Evaluation of serum KL-6 levels in patients with pulmonary tuberculosis

Thinking Beyond Disease Silos: Dysregulated Genes Common in Tuberculosis and Lung Cancer as Identified by Systems Biology and Machine Learning

The traditional way of thinking about human diseases across clinical and narrow phenomics silos often masks the underlying shared molecular substrates across human diseases. One Health and planetary health fields particularly address such complexities and invite us to think across the conventional disease nosologies. For example, tuberculosis (TB) and lung cancer (LC) are major pulmonary diseases with significant planetary health implications. Despite distinct etiologies, they can coexist in a given community or patient. This is both a challenge and an opportunity for preventive medicine, diagnostics, and therapeutics innovation. This study reports a bioinformatics analysis of publicly available gene expression data, identifying overlapping dysregulated genes, downstream regulators, and pathways in TB and LC. Analysis of NCBI-GEO datasets (GSE83456 and GSE103888) unveiled differential expression of CEACAM6, MUC1, ADM, DYSF, PLOD2, and GAS6 genes in both diseases, with pathway analysis indicating association with lysine degradation pathway. Random forest, a machine-learning-based classification, achieved accuracies of 84% for distinguishing TB from controls and 83% for discriminating LC from controls using these specific genes. Additionally, potential drug targets were identified, with molecular docking confirming the binding affinity of warfarin to GAS6. Taken together, the present study speaks of the pressing need to rethink clinical diagnostic categories of human diseases and that TB and LC might potentially share molecular substrates. Going forward, planetary health and One Health scholarship are poised to cultivate new ways of thinking about diseases not only across medicine and ecology but also across traditional diagnostic conventions.

Association of Serum Krebs von den Lungen-6 (KL-6) Levels and Disease Severity in Patients Hospitalized with COVID-19

Objective

We aimed to evaluate Krebs von den Lungen-6 (KL-6) as a possible biomarker in determining disease severity in patients with moderate and severe COVID-19.

Materials and Methods

This cross-sectional study included moderate or severe COVID-19 patients; critically ill patients who were followed up in the intensive care unit were not included. KL-6 level and routine laboratory test measurements were performed on the first day of admission. The patients were also categorized according to their hyperinflammatory state.

Results

The study included 92 patients, 56 (61%) women. The National Institutes of Health (NIH) score was 2 in 52.2% of the patients and 3 in 47.8%. KL-6 levels did not significantly differ in disease severity (NIH score 2 vs. 3; p=0.15). Median KL-6 values were 52.7 (29.1) in patients with <2 COVID-19 hyperinflammatory syndrome score (cHIS) and 61.7 (32.2) in patients with cHIS ≥ 2 (p= 0.077). KL-6 values tended to be higher among the patients with lower lymphocyte counts, but the difference was not statistically significant (<1000 mm³/L p=0.006 and higher cHIS scores ≥2 p=0.07). KL-6 values were also higher in the patients with diabetes mellitus compared to the remaining patients (p =0.036).

Conclusion

There was no significant association between the serum KL-6 measured at admission and the severity of COVID-19.

Serum KL-6 levels predict clinical outcomes and are associated with MUC1 polymorphism in Japanese patients with COVID-19

BACKGROUND

Krebs von den Lungen-6 (KL-6) is a known biomarker for diagnosis and monitoring of interstitial lung diseases. However, the role of serum KL-6 and the mucin 1 (MUC1) variant (rs4072037) in COVID-19 outcomes remains to be elucidated. We aimed to evaluate the relationships among serum KL-6 levels, critical outcomes and the MUC1 variant in Japanese patients with COVID-19.

METHODS

This is a secondary analysis of a multicentre retrospective study using data from the Japan COVID-19 Task Force collected from February 2020 to November 2021, including 2226 patients with COVID-19 whose serum KL-6 levels were measured. An optimal serum KL-6 level cut-off to predict critical outcomes was determined and used for multivariable logistic regression analysis. Furthermore, the relationship among the allele dosage of the MUC1 variant, calculated from single nucleotide polymorphism typing data of genome-wide association studies using the imputation method, serum KL-6 levels and COVID-19 critical outcomes was evaluated.

