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1.
Vet Microbiol ; 233: 164-173, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31176404

RESUMO

Exosomes are small membrane-enclosed vesicles that participate in intercellular communication between cells. Numerous evidences suggested that exosomes derived from virus-infected cells can mediate virus transmission or/and regulate immune response. Foot-and-mouth disease virus (FMDV) is the prototype member of the Aphthovirus genus of the Picornaviridae family. It can cause highly infectious disease of cloven-hoofed livestock and significantly increase public awareness. However, the role of exosomes in the transmission of FMDV has still remained unknown. In this study, full length of FMDV genomic RNA and partial viral proteins were identified in purified exosomes isolated from FMDV-infected PK-15 cells with qRT-PCR and /MS. Exosomes from FMDV-infected cells were capable of transmitting infection to naive PK-15 cells and suckling mice. Furthermore, exosome-mediated infection cannot be fully blocked by FMDV-specific neutralizing antibodies. This finding highlights that FMDV transmission by exosomes as a potential immune evasion mechanism.


Assuntos
Exossomos/virologia , Vírus da Febre Aftosa/patogenicidade , Febre Aftosa/transmissão , Interações Hospedeiro-Patógeno , Evasão da Resposta Imune , Animais , Animais Recém-Nascidos , Anticorpos Neutralizantes , Exossomos/fisiologia , Vírus da Febre Aftosa/genética , Rim/citologia , Rim/virologia , Camundongos , Camundongos Endogâmicos C57BL , RNA Viral , Proteínas Virais/metabolismo
2.
J Microbiol Biotechnol ; 29(6): 989-998, 2019 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-31154748

RESUMO

Autophagy is crucial for immune defense against Mycobacterium tuberculosis (Mtb) infection. Mtb can evade host immune attack and survival within macrophages by manipulating the autophagic process. MicroRNAs (miRNAs) are small, non-coding RNAs that are involved in regulating vital genes during Mtb infection. The precise role of miRNAs in autophagy with the exits of Mtb remains largely unknown. In this study, we found miR-1958, a new miRNA that could regulate autophagy by interacting with 3'UTR of autophagy-related gene 5 (Atg5). In addition, Mtb infection triggered miR-1958 expression in RAW264.7 cells. What's more, miR- 1958 overexpression blocked autophagic flux by impairing the fusion of autophagosomes and lysosomes. Overexpression of miR-1958 reduced Atg5 expression and LC3 puncta while inhibition of miR-1958 brought an increase of Atg5 and LC3 puncta; the opposite results were observed in detection of p62. The survival of Mtb in RAW264.7 cells transfected with mimic of miR-1958 was enhanced. Taken together, our research demonstrated that a novel miR-1958 could inhibit autophagy by interacting with Atg5 and favored intracellular Mtb survival in RAW264.7 cells.


Assuntos
Proteína 5 Relacionada à Autofagia/genética , Autofagia/fisiologia , MicroRNAs/metabolismo , Viabilidade Microbiana/genética , Mycobacterium tuberculosis/fisiologia , Regiões 3' não Traduzidas , Animais , Autofagossomos/metabolismo , Expressão Gênica , Evasão da Resposta Imune , Lisossomos/metabolismo , Macrófagos/metabolismo , Macrófagos/microbiologia , Macrófagos/patologia , Camundongos , MicroRNAs/genética , Mycobacterium tuberculosis/imunologia , Células RAW 264.7
3.
Vet Res ; 50(1): 51, 2019 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-31234931

RESUMO

Mycoplasma hyopneumoniae, the agent of porcine enzootic pneumonia (EP), is able to persist in the lung tissue and evade destruction by the host for several weeks. To understand the mechanism of pathogen survival, phagocytic uptake of M. hyopneumoniae by primary porcine alveolar macrophages was investigated. Intracellular location and survival of the pathogen were explored using gentamicin survival assays, flow cytometry and confocal microscopy of M. hyopneumoniae 232 labelled with green fluorescent protein (GFP). Following 1 h and 16 h of co-incubation, few viable M. hyopneumoniae were recovered from inside macrophages. Flow cytometric analysis of macrophages incubated with M. hyopneumoniae expressing GFP indicated that the mycoplasmas became associated with macrophages, but were shown to be extracellular when actin-dependent phagocytosis was blocked with cytochalasin D. Confocal microscopy detected GFP-labelled M. hyopneumoniae inside macrophages and the numbers increased modestly with time of incubation. Neither the addition of porcine serum complement or convalescent serum from EP-recovered pigs was able to enhance engulfment of M. hyopneumoniae. This investigation suggests that M. hyopneumoniae evades significant uptake by porcine alveolar macrophages and this may be a mechanism of immune escape by M. hyopneumoniae in the porcine respiratory tract.


