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Andrew H Limper

Publications and source records attributed to Andrew H Limper.

At least 19 recordsLinked to original sources
PubMed2006

Pneumocystis cell wall beta-glucans induce dendritic cell costimulatory molecule expression and inflammatory activation through a Fas-Fas ligand mechanism.

Respiratory failure during Pneumocystis pneumonia is mainly a consequence of exaggerated inflammatory responses to the organism. Dendritic cells (DCs) are the most potent APCs in the lung and are key to the regulation of innate and adaptive immune responses. However, their participation in the inflammatory response directed against Pneumocystis infection has not been fully elucidated. Therefore, we studied the role of Pneumocystis carinii, as well as Saccharomyces cerevisiae, cell wall-derived beta-glucans, in DC costimulatory molecule expression. We further studied the impact of beta-glucans on subsequent T cell activation. Because cytokine secretion by DCs has recently been shown to be regulated by Fas ligand (FasL), its role in beta-glucan activation of DCs was also investigated. beta-Glucan-induced DC activation occurred in part through dectin-1 receptors. We demonstrated that DC activation by beta-glucans elicits T cell activation and polarization into a Th1 patterned response, but with the conspicuous absence of IL-12. These observations differed from LPS-driven T cell polarization, suggesting that beta-glucans and LPS signal DC activation through different mechanisms. We additionally determined that IL-1beta and TNF-alpha secretion by beta-glucan-stimulated DCs was partially regulated by Fas-FasL. This suggests that dysregulation of FasL could further enhance exuberant and prolonged cytokine production by DCs following DC-T cell interactions, further promoting lung inflammation typical of Pneumocystis pneumonia.

Animals↗
PubMed2006

A real-time polymerase chain reaction assay for detection of Pneumocystis from bronchoalveolar lavage fluid.

Pneumocystis jiroveci is an important cause of pneumonia in immunocompromised individuals. This organism cannot be cultured, and therefore, diagnosis relies on microscopic identification of the organism using stains or antibodies. Although simple, these tests are insensitive and require expertise for accurate interpretation. We developed a real-time polymerase chain reaction (PCR) assay that provides sensitive and objective detection of Pneumocystis from bronchoalveolar lavage fluid. Primers and fluorescence resonance energy transfer probes were developed that target the cdc2 gene of P. jiroveci. Assay sensitivity is 6 copies of target per microliter of sample. No cross-reactivity occurs with other pathogens, and the PCR assay has a 21% increase in clinical sensitivity as compared with Calcofluor white staining. The real-time PCR assay provides a sensitive, rapid, and objective method for the detection of Pneumocystis from bronchoalveolar lavage fluid.

Benzenesulfonates↗
PubMed2006

Idiopathic pulmonary fibrosis: is it a familial disease?

PURPOSE OF REVIEW: Idiopathic pulmonary fibrosis is a progressively fatal interstitial lung disease associated with pathological findings of usual interstitial pneumonia. Its pathogenesis is unknown, and there are no proven effective therapies. Familial cases account for 0.5-2% of idiopathic pulmonary fibrosis. Familial idiopathic pulmonary fibrosis occurs as an autosomal dominant disorder with variable penetrance. The clinical characteristics of familial idiopathic pulmonary fibrosis are indistinguishable from sporadic idiopathic pulmonary fibrosis. These marked similarities support the hypothesis there may, in part, be a genetic basis for idiopathic pulmonary fibrosis. RECENT FINDINGS: Many investigations have evaluated genetic polymorphisms and idiopathic pulmonary fibrosis. Candidate genes include cytokines and surfactant protein genes. To date, no gene has been consistently identified to be associated with idiopathic pulmonary fibrosis. Recent studies in familial idiopathic pulmonary fibrosis have demonstrated a strong association with surfactant protein C gene mutations in one large kindred. SUMMARY: The pathogenesis of both idiopathic pulmonary fibrosis and familial idiopathic pulmonary fibrosis remains unclear. A consistent genetic basis has not yet been demonstrated in all cases. Other factors, including variable gene expression, co-carriage of other modifying genes and environmental stimuli, particularly cigarette smoke, significantly contribute to disease expression.

