Intersection of autophagy with pathways of antigen presentation

Traditionally,macroautophagy(autophagy)is viewed as a pathway of cell survival.Autophagy ensures the elimination of damaged or unwanted cytosolic components and provides a source of cellular nutrients during periods of stress.Interestingly,autophagy can also directly intersect with,and impact,other major pathways of cellular function.Here,we will review the contribution of autophagy to pathways of antigen presentation.The autophagy machinery acts to modulate both MHCⅠ and MHCⅡ antigen presentation.As such autophagy is an important participant in pathways that elicit host cell immunity and the elimination of infectious pathogens.

MHC Class Ⅰ Antigen Presentation-Recently Trimmed and Well Presented

Presentation of antigenic peptide to T cells by major histocompatibility complex (MHC) class I molecules is the key to the cellular immune response.Non-self intracellular proteins are processed into short peptides and transported into endoplasmic reticulum (ER) where they are assembled with class I molecules assisted by several chaperone proteins to form trimeric complex.MHC class I complex loaded with optimised peptides travels to the cell surface of antigen presentation cells to be recognised by T cells.The cells presenting non-self peptides are cleared by CD8 positive T cells.In order to ensure that T cells detect an infection or mutation within the target cells the process of peptide loading and class I expression must be carefully regulated.Many of the cellular components involved in antigen processing and class I presentation are known and their various functions are now becoming clearer.Cellular & Molecular Immunology.2004;1(1):22-30.

Antigen presentation,autoantibody production,and therapeutic targets in autoimmune liver disease

The liver is an important immunological organ that controls systemic tolerance.The liver harbors professional and unconventional antigen-presenting cells that are crucial for tolerance induction and maintenance.Orchestrating the immune response in homeostasis depends on a healthy and well-toned immunological liver microenvironment,which Is maintained by the crosstalk of liver-resident antigen-presenting cells and intrahepatic and liver-infiltrating leukocytes.In response to pathogens or autoantigens,tolerance is disrupted by unknown mechanisms.Intrahepatic parenchymal and nonparenchymal cells exhibit unique antigen-presenting properties.The presentation of microbial and endogenous lipid-,metabolite-and peptide-derived antigens from the gut via conventional and nonconventional mechanisms can educate intrahepatic immune cells and elicit effector responses or tolerance.Perturbation of this balance results in autoimmune liver diseases,such as autoimmune hepatitis,primary biliary cholangitis,and primary sclerosing cholangitis.Although the exact etiologies of these autoimmune liver diseases are unknown,it is thought that the disruption of tolerance towards self-antigens and microbial metabolites and lipids,as well as alterations in bile acid composition,may result in changes in effector cell activation and polarization and may reduce or impair protective antiinflammatory regulatory T and B cell responses.Additionally,the canonical and noncanonical transmission of antigens and antigen:MHC complexes via trogocytosis or extracellular vesicles between different(non)immune cells in the liver may play a role in the induction of hepatic inflammation and tolerance.Here,we summarize emerging aspects of antigen presentation,autoantibody production,and the application of novel therapeutic approaches in the characterization and treatment of autoimmune liver diseases.

Effects of antigen presentation of eosinophils on lung Th1/Th2 imbalance

Background Antigen loaded eosinophils (EOSs) instilled intratracheally into mice were capable of inducing Th2 type cytokine production in the draining lymph nodes The aim of the present study was to evaluate whether EOSs within the tracheobronchial lumen can stimulate Th2 cell expansion in the lung tissues Methods Airway EOSs were recovered from ovalbumin sensitized and challenged BALB/c mice, these EOSs were then cocultured with CD4 + cells isolated from sensitized mice in the absence or presence of anti CD80 or/and CD86 monoclonal antibodies Airway EOSs were instilled into the trachea of sensitized mice. At the day 3 thereafter, the lung tissues were removed and prepared into cell suspensions for culture Cell free culture supernatants were collected for detection of cytokines Results Airway EOSs functioned as CD80 and CD86 dependent antigen presenting cells to stimulate lung CD4 + lymphocytes to produce interleukin 4, interleukin 5 and interleukin 13, but not interferon γ in in vitro assay When instilled intratracheally in sensitized recipient mice, airway EOSs primed lung Th2 cells in vivo for interleukin 4, interleukin 5 and interleukin 13, but not interferon γ, production during the in vitro culture that was also CD80 and CD86 dependent Conclusion EOSs within the lumina of airways could process inhaled antigen and function in vitro and in vivo as antigen presenting cells to promote expansion of Th2 cells in the lungs