Assuntos
Evasão da Resposta Imune , Macrófagos Alveolares/fisiologia , Mycoplasma hyopneumoniae/fisiologia , Pneumonia Suína Micoplasmática/fisiopatologia , Animais , Macrófagos Alveolares/virologia , Fagocitose , Suínos
4.
Eur J Med Chem ; 178: 13-29, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31173968

RESUMO

The oncogenic Epstein-Barr virus (EBV) evades the immune system through limiting the expression of its highly antigenic and essential genome maintenance protein, EBNA1, to the minimal level to ensure viral genome replication, thereby also minimizing the production of EBNA1-derived antigenic peptides. This regulation is based on inhibition of translation of the virally-encoded EBNA1 mRNA, and involves the interaction of host protein nucleolin (NCL) with G-quadruplex (G4) structures that form in the glycine-alanine repeat (GAr)-encoding sequence of the EBNA1 mRNA. Ligands that bind to these G4-RNA can prevent their interaction with NCL, leading to disinhibition of EBNA1 expression and antigen presentation, thereby interfering with the immune evasion of EBNA1 and therefore of EBV (M.J. Lista et al., Nature Commun., 2017, 8, 16043). In this work, we synthesized and studied a series of 20 cationic bis(acylhydrazone) derivatives designed as G4 ligands. The in vitro evaluation showed that most derivatives based on central pyridine (Py), naphthyridine (Naph) or phenanthroline (Phen) units were efficient G4 binders, in contrast to their pyrimidine (Pym) counterparts, which were poor G4 binders due to a significantly different molecular geometry. The influence of lateral heterocyclic units (N-substituted pyridinium or quinolinium residues) on G4-binding properties was also investigated. Two novel compounds, namely PyDH2 and PhenDH2, used at a 5 µM concentration, were able to significantly enhance EBNA1 expression in H1299 cells in a GAr-dependent manner, while being significantly less toxic than the prototype drug PhenDC3 (GI50 > 50 µM). Antigen presentation, RNA pull-down and proximity ligation assays confirmed that the effect of both drugs was related to the disruption of NCL-EBNA1 mRNA interaction and the subsequent promotion of GAr-restricted antigen presentation. Our work provides a novel modular scaffold for the development of G-quadruplex-targeting drugs acting through interference with G4-protein interaction.


Assuntos
Hidrazonas/farmacologia , Evasão da Resposta Imune/efeitos dos fármacos , Fatores Imunológicos/farmacologia , Fosfoproteínas/metabolismo , Ligação Proteica/efeitos dos fármacos , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Animais , Linhagem Celular Tumoral , Antígenos Nucleares do Vírus Epstein-Barr/genética , Antígenos Nucleares do Vírus Epstein-Barr/metabolismo , Quadruplex G , Herpesvirus Humano 4/genética , Humanos , Hidrazonas/síntese química , Hidrazonas/química , Fatores Imunológicos/síntese química , Fatores Imunológicos/química , Ligantes , Camundongos , RNA Mensageiro/genética
5.
Gan To Kagaku Ryoho ; 46(5): 841-844, 2019 May.
Artigo em Japonês | MEDLINE | ID: mdl-31189800

RESUMO

Although immune checkpoint blockade therapy using anti-PD-1/PD-L1 antibodies can induce durable remission in a variety of human malignancies, the mechanisms regulating the expression of PD-1 ligands(PD-L1 and PD-L2)have not been fully investigated. Recently, we newly identified structural variations(SVs)disrupting the 3'-untranslated region(UTR)of the PD- L1/PD-L2 genes in various cancers, which caused a marked upregulation of these molecules and mediated immune escape of tumor cells. Particularly, these alterations were frequently observed in virus-related lymphomas, such as adult T-cell leukemia/ lymphoma as well as Epstein-Barr virus-positive diffuse large B-cell lymphoma and extranodal NK/T-cell lymphoma. These results suggest a pivotal role of PD-L1/PD-L2-mediated immune evasion in the pathogenesis of virus-related tumors. Here we summarize the genetic alterations involving the PD-L1/PD-L2 genes in human cancers, highlighting their relevance in virusassociated tumors.


Assuntos
Neoplasias/genética , Regiões 3' não Traduzidas , Antígeno B7-H1 , Humanos , Evasão da Resposta Imune , Linfoma Difuso de Grandes Células B , Mutação , Proteína 2 Ligante de Morte Celular Programada 1
6.
Cancer Treat Rev ; 76: 22-32, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31079031