Humans↗
PubMed2006

Pneumocystis melanins confer enhanced organism viability.

Pneumocystis continues to represent an important opportunistic fungal pathogen of those with compromised immunity. Thus, it is crucial to identify factors that affect its viability and pathogenicity. We previously reported the first identification of melanins in Pneumocystis. In the present study, we sought to further characterize these components and define the function for these melanins. Melanins extracted from Pneumocystis and melanized Pneumocystis cells were analyzed by electron spin resonance spectroscopy, revealing spectra consistent with melanins from other fungi. Immunofluorescence assays using anti-melanin monoclonal antibodies showed that melanins are widely present across Pneumocystis host species, including mouse-, ferret-, and human-derived Pneumocystis organisms, as well as Pneumocystis carinii derived from rat. Using immunoelectron microscopy, melanins were found to localize to the cell wall and cytoplasm of P. carinii cysts, as well as to intracystic bodies within mature cysts. Next, the role of melanins on the maintenance of Pneumocystis viability was determined by using quantitative reverse transcription-PCR measurement of the heat shock protein mRNA under adverse environmental conditions. Using a new method to promote the melanization of Pneumocystis, we observed that strongly melanized Pneumocystis retained viability to a greater degree when exposed to UV irradiation or desiccation compared to less-pigmented organisms. These studies support our previous identification of Pneumocystis melanins across the genus, further characterize these Pneumocystis components, and demonstrate that melanins protect Pneumocystis from environmental stressors.

Animals↗
PubMed2006

An Official ATS Workshop Summary: Recent advances and future directions in pneumocystis pneumonia (PCP).

Pneumocystis pneumonia (PCP) is a major cause of morbidity and mortality among immunocompromised persons, and it remains a leading acquired immune deficiency syndrome (AIDS)-defining opportunistic infection in human immunodeficiency virus (HIV)-infected individuals throughout the world. Pneumocystis has proven difficult to study, in part due to the lack of a reliable culture system for the organism. With the development of molecular techniques, significant advances in our understanding of the organism and the disease have been made over the past several years. These advances include an improved understanding of host-organism interactions and host defense, the development of noninvasive polymerase chain reaction (PCR)-based diagnostic assays, and the emerging data regarding the possible development of trimethoprim-sulfamethoxazole-resistant Pneumocystis. In addition, the recognition that patients without PCP may nevertheless be carriers of or colonized with Pneumocystis, and observations that suggest a role for Pneumocystis in the progression of pulmonary disease, combine to signal the need for a comprehensive and accessible review. In May 2005, the American Thoracic Society sponsored a one-day workshop, "Recent Advances and Future Directions in Pneumocystis Pneumonia (PCP)," which brought together 45 Pneumocystis researchers. The workshop included 21 presentations on diverse topics, which are summarized in this report. The workshop participants identified priorities for future research, which are summarized in this document.

AIDS-Related Opportunistic Infections↗
PubMed2005

Multiple TLRs are expressed in human cholangiocytes and mediate host epithelial defense responses to Cryptosporidium parvum via activation of NF-kappaB.

Infection of epithelial cells by Cryptosporidium parvum triggers a variety of host-cell innate and adaptive immune responses including release of cytokines/chemokines and up-regulation of antimicrobial peptides. The mechanisms that trigger these host-cell responses are unclear. Thus, we evaluated the role of TLRs in host-cell responses during C. parvum infection of cultured human biliary epithelia (i.e., cholangiocytes). We found that normal human cholangiocytes express all known TLRs. C. parvum infection of cultured cholangiocytes induces the selective recruitment of TLR2 and TLR4 to the infection sites. Activation of several downstream effectors of TLRs including IL-1R-associated kinase, p-38, and NF-kappaB was detected in infected cells. Transfection of cholangiocytes with dominant-negative mutants of TLR2 and TLR4, as well as the adaptor molecule myeloid differentiation protein 88 (MyD88), inhibited C. parvum-induced activation of IL-1R-associated kinase, p-38, and NF-kappaB. Short-interfering RNA to TLR2, TLR4, and MyD88 also blocked C. parvum-induced NF-kappaB activation. Moreover, C. parvum selectively up-regulated human beta-defensin-2 in directly infected cells, and inhibition of TLR2 and TLR4 signals or NF-kappaB activation were each associated with a reduction of C. parvum-induced human beta-defensin-2 expression. A significantly higher number of parasites were detected in cells transfected with a MyD88 dominant-negative mutant than in the control cells at 48-96 h after initial exposure to parasites, suggesting MyD88-deficient cells were more susceptible to infection. These findings demonstrate that cholangiocytes express a variety of TLRs, and suggest that TLR2 and TLR4 mediate cholangiocyte defense responses to C. parvum via activation of NF-kappaB.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Characterization of lymphocyte populations in nonspecific interstitial pneumonia.

