Alpha-1 Asthma Overlap Syndrome: a Clinical Overview.

PURPOSE OF REVIEW: Alpha-1 antitrypsin deficiency (AATD) is one of the most common genetic diseases that is associated with severe complications and yet remains underdiagnosed. The pulmonary symptoms of both AATD and asthma include cough, excessive sputum production, dyspnea, and wheezing. These symptoms overlap significantly leading to difficulty distinguishing between these two conditions and suspicion that there may be an overlap syndrome. We aim to discuss the pathophysiology, clinical manifestations, and treatment of both alpha-1 antitrypsin and asthma and how they may overlap. RECENT FINDINGS: Recent literature suggests that there is an association between asthma and AATD. This association has been hypothesized to be secondary to an imbalance of elastase and anti-elastase leading to a pro-inflammatory state in patients with AATD. This review serves to overview the pathophysiology, clinical manifestations, and treatment of alpha-1 antitrypsin, asthma, and the increasingly recognized intersection of the two, AATD-asthma overlap syndrome.

Asthma in Cystic Fibrosis: Definitions and Implications of This Overlap Syndrome.

PURPOSE OF REVIEW: Cystic fibrosis (CF) is a multisystem, autosomal recessive disease that leads to progressive loss of lung function. Respiratory symptoms for both CF and asthma include cough, wheezing, and dyspnea. There is debate within the CF community on how to best define and distinguish CF-asthma overlap syndrome (CFAOS) from asthma-like features, though CFAOS is well-recognized. We aim to review the epidemiology, diagnosis, and treatment of asthma in CF and explore areas where further research is needed. RECENT FINDINGS: There has been considerable improvement in the understanding and treatment of asthma over the past two decades leading to novel therapies such as biologic agents that target the airway inflammation in asthmatics based on their asthma phenotype. These therapies are being studied in CFAOS and are promising treatments. This review provides a comprehensive overview of the definition, epidemiology, diagnosis, and current treatment of CFAOS.

Regulation and Role of Chitotriosidase during Lung Infection with Klebsiella pneumoniae.

Chitinases and chitinase-like proteins are an evolutionary conserved group of proteins. In the absence of chitin synthesis in mammals, the conserved presence of chitinases suggests their roles in physiology and immunity, but experimental evidence to prove these roles is scarce. Chitotriosidase (chit1) is one of the two true chitinases present in mammals and the most prevalent chitinase in humans. In this study, we investigated the regulation and the role of chit1 in a mouse model of Klebsiella pneumoniae lung infection. We show that chitinase activity in bronchoalveolar lavage fluid is significantly reduced during K. pneumoniae lung infection. This reduced activity is inversely correlated with the number of neutrophils. Further, instilling neutrophil lysates in lungs decreased chitinase activity. We observed degradation of chit1 by neutrophil proteases. In a mouse model, chit1 deficiency provided a significant advantage to the host during K. pneumoniae lung infection by limiting bacterial dissemination. This phenotype was independent of inflammatory changes in chit1-/- mice as they exerted a similar inflammatory response. The decreased dissemination resulted in improved survival in chit1-/- mice infected with K. pneumoniae in the presence or absence of antibiotic therapy. The beneficial effects of chit1 deficiency were associated with altered Akt activation in the lungs. Chit1-/- mice induced a more robust Akt activation postinfection. The role of the Akt pathway in K. pneumoniae lung infection was confirmed by using an Akt inhibitor, which impaired health and survival. These data suggest a detrimental role of chit1 in K. pneumoniae lung infections.

Toll-Like Receptors 2 and 4 Modulate Pulmonary Inflammation and Host Factors Mediated by Outer Membrane Vesicles Derived from Acinetobacter baumannii.

Pneumonia due to Gram-negative bacteria is associated with high mortality. Acinetobacter baumannii is a Gram-negative bacterium that is associated with hospital-acquired and ventilator-associated pneumonia. Bacteria have been described to release outer membrane vesicles (OMVs) that are capable of mediating systemic inflammation. The mechanism by which A. baumannii OMVs mediate inflammation is not fully defined. We sought to investigate the roles that Toll-like receptors (TLRs) play in A. baumannii OMV-mediated pulmonary inflammation. We isolated OMVs from A. baumannii cultures and intranasally introduced the OMVs into mice. Intranasal introduction of A. baumannii OMVs mediated pulmonary inflammation, which is associated with neutrophil recruitment and weight loss. In addition, A. baumannii OMVs increased the release of several chemokines and cytokines in the mouse lungs. The proinflammatory responses were partially inhibited in TLR2- and TLR4-deficient mice compared to those of wild-type mice. This study highlights the important roles of TLRs in A. baumannii OMV-induced pulmonary inflammation in vivo.