RESULTS

Serum KL-6 levels were significantly higher in patients with COVID-19 with critical outcomes (511±442 U/mL) than those without (279±204 U/mL) (p<0.001). Serum KL-6 levels ≥304 U/mL independently predicted critical outcomes (adjusted OR (aOR) 3.47, 95% CI 2.44 to 4.95). Moreover, multivariable logistic regression analysis with age and sex indicated that the MUC1 variant was independently associated with increased serum KL-6 levels (aOR 0.24, 95% CI 0.28 to 0.32) but not significantly associated with critical outcomes (aOR 1.11, 95% CI 0.80 to 1.54).

CONCLUSION

Serum KL-6 levels predicted critical outcomes in Japanese patients with COVID-19 and were associated with the MUC1 variant. Therefore, serum KL-6 level is a potentially useful biomarker of critical COVID-19 outcomes.

The Potential of Lung Epithelium Specific Proteins as Biomarkers for COVID-19-Associated Lung Injury

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection was first reported in Wuhan, China, and was declared a pandemic by the World Health Organization (WHO) on 20 March 2020. The respiratory system is the major organ system affected by COVID-19. Numerous studies have found lung abnormalities in patients with COVID-19, including shortness of breath, respiratory failure, and acute respiratory distress syndrome. The identification of lung-specific biomarkers that are easily measurable in serum would be valuable for both clinicians and patients with such conditions. This review is focused on the pneumoproteins and their potential to serve as biomarkers for COVID-19-associated lung injury, including Krebs von den Lungen-6 (KL-6), surfactant proteins (SP-A, SP-B, SP-C, SP-D), and Clara cell secretory protein (CC16). The current findings indicate the aforementioned pneumoproteins may reflect the severity of pulmonary manifestations and could serve as potential biomarkers in COVID-19-related lung injury.

Serum Krebs von den Lungen-6 levels are associated with mortality and severity in patients with coronavirus disease 2019

Background

The serum Krebs von den Lungen-6 (KL-6) level is a predictive factor for acute respiratory distress syndrome (ARDS). The development of ARDS has been reported in patients with coronavirus disease 2019 (COVID-19). This study aimed to determine whether serum KL-6 levels are associated with mortality and severity in patients with COVID-19.

Methods

Among 361 Japanese patients with COVID-19 who were hospitalized at Kanagawa Cardiovascular and Respiratory Center between February 2020 and December 2020, 356 patients with data on serum KL-6 levels were enrolled and their medical records were retrospectively analyzed.

Results

A negative correlation was observed between KL-6 levels and the ratio of the arterial partial pressure of oxygen to the fraction of inspired oxygen on admission. The KL-6 levels on admission and the maximal KL-6 levels were higher in patients with severe disease (n = 60) than in those with nonsevere disease (n = 296). Furthermore, the maximal KL-6 levels were higher in nonsurvivors (n = 6) than in survivors (n = 350). In nonsurvivors, the KL-6 levels increased as the disease progressed. The optimal cutoff value of the maximal KL-6 level for discriminating between survivors and nonsurvivors was 684 U/mL, with a sensitivity of 83.3%, a specificity of 90.5%, and an area under the curve of 0.89.

Conclusions

The serum KL-6 level was associated with disease severity. Patients with KL-6 levels ≥684 U/mL had a significantly poorer outcome than those with KL-6 levels <684 U/mL.

Serum Krebs von den Lungen-6 level in the disease progression and treatment of Mycobacterium avium complex lung disease

BACKGROUND AND OBJECTIVE

The lack of useful biomarkers reflecting the disease state limits the management of Mycobacterium avium complex lung disease (MAC-LD). We clarified the associations between serum KL-6 level, disease progression and treatment response.

METHODS

Resected lung tissues from MAC-LD patients were immunostained for KL-6. We compared serum KL-6 levels between MAC-LD and healthy control or bronchiectasis patients without nontuberculous mycobacterial lung disease (NTM-LD). Serum KL-6 level was assessed in a prospective observational study at Keio University Hospital between May 2012 and May 2016. We investigated associations between serum KL-6 level and disease progression and treatment response in patients untreated for MAC-LD on registration (n = 187).