RESUMO

A better knowledge of the complex interactions between cancer cells and the immune system has led to novel immunotherapy approaches. Treatment with selective anti-PD1, anti-PD-L1 and/or anti-CTLA-4 monoclonal antibodies (mAbs) has been a revolution in the therapeutic scenario of several cancer types, with the highest clinical efficacy in melanoma and in lung cancer. Colorectal cancer is one of the tumours in which immunotherapy has been shown less effective. Whereas in deficient mismatch repair (MMR) or in highly microsatellite instable (MSI-H) metastatic colorectal cancer there is clear clinical evidence for a therapeutic role of immune checkpoint inhibitors, the vast majority of patients with proficient MMR or with microsatellite stable (MSS) tumours do not benefit from immunotherapy. Defining the molecular mechanisms for immunogenicity in metastatic colorectal cancer is needed in order to develop predictive biomarkers and effective therapeutic combination strategies. A major challenge will be to identify, among the heterogeneous spectrum of this disease, those patients with specific tumour and tumour infiltrating stroma molecular and functional characteristics, that could be effectively treated with immunotherapy. In this review, we discuss the role of immune response in the context of metastatic colorectal cancer. We summarize the available clinical data with the use of anti PD-1/PD-L1 mAbs as single agents or in combination with anti CTLA-4 mAbs in MSI-H patients. Finally, we address the challenges and the potential strategies for rendering the more frequent microsatellite stable (MSS) tumours "immune-competent" and, therefore, amenable for effective immunotherapy interventions.


Assuntos
Antineoplásicos Imunológicos/uso terapêutico , Neoplasias Colorretais/tratamento farmacológico , Animais , Antígeno B7-H1/antagonistas & inibidores , Antígeno B7-H1/imunologia , Antígeno CTLA-4/antagonistas & inibidores , Antígeno CTLA-4/imunologia , Neoplasias Colorretais/imunologia , Humanos , Evasão da Resposta Imune , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Receptor de Morte Celular Programada 1/imunologia
7.
Curr Top Microbiol Immunol ; 421: 229-265, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31123892

RESUMO

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4+ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.


Assuntos
Linfócitos B/patologia , Infecções por Helicobacter/imunologia , Helicobacter pylori/imunologia , Evasão da Resposta Imune , Linfócitos T/patologia , Linfócitos B/imunologia , Mucosa Gástrica/imunologia , Mucosa Gástrica/microbiologia , Infecções por Helicobacter/microbiologia , Humanos , Linfócitos T/imunologia
8.
MBio ; 10(2)2019 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-31040235

RESUMO

We previously showed that Entamoeba histolytica kills human cells through a mechanism that we termed trogocytosis ("trogo-" means "nibble"), due to its resemblance to trogocytosis in other organisms. In microbial eukaryotes like E. histolytica, trogocytosis is used to kill host cells. In multicellular eukaryotes, trogocytosis is used for cell killing and cell-cell communication in a variety of contexts. Thus, nibbling is an emerging theme in cell-cell interactions both within and between species. When trogocytosis occurs between mammalian immune cells, cell membrane proteins from the nibbled cell are acquired and displayed by the recipient cell. In this study, we tested the hypothesis that through trogocytosis, amoebae acquire and display human cell membrane proteins. We demonstrate that E. histolytica acquires and displays human cell membrane proteins through trogocytosis and that this leads to protection from lysis by human serum. Protection from human serum occurs only after amoebae have undergone trogocytosis of live cells but not phagocytosis of dead cells. Likewise, mutant amoebae defective in phagocytosis, but unaltered in their capacity to perform trogocytosis, are protected from human serum. Our studies are the first to reveal that amoebae can display human cell membrane proteins and suggest that the acquisition and display of membrane proteins is a general feature of trogocytosis. These studies have major implications for interactions between E. histolytica and the immune system and also reveal a novel strategy for immune evasion by a pathogen. Since other microbial eukaryotes use trogocytosis for cell killing, our findings may apply to the pathogenesis of other infections.IMPORTANCE Entamoeba histolytica causes amoebiasis, a potentially fatal diarrheal disease. Abscesses in organs such as the liver can occur when amoebae are able to breach the intestinal wall and travel through the bloodstream to other areas of the body. Therefore, understanding how E. histolytica evades immune detection is of great interest. Here, we demonstrate for the first time that E. histolytica acquires and displays human cell membrane proteins by taking "bites" of human cell material in a process named trogocytosis ("trogo-" means "nibble"), and that this allows amoebae to survive in human serum. Display of acquired proteins through trogocytosis has been previously characterized only in mammalian immune cells. Our study suggests that this is a more general feature of trogocytosis not restricted to immune cells and broadens our knowledge of eukaryotic biology. These findings also reveal a novel strategy for immune evasion by a pathogen and may apply to the pathogenesis of other infections.


Assuntos
Entamoeba histolytica/imunologia , Entamoeba histolytica/metabolismo , Interações Hospedeiro-Patógeno , Evasão da Resposta Imune , Proteínas de Membrana/metabolismo , Fagocitose , Humanos , Células Jurkat
9.
Microb Pathog ; 133: 103543, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31102653

