Cross-presentation of viral antigens in dribbles leads to efficient activation of virus-specific human memory T cells

Canonical and Non-Canonical Functions of the Autophagy Machinery in MHC Restricted Antigen Presentation

Macroautophagy delivers cytoplasmic constituents for lysosomal degradation. Since major histocompatibility complex (MHC) class II molecules sample peptides after lysosomal degradation for presentation to CD4+ T cells, it was originally described that these peptides can also originate from macroautophagy substrates. In recent years it has become clear that in addition to this canonical function of the macroautophagy machinery during MHC class II restricted antigen presentation at least parts of this machinery are also used to regulate phagocytosis of antigens, degradation of MHC class I molecules, and unconventional secretion of antigens in extracellular vesicles, including virus particles. This review discusses how both canonical and non-canonical functions of the macroautophagy machinery influence antigen presentation on MHC class I and II molecules to CD8+ and CD4+ T cells. A better understanding of the molecular mechanisms by which the macroautophagy machinery is distributed between its canonical and non-canonical functions should allow targeting of antigens to these different pathways to influence MHC restricted presentation during vaccination against infectious diseases and tumors.

Non-canonical functions of autophagy proteins in immunity and infection

The molecular machinery of macroautophagy, a catabolic pathway for cytoplasmic constituent degradation in lysosomes, remodels membranes by lipid phosphorylation and conjugation of LC3 and GABARAP proteins. In recent year it has become clear that these membrane modifications also regulate endo- and exocytosis. Here I will discuss recent evidence of how such non-canonical functions of the macroautophagy machinery with its autophagy related gene (atg) products influences infectious viral particle secretion, inflammation, and MHC restricted antigen presentation. Especially LC3-Associated Phagocytosis and ATG supported exocytosis will be high-lighted during immunity and infection.

Tumor-Derived Autophagosomes (DRibbles) Activate Human B Cells to Induce Efficient Antigen-Specific Human Memory T-Cell Responses

We have reported that tumor-derived autophagosomes (DRibbles) were efficient carriers of tumor antigens and DRibbles antigens could be present by DRibbles-activated B cells to stimulate effect and naïve T cells in mice. However, the effect of DRibbles on human B cells remains unclear. Herein, we found that DRibbles can also efficiently induce proliferation and activation of human B cells and lead to the production of chemokines, cytokines and hematopoietic growth factors. We further demonstrated human B cells can effectively phagocytose DRibbles directly and cross-present DRibbles antigens to stimulate antigen-specific memory T cells. Furthermore, we found that membrane-bound high-mobility group B1 (HMGB1) on DRibbles was crucial for inducing human B cells activation. Therefore, these findings provide further evidence to promote the clinical application of B-DRibbles vaccines.

Emerging role of autophagy in anti-tumor immunity: Implications for the modulation of immunotherapy resistance

Immunotherapies such as CAR-T cell transfer and antibody-targeted therapy have produced promising clinical outcomes in patients with advanced and metastatic cancer that are resistant to conventional therapies. However, with increasing use of cancer immunotherapy in clinical treatment, multiple therapy-resistance mechanisms have gradually emerged. The tumor microenvironment (TME), an integral component of cancer, can significantly influence the therapeutic response. Thus, it is worth exploring the potential of TME in modulating therapy resistance, in the hope to devise novel strategies to reinforcing anti-cancer treatments such as immunotherapy. As a crucial recycling process in the complex TME, the role of autophagy in tumor immunity has been increasingly appreciated. Firstly, autophagy in tumor cells can affect their immune response through modulating MHC-I-antigen complexes, thus modulating immunogenic tumor cell death, changing functions of immune cells via secretory autophagy, reducing the NK- and CTL-mediated cell lysis and degradation of immune checkpoint proteins. Secondly, autophagy is critical for the differentiation, maturation and survival of immune cells in the TME and can significantly affect the immune function of these cells, thereby regulating the anti-tumor immune response. Thirdly, alteration of autophagic activity in stromal cells, especially in fibroblasts, can reconstruct the three-dimensional stromal environment and metabolic reprogramming in the TME. A number of studies have demonstrated that optimal induction or inhibition of autophagy may lead to effective therapeutic regimens when combined with immunotherapy. This review discusses the important roles of autophagy in tumor cells, immune cells and stromal cells in the context of tumor immunity, and the potential of combining the autophagy-based therapy with immunotherapy as novel therapeutic approaches against cancer.