RESULTS

The KL-6⁺ alveolar type 2 cell population in the lung and serum KL-6 level were significantly higher in MAC-LD patients than in controls. Serum KL-6 level in bronchiectasis patients without NTM-LD showed no significant increase. Of the 187 patients who did not receive treatment on registration, 53 experienced disease progression requiring treatment. Multivariable Cox analysis revealed that the serum KL-6 level (aHR: 1.18, P = 0.005), positive acid-fast bacilli smear (aHR: 2.64, P = 0.001) and cavitary lesions (aHR: 3.01, P < 0.001) were significantly associated with disease progression. The change in serum KL-6 (ΔKL-6) was significantly higher in the disease progression group; it decreased post-treatment, reflecting the negative sputum culture conversion.

CONCLUSION

Serum KL-6 level is associated with disease progression and treatment response. Longitudinal assessment combined with AFB smear status and presence of cavitary lesions may aid MAC-LD management.

Incidence and etiology of chronic pulmonary infections in patients with idiopathic pulmonary fibrosis

BACKGROUND

The incidence and etiologies of chronic pulmonary infection (CPI) in patients with idiopathic pulmonary fibrosis (IPF) have been poorly investigated.

METHODS

We conducted a retrospective study of 659 patients with IPF to assess the incidence, etiologies, and risk factors of CPI development. CPI was defined if the etiology of infection was diagnosed one or more months after the onset of symptoms or upon the appearance of new shadows on pulmonary radiological images.

RESULTS

At IPF diagnosis, 36 (5.5%) patients had CPI, and 46 (7.0%) patients without CPI at IPF diagnosis developed CPI over a median follow-up period of 6.1 years. The incidence density of CPI development was 18.90 cases per 1000 person-years. Detected organisms from these 46 patients were Mycobacterium avium complex in 20 patients, other nontuberculous mycobacteria in 4, M. tuberculosis in 7, Aspergillus spp. in 22, and Nocardia sp. in one. In a multivariate Cox regression hazard model, PaO2 <70 Torr and KL-6 ≥2000 U/mL were associated with CPI development.

CONCLUSIONS

Nontuberculous mycobacteria, M. tuberculosis, and Aspergillus and Nocardia spp. were the four most frequent etiologies of CPI in patients with IPF. During follow-up of IPF, clinicians should pay attention to the development of CPI, especially in patients with PaO2 <70 Torr or KL-6 ≥2000 U/mL.

Sequential changes of serum KL-6 predict the progression of interstitial lung disease

Background

Interstitial lung disease (ILD) is a slowly progressing fatal fibrotic lung disease with a widely variable clinical course and a poor prognosis. Clinicians and patients would benefit from a highly efficient and accurate predictor for ILD. The purpose of this study was to evaluate whether blood biomarkers can predict ILD progression.

Methods

In this study, 85 patients diagnosed as having ILD at the Guangzhou Institute of Respiratory Health participated, including 20 patients with idiopathic pulmonary fibrosis (IPF). During the mean follow-up time of 12 months, every patient was examined during four or five visits in our center. Serum samples were collected at baseline, and after 1, 2, 6, and 12 months and tested for the Klebs von den Lungen-6 (KL-6) concentration. Dynamic fluctuations in this biomarker concentration were examined using a logistic regression model to see if they reflected the progression of ILD.

Results

The baseline levels of serum KL-6 in the ILD patients were significantly increased compared to healthy controls. Serum KL-6 levels were significantly elevated in patients with progression of disease (1,985.2±1,497.8 vs. 1,387.6±1,313.1 µg/mL; P<0.001). Logistic regression revealed sequential changes of KL-6 was a significant predictor of ILD progression in the next follow-up (OR, 2.569; 95% CI, 2.260-2.880; P=0.001), and that sequential changes of KL-6 were significant predictors for the progression of IPF (OR, 3.611; 95% CI, 1.048-12.442; P<0.01). Baseline concentrations were not predictive for ILD or IPF. Univariate Cox analysis showed that KL-6 was significantly associated with survival [relative risk (RR), 1.901; 95% CI, 1.294-2.793; P<0.001], along with other variables.

Conclusions

Serum levels of KL-6 were elevated in ILD patients with severe respiratory function compared to those without. The rate of poor prognosis and mortality was associated with increased biomarker concentrations. Sequential measurements of biomarkers could be valuable in disease monitoring and evaluations in clinical management.