STUDY OBJECTIVES: Nonspecific interstitial pneumonia (NSIP) has been identified as a distinct entity with a more favorable prognosis and better response to immunosuppressive therapies than usual interstitial pneumonia (UIP). However the inflammatory profile of NSIP has not been characterized. DESIGN: Using immunohistochemistry techniques on open lung biopsy specimens, the infiltrate in NSIP was characterized in terms of T and B cells, and macrophages, and the T cell population further identified as either CD4 (helper) or CD8 (suppressor-cytotoxic) T cells. The extent of Th1 and Th2 cytokine producing cells was determined and compared to specimens from patients with UIP. RESULTS: In ten NSIP tissue samples 41.4 +/- 4% of mononuclear cells expressed CD3, 24.7 +/- 1.8% CD4, 19.1 +/- 2% CD8, 27.4 +/- 3.9% CD20, and 14.3 +/- 1.6% had CD68 expression. Mononuclear cells expressed INFgamma 21.9 +/- 1.9% of the time and IL-4 in 3.0 +/- 1%. In contrast, biopsies from eight patients with UIP demonstrated substantially less cellular staining for either cytokine (INFgamma; 4.6 +/- 1.7% and IL-4; 0.6 +/- 0.3%). Significant populations of CD20 positive B-cells were also identified. CONCLUSION: The lymphocytic infiltrate in NSIP is characterized by an elevated CD4/CD8 T-cell ratio, and is predominantly of Th1 type, with additional populations rich in B-cells. Such features are consistent with the favorable clinical course observed in patients with NSIP compared to UIP.

Adolescent↗
PubMed2005

Surfactant protein D enhances Pneumocystis infection in immune-suppressed mice.

To further determine the role of surfactant protein (SP)-D in the pathogenesis of Pneumocystis pneumonia, a mouse model of transgenic overexpression (OE) of SP-D was studied. These animals produce roughly 30- to 50-fold greater SP-D than their wild-type (WT) counterparts but show no other differences in lung morphology and function. Animals in both the SP-D OE and WT groups were depleted of CD4 lymphocytes with weekly injections of GK1.5 antibody, before Pneumocystis inoculation, and throughout the subsequent infection period. At various time points, mice were killed and analyzed for inflammatory parameters and organism burden. Proinflammatory cytokines in bronchoalveolar lavage fluid were elevated throughout the period of infection, with OE animals exhibiting significantly higher levels of TNF-alpha and macrophage inflammatory protein-2 compared with WT controls. The total number of cells in the lavage fluid was also increased significantly only in the OE group, whereas the cell differential composition demonstrated lymphocyte and eosinophil infiltration in both groups of animals. Significantly, the organism burden was markedly higher in the SP-D OE animals, whereas the WT mice demonstrated little alteration in organism number over the course of infection. These results further indicate that SP-D facilitates the development of Pneumocystis infection and related lung inflammation in an immunosuppressed mouse model.

Animals↗
PubMed2005

Pneumocystis cell wall beta-glucans stimulate alveolar epithelial cell chemokine generation through nuclear factor-kappaB-dependent mechanisms.