Defining Immunogenic and Radioimmunogenic Tumors

In the cancer literature tumors are inconsistently labeled as ‘immunogenic’, and experimental results are occasionally dismissed since they are only tested in known ‘responsive’ tumor models. The definition of immunogenicity has moved from its classical definition based on the rejection of secondary tumors to a more nebulous definition based on immune infiltrates and response to immunotherapy interventions. This review discusses the basis behind tumor immunogenicity and the variation between tumor models, then moves to discuss how these principles apply to the response to radiation therapy. In this way we can identify radioimmunogenic tumor models that are particularly responsive to immunotherapy only when combined with radiation, and identify the interventions that can convert unresponsive tumors so that they can also respond to these treatments.

The Macroautophagy Machinery in MHC Restricted Antigen Presentation

Autophagy-related (ATG) gene products regulate macroautophagy, LC3-associated phagocytosis (LAP) and LC3-dependent extracellular vesicle loading and secretion (LDELS). These processes also influence antigen processing for presentation on major histocompatibility complex (MHC) molecules to T cells. Here, I summarize how these different pathways use the macroautophagy machinery, contribute to MHC class I and II restricted antigen presentation and influence autoimmunity, tumor immunology and immune control of infectious diseases. Targeting these different pathways should allow the regulation of intracellular and extracellular antigen presentation to T cells to modulate protective and pathological immune responses.

Anti-Cancer Nanomedicines: A Revolution of Tumor Immunotherapy

Immunotherapies have been accelerating the development of anti-cancer clinical treatment, but its low objective responses and severe off-target immune-related adverse events (irAEs) limit the range of application. Strategies to remove these obstacles primarily focus on the combination of different therapies and the exploitation of new immunotherapeutic agents. Nanomedicine potentiates the effects of activating immune cells selectively and reversing tumor induced immune deficiency microenvironment through multiple mechanisms. In the last decade, a variety of nano-enabled tumor immunotherapies was under clinical investigation. As time goes by, the advantages of nanomedicine are increasingly prominent. With the continuous development of nanotechnology, nanomedicine will offer more distinctive perspectives in imaging diagnosis and treatment of tumors. In this Review, we wish to provide an overview of tumor immunotherapy and the mechanisms of nanomaterials that aim to enhance the efficacy of tumor immunotherapy under development or in clinic treatment.

The expression and function of immunoglobulin-like transcript 4 in dendritic cells from patients with hepatocellular carcinoma

Due to their easy availability and expansion in vitro, monocyte-derived dendritic cells (moDCs) are most frequently used for tumor vaccination. Immunoglobulin-like transcript 4 (ILT4), as inhibitory receptor, has been reported to be related to DC tolerance. However, the influence of ILT4 for DC tolerance in hepatocellular carcinoma (HCC) patients has not been illustrated. In this research, we explored the expression of ILT4 on moDCs from HCC patients and its effect on moDC function. We demonstrated that the expression of ILT4 on mature DCs (mDCs) was higher in the peripheral blood from HCC patients than in that from healthy donors. The levels of cytokines IL-1β and IL-6 secreted by mDCs from both HCC patients and healthy controls, stimulated by anti-ILT4 agonistic mAb, were decreased. In contrast, the levels of IL-10 and IL-23 were upregulated. In addition, ILT4, triggered by anti-ILT4 agonistic mAb, could reduce allogeneic T cell proliferation stimulated by the mDCs. Moreover, ILT4 triggered by anti-ILT4 agonistic mAb could also reduce the ability of the mDCs to stimulate tumor cell antigen-specific autologous CD4⁺ T cells (production of IFN-γ) and CD8⁺ T cells (production of IFN-γ and IL-2). Furthermore, ILT4 expression impaired the cytotoxicity of autologous T cells induced by the mDCs against the HCC tumor cell line SMMC-7721. Our data revealed that the high expression of ILT4 promoted the immune tolerance of DCs, resulting in an inefficiency of the T cell response, a process that is exacerbated in HCC patients.

