Allergic airway sensitization impairs antibacterial IgG antibody responses during bacterial respiratory tract infections.

BACKGROUND: Mycoplasma pneumoniae, an atypical human pathogen, has been associated with asthma initiation and exacerbation. Asthmatic patients have been reported to have higher carriage rates of M pneumoniae compared with nonasthmatic subjects and are at greater risk for invasive respiratory infections. OBJECTIVE: We sought to study whether prior allergen sensitization affects the host response to chronic bacterial infection. METHODS: BALB/cJ and IL-4 receptor α-/- mice were sensitized with ovalbumin (OVA) and then infected with M pneumoniae or Streptococcus pneumoniae. Immune parameters were analyzed at 30 days postinfection and included cellular profiles in bronchoalveolar lavage fluid (BALF) and serum IgG and IgE antibody levels to whole bacterial lysate, recombinant P1 adhesin, and OVA. Total lung RNA was examined for transcript levels, and BALF was examined for cytokine protein profiles. RESULTS: Anti-M pneumoniae antibody responses were decreased in allergen-sensitized, M pneumoniae-infected animals compared with control animals, but OVA-specific IgG responses were unaffected. Similar decreases in anti-S pneumoniae antibody levels were found in OVA-sensitized animals. However, M pneumoniae, but not S pneumoniae, infection augmented anti-OVA IgE antibody responses. Loss of IL-4 receptor signaling partially restored anti-M pneumoniae antibody responses in IgG2a and IgG2b subclasses. Inflammatory cytokine levels in BALF from OVA-sensitized, M pneumoniae-infected or S pneumoniae-infected animals were reduced compared with those in uninfected OVA-sensitized control animals. Unexpectedly, airway hyperreactivity to methacholine was essentially ablated in M pneumoniae-infected, OVA-sensitized animals. CONCLUSIONS: An established type 2-biased host immune response impairs the host immune response to respiratory bacterial infection in a largely pathogen-independent manner. Some pathogens, such as M pneumoniae, can augment ongoing allergic responses and inhibit pulmonary type 2 cytokine responses and allergic airway hyperreactivity.

Effects of second-line anti-tuberculosis drugs on the intestinal microbiota of patients with rifampicin-resistant tuberculosis.

Objective: To determine the effects of second-line anti-tuberculosis (TB) drugs on the composition and functions of intestinal microbiota in patients with rifampicin-resistant TB (RR-TB). Methods: In this cross-sectional study, stool samples and relevant clinical information were collected from patients with RR-TB admitted to the Drug-resistant Specialty Department at Hunan Chest Hospital (Hunan Institute For Tuberculosis Control). The composition and functions of intestinal microbiota were analyzed using metagenomic sequencing and bioinformatics methods. Results: Altered structural composition of the intestinal microbiota was found when patients from the control, intensive phase treatment, and continuation phase treatment groups were compared (P<0.05). Second-line anti-TB treatment resulted in a decrease in the relative abundance of species, such as Prevotella copri, compared with control treatment. However, the relative abundance of Escherichia coli, Salmonella enterica, and 11 other conditionally pathogenic species increased significantly in the intensive phase treatment group. Based on differential functional analysis, some metabolism-related functions, such as the biosynthesises of phenylalanine, tyrosine, and tryptophan, were significantly inhibited during second-line anti-TB drug treatment, while other functions, such as phenylalanine metabolism, were significantly promoted during the intensive phase of treatment. Conclusion: Second-line anti-TB drug treatment caused changes in the structural composition of the intestinal microbiota in patients with RR-TB. In particular, this treatment induced a significant increase in the relative abundance of 11 conditionally pathogenic species, including Escherichia coli. Functional analysis revealed significantly decreased biosynthesises of phenylalanine, tyrosine, and tryptophan and significantly increased phenylalanine metabolism.

Circ-WDR27 regulates mycobacterial vitality and secretion of inflammatory cytokines in Mycobacterium tuberculosis-infected macrophages via the miR-370-3p/FSTL1 signal network.

Tuberculosis (TB) is a common disease caused by Mycobacterium tuberculosis (M.tb) infection. Our study was to explore the function and mechanism of circular RNA WD repeat domain 27 (circ-WDR27) in TB progression. Cell viability and apoptosis were detected by 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide assay and flow cytometry. Protein quantification was performed by Western blot. Inflammatory cytokines were examined using enzyme-linked immunosorbent assay. RNA levels were assayed via quantitative reverse-transcription polymerase chain reaction. M.tb survival was assessed using colony-forming unit assay. Target binding was analyzed via dual-luciferase reporter assay and RNA immunoprecipitation assay. Cell damages were induced by M.tb infection, and inflammatory cytokines were secreted in human macrophages. Circ-WDR27 was downregulated in TB patients and M.tb-infected macrophages. Circ-WDR27 overexpression reduced M.tb survival and released inflammatory cytokines in macrophages. Circ-WDR27 acted as a sponge for miR-370-3p. Circ-WDR27-mediated inhibition of TB progression was partly achieved by sponging miR-370-3p. miR-370-3p directly targeted Follistatin-like protein 1 (FSTL1). FSTL1 suppressed M.tb-induced cell damages, and reversed the protective role of miR-370-3p inhibition in TB progression. Circ- WDR27 regulated FSTL1 expression by targeting miR-370-3p. These results showed that circ-WDR27 repressed M.tb vitality and stimulated pro-inflammatory cytokines in M.tb-infected macrophages by affecting the miR-370-3p/FSTL1 axis.