Exuberant inflammatory responses are associated with respiratory failure during Pneumocystis pneumonia. Alveolar epithelial cells (AECs) promote Pneumocystis attachment and proliferation, but also contribute prominently to host cytokine-mediated inflammation during pneumonia. Recent investigations indicate that AECs produce macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-alpha (TNF-alpha) following challenge with Pneumocystis carinii. Nuclear factor-kappaB (NF-kappaB) is a ubiquitous transcription factor critical for regulation of proinflammatory cytokine expression. Herein, we assess rat AEC NF-kappaB responses to challenge with a P. carinii beta-glucan cell wall component (PCBG). Prominent nuclear translocation of p65 NF-kappaB was demonstrated following PCBG challenge. NF-kappaB activation was in part mediated through Protein Kinase C (PKC) signaling pathways. PCBG challenge of AECs was also shown to induce MIP-2 and TNF-alpha mRNA production, a response that was ameliorated by NF-kappaB inhibition. MIP-2 protein expression was also dramatically increased by PCBG challenge, in a manner that was significantly attenuated by both PKC and NF-kappaB inhibition. The data further demonstrate that AEC chemokine responses were not mediated by the recently described dectin-1 receptor, but instead involved participation of cell surface lactosylceramide. These data support a significant role for AECs in host responses during Pneumocystis pneumonia, and further indicate that beta-glucan induces inflammatory cytokine production through NF-kappaB-dependent mechanisms.

Animals↗
PubMed2005

Increased CD4+ T cell infiltrates in rheumatoid arthritis-associated interstitial pneumonitis compared with idiopathic interstitial pneumonitis.

OBJECTIVE: To study lymphocyte markers in rheumatoid arthritis (RA)-associated interstitial pneumonitis (IP) compared with idiopathic IP. METHODS: Paraffin-embedded lung biopsy specimens from patients with RA (n = 15) and from those without RA (n = 16), all of whom had a diagnosis of either nonspecific IP or usual IP, were studied. Tissue sections from each patient were reviewed by a pathologist, who was blinded to the clinical data. Age and pulmonary function test results were similar in RA and non-RA patients. After high-temperature antigen unmasking, sections were incubated with mouse monoclonal antibodies directed against CD3, CD4, CD8, CD16, and CD20. All slides were coded, and digital images (100x magnification) of the entire tissue area were obtained. Staining was quantified using computer-assisted image analysis. RESULTS: Staining for CD4 was more prominent in patients with RA than in the non-RA comparison group (median 9.3 cells/mm(2), interquartile range [IQR] 5.5-27.3 versus 0.6 cells/mm(2), IQR 0.2-1.9; P = 0.002). CD4+ cell counts were increased in RA patients with nonspecific IP as well as in RA patients with usual IP, with no major difference between these groups. Results were similar for quantification of CD3 (P = 0.012). There was a less striking trend toward more CD8+ cells in RA patients (P = 0.27 versus those with non-RA lung disease). CONCLUSION: IP lesions in patients with RA are characterized by an increased number of CD4+ cells, as compared with that in patients with idiopathic IP. This finding suggests that CD4+ T cells are critical for the development of pulmonary manifestations in RA, and may have implications for the treatment of RA-associated lung disease.

Aged↗
PubMed2005

Macrophage internalization of fungal beta-glucans is not necessary for initiation of related inflammatory responses.

Cell wall beta-glucans are highly conserved structural components of fungi that potently trigger inflammatory responses in an infected host. Identification of molecular mechanisms responsible for internalization and signaling of fungal beta-glucans should enhance our understanding of innate immune responses to fungi. In this study, we demonstrated that internalization of fungal beta-glucan particles requires actin polymerization but not participation of components of caveolar uptake mechanisms. Using fluorescence microscopy, we observed that uptake of 5-([4,6-dichlorotriazin-2-yl] amino)-fluorescein hydrochloride-Celite complex-labeled Saccharomyces cerevisiae beta-glucan by RAW macrophages was substantially reduced in the presence of cytochalasin D, which antagonizes actin-mediated internalization pathways, but not by treatment with nystatin, which blocks caveolar uptake. Interestingly, beta-glucan-induced NF-kappaB translocation, which is necessary for inflammatory activation, and tumor necrosis factor alpha production were both normal in the presence of cytochalasin D, despite defective internalization of beta-glucan particles following actin disruption. Dectin-1, a major beta-glucan receptor on macrophages, colocalized to phagocytic cups on macrophages and exhibited tyrosine phosphorylation after challenge with beta-glucan particles. Dectin-1 localization and other membrane markers were not affected by treatment with cytochalasin D. Furthermore, dectin-1 receptors rather than Toll-like receptor 2 receptors were shown to be necessary for both efficient internalization of beta-glucan particles and cytokine release in response to the fungal cell wall component.