Harnessing the Complete Repertoire of Conventional Dendritic Cell Functions for Cancer Immunotherapy

The onset of checkpoint inhibition revolutionized the treatment of cancer. However, studies from the last decade suggested that the sole enhancement of T cell functionality might not suffice to fight malignancies in all individuals. Dendritic cells (DCs) are not only part of the innate immune system, but also generals of adaptive immunity and they orchestrate the de novo induction of tolerogenic and immunogenic T cell responses. Thus, combinatorial approaches addressing DCs and T cells in parallel represent an attractive strategy to achieve higher response rates across patients. However, this requires profound knowledge about the dynamic interplay of DCs, T cells, other immune and tumor cells. Here, we summarize the DC subsets present in mice and men and highlight conserved and divergent characteristics between different subsets and species. Thereby, we supply a resource of the molecular players involved in key functional features of DCs ranging from their sentinel function, the translation of the sensed environment at the DC:T cell interface to the resulting specialized T cell effector modules, as well as the influence of the tumor microenvironment on the DC function. As of today, mostly monocyte derived dendritic cells (moDCs) are used in autologous cell therapies after tumor antigen loading. While showing encouraging results in a fraction of patients, the overall clinical response rate is still not optimal. By disentangling the general aspects of DC biology, we provide rationales for the design of next generation DC vaccines enabling to exploit and manipulate the described pathways for the purpose of cancer immunotherapy in vivo. Finally, we discuss how DC-based vaccines might synergize with checkpoint inhibition in the treatment of malignant diseases.

Targeting Autophagy in Innate Immune Cells: Angel or Demon During Infection and Vaccination?

Innate immune cells are the "doorkeepers" in the immune system and are important for the initiation of protective vaccine responses against infection. Being an essential regulatory component of the immune system in these cells, autophagy not only mediates pathogen clearance and cytokine production, but also balances the immune response by preventing harmful overreaction. Interestingly, recent literature indicates that autophagy is positively or negatively regulating the innate immune response in a cell type-specific manner. Moreover, autophagy serves as a bridge between innate and adaptive immunity. It is involved in antigen presentation by delivering pathogen compounds to B and T cells, which is important for effective immune protection. Upon infection, autophagy can also be hijacked by some pathogens for replication or evade host immune responses. As a result, autophagy seems like a double-edged sword to the immune response, strongly depending on the cell types involved and infection models used. In this review, the dual role of autophagy in regulating the immune system will be highlighted in various infection models with particular focus on dendritic cells, monocytes/macrophages and neutrophils. Targeting autophagy in these cells as for therapeutic application or prophylactic vaccination will be discussed considering both roles of autophagy, the "angel" enhancing innate immune responses, antigen presentation, pathogen clearance and dampening inflammation or the "demon" enabling viral replication and degrading innate immune components. A better understanding of this dual potential will help to utilize autophagy in innate immune cells in order to optimize vaccines or treatments against infectious diseases.

Interactions between Autophagy and DNA Viruses

Autophagy is a catabolic biological process in the body. By targeting exogenous microorganisms and aged intracellular proteins and organelles and sending them to the lysosome for phagocytosis and degradation, autophagy contributes to energy recycling. When cells are stimulated by exogenous pathogenic microorganisms such as viruses, activation or inhibition of autophagy is often triggered. As autophagy has antiviral effects, many viruses may escape and resist the process by encoding viral proteins. At the same time, viruses can also use autophagy to enhance their replication or increase the persistence of latent infections. Here, we give a brief overview of autophagy and DNA viruses and comprehensively review the known interactions between human and animal DNA viruses and autophagy and the role and mechanisms of autophagy in viral DNA replication and DNA virus-induced innate and acquired immunity.

IFN-DC Loaded with Autophagosomes containing Virus Antigen is Highly Efficient in Inducing Virus-Specific Human T Cells