Orchestrating antigen delivery and presentation efficiency in lymph node by nanoparticle shape for immune response

Activating humoral and cellular immunity in lymph nodes(LNs)of nanoparticle-based vaccines is critical to controlling tumors.However,how the physical properties of nanovaccine carriers orchestrate antigen capture,lymphatic delivery,antigen presentation and immune response in LNs is largely unclear.Here,we manufactured gold nanoparticles(AuNPs)with the same size but different shapes(cages,rods,and stars),and loaded tumor antigen as nanovaccines to explore their disparate characters on above four areas.Results revealed that star-shaped AuNPs captured and retained more repetitive antigen epitopes.On lymphatic delivery,both rods and star-shaped nanovaccines mainly drain into the LN follicles region while cage-shaped showed stronger paracortex retention.A surprising finding is that the star-shaped nanovaccines elicited potent humoral immunity,which is mediated by CD4^(+)T helper cell and follicle B cell cooperation significantly preventing tumor growth in the prophylactic study.Interestingly,cage-shaped nanovaccines preferentially presented peptide-MHC I complexes to evoke robust CD8^(+)T cell immunity and showed the strongest therapeutic efficacy when combined with the PD-1 checkpoint inhibitor in established tumor study.These results highlight the importance of nanoparticle shape on antigen delivery and presentation for immune response in LNs,and our findings support the notion that different design strategies are required for prophylactic and therapeutic vaccines.

Stress increases MHC-I expression in dopaminergic neurons and induces autoimmune activation in Parkinson’s disease

The expression of major histocompatibility complex class I(MHC-I),a key antigen-presenting protein,can be induced in dopaminergic neurons in the substantia nigra,thus indicating its possible involvement in the occurrence and development of Parkinson’s disease.However,it remains unclear whether oxidative stress induces Parkinson’s disease through the MHC-I pathway.In the present study,polymerase chain reaction and western blot assays were used to determine the expression of MHC-I in 1-methyl-4-phenylpyridinium(MPP+)-treated SH-SY5Y cells and a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced Parkinson’s disease mouse model.The findings revealed that MHC-I was expressed in both models.To detect whether the expression of MHC-I was able to trigger the infiltration of cytotoxic T cells,immunofluorescence staining was used to detect cytotoxic cluster of differentiation 8(CD8)+T cell infiltration in the substantia nigra of MPTP-treated mice.The results indicated that the presentation of MHC-I in dopaminergic neurons was indeed accompanied by an increase in the number of CD8+T cells.Moreover,in MPTP-induced Parkinson’s disease model mice,the genetic knockdown of endogenous MHC-I,which was caused by injecting specific adenovirus into the substantia nigra,led to a significant reduction in CD8+T cell infiltration and alleviated dopaminergic neuronal death.To further investigate the molecular mechanisms of oxidative stress-induced MHC-I presentation,the expression of PTEN-induced kinase 1(PINK1)was silenced in MPP+-treated SH-SY5Y cells using specific small interfering RNA(siRNA),and there was more presentation of MHC-I in these cells compared with control siRNA-treated cells.Taken together,MPP+-/MPTP-induced oxidative stress can trigger MHC-I presentation and autoimmune activation,thus rendering dopaminergic neurons susceptible to immune cells and degeneration.This may be one of the mechanisms of oxidative stress-induced Parkinson’s disease,and implies the potential neuroprotective role of PINK1 in oxidative stress-induced MHC-I presentation.All animal experiments were approved by the Southern Medical University Ethics Committee(No.81802040,approved on February 25,2018).