RESUMO

PURPOSE: Whole genome sequencing (WGS) analysis of Staphylococcus aureus is increasingly used in clinical practice. Although bioinformatics tools used in WGS analysis readily define the S. aureus virulome, the clinical value of this type of analysis is unclear. Here, virulence genes in S. aureus bacteremia (SAB) isolates were evaluated by WGS, with superantigens (SAgs) further evaluated by conventional PCR and functional assays, and results correlated with mortality. METHODS: 152 SAB isolates collected throughout 2015 at a large Minnesota medical center were studied and associated clinical data analyzed. Virulence genes were identified from previously-reported WGS data (https://doi.org/10.1371/journal.pone.0179003). SAg genes sea, seb, sec, sed, see, seg, seh, sei, sej, and tst were also assessed by individual PCR assays. Mitogenicity of SAgs was assessed using an in vitro proliferation assay with splenocytes from HLA-DR3 transgenic mice. RESULTS: Of the 152 SAB isolates studied, 106 (69%) were methicillin-susceptible S. aureus (MSSA). The number of deaths attributed and not attributed to SAB, and 30-day survivors were 24 (16%), 2 (1%), and 128 (83%), respectively. From WGS data, both MSSA and MRSA had high proportions of adhesion (>80%) and immune-evasion (>70%) genes. There was no difference in virulomes between survivor- and non-survivor-associated isolates. Although over 60% of SAB isolates produced functional SAgs, there were no differences in the distribution or prevalence of SAg genes between survivor- and non-survivor-associated isolates. CONCLUSION: In this study of one year of SAB isolates from a large medical center, the S. aureus virulome, as assessed by WGS, and also for SAgs using individual PCRs and phenotypic characterization, did not impact mortality.


Assuntos
Bacteriemia/microbiologia , Bacteriemia/mortalidade , Farmacorresistência Bacteriana/genética , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/mortalidade , Staphylococcus aureus/genética , Staphylococcus aureus/patogenicidade , Idoso , Idoso de 80 Anos ou mais , Animais , Bacteriemia/imunologia , Aderência Bacteriana/genética , Sequência de Bases , Proliferação de Células , Feminino , Antígeno HLA-DR3 , Humanos , Evasão da Resposta Imune/genética , Masculino , Staphylococcus aureus Resistente à Meticilina/genética , Camundongos , Camundongos Transgênicos , Pessoa de Meia-Idade , Minnesota , Reação em Cadeia da Polimerase , Infecções Estafilocócicas/imunologia , Superantígenos/genética , Superantígenos/imunologia , Virulência/genética , Fatores de Virulência/genética
10.
Int J Mol Sci ; 20(9)2019 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-31083555

RESUMO

Candida albicans and Candida glabrata are the two most prevalent etiologic agents of candidiasis worldwide. Although both are recognized as pathogenic, their choice of virulence traits is highly divergent. Indeed, it appears that these different approaches to fungal virulence may be equally successful in causing human candidiasis. In this review, the virulence mechanisms employed by C. albicans and C. glabrata are analyzed, with emphasis on the differences between the two systems. Pathogenesis features considered in this paper include dimorphic growth, secreted enzymes and signaling molecules, and stress resistance mechanisms. The consequences of these traits in tissue invasion, biofilm formation, immune system evasion, and macrophage escape, in a species dependent manner, are discussed. This review highlights the observation that C. albicans and C. glabrata follow different paths leading to a similar outcome. It also highlights the lack of knowledge on some of the specific mechanisms underlying C. glabrata pathogenesis, which deserve future scrutiny.


Assuntos
Candida albicans/patogenicidade , Candida glabrata/patogenicidade , Animais , Biofilmes/crescimento & desenvolvimento , Candida albicans/imunologia , Candida albicans/fisiologia , Candida glabrata/imunologia , Candida glabrata/fisiologia , Interações Hospedeiro-Patógeno/imunologia , Humanos , Evasão da Resposta Imune , Virulência/imunologia
11.
MBio ; 10(3)2019 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-31064827

RESUMO

Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative bacterial pathogen that is adapted exclusively to human hosts. NTHi utilizes sialic acid from the host as a carbon source and as a terminal sugar on the outer membrane glycolipid lipooligosaccharide (LOS). Sialic acid expressed on LOS is critical in NTHi biofilm formation and immune evasion. There are two major forms of sialic acids in most mammals, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), the latter of which is derived from Neu5Ac. Humans lack the enzyme to convert Neu5Ac to Neu5Gc and do not express Neu5Gc in normal tissues; instead, Neu5Gc is recognized as a foreign antigen. A recent study showed that dietary Neu5Gc can be acquired by NTHi colonizing humans and then presented on LOS, which acts as an antigen for the initial induction of anti-Neu5Gc antibodies. Here we examined Neu5Gc uptake and presentation on NTHi LOS. We show that, although Neu5Gc and Neu5Ac are utilized equally well as sole carbon sources, Neu5Gc is not incorporated efficiently into LOS. When equal amounts of Neu5Gc and Neu5Ac are provided in culture media, there is ∼4-fold more Neu5Ac incorporated into LOS, suggesting a bias in a step of the LOS biosynthetic pathway. CMP-Neu5Ac synthetase (SiaB) was shown to have ∼4,000-fold-higher catalytic efficiency for Neu5Ac than for Neu5Gc. These data suggest that NTHi has adapted preferential utilization of Neu5Ac, thus avoiding presentation of the nonhuman Neu5Gc in the bacterial cell surface. The selective pressure for this adaptation may represent the human antibody response to the Neu5Gc xenoantigen.IMPORTANCE Host-adapted bacterial pathogens such as NTHi cannot survive out of their host environment and have evolved host-specific mechanisms to obtain nutrients and evade the immune response. Relatively few of these host adaptations have been characterized at the molecular level. NTHi utilizes sialic acid as a nutrient and also incorporates this sugar into LOS, which is important in biofilm formation and immune evasion. In the present study, we showed that NTHi has evolved to preferentially utilize the Neu5Ac form of sialic acid. This adaptation is due to the substrate preference of the enzyme CMP-Neu5Ac synthetase, which synthesizes the activated form of Neu5Ac for macromolecule biosynthesis. This adaptation allows NTHi to evade killing by a human antibody response against the nonhuman sialic acid Neu5Gc.