Autophagy plays a critical role in the regulation of innate and adaptive immune responses to pathogens and tumors. A previous study utilized proteasome and lysosome inhibitors to form autophagosomes (DRibbles) and the effect of dendritic cells (DCs) loaded with DRibbles in activating antigen-specific T cells has been demonstrated in a mouse experiment and human IL-4-DC. In this study, CMV-DRibbles derived from MDA cell lines expressing cytomegalovirus (CMV) pp65 protein were loaded onto human IFN-DC and IL-4-DC derived from monocytes, respectively. We observed that CMV-DRibbles resulted in the up-regulation of HLA-DR, CD11c, and CD83, but not co-stimulatory molecules CD 80 and CD86 on IFN-DC. Meanwhile, the expression of HLA-DR, CD80, CD83, and CD86, except for CD11c on IL-4-DC loaded with CMV-DRibbles were up-regulated. Moreover, CMV-DRibbles had no ability to stimulate these two moDCs to secrete cytokines IL-6, IL-1β and IL-10. Then, we optimized the conditions for antigen up-take by DCs and found that mature moDCs had a superior ability to up-take CMV-DRibbles compared with immature DCs in a dose-dependent manner. Furthermore, the efficiency of CMV-DRibbles up-take by IFN-DC was superior compared to IL-4-DC. Finally, we observed that mIFN-DC was significantly more efficient at stimulating autologous CMV-specific CD4+ T cells (0.39 vs. 0.28 %, p<0.05) and CD8+ T cells (0.36 vs. 0.12%, p<0.05) to secrete IFN-γ compared with mIL-4-DC. Therefore, DRibbles containing specific viral antigens were efficient activators of human antigen-specific T cells. Our results demonstrated that IFN-DC loaded with CMV-DRibbles revealed a superior ability to induce CMV-specific T cells.

Autophagosome-based strategy to monitor apparent tumor-specific CD8 T cells in patients with prostate cancer

The immune system plays an essential role in eradicating cancer in concert with various treatment modalities. In the absence of autologous tumor material, no standardized method exists to assess T cell responses against the many antigens that may serve as cancer rejection antigens. Thus, development of methods to screen for therapy-induced anti-tumor responses is a high priority that could help tailor therapy. Here we tested whether a tumor-derived antigen source called DRibbles®, which contain a pool of defective ribosomal products (DRiPs), long-lived and short-lived proteins (SLiPs) and danger-associated molecular patterns (DAMPs), can be used to identify tumor-associated antigen (TAA)-specific responses in patients before or after immunotherapy treatment. Protein content, gene expression and non-synonymous - single nucleotide variants (ns-SNVs) present in UbiLT3 DRibbles were compared with prostate adenocarcinomas and the prostate GVAX vaccine cell lines (PC3/LNCaP). UbiLT3 DRibbles were found to share proteins, as well as match tumor sequences for ns-SNVs with prostate adenocarcinomas and with the cell lines PC3 and LNCaP. UbiLT3 DRibbles were used to monitor anti-tumor responses in patients vaccinated with allogeneic prostate GVAX. UbiLT3-DRibble-reactive CD8+ T-cell responses were detected in post-vaccine PBMC of 6/12 patients (range 0.85-22% of CD8+ cells) after 1 week in vitro stimulation (p = 0.007 vs. pre-vaccine). In conclusion, a cancer-derived autophagosome-enriched preparation, packaging over 100 proteins over-expressed in prostate cancer into microvesicles containing DAMPs, could be used to identify CD8+ T cells in peripheral blood from patients after prostate GVAX vaccination and may represent a general method to monitor anti-cancer T cell responses following immunotherapy.

1-Methyl-D-tryptophan Reduces Tumor CD133+ cells, Wnt/β-catenin and NF-κβp65 while Enhances Lymphocytes NF-κβ2, STAT3, and STAT4 Pathways in Murine Pancreatic Adenocarcinoma

1-Methyl-D-tryptophan (1-MT) is extensively utilized in preclinical trials to deplete indoleamine 2,3-dioxigenase (IDO) activity and kynurenine pathway. Since IDO related signaling pathways aren’t well understood, some clinical reports affirmed IDO inhibiting therapeutic significance. Therefore, we did use direct tumor autologous antigens vaccination and 1-MT without chemotherapy to explore biological mechanisms and immunomodulations of 1-MT that motivate antitumor responses. However, DCs antigen-uptake capability, anti-tumor efficiency, intra-tumor and intracellular cytokines were assessed. Besides, CD133+ cells viability and tumor biomarkers were investigated. Splenocytes responses and their signaling pathways such TLRs 2 to 9, NF-κβ1-2, Wnt/β-catenin and TGF-β were dissected. Results evinced that a regimen of 1-MT and TAAs significantly reduced CSC CD133 + viability inside tumor microenvironment, besides increasing tumor cells necrosis and apoptosis. Expression of TGF-β, IDO, RANTES, and PDL-1 was also significantly reduced. Interestingly, 1-MT enhanced lymphocytes TLR2, TLR7, TLR8, and TLR9 pathways. It motivated lymphocytes’ NF-κβ2, STAT3, and STAT4 pathways, while reduced tumors’ NF-κβp65 and Wnt/β-catenin signaling pathways. We found that periphery and intra-tumor Treg cells were significantly decreased. In conclusion, depletion of indoleamine 2,3-dioxigenase activity evidenced IDO relation with tumor stem cells proliferation pathways. Furthermore, 1-MT supports immunotherapeutic vaccines susceptibility and tumor specific targeting by reducing tumorgensis signaling pathways.

