CX₃CR1-dependent renal macrophage survival promotes Candida control and host survival

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Abstract

Systemic Candida albicans infection causes high morbidity and mortality and is associated with neutropenia; however, the roles of other innate immune cells in pathogenesis are poorly defined. Here, using a mouse model of systemic candidiasis, we found that resident macrophages accumulated in the kidney, the main target organ of infection, and formed direct contacts with the fungus in vivo mainly within the first few hours after infection. Macrophage accumulation and contact with Candida were both markedly reduced in mice lacking chemokine receptor CX₃CR1, which was found almost exclusively on resident macrophages in uninfected kidneys. Infected Cx3cr1^–/– mice uniformly succumbed to Candida-induced renal failure, but exhibited clearance of the fungus in all other organs tested. Renal macrophage deficiency in infected Cx3cr1^–/– mice was due to reduced macrophage survival, not impaired proliferation, trafficking, or differentiation. In humans, the dysfunctional CX₃CR1 allele CX₃CR1-M280 was associated with increased risk of systemic candidiasis. Together, these data indicate that CX₃CR1-mediated renal resident macrophage survival is a critical innate mechanism of early fungal control that influences host survival in systemic candidiasis.

Authors

Michail S. Lionakis, Muthulekha Swamydas, Brett G. Fischer, Theo S. Plantinga, Melissa D. Johnson, Martin Jaeger, Nathaniel M. Green, Andrius Masedunskas, Roberto Weigert, Constantinos Mikelis, Wuzhou Wan, Chyi-Chia Richard Lee, Jean K. Lim, Aymeric Rivollier, John C. Yang, Greg M. Laird, Robert T. Wheeler, Barbara D. Alexander, John R. Perfect, Ji-Liang Gao, Bart-Jan Kullberg, Mihai G. Netea, Philip M. Murphy

Rice-based oral antibody fragment prophylaxis and therapy against rotavirus infection

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Abstract

Rotavirus-induced diarrhea is a life-threatening disease in immunocompromised individuals and in children in developing countries. We have developed a system for prophylaxis and therapy against rotavirus disease using transgenic rice expressing the neutralizing variable domain of a rotavirus-specific llama heavy-chain antibody fragment (MucoRice-ARP1). MucoRice-ARP1 was produced at high levels in rice seeds using an overexpression system and RNAi technology to suppress the production of major rice endogenous storage proteins. Orally administered MucoRice-ARP1 markedly decreased the viral load in immunocompetent and immunodeficient mice. The antibody retained in vitro neutralizing activity after long-term storage (>1 yr) and boiling and conferred protection in mice even after heat treatment at 94°C for 30 minutes. High-yield, water-soluble, and purification-free MucoRice-ARP1 thus forms the basis for orally administered prophylaxis and therapy against rotavirus infections.

Authors

Daisuke Tokuhara, Beatriz Álvarez, Mio Mejima, Tomoko Hiroiwa, Yuko Takahashi, Shiho Kurokawa, Masaharu Kuroda, Masaaki Oyama, Hiroko Kozuka-Hata, Tomonori Nochi, Hiroshi Sagara, Farah Aladin, Harold Marcotte, Leon G.J. Frenken, Miren Iturriza-Gómara, Hiroshi Kiyono, Lennart Hammarström, Yoshikazu Yuki

Cross-species malaria immunity induced by chemically attenuated parasites

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Abstract

Vaccine development for the blood stages of malaria has focused on the induction of antibodies to parasite surface antigens, most of which are highly polymorphic. An alternate strategy has evolved from observations that low-density infections can induce antibody-independent immunity to different strains. To test this strategy, we treated parasitized red blood cells from the rodent parasite Plasmodium chabaudi with seco-cyclopropyl pyrrolo indole analogs. These drugs irreversibly alkylate parasite DNA, blocking their ability to replicate. After administration in mice, DNA from the vaccine could be detected in the blood for over 110 days and a single vaccination induced profound immunity to different malaria parasite species. Immunity was mediated by CD4⁺ T cells and was dependent on the red blood cell membrane remaining intact. The human parasite, Plasmodium falciparum, could also be attenuated by treatment with seco-cyclopropyl pyrrolo indole analogs. These data demonstrate that vaccination with chemically attenuated parasites induces protective immunity and provide a compelling rationale for testing a blood-stage parasite-based vaccine targeting human Plasmodium species.