p38α has an important role in antigen cross-presentation by dendritic cells

The role of the p38 signaling pathway in the innate and adaptive immune responses has been well documented,especially in inflammatory cytokine production by dendritic cells(DCs).However,whether the p38 signaling pathway affects the important antigen(Ag)presentation function of DCs remains largely unknown.In this study,we reported that the deletion of p38αresulted in an impaired cross-presentation ability of CD8^(+) conventional DCs(cDCs)and a reduction in the direct presentation ability of CD8−cDCs ex vivo.Further study revealed that p38αhad a crucial role in Ag processing by CD8^(+) cDCs but did not affect the Ag uptake or co-stimulation of T cells.Moreover,p38αdeficiency led to reduced cross-priming of T cells in vivo.The production of the IL-12p40 and IL-12p70 cytokines by p38α-deficient cDCs was also significantly reduced.Our study identified a new role for p38αin modulating the important antigen cross-presentation function of DCs.

Role of Dendritic Cells in Myocarditis Induced by Coxsackie B_3 Virus in Mouse

Background and Objectives Autoimmune reaction may play an important role in the pathogenesis and progress in virus myocarditis. Dendritic cells are the initiators of immune reaction to foreign antigens and are considered to be key players in the induction and maintenance of autoimmune reactions. This study was undertaken to investigate the role of DC in mice with virus myocarditis. Methods and Results Fifty Balb/c mice were injected Coxsackie B3 virus to induce myocarditis and ten mice were injected culture liquid as control group. The hearts of virus - infected mice were harvested on day 3, 7, 14, 28 after the injection. All the hearts were sliced to do HE staining, MHC Ⅱ antigen and S - 100 protein immunohistochemical staining. The inflammation response and expression of MHC Ⅱ antigen and S - 100 protein positive stained cells were observed. The MHC Ⅱ antigen positive score were 1.42±0.95, 2.24 ±1. 00, 3. 23± 1. 16, 2. 58 ± 1. 05 respectively in group 3d, 7 d, 14 d, 28 d, which were significant different from control group(0. 50 ±0.75, P <0. 05). The S-100 positive staining cells in control group was 3. 2±1. 0. And the numbers were 6. 7 ± 1. 4 , 16. 4 ± 2. 5 , 21. 2±3. 3 , 13. 4 ± 2. 3 respectively in group 3 d, 7 d, 14 d, 28 d, and there were significant differences compared with the control group ( P < 0. 01) . Conclusions Immune reaction was involved in the pathogenesis in Coxsackie B3 virus - induced myocarditis in mouse, and dendritic cell might play an important role in the immune reaction.

HBsAg loading on dendritic cells in patients with chronic hepatitis B: expressions of phenotypic molecules

BACKGROUND: The antigen reducing ability of dentritic cells (DCs), a kind of antigen presenting cells (APCs) initiating immune response, is associated with the specific immune tolerance of chronic hepatitis B(CHB) patients. However, the dysfunction of DCs can be possibly reversed by the stimulation of antigen peptides. In this study, DCs were cultured from peripheral blood monocytes (PBMCs) in patients with CHB in vitro, and the expression of phenotypic molecules on DCs loaded by different concentrations of HBsAg was observed. METHODS: Forty patients with CHB were divided randomly into 4 groups(10 patients in each group). PBMCs were isolated, and DCs were cultured after addition of granulocyte/macrophage colony-stimulating factor (GMCSF) and interleukin 4(IL-4). On the 9th day, DCs of the experimental groups were loaded at HBsAg concentrations of 2.5mg/L, 5mg/L and 10mg/L for 24 hours, whereas those of the control group were not loaded. An electron microscope was used to analyze the morphological changes of the DCs. The expression of phenotypic molecules on DCs in different groups was detected with flow cytometry. RESULTS: A combination of GM-CSF and IL-4 produced DCs from PBMCs in patients with CHB after being cultured for 9 days, whose morphological changes were tested by an electron microscope. The expression of phenotypic molecules on DCs in the control group was as low as CD83 (8.02±3.99)%, CD80(8.77±2.06)%, and MHC-DR (14.05±2.66)%. Loaded by different concentrations of HBsAg, the up-regulation of phenotypic molecules on DCs was found, with CD83(18.35±2.93)%, CD80(42.63±7.15)% and MHC-DR(47.49±6.59)% in 2.5mg/L HBsAg loading group, CD83(17.88±3.12)%, CD80(45.24± 10.93)% and MHC-DR(47.07±8.52)% in 5mg/L HBsAg loading group and CD83(16.74±2.86)%, CD80(44.59±6.99)% and MHC-DR(48.59±7.42)% in 10mg/L HBsAg loading group, respectively. Compared with the control group, the phenotypic molecules in the experimental groups were all different significantly (P<0.01), but among them, there were no differences (P>0.05). CONCLUSIONS: DCs cultured from PBMCs in the patients with CHB under the conditions of GM-CSF and IL-4 present on the typical dendritic morphology but are immature for expressing low phenotypic molecules. Loaded by different concentrations of HBsAg, the immature DCs can differentiate to mature DCs for expressing increasing phenotypic molecules.

