Screening of surface exposed lipoproteins of Leptospira involved in modulation of host innate immune response

Leptospira, a zoonotic pathogen is capable of causing both chronic and acute infection in susceptible host. Surface exposed lipoproteins play major role in modulating the host immune response by activating the innate cells like macrophages and DCs or evading complement attack and killing by phagocytes like neutrophils to favour pathogenesis and establish infection. In this study we screened some of surface exposed lipoproteins which are known to be involved in pathogenesis for their possible role in immune modulation (innate immune activation or evasion). Surface proteins of Len family (LenB, LenD, LenE), Lsa30, Loa22 and Lipl21 were purified in recombinant form and then tested for their ability to activate macrophages of different host (mouse, human and bovine). These proteins were tested for binding with complement regulators (FH, C4BP), host protease (plasminogen, PLG) and as nucleases to access their possible role in innate immune evasion. Our results show that of various proteins tested Loa22 induced strong innate activation and Lsa30 was least stimulatory as evident from production of pro-inflammatory cytokines (IL-6, TNF-a) and expression of surface markers (CD80, CD86, MHCII). All the tested proteins were able to bind to FH, C4BP and PLG, however Loa22 showed strong binding to PLG correlating to plasmin activity. All the proteins except Loa22 showed nuclease activity albeit with requirement of different metal ions. The nuclease activity of these proteins correlated to in vitro degradation of Neutrophil extracellular trap (NET). These results indicate that these surface proteins are involved in innate immune modulation and may play critical role in assisting the bacteria to invade and colonize the host tissue for persistent infection.

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Deciphering the Role of Leptospira Surface Protein LigA in Modulating the Host Innate Immune Response

Frontiers in Immunology ◽

10.3389/fimmu.2021.807775 ◽

2021 ◽

Vol 12 ◽

Author(s):

Ajay Kumar ◽

Vivek P. Varma ◽

Kavela Sridhar ◽

Mohd Abdullah ◽

Pallavi Vyas ◽

...

Keyword(s):

Immune Response ◽

Immune Modulation ◽

Protein A ◽

Adaptive Immune Response ◽

Surface Protein ◽

Variable Region ◽

Nuclease Activity ◽

Innate Immune ◽

Surface Proteins

Leptospira, a zoonotic pathogen, is known to infect various hosts and can establish persistent infection. This remarkable ability of bacteria is attributed to its potential to modulate (activate or evade) the host immune response by exploiting its surface proteins. We have identified and characterized the domain of the variable region of Leptospira immunoglobulin-like protein A (LAV) involved in immune modulation. The 11th domain (A11) of the variable region of LigA (LAV) induces a strong TLR4 dependent innate response leading to subsequent induction of humoral and cellular immune responses in mice. A11 is also involved in acquiring complement regulator FH and binds to host protease Plasminogen (PLG), there by mediating functional activity to escape from complement-mediated killing. The deletion of A11 domain significantly impaired TLR4 signaling and subsequent reduction in the innate and adaptive immune response. It also inhibited the binding of FH and PLG thereby mediating killing of bacteria. Our study discovered an unprecedented role of LAV as a nuclease capable of degrading Neutrophil Extracellular Traps (NETs). This nuclease activity was primarily mediated by A11. These results highlighted the moonlighting function of LigA and demonstrated that a single domain of a surface protein is involved in modulating the host innate immune defenses, which might allow the persistence of Leptospira in different hosts for a long term without clearance.

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Leptospira surface protein LigA plays a multifaceted role in modulating the host innate immune response

10.1101/2020.10.12.329177 ◽

2020 ◽

Author(s):

Ajay Kumar ◽

Vivek P. Varma ◽

Kavela Sridhar ◽

Mohd Abdullah ◽

Pallavi Vyas ◽

...

Keyword(s):

Immune Response ◽

Innate Immune Response ◽

Protein A ◽

Surface Protein ◽

Variable Region ◽

Nuclease Activity ◽

Innate Immune ◽

Surface Proteins ◽

Host Innate Immune Response ◽

Complement Regulators

AbstractLeptospira, a zoonotic pathogen is known to infect a variety of hosts and capable of establishing persistent infection. This remarkable ability of bacteria is attributed to its potential to evade or modulate the host immune response by exploiting its surface proteins. We have identified and characterized the domain of Leptospira immunoglobulin-like protein A (LigA) that is involved in modulating the host innate immune response. We identified that the 11th domain (A11) of the variable region of LigA (LAV) induces strong TLR4 dependent innate response in mouse macrophages via signalling through MAP kinase pathway leading to the production of pro-inflammatory cytokines (IL-6 and TNF-α) and expression of costimulatory molecules (CD80, CD86, CD40) and maturation marker (MHC-II). A11 is also involved in acquiring complement regulators like FH, C4b binding protein and Plasminogen and mediating functional activity to escape from both classical and alternate pathways of complement-mediated killing. The deletion of A11 significantly impaired TLR4 signalling and subsequent activation of innate immune cells and also inhibited the binding of complement regulators leading to the killing of bacteria. Our study discovered an unprecedented role of LAV as nuclease capable of degrading Neutrophil Extracellular Traps (NETs). This nuclease activity was mediated by A11 and was inhibited with anti-LAV antibodies. These results highlight the moonlighting function of LigA and demonstrates that a single domain of a surface protein is involved in evading a myriad of host innate immune defences, which might allow the persistence of Leptospira in different hosts for a long term without clearance.