Knockdown of long non­coding RNA DLEU2 suppresses idiopathic pulmonary fibrosis by regulating the microRNA­369­3p/TRIM2 axis.

Idiopathic pulmonary fibrosis (IPF) is the most common form of idiopathic interstitial pneumonia with an increasing incidence. In the present study, Genome Expression Omnibus (GEO) datasets (GSE10667, GSE24206 and GSE32537) were applied to identify lncRNA DLEU2 in IPF. Through prediction using starBase, TargetScan, miRTarBase and miRDB, tripartite motif containing 2 (TRIM2) and prostaglandin F2 receptor inhibitor (PTGFRN) were found to be upregulated in IPF. DLEU2 expression, the mRNA expression of TRIM2 and PTGFRN, and miR­369­3p expression in A549 cells and lung tissues were detected by RT­qPCR. The protein expression of TRIM2 and PTGFRN in lung tissues and A549 cells was detected by western blot analysis. The proliferation and migration of A549 cells was respectively detected by CCK­8 assay and wound healing assay. The expression of collagen I, α­smooth muscle actin (SMA) and E­cadherin was detected by immunofluorescence assay in A549 cells, and collagen I expression was detected by immunohistochemistry assay in lung tissues. The expression of collagen I, α­SMA and E­cadherin was also detected by western blot analysis in A549 cells and lung tissues. Dual­luciferase reporter assay was used to confirm the association between DLEU2 and miR­369­3p, and miR­369­3p and TRIM2. As a result, DLEU2 expression was found to be upregulated in IPF and in transforming growth factor (TGF)­ß1­stimulated A549 cells. The silencing of DLEU2 inhibited the TGF­ß1­induced proliferation, migration and epithelial­mesenchymal transition (EMT) of A549 cells and bleomycin (BLM)­induced pulmonary fibrosis in mice. TRIM2 expression was increased and miR­369­3p expression was decreased in the lung tissues of mice with BLM­induced fibrosis and in TGF­ß1­stimulated A549 cells. DLEU2 directly targeted miR­369­3p. The effect of the silencing of DLEU2 on TGF­ß1­stimulated A549 cells was suppressed by the silencing of miR­369­3p. TRIM2 was the target protein of miR­369­3p. On the whole, the present study demonstrates that the silencing of DLEU2 suppressed IPF by upregulating miR­369­3p expression and downregulating TRIM2 expression.

Inhibition of message for FcepsilonRI alpha chain blocks mast cell IL-4 production induced by co-culture with Mycoplasma pneumoniae.

We have previously described the activation of RBL-2H3 mast cells for IL-4 production by Mycoplasma pneumoniae but the mechanism remains unclear. M. pneumoniae binds eukaryotic cells primarily through sialoglycoproteins on the target cell surface. This study was undertaken to determine whether the sialated FcepsilonRI alpha chain on RBL cells is important for M. pneumoniae-induced IL-4 production. We found that IgE-mediated IL-4 release by a series of RBL sublines correlated with the release induced by M. pneumoniae. Further, aggregation of FcgammaRII (CD32) in RBL cells using a monoclonal antibody inhibited both IgE-mediated and mycoplasma-induced IL-4 production, providing further evidence for an Fc receptor-mediated mechanism of activation. To examine the role of FcepsilonRI in mycoplasma-induced IL-4 release, we created stably transfected RBL sublines using a vector expressing a short hairpin sequence designed to inhibit message for the FcepsilonRI alpha chain. IgE-induced IL-4 production by the transfected sublines was reduced in similar proportion to the degree of message suppression. M. pneumoniae-induced IL-4 production in the four transfected sublines was completely blocked in contrast to results with the controls or parent RBL cells. We conclude that the heavily glycosylated FcepsilonRI alpha chain is required for activation of mast cells for IL-4 production by M. pneumoniae.

Purification, nanocrystallization and preliminary X-ray analysis of a C-terminal part of tropomodulin protein 1, isoform A, from Caenorhabditis elegans.

The C-terminal part of tropomodulin protein 1, isoform A, from Caenorhabditis elegans was expressed in Escherichia coli and purified to homogeneity. Optimized from the initial nanoscreen, crystals grew to dimensions of 0.25 x 0.15 x 0.15 mm at 277 K using 28.0%(v/v) PEG 400 as the precipitant by the hanging-drop vapor-diffusion technique. A data set of 94.9% completeness was collected to a resolution of 1.98 A at 100 K using a synchrotron X-ray source (SER-CAT). The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 31.7, b = 50.6, c = 107.1 A, and contained one molecule per asymmetric unit.

An exposed domain in the severe acute respiratory syndrome coronavirus spike protein induces neutralizing antibodies.

Exposed epitopes of the spike protein may be recognized by neutralizing antibodies against severe acute respiratory syndrome (SARS) coronavirus (CoV). A protein fragment (S-II) containing predicted epitopes of the spike protein was expressed in Escherichia coli. The properly refolded protein fragment specifically bound to the surface of Vero cells. Monoclonal antibodies raised against this fragment recognized the native spike protein of SARS CoV in both monomeric and trimeric forms. These monoclonal antibodies were capable of blocking S-II attachment to Vero cells and exhibited in vitro antiviral activity. These neutralizing antibodies mapped to epitopes in two peptides, each comprising 20 amino acids. Thus, this region of the spike protein might be a target for generation of therapeutic neutralizing antibodies against SARS CoV and for vaccine development to elicit protective humoral immunity.