CD4^+ T cell-mediated presentation of non-infectious HIV-1 virion antigens to HIV-specific CD8^+ T cells

Background The mechanism of chronic immune activation and impairment of HIV-specific immune responses during chronic infection is not fully understood. However, it is known that high immune activation leads to more rapid progression to AIDS. We hypothesize that CD4^＋ T cell-mediated viral antigen presentation contributes to this pathologic immune activation in HIV-infected individuals. Methods HIV-specific T cells, responding to noninfectious HIV-1 virions as antigen, were measured by flow cytometric assays. These experimental conditions reflect the in vivo condition where noninfectious HIV-1 represents more than 99% of the antigens. Results CD4^＋ T cells purified from HIV-infected individuals were capable of cross presenting exogenous noninfectious HIV-1 virions to HIV-1-specific CD8^＋ T cells. Cross presentation required the entry of HIV-1 to CD4^＋ T cells and antigen translocation from endoplasmic reticulum to the Golgi complex. Blocking CD4^＋ mediated activation of HIV-specific CD8^＋ T cells and redirecting the viral antigens to antigen presenting cells improved HIV-specific T cell responses. Contusions One possible cause of chronic immune activation and impairment of HIV-1 specific T cell responses is represented by HIV-1 harboring CD4^＋ T cells cross presenting HIV-1 antigen to activate CD8^＋ T cells. This new mechanism provides the first evidence that cross presentation of noninfectious HIV-1 virions play a role in the immunopathogenesis of HIV-1 infection.

Radiation-induced Bystander Effect in Immune Response

Objective Since most reports on bystander effect have been only concerned with radiation-induced damage, the present paper aimed at disclosing whether low dose radiation could induce a stimulatory or beneficial bystander effect. Methods A co-culture system containing irradiated antigen presenting cells (J774A.1) and unirradiated T lymphocytes (EL-4) was established to observe the effect of J774A.1 cells exposed to both low and high doses of X-rays on the unirradiated EL-4 cells. Incorporation of 3H-TdR was used to assess the proliferation of the EL-4 cells, expression of CD80/86 and CD48 on J774A.1 cells was measured with immunohistochemistry and flow cytometry, respectively. NO release from J774A.1 cells was estimated with nitrate reduction method. Results Low dose-irradiated J774A.1 cells could stimulate the proliferation of the unirradiated EL-4 cells while the high dose-irradiated J774A.1 cells exerted an inhibitory effect on the proliferation of the unirradiated EL-4 cells. Preliminary mechanistic studies illustrated that the differential changes in CD48 expression and NO production by the irradiated J774A.1 cells after high and low dose radiation might be important factors underlying the differential bystander effect elicited by different doses of radiation. Conclusion Stimulatory bystander effect can be induced in immune cells by low dose radiation.