Actins↗
PubMed2005

Familial idiopathic pulmonary fibrosis: clinical features and outcome.

STUDY OBJECTIVES: Familial idiopathic pulmonary fibrosis (FIPF) has been defined as idiopathic pulmonary fibrosis (IPF) occurring in two or more members of a family. The clinical course of FIPF has not been fully defined. Accordingly, the current study was undertaken to establish clinical, radiologic, and histologic features, and survival in a consecutive series of patients with FIPF. DESIGN: Retrospective analysis of clinical, radiologic, and pathologic data from a consecutive series of patients with FIPF who were seen at Mayo Medical Center. Survival in patients with FIPF was contrasted to that of previously characterized patients with nonfamilial IPF who were evaluated at our institution. SETTING: Tertiary referral medical center. PATIENTS: We screened 47 patients and family members with FIPF from 15 families who were identified between the years 1992 and 2002. We further analyzed the subgroup of FIPF patients that was composed of 27 patients from 15 families in whom the complete clinical course was monitored at our institution. MEASUREMENTS: All patients exhibited clinical features that were compatible with IPF and either compatible high-resolution CT (HRCT) scan findings or histologic evidence of usual interstitial pneumonia. Clinical data, including symptoms, physical findings, HRCT scan findings, lung function test results, biopsy results, and survival were abstracted from the clinical records. RESULTS: Compared to patients with nonfamilial IPF, patients with FIPF did not demonstrate any notable differences in clinical, radiologic, or pathologic features. We observed that the total number of affected members in a family with FIPF was a significant risk factor for earlier mortality (p = 0.0157; hazard ratio, 1.434). Overall, however, patients with FIPF had a statistically similar outcome to those patients with nonfamilial IPF. CONCLUSIONS: Although uncommon, FIPF represents a distinct syndrome, which has clinical features and patient survival rates that are similar to those of nonfamilial IPF.

Adult↗
PubMed2005

Acute respiratory failure due to pneumocystis pneumonia in patients without human immunodeficiency virus infection: outcome and associated features.

OBJECTIVE: To examine outcome and associated factors of acute respiratory failure (ARF) in non-HIV-related Pneumocystis pneumonia (PCP) in patients admitted to a medical ICU between 1995 and 2002. DESIGN: A retrospective review of medical records and an APACHE (acute physiology and chronic health evaluation) III database. SETTING: Academic tertiary medical center. RESULTS: We identified 30 patients with non-HIV-related PCP and ARF. In-hospital, 6-month, and 1-year mortality rates were 67%, 77%, and 80%, respectively. Median age was 63.5 years. Median APACHE III score on day 1 was 65.5. Median ICU and hospital lengths of stay were 13 days and 21 days, respectively. All seven patients having a pneumothorax died. All but one patient had an elevated lactate dehydrogenase level (median, 563 U/L). The diagnosis was made using BAL in 28 patients and by transbronchial biopsy in the remaining 2 patients. All patients were immunosuppressed (eight were receiving corticosteroids, seven were receiving chemotherapy, and the remainder received both). Median immunosuppressive prednisone-equivalent dose was 40 mg (median length of treatment, 4.5 months). Not a single patient received PCP prophylaxis. All but one patient required intubation and invasive positive pressure ventilation (PPV). Hospital mortality was associated with high APACHE III scores on day 1 (p = 0.05), intubation delay (p = 0.03), length of PPV (p = 0.003), and development of pneumothorax (p = 0.033). Logistic regression analysis demonstrated that association of intubation delay with hospital mortality persisted after adjusting for severity of illness (p = 0.03). CONCLUSIONS: Among patients with ARF secondary to non-HIV-related PCP, poor prognostic factors include high APACHE III scores, intubation delay, longer duration of PPV, and development of pneumothorax. None of the patients in this series received PCP prophylaxis prior to the development of pneumonia.