Polyethyleneimine modification of aluminum hydroxide nanoparticle enhances antigen transportation and cross-presentation of dendritic cells

Background

The aim of this study was to explore the feasibility of delivering tumor antigens and enhancing the antigen cross-presentation of dendritic cells (DCs) by aluminum hydroxide nanoparticle with polyethyleneimine (PEI) modification (LV@HPA/PEI).

Materials and methods

The LV@HPA nanoparticles were modified by PEI first, then the influence of LV@HPA/PEI on DCs was examined. The distinct expression of ovalbumin (OVA) protein transported into DCs by LV@HPA/PEI was observed by flow cytometry and Western blot. The biocompatibility of LV@HPA/PEI, maturity and antigen cross-presentation of DCs was observed in vitro. Tumor derived autophagosomes (DRibbles) combined with LV@HPA/PEI were loaded into DCs, and DC vaccines were used to immunize mice. The percentage of CD3⁺CD8⁺IFN-γ⁺ T cells in immunized mice was determined by flow cytometry. Additionally, the functional properties of the LV@HPA/PEI-DRibble-DCs vaccine were examined in vivo in PancO2 tumor-bearing mice.

Results

In our study, we described how LV@HPA/PEI can be a functionalized antigen delivery system with notable antigen transport effect and negligible cytotoxicity. It was found that LV@HPA/PEI could be easily internalized into DCs to assist antigen release into the cytoplasm. In addition, DCs matured gradually after loading with LV@HPA/PEI-OVA, which increased significantly the cytokine IL-12 secretion and expression of surface molecules CD80 and CD86. Interestingly, DCs loaded with LV@HPA/PEI-DRibbles could promote the activation of tumor-specific T cells both in murine and in human T cells. In the following in vivo experiments, the vaccine of LV@HPA/PEI-DRibble-DCs significantly inhibited tumor growth and improved the survival rate of the PancO2 tumor-bearing mice.

Conclusion

We established a high-performance anti-tumor vaccine of DCs loaded with LV@ HPA/PEI nanoparticles and tumor-associated antigens in autophagosomes (DRibbles), which could serve as a therapeutic strategy in cancer immunotherapy.

Ubiquitinated Proteins Isolated From Tumor Cells Are Efficient Substrates for Antigen Cross-Presentation

We have previously shown that inhibition of the proteasome causes defective ribosomal products to be shunted into autophagosomes and subsequently released from tumor cells as defective ribosomal products in Blebs (DRibbles). These DRibbles serve as an excellent source of antigens for cross-priming of tumor-specific T cells. Here, we examine the role of ubiquitinated proteins (Ub-proteins) in this pathway. Using purified Ub-proteins from tumor cells that express endogenous tumor-associated antigen or exogenous viral antigen, we tested the ability of these proteins to stimulate antigen-specific T-cell responses, by activation of monocyte-derived dendritic cells generated from human peripheral blood mononuclear cells. Compared with total cell lysates, we found that purified Ub-proteins from both a gp100-specific melanoma cell line and from a lung cancer cell line expressing cytomegalovirus pp65 antigen produced a significantly higher level of IFN-γ in gp100- or pp65-specific T cells, respectively. In addition, Ub-proteins from an allogeneic tumor cell line could be used to stimulate tumor-infiltrating lymphocytes isolated and expanded from non-small cell lung cancer patients. These results establish that Ub-proteins provide a relevant source of antigens for cross-priming of antitumor immune responses in a variety of settings, including endogenous melanoma and exogenous viral antigen presentation, as well as antigen-specific tumor-infiltrating lymphocytes. Thus, ubiquitin can be used as an affinity tag to enrich for unknown tumor-specific antigens from tumor cell lysates to stimulate tumor-specific T cells ex vivo or to be used as vaccines to target short-lived proteins.