Assuntos
Adaptação Fisiológica , Haemophilus influenzae/fisiologia , Ácido N-Acetilneuramínico/metabolismo , Membrana Celular/metabolismo , Interações entre Hospedeiro e Microrganismos , Humanos , Evasão da Resposta Imune , Ácidos Siálicos/metabolismo , Especificidade por Substrato
12.
Nat Microbiol ; 4(6): 910-911, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31118503
13.
Emerg Microbes Infect ; 8(1): 734-748, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31130074

RESUMO

Many pathogens infect hosts through various immune evasion strategies. However, the molecular mechanisms by which pathogen proteins modulate and evade the host immune response remain unclear. Enterohemorrhagic Escherichia coli (EHEC) is a pathological strain that can induce mitogen-activated protein (MAP) kinase (Erk, Jnk and p38 MAPK) and NF-κB pathway activation and proinflammatory cytokine production, which then causes diarrheal diseases such as hemorrhagic colitis and hemolytic uremic syndrome. Transforming growth factor ß-activated kinase-1 (TAK1) is a key regulator involved in distinct innate immune signalling pathways. Here we report that EHEC translocated intimin receptor (Tir) protein inhibits the expression of EHEC-induced proinflammatory cytokines by interacting with the host tyrosine phosphatase SHP-1, which is dependent on the phosphorylation of immunoreceptor tyrosine-based inhibition motifs (ITIMs). Mechanistically, the association of EHEC Tir with SHP-1 facilitated the recruitment of SHP-1 to TAK1 and inhibited TAK1 phosphorylation, which then negatively regulated K63-linked polyubiquitination of TAK1 and downstream signal transduction. Taken together, these results suggest that EHEC Tir negatively regulates proinflammatory responses by inhibiting the activation of TAK1, which is essential for immune evasion and could be a potential target for the treatment of bacterial infection.


Assuntos
Escherichia coli Êntero-Hemorrágica/patogenicidade , Infecções por Escherichia coli/fisiopatologia , Proteínas de Escherichia coli/metabolismo , Interações Hospedeiro-Patógeno , Evasão da Resposta Imune , MAP Quinase Quinase Quinases/antagonistas & inibidores , Receptores de Superfície Celular/metabolismo , Fatores de Virulência/metabolismo , Animais , Infecções por Escherichia coli/microbiologia , Células HEK293 , Humanos , Macrófagos Peritoneais , Camundongos , Camundongos Endogâmicos C57BL , Ligação Proteica , Proteína Tirosina Fosfatase não Receptora Tipo 6/metabolismo , Células RAW 264.7
14.
MBio ; 10(2)2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-31015326

RESUMO

Chlamydia trachomatis is the most common bacterial cause of sexually transmitted infections. C. trachomatis sexually transmitted infections are commonly asymptomatic, implying a pathogenic strategy for the evasion of innate inflammatory immune responses, a paradox as the C. trachomatis outer membrane contains lipopolysaccharide (LPS), a known potent agonist of inflammatory innate immunity. Here, we studied the ability of chlamydial LPS to activate the proinflammatory canonical and noncanonical inflammasome pathways in mouse bone marrow-derived macrophages (BMDM). We show, in comparison to Escherichia coli LPS, that C. trachomatis LPS-treated BMDM produce significantly less IL-6, TNF, and type I interferon mRNA, indicating that downstream signaling through the canonical TLR4 myddosome and triffosome pathways was blocked. We confirmed this in C. trachomatis LPS-treated BMDM by showing the lack of NF-κB and IRF3 phosphorylation, respectively. Interestingly, C. trachomatis LPS bound CD14 and promoted its endocytosis; however; it did not promote efficient TLR4/MD-2 dimerization or endocytosis, known requirements for myddosome and triffosome signaling pathways. We further found that transfection of BMDM with C. trachomatis LPS did not cause pyroptotic cell ballooning, cytotoxicity, or IL-1ß secretion, all characteristic features of noncanonical inflammasome activation. Western blotting confirmed that cytosolic C. trachomatis LPS failed to signal through caspase-11, as shown by the lack of gasdermin D, caspase-1, or IL-1ß proteolytic cleavage. We propose that chlamydiae evolved a unique LPS structure as a pathogenic strategy to avoid canonical and noncanonical innate immune signaling and conclude that this strategy might explain the high incidence of asymptomatic infections.IMPORTANCE Chlamydia trachomatis is the most common bacterial cause of sexually transmitted infections (STI). C. trachomatis STI are commonly asymptomatic, implying a pathogenic strategy for the evasion of innate inflammatory immune responses, a paradox as the C. trachomatis outer membrane contains lipopolysaccharide (LPS), a known potent agonist of inflammatory innate immunity. Here, we found that C. trachomatis LPS is not capable of engaging the canonical TLR4/MD-2 or noncanonical caspase-11 inflammatory pathways. The inability of C. trachomatis LPS to trigger innate immunity inflammatory pathways is related to its unique fatty acid structure. Evolutionary modification of the LPS structure likely evolved as a pathogenic strategy to silence innate host defense mechanisms. The findings might explain the high incidence of asymptomatic chlamydial genital infection.


