Thymic Stromal Lymphopoietin: A Promising Target in the Treatment of Asthma? / Linfopoyetina del estroma tímico: ¿un objetivo prometedor para el tratamiento del asma?

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The TLR4-TRIF pathway can protect against the development of experimental allergic asthma.

The Toll-like receptor (TLR) adaptor proteins myeloid differentiating factor 88 (MyD88) and Toll, interleukin-1 receptor and resistance protein (TIR) domain-containing adaptor inducing interferon-ß (TRIF) comprise the two principal limbs of the TLR signalling network. We studied the role of these adaptors in the TLR4-dependent inhibition of allergic airway disease and induction of CD4+ ICOS+ T cells by nasal application of Protollin™, a mucosal adjuvant composed of TLR2 and TLR4 agonists. Wild-type (WT), Trif-/- or Myd88-/- mice were sensitized to birch pollen extract (BPEx), then received intranasal Protollin followed by consecutive BPEx challenges. Protollin's protection against allergic airway disease was TRIF-dependent and MyD88-independent. TRIF deficiency diminished the CD4+ ICOS+ T-cell subsets in the lymph nodes draining the nasal mucosa, as well as their recruitment to the lungs. Overall, TRIF deficiency reduced the proportion of cervical lymph node and lung CD4+ ICOS+ Foxp3- cells, in particular. Adoptive transfer of cervical lymph node cells supported a role for Protollin-induced CD4+ ICOS+ cells in the TRIF-dependent inhibition of airway hyper-responsiveness. Hence, our data demonstrate that stimulation of the TLR4-TRIF pathway can protect against the development of allergic airway disease and that a TRIF-dependent adjuvant effect on CD4+ ICOS+ T-cell responses may be a contributing mechanism.

Inhaled birch pollen extract induces airway hyperresponsiveness via oxidative stress but independently of pollen-intrinsic NADPH oxidase activity, or the TLR4-TRIF pathway.

Oxidative stress in allergic asthma may result from oxidase activity or proinflammatory molecules in pollens. Signaling via TLR4 and its adaptor Toll-IL-1R domain-containing adapter inducing IFN-ß (TRIF) has been implicated in reactive oxygen species-mediated acute lung injury and in Th2 immune responses. We investigated the contributions of oxidative stress and TLR4/TRIF signaling to experimental asthma induced by birch pollen exposure exclusively via the airways. Mice were exposed to native or heat-inactivated white birch pollen extract (BPEx) intratracheally and injected with the antioxidants, N-acetyl-L-cysteine or dimethylthiourea, prior to sensitization, challenge, or all allergen exposures, to assess the role of oxidative stress and pollen-intrinsic NADPH oxidase activity in allergic sensitization, inflammation, and airway hyperresponsiveness (AHR). Additionally, TLR4 signaling was antagonized concomitantly with allergen exposure, or the development of allergic airway disease was evaluated in TLR4 or TRIF knockout mice. N-acetyl-L-cysteine inhibited BPEx-induced eosinophilic airway inflammation and AHR except when given exclusively during sensitization, whereas dimethylthiourea was inhibitory even when administered with the sensitization alone. Heat inactivation of BPEx had no effect on the development of allergic airway disease. Oxidative stress-mediated AHR was also TLR4 and TRIF independent; however, TLR4 deficiency decreased, whereas TRIF deficiency increased BPEx-induced airway inflammation. In conclusion, oxidative stress plays a significant role in allergic sensitization to pollen via the airway mucosa, but the pollen-intrinsic NADPH oxidase activity and TLR4 or TRIF signaling are unnecessary for the induction of allergic airway disease and AHR. Pollen extract does, however, activate TLR4, thereby enhancing airway inflammation, which is restrained by the TRIF-dependent pathway.

ICOS-expressing CD4 T cells induced via TLR4 in the nasal mucosa are capable of inhibiting experimental allergic asthma.