Chitinase 3-Like 1 (Chil1) Regulates Survival and Macrophage-Mediated Interleukin-1ß and Tumor Necrosis Factor Alpha during Pseudomonas aeruginosa Pneumonia.

Pseudomonas aeruginosa causes hospital-acquired pneumonia and is associated with high mortality. An effective response to such an infection includes efficient clearance of pathogenic organisms while limiting collateral damage from the host inflammatory response, known as host resistance and host tolerance, respectively. P. aeruginosa expresses a type III secretion system (T3SS) needle complex that induces NLRC4 (NOD-like receptor C4) activation, interleukin-1ß (IL-1ß) production, and host tissue damage. Chitinase 3-like-1 (Chil1) is expressed during infection and binds to its receptor, IL-13 receptor α2 (IL-13Rα2), to regulate the pathogen-host response during Streptococcus pneumoniae infection, but the role Chil1 plays in balancing the host resistance and host tolerance during P. aeruginosa pneumonia is not known. We conducted experiments using C57BL/6 mice with or without a genetic deficiency of Chil1 and demonstrated that Chil1-deficient mice succumb to P. aeruginosa infection more rapidly than the wild type (WT). The decreased survival time in infected Chil1-deficient mice is associated with more neutrophils recruited to the airways, more lung parenchymal damage, and increased pulmonary consolidation while maintaining equivalent bacterial killing compared to WT mice. Infected Chil1-deficient mice and bone marrow-derived macrophages (BMDMs) from Chil1-deficient mice have increased production of tumor necrosis factor alpha (TNF-α) and IL-1ß compared to infected WT mice and macrophages. Infection of Chil1-deficient BMDMs with non-NLRC4-triggering P. aeruginosa, which is deficient in the T3SS needle complex, did not alter the excessive IL-1ß production compared to BMDMs from WT mice. The addition of recombinant Chil1 decreases the excessive IL-1ß production but only partially rescues stimulated BMDMs from IL-13Rα2-deficient mice. Our data provide mechanistic insights into how Chil1 regulates P. aeruginosa-induced host responses.

Impact of Bronchiectasis on COPD Severity and Alpha-1 Antitrypsin Deficiency as a Risk Factor in Individuals with a Heavy Smoking History.

Rationale: Bronchiectasis is common among those with heavy smoking histories, but risk factors for bronchiectasis, including alpha-1 antitrypsin deficiency, and its implications for COPD severity are uncharacterized in such individuals. Objectives: To characterize the impact of bronchiectasis on COPD and explore alpha-1antitrypsin as a risk factor for bronchiectasis. Methods: SubPopulations and InteRmediate Outcome Measures In COPD Study (SPIROMICS) participants (N=914; ages 40-80 years; ≥20-pack-year smoking) had high-resolution computed tomography (CT) scans interpreted visually for bronchiectasis, based on airway dilation without fibrosis or cicatrization. We performed regression-based models of bronchiectasis with clinical outcomes and quantitative CT measures. We deeply sequenced the gene encoding -alpha-1 antitrypsin, SERPINA1, in 835 participants to test for rare variants, focusing on the PiZ genotype (Glu366Lys, rs28929474). Measurements and Main Results: We identified bronchiectasis in 365 (40%) participants, more frequently in women (45% versus 36%, p=0.0045), older participants (mean age=66[standard deviation (SD)=8.3] versus 64[SD=9.1] years, p=0.0083), and those with lower lung function (forced expiratory volume in 1 second [FEV1 ] percentage predicted=66%[SD=27] versus 77%[SD=25], p<0.0001; FEV1 to forced vital capacity [FVC] ratio=0.54[0.17] versus 0.63[SD=0.16], p<0.0001). Participants with bronchiectasis had greater emphysema (%voxels ≤-950 Hounsfield units, 11%[SD=12] versus 6.3%[SD=9], p<0.0001) and parametric response mapping functional small airways disease (26[SD=15] versus 19[SD=15], p<0.0001). Bronchiectasis was more frequent in the combined PiZZ and PiMZ genotype groups compared to those without PiZ, PiS, or other rare pathogenic variants (N=21 of 40 [52%] versus N=283 of 707[40%], odds ratio [OR]=1.97; 95% confidence interval [CI]=1.002, 3.90, p=0.049), an association attributed to White individuals (OR=1.98; 95%CI = 0.9956, 3.9; p=0.051). Conclusions: Bronchiectasis was common in those with heavy smoking histories and was associated with detrimental clinical and radiographic outcomes. Our findings support alpha-1antitrypsin guideline recommendations to screen for alpha-1 antitrypsin deficiency in an appropriate bronchiectasis subgroup with a significant smoking history.