Authors

Michael F. Good, Jennifer M. Reiman, I. Bibiana Rodriguez, Koichi Ito, Stephanie K. Yanow, Ibrahim M. El-Deeb, Michael R. Batzloff, Danielle I. Stanisic, Christian Engwerda, Terry Spithill, Stephen L. Hoffman, Moses Lee, Virginia McPhun

Antigen-activated dendritic cells ameliorate influenza A infections

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Abstract

Influenza A viruses cause significant morbidity and mortality worldwide. There is a need for alternative or adjunct therapies, as resistance to currently used antiviral drugs is emerging rapidly. We tested ligand epitope antigen presentation system (LEAPS) technology as a new immune-based treatment for influenza virus infection in a mouse model. Influenza-J-LEAPS peptides were synthesized by conjugating the binding ligand derived from the β2-microglobulin chain of the human MHC class I molecule (J-LEAPS) with 15 to 30 amino acid–long peptides derived from influenza virus NP, M, or HA proteins. DCs were stimulated with influenza-J-LEAPS peptides (influenza-J-LEAPS) and injected intravenously into infected mice. Antigen-specific LEAPS-stimulated DCs were effective in reducing influenza virus replication in the lungs and enhancing survival of infected animals. Additionally, they augmented influenza-specific T cell responses in the lungs and reduced the severity of disease by limiting excessive cytokine responses, which are known to contribute to morbidity and mortality following influenza virus infection. Our data demonstrate that influenza-J-LEAPS–pulsed DCs reduce virus replication in the lungs, enhance survival, and modulate the protective immune responses that eliminate the virus while preventing excessive cytokines that could injure the host. This approach shows promise as an adjunct to antiviral treatment of influenza virus infections.

Authors

Kobporn Boonnak, Leatrice Vogel, Marlene Orandle, Daniel Zimmerman, Eyal Talor, Kanta Subbarao

Bacterial control of host gene expression through RNA polymerase II

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Abstract

The normal flora furnishes the host with ecological barriers that prevent pathogen attack while maintaining tissue homeostasis. Urinary tract infections (UTIs) constitute a highly relevant model of microbial adaptation in which some patients infected with Escherichia coli develop acute pyelonephritis, while other patients with bacteriuria exhibit an asymptomatic carrier state similar to bacterial commensalism. It remains unclear if the lack of destructive inflammation merely reflects low virulence or if carrier strains actively inhibit disease-associated responses in the host. Here, we identify a new mechanism of bacterial adaptation through broad suppression of RNA polymerase II–dependent (Pol II–dependent) host gene expression. Over 60% of all genes were suppressed 24 hours after human inoculation with the prototype asymptomatic bacteriuria (ABU) strain E. coli 83972, and inhibition was verified by infection of human cells. Specific repressors and activators of Pol II–dependent transcription were modified, Pol II phosphorylation was inhibited, and pathogen-specific signaling was suppressed in cell lines and inoculated patients. An increased frequency of strains inhibiting Pol II was epidemiologically verified in ABU and fecal strains compared with acute pyelonephritis, and a Pol II antagonist suppressed the disease-associated host response. These results suggest that by manipulating host gene expression, ABU strains promote tissue integrity while inhibiting pathology. Such bacterial modulation of host gene expression may be essential to sustain asymptomatic bacterial carriage by ensuring that potentially destructive immune activation will not occur.