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Ubiquitination as an Important Host-Immune Response Strategy in Penaeid Shrimp: Inferences From Other Species

Frontiers in Immunology ◽

10.3389/fimmu.2021.697397 ◽

2021 ◽

Vol 12 ◽

Author(s):

Zhaoxue Zhang ◽

Jude Juventus Aweya ◽

Defu Yao ◽

Zhihong Zheng ◽

Ngoc Tuan Tran ◽

...

Keyword(s):

Immune Response ◽

Immune Modulation ◽

Critical Role ◽

Penaeid Shrimp ◽

Short Review ◽

Vital Role ◽

Innate Immune ◽

Microbial Pathogens ◽

Response Strategy ◽

Ubiquitin System

Shrimp aquaculture is an essential economic venture globally, but the industry faces numerous challenges, especially pathogenic infections. As invertebrates, shrimp rely mainly on their innate immune system for protection. An increasing number of studies have shown that ubiquitination plays a vital role in the innate immune response to microbial pathogens. As an important form of posttranslational modification (PTM), both hosts and pathogens have exploited ubiquitination and the ubiquitin system as an immune response strategy to outwit the other. This short review brings together recent findings on ubiquitination and how this PTM plays a critical role in immune modulation in penaeid shrimps. Key findings inferred from other species would help guide further studies on ubiquitination as an immune response strategy in shrimp-pathogen interactions.

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Loss of Nckx3 Exacerbates Experimental DSS-Induced Colitis in Mice through p53/NF-κB Pathway

International Journal of Molecular Sciences ◽

10.3390/ijms22052645 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2645

Author(s):

Dinh Nam Tran ◽

Seon Myeong Go ◽

Seon-Mi Park ◽

Eui-Man Jung ◽

Eui-Bae Jeung

Keyword(s):

Immune Response ◽

Cellular Proliferation ◽

Intestinal Inflammation ◽

Critical Role ◽

Experimental Colitis ◽

Innate Immune ◽

Inflammatory Conditions ◽

Bowel Diseases ◽

Inflammatory Bowel ◽

Microarray Analyses

Inflammatory bowel diseases (IBDs) comprises a range of chronic inflammatory conditions of the intestinal tract. The incidence and prevalence of IBDs are increasing worldwide, but the precise etiology of these diseases is not completely understood. Calcium signaling plays a regulatory role in cellular proliferation. Nckx3, a potassium-dependent Na+/Ca2+ exchanger, is not only expressed in the brain but also in the aortic, uterine, and intestinal tissues, which contain abundant smooth muscle cells. This study investigated the role of Nckx3 in intestinal inflammation. Microarray analyses revealed the upregulation of the innate immune response-associated genes in the duodenum of Nckx3 knockout (KO) mice. The Nckx3 KO mice also showed an increase in IBD- and tumorigenesis-related genes. Using dextran sodium sulfate (DSS)-induced experimental colitis mice models, the Nckx3 KO mice showed severe colitis. Furthermore, the pathways involving p53 and NF-κB signaling were significantly upregulated by the absence of Nckx3. Overall, Nckx3 plays a critical role in the innate immune and immune response and may be central to the pathogenesis of IBD.

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GM-CSF and the impaired pulmonary innate immune response following hyperoxic stress

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00016.2006 ◽

2006 ◽

Vol 291 (6) ◽

pp. L1246-L1255 ◽

Cited By ~ 27

Author(s):

Carlos E. O. Baleeiro ◽

Paul J. Christensen ◽

Susan B. Morris ◽

Michael P. Mendez ◽

Steven E. Wilcoxen ◽

...