Neutrophils in Atlantic salmon(Salmo salar L.)are MHC class II^(+)and secret IL-12p40 upon bacterial exposure

Antigen-presentation via major histocompatibility complex(MHC)to T cells is the key event to initiate adaptive immune responses.In teleosts,as in mammals,the main types of professional antigen-presenting cells(APCs)are dendritic cells(DCs),monocytes/macrophages,and B cells.In the current study,flow cytometry,immunostaining and qPCR have been used to show that neutrophils in the teleost fish Atlantic salmon(Salmo salar L.)have antigen-presenting properties.The neutrophils were positive for MHC class II,CD83 and CD80/86,and upon in vitro bacterial exposure,gene expression analysis of purified neutrophils showed that IL-12p40,which is essential for proliferation of naïve T cells,was highly upregulated at both 6 and 24 h post bacterial exposure.Based on presence of MHC class II and upregulation of molecules involved in antigen presentation and T cell activation,we suggest that neutrophils in Atlantic salmon have potential to function as professional APCs.This work makes an important basis for further exploring the potential of using neutrophils to develop new,targeted immunoprophylactic measures.

Manganese salts function as potent adjuvants

Aluminum-containing adjuvants have been used for nearly 100 years to enhance immune responses in billions of doses of vaccines.To date,only a few adjuvants have been approved for use in humans,among which aluminum-containing adjuvants are the only ones widely used.However,the medical need for potent and safe adjuvants is currently continuously increasing,especially those triggering cellular immune responses for cytotoxic T lymphocyte activation,which are urgently needed for the development of efficient virus and cancer vaccines.Manganese is an essential micronutrient required for diverse biological activities,but its functions in immunity remain undefined.We previously reported that Mn^(2+) is important in the host defense against cytosolic dsDNA by facilitating cGAS-STING activation and that Mn^(2+)alone directly activates cGAS independent of dsDNA,leading to an unconventional catalytic synthesis of 2′3′-cGAMP.Herein,we found that Mn^(2+) strongly promoted immune responses by facilitating antigen uptake,presentation,and germinal center formation via both cGAS-STING and NLRP3 activation.Accordingly,a colloidal manganese salt(Mn jelly,MnJ)was formulated to act not only as an immune potentiator but also as a delivery system to stimulate humoral and cellular immune responses,inducing antibody production and CD4^(+)/CD8^(+)T-cell proliferation and activation by either intramuscular or intranasal immunization.When administered intranasally,MnJ also worked as a mucosal adjuvant,inducing high levels of secretory IgA.MnJ showed good adjuvant effects for all tested antigens,including T cell-dependent and T cell-independent antigens,such as bacterial capsular polysaccharides,thus indicating that it is a promising adjuvant candidate.

Classical and non-classical MHC I molecule manipulation by human cytomegalovirus： so many targets--but how many arrows in the quiver？

Major mechanisms for the recognition of pathogens by immune cells have evolved to employ classical and non-classical major histocompatibility complex class I （MHC I） molecules. Classical MHC I molecules present antigenic peptide ligands on infected cells to CD8＋ T cells, whereas a key function for non-classical MHC I molecules is to mediate inhibitory or activating stimuli in natural killer （NK） cells. The structural diversity of MHC I puts immense pressure on persisting viruses, including cytomegaloviruses. The very large coding capacity of the human cytomegalovirus allows it to express a whole arsenal of immunoevasive factors assigned to individual MHC class I targets. This review summarizes achievements from more than two decades of intense research on how human cytomegalovirus manipulates MHC I molecules and escapes elimination by the immune system.

Tetrahedral DNA nanostructures synergize with MnO_(2) to enhance antitumor immunity via promoting STING activation and M1 polarization

Stimulator of interferon genes(STING) is a cytosolic DNA sensor which is regarded as a potential target for antitumor immunotherapy. However, clinical trials of STING agonists display limited anti-tumor effects and dose-dependent side-effects like inflammatory damage and cell toxicity. Here,we showed that tetrahedral DNA nanostructures(TDNs) actively enter macrophages to promote STING activation and M1 polarization in a size-dependent manner, and synergized with Mn^(2+) to enhance the expressions of IFN-β and iNOS, as well as the co-stimulatory molecules for antigen presentation. Moreover, to reduce the cytotoxicity of Mn^(2+),we constructed a TDN-MnO_(2) complex and found that it displayed a much higher efficacy than TDN plus Mn^(2+) to initiate macrophage activation and anti-tumor response both in vitro and in vivo. Together, our studies explored a novel immune activation effect of TDN in cancer therapy and its synergistic therapeutic outcomes with MnO_(2).These findings provide new therapeutic opportunities for cancer therapy.