Acute Disease↗
PubMed2004

Pneumocystis pneumonia.

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AIDS-Related Opportunistic Infections↗
PubMed2004

Chemotherapy-induced lung disease.

The lung has significant susceptibility to injury from a variety of chemotherapeutic agents. The clinician must be familiar with classic chemotherapeutic agents with well-described pulmonary toxicities and must also be vigilant about a host of new agents that may exert adverse effects on lung function. The diagnosis of chemotherapy-associated lung disease remains an exclusionary process, particularly with respect to considering usual and atypical infections, as well as recurrence of the underlying neoplastic process in these immune compromised patients. In many instances, chemotherapy-associated lung disease may respond to withdrawal of the offending agent and to the judicious application of corticosteroid therapy.

Antibiotics, Antineoplastic↗
PubMed2004

Pneumocystis carinii cell wall biosynthesis kinase gene CBK1 is an environmentally responsive gene that complements cell wall defects of cbk-deficient yeast.

Pneumocystis species remain an important cause of life-threatening pneumonia in immunocompromised hosts, including those with AIDS. Responses of the organism to environmental cues both within the lung and elsewhere have been poorly defined. Herein, we report the identification of a cell wall biosynthesis kinase gene (CBK1) homologue in Pneumocystis carinii, isolated by differential display PCR, that is expressed optimally at physiological pH (7 to 8) as opposed to more acidic environments. Expression of Pneumocystis CBK1 was also induced by contact with lung epithelial cells and extracellular matrix. Translation of this gene revealed extensive homology to other fungal CBK1 kinases. Pneumocystis CBK1 expression was equal in the cyst and trophic life forms of the organisms. We further demonstrate that Pneumocystis CBK1 expressed in cbk1 Delta Saccharomyces cerevisiae cells restored defective cell wall separation during proliferation. Consistent with this, Pneumocystis CBK1 expression also stimulated transcription of the CTS1 chitinase in cbk1 Delta mutant yeast cells, an event necessary for cell wall separation. In addition, Pneumocystis CBK1 cDNA supported normal mating projection formation in response to alpha-factor in the cbk1 Delta yeast cells. Site-directed mutations of serine-303 and threonine-494, potential regulatory phosphorylation sites in Pneumocystis CBK1, abolished mating projection formation, indicating a role for these amino acid residues in CBK1 activity. These findings indicate that Pneumocystis CBK1 is an environmentally responsive gene that may function in signaling pathways necessary for cell growth and mating.

Amino Acid Sequence↗
PubMed2004

Imatinib mesylate inhibits the profibrogenic activity of TGF-beta and prevents bleomycin-mediated lung fibrosis.

Idiopathic pulmonary fibrosis is a progressive and fatal fibrotic disease of the lungs with unclear etiology. Prior efforts to treat idiopathic pulmonary fibrosis that focused on anti-inflammatory therapy have not proven to be effective. Recent insight suggests that the pathogenesis is mediated through foci of dysregulated fibroblasts driven by profibrotic cytokine signaling. TGF-beta and PDGF are 2 of the most potent of these cytokines. In the current study, we investigated the role of TGF-beta-induced fibrosis mediated by activation of the Abelson (Abl) tyrosine kinase. Our data indicate that fibroblasts respond to TGF-beta by stimulating c-Abl kinase activity independently of Smad2/3 phosphorylation or PDGFR activation. Moreover, inhibition of c-Abl by imatinib prevented TGF-beta-induced ECM gene expression, morphologic transformation, and cell proliferation independently of any effect on Smad signaling. Further, using a mouse model of bleomycin-induced pulmonary fibrosis, we found a significant inhibition of lung fibrosis by imatinib. Thus, Abl family members represent common targets for the modulation of profibrotic cytokine signaling.

Animals↗