Keyword(s):

Immune Response ◽

Epithelial Cell ◽

Innate Immune Response ◽

Alveolar Epithelial Cell ◽

Critical Role ◽

Innate Immune ◽

Alveolar Epithelial Cells ◽

Bacterial Colony ◽

Alveolar Epithelial ◽

Gm Csf

We have previously demonstrated that mice exposed to sublethal hyperoxia (an atmosphere of >95% oxygen for 4 days, followed by return to room air) have significantly impaired pulmonary innate immune response. Alveolar macrophages (AM) from hyperoxia-exposed mice exhibit significantly diminished antimicrobial activity and markedly reduced production of inflammatory cytokines in response to stimulation with LPS compared with AM from control mice in normoxia. As a consequence of these defects, mice exposed to sublethal hyperoxia are more susceptible to lethal pneumonia with Klebsiella pneumoniae than control mice. Granulocyte/macrophage colony-stimulating factor (GM-CSF) is a growth factor produced by normal pulmonary alveolar epithelial cells that is critically involved in maintenance of normal AM function. We now report that sublethal hyperoxia in vivo leads to greatly reduced alveolar epithelial cell GM-CSF expression. Systemic treatment of mice with recombinant murine GM-CSF during hyperoxia exposure preserved AM function, as indicated by cell surface Toll-like receptor 4 expression and by inflammatory cytokine secretion following stimulation with LPS ex vivo. Treatment of hyperoxic mice with GM-CSF significantly reduced lung bacterial burden following intratracheal inoculation with K. pneumoniae, returning lung bacterial colony-forming units to the level of normoxic controls. These data point to a critical role for continuous GM-CSF activity in the lung in maintenance of normal AM function and demonstrate that lung injury due to hyperoxic stress results in significant impairment in pulmonary innate immunity through suppression of alveolar epithelial cell GM-CSF expression.

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Regulation of the Ebola Virus VP24 Protein by SUMO

Journal of Virology ◽

10.1128/jvi.01687-19 ◽

2019 ◽

Vol 94 (1) ◽

Cited By ~ 6

Author(s):

Santiago Vidal ◽

Ahmed El Motiam ◽

Rocío Seoane ◽

Viktorija Preitakaite ◽

Yanis Hichem Bouzaher ◽

...

Keyword(s):

Immune Response ◽

Innate Immune Response ◽

Viral Protein ◽

Matrix Protein ◽

Ebola Virus ◽

Nuclear Translocation ◽

Critical Role ◽

Innate Immune ◽

Type I ◽

Negative Modulator

ABSTRACT Some viruses take advantage of conjugation of ubiquitin or ubiquitin-like proteins to enhance their own replication. One example is Ebola virus, which has evolved strategies to utilize these modification pathways to regulate the viral proteins VP40 and VP35 and to counteract the host defenses. Here, we show a novel mechanism by which Ebola virus exploits the ubiquitin and SUMO pathways. Our data reveal that minor matrix protein VP24 of Ebola virus is a bona fide SUMO target. Analysis of a SUMOylation-defective VP24 mutant revealed a reduced ability to block the type I interferon (IFN) pathway and to inhibit IFN-mediated STAT1 nuclear translocation, exhibiting a weaker interaction with karyopherin 5 and significantly diminished stability. Using glutathione S-transferase (GST) pulldown assay, we found that VP24 also interacts with SUMO in a noncovalent manner through a SIM domain. Mutation of the SIM domain in VP24 resulted in a complete inability of the protein to downmodulate the IFN pathway and in the monoubiquitination of the protein. We identified SUMO deubiquitinating enzyme ubiquitin-specific-processing protease 7 (USP7) as an interactor and a negative modulator of VP24 ubiquitination. Finally, we show that mutation of one ubiquitination site in VP24 potentiates the IFN modulatory activity of the viral protein and its ability to block IFN-mediated STAT1 nuclear translocation, pointing to the ubiquitination of VP24 as a negative modulator of the VP24 activity. Altogether, these results indicate that SUMO interacts with VP24 and promotes its USP7-mediated deubiquitination, playing a key role in the interference with the innate immune response mediated by the viral protein. IMPORTANCE The Ebola virus VP24 protein plays a critical role in escape of the virus from the host innate immune response. Therefore, deciphering the molecular mechanisms modulating VP24 activity may be useful to identify potential targets amenable to therapeutics. Here, we identify the cellular proteins USP7, SUMO, and ubiquitin as novel interactors and regulators of VP24. These interactions may represent novel potential targets to design new antivirals with the ability to modulate Ebola virus replication.

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Crosstalk between Dendritic Cells and Immune Modulatory Agents against Sepsis

Genes ◽

10.3390/genes11030323 ◽

2020 ◽

Vol 11 (3) ◽

pp. 323 ◽

Cited By ~ 1

Author(s):

Guoying Wang ◽

Xianghui Li ◽

Lei Zhang ◽

Abualgasim Elgaili Abdalla ◽

Tieshan Teng ◽

...