Assuntos
Chlamydia trachomatis/imunologia , Chlamydia trachomatis/patogenicidade , Evasão da Resposta Imune , Imunidade Inata , Lipopolissacarídeos/metabolismo , Fatores de Virulência/metabolismo , Animais , Citocinas/biossíntese , Escherichia coli/imunologia , Escherichia coli/patogenicidade , Perfilação da Expressão Gênica , Macrófagos/imunologia , Camundongos Endogâmicos C57BL
15.
MBio ; 10(2)2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-31015330

RESUMO

Protein kinase R (PKR) plays a major role in activating host immunity during infection by sensing double-stranded RNA (dsRNA) produced by viruses. Once activated by dsRNA, PKR phosphorylates the translation factor eukaryotic initiation factor 2α (eIF2α), halting cellular translation. Many viruses have methods of inhibiting PKR activation or its downstream effects, circumventing protein synthesis shutdown. These include sequestering dsRNA or producing proteins that bind to and inhibit PKR activation. Here we describe our finding that in multiple cell types, PKR was depleted during mouse adenovirus type 1 (MAV-1) infection. MAV-1 did not appear to be targeting PKR at the transcriptional or translational level, because total PKR mRNA levels and levels of PKR mRNA bound to polysomes were unchanged or increased during MAV-1 infection. However, inhibiting the proteasome reduced the PKR depletion seen in MAV-1-infected cells, whereas inhibiting the lysosome had no effect. This suggests that proteasomal degradation alone is responsible for PKR degradation during MAV-1 infection. Time course experiments indicated that the degradation occurs early after infection. Infecting cells with UV-inactivated virus prevented PKR degradation, whereas inhibiting viral DNA replication did not. Together, these results suggest that an early viral gene is responsible. Degradation of PKR is a rare mechanism to oppose PKR activity, and it has been described in only six RNA viruses. To our knowledge, this is the first example of a DNA virus counteracting PKR by degrading it.IMPORTANCE The first line of defense in cells during viral infection is the innate immune system, which is activated by different viral products. PKR is a part of this innate immune system and is induced by interferon and activated by dsRNA produced by DNA and RNA viruses. PKR is such an important part of the antiviral response that many viral families have gene products to counteract its activation or the resulting effects of its activity. Although a few RNA viruses degrade PKR, this method of counteracting PKR has not been reported for any DNA viruses. MAV-1 does not encode virus-associated RNAs, a human adenoviral defense against PKR activation. Instead, MAV-1 degrades PKR, and it is the first DNA virus reported to do so. The innate immune evasion by PKR degradation is a previously unidentified way for a DNA virus to circumvent the host antiviral response.


Assuntos
Interações Hospedeiro-Patógeno , Mastadenovirus/crescimento & desenvolvimento , Proteólise , Replicação Viral , eIF-2 Quinase/metabolismo , Animais , Linhagem Celular , Evasão da Resposta Imune , Imunidade Inata , Camundongos , Complexo de Endopeptidases do Proteassoma/metabolismo
16.
MBio ; 10(2)2019 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-30967460