Modulation of adaptive immune responses via the innate immune pattern recognition receptors, such as the TLRs, is an emerging strategy for vaccine development. We investigated whether nasal rather than intrapulmonary application of Protollin, a mucosal adjuvant composed of TLR2 and TLR4 ligands, is sufficient to elicit protection against murine allergic lower airway disease. Wild-type, Tlr2(-/-), or Tlr4(-/-) BALB/c mice were sensitized to a birch pollen allergen extract (BPEx), then received either intranasal or intrapulmonary administrations of Protollin or Protollin admixed with BPEx, followed by consecutive daily BPEx challenges. Nasal application of Protollin or Protollin admixed with BPEx was sufficient to inhibit allergic lower airway disease with minimal collateral lung inflammation. Inhibition was dependent on TLR4 and was associated with the induction of ICOS in cells of the nasal mucosa and on both CD4+Foxp3+ and CD4+Foxp3- T cells of the draining lymph nodes (LNs), as well as their recruitment to the lungs. Adoptive transfer of cervical LN CD4+ICOS+, but not CD4+ICOS-, cells inhibited BPEx-induced airway hyperresponsiveness and bronchoalveolar lavage eosinophilia. Thus, our data indicate that expansion of resident ICOS-expressing CD4+ T cells of the cervical LNs by nasal mucosal TLR4 stimulation may inhibit the development of allergic lower airway disease in mice.

Bacteriophages φMR299-2 and φNH-4 can eliminate Pseudomonas aeruginosa in the murine lung and on cystic fibrosis lung airway cells.

UNLABELLED: Pseudomonas aeruginosa is a common cause of infection in the lungs of patients with cystic fibrosis (CF). In addition, biofilm formation and antibiotic resistance of Pseudomonas are major problems that can complicate antibiotic therapy. We evaluated the efficacy of using bacteriophages to kill the pathogen in both biofilms and in the murine lung. We isolated and characterized two phages from a local wastewater treatment plant, a myovirus (φNH-4) and a podovirus (φMR299-2). Both phages were active against clinical isolates of P. aeruginosa. Together, the two phages killed all 9 clinical isolate strains tested, including both mucoid and nonmucoid strains. An equal mixture of the two phages was effective in killing P. aeruginosa NH57388A (mucoid) and P. aeruginosa MR299 (nonmucoid) strains when growing as a biofilm on a cystic fibrosis bronchial epithelial CFBE41o- cell line. Phage titers increased almost 100-fold over a 24-h period, confirming replication of the phage. Furthermore, the phage mix was also effective in killing the pathogen in murine lungs containing 1 × 10(7) to 2 × 10(7) P. aeruginosa. Pseudomonas was effectively cleared (reduced by a magnitude of at least 3 to 4 log units) from murine lungs in 6 h. Our study demonstrates the efficacy of these two phages in killing clinical Pseudomonas isolates in the murine lung or as a biofilm on a pulmonary cell line and supports the growing interest in using phage therapy for the control and treatment of multidrug-resistant Pseudomonas lung infections in CF patients. IMPORTANCE: Given the rise in antibiotic resistance, nonantibiotic therapies are required for the treatment of infection. This is particularly true for the treatment of Pseudomonas infection in patients with cystic fibrosis. We have identified two bacterial viruses (bacteriophages) that can kill Pseudomonas growing on human lung cells and in an animal model of lung infection. The use of bacteriophages is particularly appropriate because the killing agent can replicate on the target cell, generating fresh copies of the bacteriophage. Thus, in the presence of a target, the killing agent multiplies. By using two bacteriophages we can reduce the risk of resistant colonies developing at the site of infection. Bacteriophage therapy is an exciting field, and this study represents an important demonstration of efficacy in validated infection models.

The immunomodulatory actions of prostaglandin E2 on allergic airway responses in the rat.

PGE(2) has been reported to inhibit allergen-induced airway responses in sensitized human subjects. The aim of this study was to investigate the mechanism of anti-inflammatory actions of PGE(2) in an animal model of allergic asthma. BN rats were sensitized to OVA using Bordetella pertussis as an adjuvant. One week later, an aerosol of OVA was administered. After a further week, animals were anesthetized with urethan, intubated, and subjected to measurements of pulmonary resistance (R(L)) for a period of 8 h after OVA challenge. PGE(2) (1 and 3 micro g in 100 micro l of saline) was administered by insufflation intratracheally 30 min before OVA challenge. The early response was inhibited by PGE(2) (3 micro g). The late response was inhibited by both PGE(2) (1 and 3 micro g). Bronchoalveolar lavage fluid from OVA-challenged rats showed eosinophilia and an increase in the number of cells expressing IL-4 and IL-5 mRNA. These responses were inhibited by PGE(2). Bronchoalveolar lavage fluid levels of cysteinyl-leukotrienes were elevated after OVA challenge and were reduced after PGE(2) to levels comparable with those of sham challenged animals. We conclude that PGE(2) is a potent anti-inflammatory agent that may act by reducing allergen-induced Th2 cell activation and cysteinyl-leukotriene synthesis in the rat.