Authors

Nataliya Lutay, Ines Ambite, Jenny Grönberg Hernandez, Gustav Rydström, Bryndís Ragnarsdóttir, Manoj Puthia, Aftab Nadeem, Jingyao Zhang, Petter Storm, Ulrich Dobrindt, Björn Wullt, Catharina Svanborg

Persistent G. lamblia impairs growth in a murine malnutrition model

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Abstract

Giardia lamblia infections are nearly universal among children in low-income countries and are syndemic with the triumvirate of malnutrition, diarrhea, and developmental growth delays. Amidst the morass of early childhood enteropathogen exposures in these populations, G. lamblia–specific associations with persistent diarrhea, cognitive deficits, stunting, and nutrient deficiencies have demonstrated conflicting results, placing endemic pediatric giardiasis in a state of equipoise. Many infections in endemic settings appear to be asymptomatic/subclinical, further contributing to uncertainty regarding a causal link between G. lamblia infection and developmental delay. We used G. lamblia H3 cyst infection in a weaned mouse model of malnutrition to demonstrate that persistent giardiasis leads to epithelial cell apoptosis and crypt hyperplasia. Infection was associated with a Th2-biased inflammatory response and impaired growth. Malnutrition accentuated the severity of these growth decrements. Faltering malnourished mice exhibited impaired compensatory responses following infection and demonstrated an absence of crypt hyperplasia and subsequently blunted villus architecture. Concomitantly, severe malnutrition prevented increases in B220⁺ cells in the lamina propria as well as mucosal Il4 and Il5 mRNA in response to infection. These findings add insight into the potential role of G. lamblia as a “stunting” pathogen and suggest that, similarly, malnourished children may be at increased risk of G. lamblia–potentiated growth decrements.

Authors

Luther A. Bartelt, James Roche, Glynis Kolling, David Bolick, Francisco Noronha, Caitlin Naylor, Paul Hoffman, Cirle Warren, Steven Singer, Richard Guerrant

Mycolactone activation of Wiskott-Aldrich syndrome proteins underpins Buruli ulcer formation

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Abstract

Mycolactone is a diffusible lipid secreted by the human pathogen Mycobacterium ulcerans, which induces the formation of open skin lesions referred to as Buruli ulcers. Here, we show that mycolactone operates by hijacking the Wiskott-Aldrich syndrome protein (WASP) family of actin-nucleating factors. By disrupting WASP autoinhibition, mycolactone leads to uncontrolled activation of ARP2/3-mediated assembly of actin in the cytoplasm. In epithelial cells, mycolactone-induced stimulation of ARP2/3 concentrated in the perinuclear region, resulting in defective cell adhesion and directional migration. In vivo injection of mycolactone into mouse ears consistently altered the junctional organization and stratification of keratinocytes, leading to epidermal thinning, followed by rupture. This degradation process was efficiently suppressed by coadministration of the N-WASP inhibitor wiskostatin. These results elucidate the molecular basis of mycolactone activity and provide a mechanism for Buruli ulcer pathogenesis. Our findings should allow for the rationale design of competitive inhibitors of mycolactone binding to N-WASP, with anti–Buruli ulcer therapeutic potential.

Authors

Laure Guenin-Macé, Romain Veyron-Churlet, Maria-Isabel Thoulouze, Guillaume Romet-Lemonne, Hui Hong, Peter F. Leadlay, Anne Danckaert, Marie-Thérèse Ruf, Serge Mostowy, Chiara Zurzolo, Philippe Bousso, Fabrice Chrétien, Marie-France Carlier, Caroline Demangel

Activation of inflammasome signaling mediates pathology of acute P. aeruginosa pneumonia