DNA sequencing analysis of cystic fibrosis transmembrane conductance regulator gene identifies cystic fibrosis-associated variants in the Severe Asthma Research Program.

BACKGROUND: Heterozygote carriers of potentially pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have increased asthma risk. However, the frequency and impact of CFTR variation among individuals with asthma is unknown. OBJECTIVE: To determine whether potentially pathogenic CFTR variants associate with disease severity and whether individuals with two potentially pathogenic variants exist in a severe asthma-enriched cohort. METHODS: We analyzed sequencing data spanning a 190.5Kb region of CFTR in participants from the Severe Asthma Research Program (SARP1-3). Potentially pathogenic, rare CFTR variants (frequency < 0.05) were classified as CF-causing or of varying clinical consequences (VVCC) (CFTR2. org). Regression-based models tested for association between CFTR genotypes (0-2 potentially pathogenic variants) and severity outcomes. RESULTS: Of 1401 participants, 9.5% (134) had one potentially pathogenic variant, occurring more frequently in non-Hispanic white (NHW, 10.1% [84 of 831]) compared to African American individuals (AA, 5.2% [22 of 426]). We found ≥2 potentially pathogenic CFTR variants in 1.4% (19); 0.5% (4) of NHW and 2.8% (12) of AA. Potentially pathogenic CFTR variant genotypes (≥1 or ≥2 variants) were not cumulatively associated with lung function or exacerbations. In NHW, we found three F508del compound heterozygotes with F508del and a VVCC (two 5 T; TG12[c.1210-11 T > G] and one Arg1070Trp) and a homozygote for the VVCC, 5 T; TG12. CONCLUSIONS: We found potentially pathogenic CFTR variants within a severe asthma-enriched cohort, including three compound heterozygote genotypes variably associated with CF in NHW individuals. These findings provide the rationale for CFTR sequencing and phenotyping of CF-related traits in individuals with severe asthma.

Atypical Pneumonia: Updates on Legionella, Chlamydophila, and Mycoplasma Pneumonia.

Community-acquired pneumonia (CAP) has multiple causes and is associated with illness that requires admission to the hospital and mortality. The causes of atypical CAP include Legionella species, Chlamydophila, and Mycoplasma. Atypical CAP remains a diagnostic challenge and, therefore, likely is undertreated. This article reviews the advancements in the evaluation and treatment of patients and discusses current conflicts and controversies of atypical CAP.

Outcome and immune responses after Brucella abortus infection in young adult and aged mice.

Aging results in a general waning of immunity and enhanced susceptibility to many intracellular pathogens. However, in some instances, aging is accompanied by alternative immune responses that can be equal to, or even more effective, than those of young adults. Brucella spp. are intracellular bacteria and important human and animal pathogens, but there are no data regarding the effect of age on host defense in brucellosis. Young or old adult mice (DBA/2 or BALB/c) were infected with either an attenuated B. abortus strain that over-expressed the Brucella superoxide dismutase (strain RB51-SOD) or a fully virulent strain (strain 2308). Survival, organism burden in the spleen, and immune responses were assessed. All young adult and aged mice survived infection with RB51-SOD (up to 6 x 10(8) cfu) or strain 2308 (up to 8 x 10(8) cfu). Old mice had a lower organism burden in the spleen than young adult mice five or more weeks after infection. Antibody and cytokine responses were Th1-focused in young adult mice, but Th-mixed in older mice, including evidence of the newly defined Th17 subtype immune response. Immunization with the RB51-SOD strain provided protection vs. strain 2308 challenge in young and aged BALB/c, but only young adult DBA/2 mice. Thus, clinical outcomes of Brucella infection in aged mice are equal or superior to those of young adult mice; immune responses in older mice are less-Th1 specific suggesting alternate pathways may contribute to host defense vs. Brucella in aged mice.