The Autophagic Machinery in Viral Exocytosis

The discovery of the molecular machinery of autophagy, namely Atg proteins, was awarded with the Nobel prize in physiology and medicine to Yoshinori Ohsumi in 2016. While this machinery was originally identified by its ability to allow cells to survive starvation via lysosomal degradation to recycle cellular components, it has recently become apparent that it also is used by cells to secrete cytoplasmic constituents. Furthermore, viruses have learned to use this Atg supported exocytosis to exit cells, acquire envelopes in the cytosol and select lipids into their surrounding membranes that might allow for increased robustness of their virions and altered infection behavior. Along these lines, picornaviruses exit infected cells in packages wrapped into autophagic membranes, herpesviruses recruit autophagic membranes into their envelopes and para- as well as orthomyxoviruses redirect autophagic membranes to the cell membrane, which increases the robustness of their envelope that they acquire at this site. These recent findings open a new exciting field on the regulation of degradation vs. release of autophagic membranes and will be discussed in this minireview.

The Macroautophagy Machinery in Endo- and Exocytosis

Macroautophagy and the autophagy-related gene (Atg) machinery execute during their canonical function cytoplasmic constituent degradation in lysosomes. This canonical function contributes to pathogen restriction and intracellular antigen presentation on major histocompatibility complex (MHC) class II molecules to CD4⁺ T cells. However, in the recent years, it has become clear that the Atg machinery is also used for other membrane transport functions, including endocytosis and exocytosis. This review describes these non-canonical functions in the context of antigen presentation on MHC class I and II molecules to CD8⁺ and CD4⁺ T cells, respectively, and during viral replication. Future studies will need to address how the Atg machinery is modified for these non-canonical functions, gets recruited to the respective sites of membrane modification, and recruits alternative Atg interactors to execute endo- and exocytosis instead of macroautophagy.

TLR and NLRP3 inflammasome-dependent innate immune responses to tumor-derived autophagosomes (DRibbles)

Autophagosomes derived from tumor cells, also referred to as defective ribosomal products in blebs (DRibbles), have been previously shown to stimulate potent T-cell responses and mediate tumor regression when used as therapeutic cancer vaccines in multiple preclinical cancer models. In this report, we investigated the underlining mechanisms by which DRibbles induced T-cell activation, particularly how DRibbles activated antigen-presenting cells (APCs). We found that DRibbles could induce a rapid differentiation of monocytes and DC precursor (pre-DC) cells into functional APCs. DRibbles triggered innate receptor signaling via Toll-like Receptors (TLR)-2, TLR4, TLR7, TLR8, and nucleotide-binding oligomerization domain-containing protein 2 (NOD2), but not TLR3, TLR5, or TLR9. DRibbles induced PBMCs to produce pro-inflammatory cytokines, such as IL-6, IL-10, TNF-α, and IL-1β. DRibbles induced IL-1β release from PBMC or THP-1 cells without LPS priming, but required the core machinery of NLRP3 inflammasomes. Active endocytosis was required for inflammasome activation and cross presentation, and blocking endosome acidification or the ER-associated degradation (ERAD) pathway resulted in opposite effects on these two processes. Our data show that DRibbles could induce strong innate immune responses via multiple pattern recognition receptors, and explain why DRibbles could function as excellent antigen carriers to induce adaptive immune responses to both tumor cells and viruses. In contrast to the well-established inhibitory effect of autophagy on the inflammasome activation of APCs, our study demonstrates that isolated autophagosomes (DRibbles) from antigen donor cells activate inflammasomes by providing first and second signals required for IL-1β production by PMBC.