RESUMO

The effectiveness of influenza vaccines against circulating A(H1N1)pdm09 viruses was modest for several seasons despite the absence of antigenic drift of hemagglutinin (HA), the primary vaccine component. Since antibodies against HA and neuraminidase (NA) contribute independently to protection against disease, antigenic changes in NA may allow A(H1N1)pdm09 viruses to escape from vaccine-induced immunity. In this study, analysis of the specificities of human NA-specific monoclonal antibodies identified antigenic sites that have changed over time. The impact of these differences on in vitro inhibition of enzyme activity was not evident for polyclonal antisera until viruses emerged in 2013 without a predicted glycosylation site at amino acid 386 in NA. Phylogenetic and antigenic cartography demonstrated significant antigenic changes that in most cases aligned with genetic differences. Typical of NA drift, the antigenic difference is observed in one direction, with antibodies against conserved antigenic domains in A/California/7/2009 (CA/09) continuing to inhibit NA of recent A(H1N1)pdm09 viruses reasonably well. However, ferret CA/09-specific antiserum that inhibited the NA of A/Michigan/45/2015 (MI/15) very well in vitro, protected mice against lethal MI/15 infection poorly. These data show that antiserum against the homologous antigen is most effective and suggest the antigenic properties of NA should not be overlooked when selecting viruses for vaccine production.IMPORTANCE The effectiveness of seasonal influenza vaccines against circulating A(H1N1)pdm09 viruses has been modest in recent years, despite the absence of antigenic drift of HA, the primary vaccine component. Human monoclonal antibodies identified antigenic sites in NA that changed early after the new pandemic virus emerged. The reactivity of ferret antisera demonstrated antigenic drift of A(H1N1)pdm09 NA from 2013 onward. Passive transfer of serum raised against A/California/7/2009 was less effective than ferret serum against the homologous virus in protecting mice against a virus with the NA of more recent virus, A/Michigan/45/2015. Given the long-standing observation that NA-inhibiting antibodies are associated with resistance against disease in humans, these data demonstrate the importance of evaluating NA drift and suggest that vaccine effectiveness might be improved by selecting viruses for vaccine production that have NAs antigenically similar to those of circulating influenza viruses.


Assuntos
Anticorpos Antivirais/imunologia , Antígenos Virais/imunologia , Deriva Genética , Vírus da Influenza A Subtipo H1N1/imunologia , Neuraminidase/imunologia , Proteínas Virais/imunologia , Animais , Anticorpos Monoclonais/imunologia , Modelos Animais de Doenças , Furões , Evasão da Resposta Imune , Imunização Passiva , Vírus da Influenza A Subtipo H1N1/genética , Camundongos , Neuraminidase/genética , Infecções por Orthomyxoviridae/prevenção & controle , Análise de Sobrevida , Resultado do Tratamento , Proteínas Virais/genética
17.
Virol Sin ; 34(2): 135-161, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31025296

RESUMO

Kaposi's sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8 (HHV-8), is etiologically linked to the development of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. These malignancies often occur in immunosuppressed individuals, making KSHV infection-associated diseases an increasing global health concern with persistence of the AIDS epidemic. KSHV exhibits biphasic life cycles between latent and lytic infection and extensive transcriptional and posttranscriptional regulation of gene expression. As a member of the herpesvirus family, KSHV has evolved many strategies to evade the host immune response, which help the virus establish a successful lifelong infection. In this review, we summarize the current research status on the biology of latent and lytic viral infection, the regulation of viral life cycles and the related pathogenesis.


Assuntos
Herpesvirus Humano 8/fisiologia , Herpesvirus Humano 8/patogenicidade , Transcrição Genética , Replicação Viral , Animais , Hiperplasia do Linfonodo Gigante/virologia , Estudos Clínicos como Assunto , Expressão Gênica , Regulação Viral da Expressão Gênica , Interações Hospedeiro-Patógeno , Humanos , Evasão da Resposta Imune , Hospedeiro Imunocomprometido , Linfoma de Efusão Primária/virologia , Camundongos , Processamento Pós-Transcricional do RNA , Sarcoma de Kaposi/virologia , Proteínas Virais/genética , Latência Viral
18.
Microbiol Spectr ; 7(2)2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30953429

RESUMO

Shigella is a genus of Gram-negative enteropathogens that have long been, and continue to be, an important public health concern worldwide. Over the past several decades, Shigella spp. have also served as model pathogens in the study of bacterial pathogenesis, and Shigella flexneri has become one of the best-studied pathogens on a molecular, cellular, and tissue level. In the arms race between Shigella and the host immune system, Shigella has developed highly sophisticated mechanisms to subvert host cell processes in order to promote infection, escape immune detection, and prevent bacterial clearance. Here, we give an overview of Shigella pathogenesis while highlighting innovative techniques and methods whose application has significantly advanced our understanding of Shigella pathogenesis in recent years.


Assuntos
Disenteria Bacilar/imunologia , Interações Hospedeiro-Patógeno/imunologia , Shigella/imunologia , Shigella/patogenicidade , Imunidade Adaptativa , Adesinas Bacterianas , Proteínas de Bactérias , Citosol/microbiologia , Disenteria Bacilar/microbiologia , Células Epiteliais/metabolismo , Células Epiteliais/microbiologia , Microbioma Gastrointestinal , Humanos , Evasão da Resposta Imune , Shigella flexneri/imunologia , Shigella flexneri/patogenicidade , Sistemas de Secreção Tipo III , Virulência , Fatores de Virulência/metabolismo
19.
Nat Commun ; 10(1): 1667, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30971685

