye disease, glaucoma, graft-vs-host disease, Sjögren’s syndrome) situations. We have found the predominance of dendritic cells in ocular surface diseases, along with the Th-related cytokines. Our goal is to improve the knowledge of immune cells in OSID and to open new dimensions in the field. The purpose of this study is not to limit ourselves in the ocular system, but to investigate the importance of dendritic cells in the disorders of other mucosal organs (e.g., lungs, gut, uterus). Holistically, we want to investigate if this is a common trend in the initiation of any disease related to the mucosal organs and find a unified therapeutic approach. In addition, we want to show the power of computational approaches to foster a collaboration between computational and biological science.

CD5 on dendritic cells regulates CD4+ and CD8+ T cell activation and induction of immune responses

The role of CD5 as a regulator of T cell signaling and tolerance is well recognized. Recent data show expression of CD5 on different subtypes of human dendritic cells, however its functional relevance in modulating DC mediated responses remains poorly understood. In this study, we show CD5 is expressed on CD11c+ DC from murine thymus, lymph node, spleen, skin and lung. Although the development of DC subpopulations in CD5-/- mice was normal, CD5-deficient DC produced significantly higher levels of IL-12 than wild type DC in response to LPS. CD5-/- DC, in comparison to CD5+/+ DC, enhanced the activation of CD4+ and CD8+ T cells in vitro and in vivo and induced significantly higher production of IL-2 and IFN-gamma by T cells. Consequently, CD5-/- DC were significantly more potent than wild type DC in the induction of anti-tumor immunity and contact hypersensitivity responses in mice. Restoration of CD5 expression in CD5-/- DC reduced IL-12 production and inhibited their capacity to stimulate T cells. Collectively, these data demonstrate that the specific expression of CD5 on DC inhibits the production of inflammatory cytokines and has a regulatory effect on their activity to stimulate T cells and induce immune responses. This study reveals a previously unrecognized regulatory role for CD5 on DC and provides novel insights into mechanisms for DC biology in immune responses.

Cutaneous immune responses mediated by dendritic cells and mast cells

In the skin, complex cellular networks maintain barrier function and immune homeostasis. Tightly regulated multicellular cascades are required to initiate innate and adaptive immune responses. Innate immune cells, particularly DCs and mast cells, are central to these networks. Early studies evaluated the function of these cells in isolation, but recent studies clearly demonstrate that cutaneous DCs (dermal DCs and Langerhans cells) physically interact with neighboring cells and are receptive to activation signals from surrounding cells, such as mast cells. These interactions amplify immune activation. In this review, we discuss the known functions of cutaneous DC populations and mast cells and recent studies highlighting their roles within cellular networks that determine cutaneous immune responses.