Sorafenib and a novel immune therapy in lung metastasis from hepatocellular carcinoma following hepatectomy: A case report

Sorafenib is the standard therapeutic strategy for recurrent hepatocellular carcinoma (HCC) following hepatectomy. However, only few patients truly benefit from this therapy. Thus, new strategies combined with sorafenib are urgently required. We herein present the case of a patient with hepatic and extrahepatic HCC recurrence following hepatectomy, who was treated by combined sorafenib, focused ultrasound knife and DRibbles-pulsed dendritic cell (DC) vaccine. Enzyme-Linked ImmunoSpot assay (ELISPOT) and intracellular staining (ICS) analysis were used to detect the secretion of interferon (IFN)-γ by T cells at different timepoints of the vaccine in order to evaluate the patient's specific T-cell response to SMMC-7721-derived DRibbles vaccine. The α-fetoprotein level decreased from 103,295 to 5 ng/ml and the patient displayed improved liver function, an Eastern Cooperative Oncology Group performance status score of 0, remission of liver metastases and disappearance of the lung metastases 8 months post-combination therapy. The computed tomography scan revealed the disappearance of liver metastases 2 years post-combination therapy. The ELISPOT data revealed a low antigen-specific T-cell response 4 weeks after the first vaccine cycle and the response decreased to nearly zero prior to the second cycle. However, high antigen-specific T-cell response was observed 2 weeks after the second vaccine cycle and did not decrease, even after 10 months, which was consistent with the result of the ICS analysis, which demonstrated that most of the secreted IFN-γ was produced by CD4⁺ T cells, whereas a low CD8⁺ T-cell response was observed (0.429 vs. 0.0665%, respectively). Our results demonstrated that antigen-specific T-cell response aimed to treat recurrent HCC may be induced through stimulation by the DC-DRibbles vaccine. The success of the treatment supports the combination of sorafenib, focused ultrasound knife and DC-DRibbles vaccine as a therapeutic strategy for patients with HCC recurrence following hepatectomy.

Autophagy proteins in antigen processing for presentation on MHC molecules

Autophagy describes catabolic pathways that deliver cytoplasmic constituents for lysosomal degradation. Since major histocompatibility complex (MHC) molecules sample protein degradation products and present them to T cells for adaptive immunity, it is maybe not too surprising that autophagy contributes to this protein antigen processing for MHC presentation. However, the recently recognized breath of pathways, by which autophagy contributes to MHC antigen processing, is exciting. Macroautophagy does not only seem to deliver intracellular but facilitates also extracellular antigen processing by lysosomal hydrolysis for MHC class II presentation. Moreover, even MHC class I molecules that usually display proteasomal products are regulated by macroautophagy, probably using a pool of these molecules outside the endoplasmic reticulum, where MHC class I molecules are loaded with peptide during canonical MHC class I antigen processing. This review aims to summarize these recent developments and point out gaps of knowledge, which should be filled by further investigation, in order to harness the different antigen-processing pathways via autophagy for vaccine improvement.

Autophagy and Mammalian Viruses: Roles in Immune Response, Viral Replication, and Beyond

Autophagy is an important cellular catabolic process conserved from yeast to man. Double-membrane vesicles deliver their cargo to the lysosome for degradation. Hence, autophagy is one of the key mechanisms mammalian cells deploy to rid themselves of intracellular pathogens including viruses. However, autophagy serves many more functions during viral infection. First, it regulates the immune response through selective degradation of immune components, thus preventing possibly harmful overactivation and inflammation. Additionally, it delivers virus-derived antigens to antigen-loading compartments for presentation to T lymphocytes. Second, it might take an active part in the viral life cycle by, eg, facilitating its release from cells. Lastly, in the constant arms race between host and virus, autophagy is often hijacked by viruses and manipulated to their own advantage. In this review, we will highlight key steps during viral infection in which autophagy plays a role. We have selected some exemplary viruses and will describe the molecular mechanisms behind their intricate relationship with the autophagic machinery, a result of host-pathogen coevolution.

Of LAP, CUPS, and DRibbles - Unconventional Use of Autophagy Proteins for MHC Restricted Antigen Presentation

Macroautophagy delivers cytoplasmic constituents for lysosomal degradation. Because MHC class II molecules are loaded with lysosomal products for CD4⁺ T-cell stimulation, macroautophagy supports intracellular antigen processing onto MHC class II molecules. The molecular machinery of macroautophagy, however, does not only support this autophagic antigen processing, but seems to also modify extracellular antigen uptake for MHC class II presentation, antigen exocytosis, and packaging for improved cross-presentation onto MHC class I molecules. The different membrane trafficking pathways with LC3-associated phagocytosis, compartment for unconventional protein secretion, and DRibbles as well as the role that autophagic proteins play in them will be discussed in this review.