Specific Serum Markers of IPF

Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive, fibrosing interstitial pneumonia of unknown cause. It is characterized by the progressive worsening of lung function and has a poor prognosis (median survival is approximately 3 years). However, the clinical course of disease shows considerable individual variability. Therefore, it is important to monitor the clinical course and to predict prognosis for optimal therapy. Serum biomarkers are both less invasive and reproducible diagnostic tools. Useful biomarkers for patients with IPF are strongly coveted; however, to date, there are no biomarkers that are globally known. In Japan, surfactant protein (SP)-A, SP-D, and KL-6 are commonly used as serum markers of interstitial pneumonia, including IPF, in the clinical setting, and empirical data has been accumulated over 10 years. SP-A and SP-D are hydrophilic proteins and members of the collectin family. These collectins have been shown to function as host defense lectins in the lung. KL-6 is a high molecular weight glycoprotein and now classified as a human MUC1 mucin protein. These three proteins are mainly synthesized by alveolar type II cells. The mechanisms of increase for these protein levels in sera of patients with IPF are probably a combination of a loss of epithelial integrity due to injury and an increased mass of type II cells due to hyperplasia. It has been revealed that those proteins are useful for monitoring the clinical course and predicting prognosis as well as for the diagnosis of IPF. In this review article, the molecular structures and biological functions of these biomarkers are outlined, and we discuss the clinical application of these biomarkers for patients with IPF.

Molecular classification of idiopathic pulmonary fibrosis: personalized medicine, genetics and biomarkers

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive fibrotic lung disease associated with high morbidity and poor survival. Characterized by substantial disease heterogeneity, the diagnostic considerations, clinical course and treatment response in individual patients can be variable. In the past decade, with the advent of high-throughput proteomic and genomic technologies, our understanding of the pathogenesis of IPF has greatly improved and has led to the recognition of novel treatment targets and numerous putative biomarkers. Molecular biomarkers with mechanistic plausibility are highly desired in IPF, where they have the potential to accelerate drug development, facilitate early detection in susceptible individuals, improve prognostic accuracy and inform treatment recommendations. Although the search for candidate biomarkers remains in its infancy, attractive targets such as MUC5B and MPP7 have already been validated in large cohorts and have demonstrated their potential to improve clinical predictors beyond that of routine clinical practices. The discovery and implementation of future biomarkers will face many challenges, but with strong collaborative efforts among scientists, clinicians and the industry the ultimate goal of personalized medicine may be realized.

Idiopathic pulmonary fibrosis: from epithelial injury to biomarkers--insights from the bench side

Idiopathic pulmonary fibrosis (IPF) is the most frequent fibrotic diffuse parenchymal lung disease. Its prognosis is devastating: >50% of the patients die within 3 years after diagnosis. Options for the treatment of IPF are limited and lung transplantation is the only 'curative' therapy. Currently, in the absence of validated indicators of disease progression/activity and diagnostic tools, the clinical management of IPF remains a major challenge. A better understanding of the pathogenesis of IPF is critical for the identification of new therapeutic targets as well as molecules that may serve as surrogate markers for clinically significant endpoints. The current paradigm on the mechanisms leading from a normal to a fibrotic lung postulates that chronic epithelial lesion leads to aberrant wound healing activation, which is characterized by deregulated fibroblast proliferation and activation together with an uncontrolled extracellular matrix synthesis. In this review, we shed light on the role of epithelial cell damage in the pathogenesis of fibrosis. Finally, we examine the markers of epithelial damage and their potential use as biomarkers and the future of this continuously expanding field.

Early control of Mycobacterium tuberculosis infection requires il12rb1 expression by rag1-dependent lineages

IL12RB1 is essential for human resistance to Mycobacterium tuberculosis infection. In the absence of a functional IL12RB1 allele, individuals exhibit susceptibility to disseminated, recurrent mycobacterial infections that are associated with defects in both RAG1-dependent and RAG1-independent hematopoietic lineages. Despite this well-established association, a causal relationship between M. tuberculosis susceptibility and IL12RB1 deficiency in either RAG1-dependent or RAG1-independent lineages has never been formally tested. Here, we use the low-dose aerosol model of experimental tuberculosis (TB) to both establish that infected il12rb1(-/-) mice recapitulate important aspects of TB in IL12RB1 null individuals and, more importantly, use radiation bone marrow chimeras to demonstrate that restriction of il12rb1 deficiency solely to rag1-dependent lineages (i.e., T and B cells) allows for the full transfer of the il12rb1(-/-) phenotype. We further demonstrate that the protection afforded by adaptive lymphocyte il12rb1 expression is mediated partially through ifng and that, within the same infection, il12rb1-sufficient T cells exhibit dominance over il12rb1-deficient T cells by enhancing ifng expression in the latter population. Collectively, our data establish a basic framework in which to understand how IL12RB1 promotes control of this significant human disease.