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Abstract

The respiratory tract is exceptionally well defended against infection from inhaled bacteria, with multiple proinflammatory signaling cascades recruiting phagocytes to clear airway pathogens. However, organisms that efficiently activate damaging innate immune responses, such as those mediated by the inflammasome and caspase-1, may cause pulmonary damage and interfere with bacterial clearance. The extracellular, opportunistic pathogen Pseudomonas aeruginosa expresses not only pathogen-associated molecular patterns that activate NF-κB signaling in epithelial and immune cells, but also flagella that activate the NLRC4 inflammasome. We demonstrate that induction of inflammasome signaling, ascribed primarily to the alveolar macrophage, impaired P. aeruginosa clearance and was associated with increased apoptosis/pyroptosis and mortality in a murine model of acute pneumonia. Strategies that limited inflammasome activation, including infection by fliC mutants, depletion of macrophages, deletion of NLRC4, reduction of IL-1β and IL-18 production, inhibition of caspase-1, and inhibition of downstream signaling in IL-1R– or IL-18R–null mice, all resulted in enhanced bacterial clearance and diminished pathology. These results demonstrate that the inflammasome provides a potential target to limit the pathological consequences of acute P. aeruginosa pulmonary infection.

Authors

Taylor S. Cohen, Alice S. Prince

A novel murine infection model for Shiga toxin–producing Escherichia coli

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Abstract

Enterohemorrhagic E. coli (EHEC) is an important subset of Shiga toxin–producing (Stx-producing) E. coli (STEC), pathogens that have been implicated in outbreaks of food-borne illness and can cause intestinal and systemic disease, including severe renal damage. Upon attachment to intestinal epithelium, EHEC generates “attaching and effacing” (AE) lesions characterized by intimate attachment and actin rearrangement upon host cell binding. Stx produced in the gut transverses the intestinal epithelium, causing vascular damage that leads to systemic disease. Models of EHEC infection in conventional mice do not manifest key features of disease, such as AE lesions, intestinal damage, and systemic illness. In order to develop an infection model that better reflects the pathogenesis of this subset of STEC, we constructed an Stx-producing strain of Citrobacter rodentium, a murine AE pathogen that otherwise lacks Stx. Mice infected with Stx-producing C. rodentium developed AE lesions on the intestinal epithelium and Stx-dependent intestinal inflammatory damage. Further, the mice experienced lethal infection characterized by histopathological and functional kidney damage. The development of a murine model that encompasses AE lesion formation and Stx-mediated tissue damage will provide a new platform upon which to identify EHEC alterations of host epithelium that contribute to systemic disease.

Authors

Emily M. Mallick, Megan E. McBee, Vijay K. Vanguri, Angela R. Melton-Celsa, Katherine Schlieper, Brad J. Karalius, Alison D. O’Brien, Joan R. Butterton, John M. Leong, David B. Schauer

Complete Plasmodium falciparum liver stage development in liver-chimeric mice

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Abstract

Plasmodium falciparum, which causes the most lethal form of human malaria, replicates in the host liver during the initial stage of infection. However, in vivo malaria liver-stage (LS) studies in humans are virtually impossible, and in vitro models of LS development do not reconstitute relevant parasite growth conditions. To overcome these obstacles, we have adopted a robust mouse model for the study of P. falciparum LS in vivo: the immunocompromised and fumarylacetoacetate hydrolase–deficient mouse (Fah–/–, Rag2–/–, Il2rg–/–, termed the FRG mouse) engrafted with human hepatocytes (FRG huHep). FRG huHep mice supported vigorous, quantifiable P. falciparum LS development that culminated in complete maturation of LS at approximately 7 days after infection, providing a relevant model for LS development in humans. The infections allowed observations of previously unknown expression of proteins in LS, including P. falciparum translocon of exported proteins 150 (PTEX150) and exported protein-2 (EXP-2), components of a known parasite protein export machinery. LS schizonts exhibited exoerythrocytic merozoite formation and merosome release. Furthermore, FRG mice backcrossed to the NOD background and repopulated with huHeps and human red blood cells supported reproducible transition from LS infection to blood-stage infection. Thus, these mice constitute reliable models to study human LS directly in vivo and demonstrate utility for studies of LS–to–blood-stage transition of a human malaria parasite.

Authors

Ashley M. Vaughan, Sebastian A. Mikolajczak, Elizabeth M. Wilson, Markus Grompe, Alexis Kaushansky, Nelly Camargo, John Bial, Alexander Ploss, Stefan H.I. Kappe