RESUMO

Neutrophils are crucial mediators of host defense that are recruited to the central nervous system (CNS) in large numbers during acute bacterial meningitis caused by Streptococcus pneumoniae. Neutrophils release neutrophil extracellular traps (NETs) during infections to trap and kill bacteria. Intact NETs are fibrous structures composed of decondensed DNA and neutrophil-derived antimicrobial proteins. Here we show NETs in the cerebrospinal fluid (CSF) of patients with pneumococcal meningitis, and their absence in other forms of meningitis with neutrophil influx into the CSF caused by viruses, Borrelia and subarachnoid hemorrhage. In a rat model of meningitis, a clinical strain of pneumococci induced NET formation in the CSF. Disrupting NETs using DNase I significantly reduces bacterial load, demonstrating that NETs contribute to pneumococcal meningitis pathogenesis in vivo. We conclude that NETs in the CNS reduce bacterial clearance and degrading NETs using DNase I may have significant therapeutic implications.


Assuntos
Líquido Cefalorraquidiano/citologia , Armadilhas Extracelulares/microbiologia , Evasão da Resposta Imune , Meningite Pneumocócica/imunologia , Neutrófilos/imunologia , Streptococcus pneumoniae/imunologia , Adolescente , Adulto , Idoso , Animais , Grupo Borrelia Burgdorferi/imunologia , Encéfalo/citologia , Encéfalo/efeitos dos fármacos , Encéfalo/imunologia , Encéfalo/microbiologia , Líquido Cefalorraquidiano/imunologia , Líquido Cefalorraquidiano/microbiologia , Desoxirribonuclease I/administração & dosagem , Modelos Animais de Doenças , Armadilhas Extracelulares/efeitos dos fármacos , Armadilhas Extracelulares/imunologia , Feminino , Humanos , Neuroborreliose de Lyme/líquido cefalorraquidiano , Neuroborreliose de Lyme/imunologia , Neuroborreliose de Lyme/microbiologia , Masculino , Meningite Pneumocócica/líquido cefalorraquidiano , Meningite Pneumocócica/tratamento farmacológico , Meningite Pneumocócica/microbiologia , Meningite Viral/líquido cefalorraquidiano , Meningite Viral/imunologia , Pessoa de Meia-Idade , Neutrófilos/microbiologia , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/administração & dosagem , Punção Espinal , Streptococcus pneumoniae/isolamento & purificação , Hemorragia Subaracnóidea/líquido cefalorraquidiano , Adulto Jovem
20.
Vet Parasitol ; 268: 73-80, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30981309

RESUMO

The infection of ruminants by Fasciola spp. always induces a non-protective Th2-type immune response. However, little is known about changes in the local and systemic immune environment during F. gigantica migration in buffalo. In this study, native swamp buffaloes were each infected with 500 viable F. gigantica metacercariae. Mesenteric lymph node (MLN), hepatic lymph node (HLN), spleen, and serum samples were collected from control and infected buffaloes at 3, 10, 28, 42, 70, and 98 days post-infection (DPI). The mRNA expression levels of the Th1- and Th2-related cytokines IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IFN-γ, TNF-α, and CD4 were measured during different infection stages in the MLNs, spleens, and HLNs using quantitative real-time PCR (qRT-PCR). Levels of the specific anti-ESP isotype antibodies IgG, IgG1, and IgG2 were used to reflect changes in humoral immunity. The results of this study indicated that swamp buffaloes were susceptible to F. gigantica infection, and that susceptibility to this infection was closely related to the cytokine environment associated with the Th2-type immune response. The MLNs showed a mixed Th1- and Th2-type immune response during the acute infection stages, after which the production of these cytokines returned to normal. Cytokine expression in the HLNs also expressed a mixed Th1- and Th2-type immune response during the early infection stages. When the infection became chronic, the typical Th2 immune response was induced in the HLNs. At the acute infection stages, the spleen exhibited a Th2 immune response. Nevertheless, cytokines associated with the Th1 and Th2 immune responses were upregulated at 98 DPI. In addition, the total IgG and IgG1 of the parasite-specific antibodies increased. This suggested that the Th2-related cytokines and IgG1 induced by F. gigantica infection might mediate successful F. gigantica infection in the natural host, swamp buffalo.


Assuntos
Búfalos/imunologia , Doenças dos Bovinos/imunologia , Citocinas/imunologia , Fasciolíase/veterinária , Evasão da Resposta Imune , Células Th2/imunologia , Animais , Anticorpos Anti-Helmínticos/imunologia , Búfalos/parasitologia , Bovinos , Doenças dos Bovinos/parasitologia , Citocinas/genética , Fasciola , Fasciolíase/imunologia , Imunidade Humoral , Imunoglobulina G/imunologia , Interleucina-10/genética , Interleucina-10/imunologia , Interleucina-4/genética , Interleucina-4/imunologia , Interleucina-5/genética , Interleucina-5/imunologia , Linfonodos/imunologia , Linfonodos/parasitologia , Metacercárias/imunologia , Reação em Cadeia da Polimerase em Tempo Real , Baço/imunologia , Baço/parasitologia , Células Th1/imunologia
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