KL-6: a serological biomarker for interstitial lung disease in patients with polymyositis and dermatomyositis

OBJECTIVES

To investigate whether Caucasian patients with polymyositis (PM) or dermatomyositis (DM) and interstitial lung disease (ILD) have elevated serum levels of KL-6 compared with patients without ILD and whether KL-6 could be used as a marker for ILD activity and treatment efficacy of ILD in PM/DM.

DESIGN AND METHODS

Thirty patients with PM/DM (seven with ILD) and 17 age- and sex-matched healthy controls were included in a retrospective, cross-sectional analysis. Twelve patients were followed for longitudinal evaluation. ILD was defined as restrictive lung function impairment with radiographic signs of ILD. Serum KL-6 levels were measured using a sandwich enzyme immunoassay kit. Groups were compared by Mann-Whitney U-test.

RESULTS

PM/DM patients with ILD had significantly higher median serum KL-6 levels compared with those without ILD: 995 (range 533-2318) versus 322 (range 132-1225) U mL(-1) (P = 0.0002). Median serum levels of healthy controls were 225 (range 136-519) U mL(-1) . Serum levels of KL-6 were inversely correlated with percentages of forced expiratory volume in 1 s (FEV1), vital capacity (VC), total lung capacity (TLC), forced VC, diffusing capacity of carbon monoxide (DLco), maximal voluntary ventilation at 40 breaths min(-1) and residual volume (RV). Changes in KL-6 levels showed a significant inverse correlation with changes in percentage FEV1, TLC, DLco and RV. At a cut-off level of 549 U mL(-1) (mean ± 2.5 SD for controls), the sensitivity and specificity for diagnosis of ILD were 83% and 100%, respectively.

CONCLUSION

The level of serum KL-6 may serve as measure of ILD in patients with PM/DM and is a promising biomarker for use in clinical practice to assess clinical response to treatment.

Utility of KL-6/MUC1 in the clinical management of interstitial lung diseases

Interstitial lung diseases (ILDs) are a diverse group of pulmonary disorders characterized by various patterns of inflammation and fibrosis in the interstitium of the lung. Because injury and/or regeneration of type II pneumocytes are prominent histological features of ILDs, substances derived from type II pneumocytes have been the focus of research investigating potential biomarkers for ILD. One important biomarker for ILD is the high-molecular-weight glycoprotein, Krebs von den Lungen-6 (KL-6). KL-6 is now classified as a human MUC1 mucin protein, and regenerating type II pneumocytes are the primary cellular source of KL-6/MUC1 in the affected lungs of patients with ILD. KL-6/MUC1 is detectable in the serum of patients with ILD, and extensive investigations performed primarily in Japan have revealed that serum KL-6/MUC1 is elevated in 70-100% of patients with various ILDs, including idiopathic interstitial pneumonias, collagen vascular disease-associated interstitial pneumonia, hypersensitivity pneumonia, radiation pneumonitis, drug-induced ILDs, acute respiratory distress syndrome, pulmonary sarcoidosis, and pulmonary alveolar proteinosis. The results from these various studies have supported the utility of KL-6/MUC1 as a serum biomarker for detecting these various ILDs. Moreover, KL-6/MUC1 serum levels have been demonstrated to be useful for evaluating disease activity and predicting the clinical outcomes of various ILD types. Based on these observations, we believe that KL-6/MUC1 is currently one of the best and most reliable serum biomarkers available for ILD management.