Keyword(s):

Immune Response ◽

Dendritic Cells ◽

Immune Responses ◽

Critical Role ◽

Innate Immune ◽

Adaptive Immune Responses ◽

Adaptive Immune ◽

Th2 Responses ◽

Novel Strategy

Dendritic cells (DCs) play a critical role in the immune system which sense pathogens and present their antigens to prime the adaptive immune responses. As the progression of sepsis occurs, DCs are capable of orchestrating the aberrant innate immune response by sustaining the Th1/Th2 responses that are essential for host survival. Hence, an in-depth understanding of the characteristics of DCs would have a beneficial effect in overcoming the obstacle occurring in sepsis. This paper focuses on the role of DCs in the progression of sepsis and we also discuss the reverse sepsis-induced immunosuppression through manipulating the DC function. In addition, we highlight some potent immunotherapies that could be used as a novel strategy in the early treatment of sepsis.

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“Eat me” and “don't eat me” signals govern the innate immune response and tissue repair in the CNS: emphasis on the critical role of the complement system

Molecular Immunology ◽

10.1016/s0161-5890(03)00109-3 ◽

2003 ◽

Vol 40 (2-4) ◽

pp. 85-94 ◽

Cited By ~ 123

Author(s):

K Elward

Keyword(s):

Immune Response ◽

Innate Immune Response ◽

Complement System ◽

Tissue Repair ◽

Critical Role ◽

Innate Immune ◽

The Complement System

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Direct Evidence That the MHC Class Ib Antigen Qa-2 Regulates the Fetal Immune Response to Prenatal Allotransplantation.

Blood ◽

10.1182/blood.v110.11.1200.1200 ◽

2007 ◽

Vol 110 (11) ◽

pp. 1200-1200

Author(s):

Emily T. Durkin ◽

Dina Elnaggar ◽

Aimen F. Shaaban

Keyword(s):

Immune Response ◽

Peripheral Blood ◽

Direct Evidence ◽

Mononuclear Cells ◽

Critical Role ◽

Innate Immune ◽

Donor Strain ◽

Mhc Class Ib ◽

Cell Dose ◽

Class Ib

Abstract The failure to achieve durable engraftment following prenatal transplantation in immunologically normal human fetal recipients calls for a closer examination of the fetal immune response to allotransplantation. Previous studies in mice suggest that the fetal innate immune system functions as a critical barrier to allogeneic engraftment mediated by recognition of MHC class Ib antigens. We hypothesized that Qa-2 (the putative murine homolog for HLA-G) might play an essential role in the modulation of fetal immune response to prenatally transplanted allogeneic cells. To address this hypothesis, we utilized B6.K1 mice as a donor strain. B6.K1 mice are Qa-2 deficient and are congenic with wild-type B6.Ly5.2 mice. Light density mononuclear cells (LDMCs) were harvested from the livers of 14 dpc fetal B6.K1 or B6.Ly5.2 mice and transplanted into age-matched allogeneic Balb/c fetal recipients at a dose of 105 cells per fetus. Following delivery, peripheral blood chimerism was assessed serially in the recipients. Survival to weaning was similar between the groups without evidence of GVHD. At 3 weeks of age, recipients of B6.K1 cells demonstrated significantly lower peripheral blood chimerism levels than recipients of B6.Ly5.2 control cells. By 6 months of age, nearly all of the recipients of B6.K1 cells had lost their chimerism. Conversely, the chimerism levels in recipients of B6.Ly5.2 control cells remained stable suggesting that donor Qa-2 expression was essential for allograft survival. To assess the competitive capacity of the B6.K1 donor cells in the absence of immunologic disparity, B6.K1 or B6.Ly5.2 fetal liver LDMCs were transplanted into congenic B6.Ly5.1 hosts at the same cell dose per fetus. This resulted in stable long-term engraftment of the B6.K1 cells in all recipients. Chimerism levels were identical to those recipients who received B6.Ly5.2 control cells, confirming that the engraftment disparities observed in the allogeneic recipients resulted from immunologic rejection. To assess the resilience of this apparent Qa-2-dependent innate immune barrier, the allogeneic transplantation experiments were then repeated at a ten-fold higher donor cell dose (106 cells/fetus). Early chimerism levels remained significantly lower in allogeneic recipients of Qa-2 deficient cells compared to controls. However, recipients of B6.K1 cells maintained their engraftment for more than 6 months indicating that the Qa-2-dependent fetal immune barrier may be overcome with higher levels of circulating antigen. From these experiments we conclude: Host allorecognition of the class Ib antigen Qa-2 is crucial for durable engraftment following in utero transplantation; The failed engraftment of Qa-2 deficient hematopoietic cells does not result from a defective competitive engraftment capacity; Qa-2 dependent fetal immune rejection may be diminished by higher levels of early chimerism. These experiments provide direct evidence for the critical role of MHC class Ib antigens in regulation of the fetal immune response to allotransplantation. Additionally, the demonstration of reliable engraftment following transplantation of higher cell doses provides a translationally relevant approach to enhance the clinical success of prenatal transplantation in immunologically normal hosts.

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