Nanomedicine-mediated ubiquitination inhibition boosts antitumor immune response via activation of dendritic cells

Tumor immunotherapy as a promising method for tumor treatment received tremendous attention. However, the problem of low clinical response rate still needs to be solved, especially in the poorly immunogenic tumors. The enhancement of tumor antigens presentation can effectively activate dendritic cells (DCs) and improve the tumor immunotherapy. In this work, TAK-243 as an inhibitor of the ubiquitin activating enzyme (UAE), was fabricated into cationic lipid-assisted nanoparticle (CLANTAK-243). The obtained CLANTAK-243 could act as an effective tumor immunotherapy enhancer to promote the maturation of DCs as well as antigen presentation, which obviously stimulated the T cells activation and proliferation. Such CLANTAK-243 injected intravenously could well trigger immune response to tumor cells in vivo. Importantly, mice treated with CLANTAK-243 could obtain a long immune memory effect to protect themselves from re-challenged tumor cells. Therefore, this work presented an effective immunotherapy strategy for poorly immunogenic tumor.

Review:Development of SARS-CoV-2 immuno-enhanced COVID-19 vaccines with nano-platform

Vaccination is the most effective way to prevent coronavirus disease 2019(COVID-19).Vaccine development approaches consist of viral vector vaccines,DNA vaccine,RNA vaccine,live attenuated virus,and recombinant proteins,which elicit a specific immune response.The use of nanoparticles displaying antigen is one of the alternative approaches to conventional vaccines.This is due to the fact that nano-based vaccines are stable,able to target,form images,and offer an opportunity to enhance the immune responses.The diameters of ultrafine nanoparticles are in the range of 1–100 nm.The application of nanotechnology on vaccine design provides precise fabrication of nanomaterials with desirable properties and ability to eliminate undesirable features.To be successful,nanomaterials must be uptaken into the cell,especially into the target and able to modulate cellular functions at the subcellular levels.The advantages of nano-based vaccines are the ability to protect a cargo such as RNA,DNA,protein,or synthesis substance and have enhanced stability in a broad range of pH,ambient temperatures,and humidity for long-term storage.Moreover,nano-based vaccines can be engineered to overcome biological barriers such as nonspecific distribution in order to elicit functions in antigen presenting cells.In this review,we will summarize on the developing COVID-19 vaccine strategies and how the nanotechnology can enhance antigen presentation and strong immunogenicity using advanced technology in nanocarrier to deliver antigens.The discussion about their safe,effective,and affordable vaccines to immunize against COVID-19 will be highlighted.

Recognition of self and altered self by T cells in autoimmunity and allergy

T cell recognition of foreign peptide antigen and toler-ance to self peptides is key to the proper function of the immune system.Usually,in the thymus T cells that rec-ognize self MHC+self peptides are deleted and those with the potential to recognize self MHC+foreign pep-tides are selected to mature.However there are excep-tions to these rules.Autoimmunity and allergy are two of the most common immune diseases that can be related to recognition of self.Many genes work together to lead to autoimmunity.Of those,particular MHC alleles are the most strongly associated,reflecting the key importance of MHC presentation of self peptides in autoimmunity.T cells specific for combinations of self MHC and self pep-tides may escape thymus deletion,and thus be able to drive autoimmunity,for several reasons:the relevant self peptide may be presented at low abundance in the thy-mus but at high level in particular peripheral tissues;the relevant self peptide may bind to MHC in an unusual register,not present in the thymus but apparent else-where;finally the relevant self peptide may be post translationally modified in a tissue specific fashion.In some types of allergy,the peptide+MHC combination may also be fully derived from self.However the combi-nation in question may be modified by the presence of other ligands,such as small drug molecules or metal ions.Thus these types of allergies may act like the post translationally modified peptides involved some types of autoimmunity.