Serum KL-6 level and the development of bronchiolitis obliterans syndrome in lung transplant recipients

KL-6 is a glycoprotein expressed by pulmonary epithelial cells, and its serum level has been used as a marker of disease activity in a variety of respiratory illnesses. Previously, we showed that KL-6 was elevated in lung transplant recipients diagnosed with BOS. In this study, we followed serum KL-6 levels and lung functions prospectively in lung transplant recipients who were within the first five-yr post-transplant and had no evidence of BOS at the time of study entry. Mean peak KL-6 levels were 596.16 ± 309.32 U/mL in the nine recipients who developed BOS compared to 352.41 ± 140.68 in 36 recipients who did not (p = 0.05). Six of the nine patients with BOS had an absolute rise in KL-6 above baseline level >200 U/mL compared to two of the 37 who had the same increase in KL-6 but did not develop BOS. Using the 200 U/mL elevation of KL-6 from baseline as a threshold for a positive test would produce a sensitivity of 67%, specificity of 95%, PPV of 75%, and a NPV of 92%. In addition, mean KL-6 levels of patients during acute rejection were not significantly elevated compared to the prerejection mean KL-6 levels (p = 0.71). We conclude that serum KL-6 is a relatively specific marker of BOS in lung transplant recipients.

Update on the diagnosis and treatment of Pneumocystis pneumonia

Pneumocystis is an opportunistic fungal pathogen that causes an often-lethal pneumonia in immunocompromised hosts. Although the organism was discovered in the early 1900s, the first cases of Pneumocystis pneumonia in humans were initially recognized in Central Europe after the Second World War in premature and malnourished infants. This unusual lung infection was known as plasma cellular interstitial pneumonitis of the newborn, and was characterized by severe respiratory distress and cyanosis with little or no fever and no pathognomic physical signs. At that time, only anecdotal cases were reported in adults and usually these patients had a baseline malignancy that led to a malnourished state. In the 1960-1970s additional cases were described in adults and children with hematological malignancies, but Pneumocystis pneumonia was still considered a rare disease. However, in the 1980s, with the onset of the HIV epidemic, Pneumocystis prevalence increased dramatically and became widely recognized as an opportunistic infection that caused potentially life-treating pneumonia in patients with impaired immunity. During this time period, prophylaxis against this organism was more generally instituted in high-risk patients. In the 1990s, with widespread use of prophylaxis and the initiation of highly active antiretroviral therapy (HAART) in the treatment of HIV-infected patients, the number of cases in this specific population decreased. However, Pneumocystis pneumonia still remains an important cause of severe pneumonia in patients with HIV infection and is still considered a principal AIDS-defining illness. Despite the decreased number of cases among HIV-infected patients over the past decade, Pneumocystis pneumonia continues to be a serious problem in immunodeficient patients with other immunosuppressive conditions. This is mostly due to increased use of immunosuppressive medications to treat patients with autoimmune diseases, following bone marrow and solid organ transplantation, and in patients with hematological and solid malignancies. Patients with hematologic disorders and solid organ and hematopoietic stem cell transplantation are currently the most vulnerable groups at risk for developing this infection. However, any patient with an impaired immunity, such as those receiving moderate doses of oral steroids for greater than 4 weeks or those receiving other immunosuppressive medications are at also at significant risk.

Clinical use of biomarkers of survival in pulmonary fibrosis

Background

Biologic predictors or biomarkers of survival in pulmonary fibrosis with a worse prognosis, more specifically in idiopathic pulmonary fibrosis would help the clinician in deciding whether or not to treat since treatment carries a potential risk for adverse events. These decisions are made easier if accurate and objective measurements of the patients' clinical status can predict the risk of progression to death.

Method

A literature review is given on different biomarkers of survival in interstitial lung disease, mainly in IPF, since this disease has the worst prognosis.

Conclusion

Serum biomarkers, and markers measured by medical imaging as HRCT, pertechnegas, DTPA en FDG-PET are not ready for clinical use to predict mortality in different forms of ILD. A baseline FVC, a change of FVC of more than 10%, and change in 6MWD are clinically helpful predictors of survival.

Differential cytokine secretion and early treatment response in patients with pulmonary tuberculosis

Biomarkers for treatment response would facilitate the testing of urgently needed new anti-tuberculous drugs. The present study investigated the profiles of 30 proinflammatory, anti-inflammatory and angiogenic factors [epidermal growth factor, eotaxin, fractalkine, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interleukin (IL)-1alpha, IL-1beta, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p40, IL-12p70, IL-13, IL-15, IL-17, interferon-gamma, interferon-inducible protein-10, Krebs von den Lungen-6, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, sCD40L, transforming growth factor-alpha, tumour necrosis factor-alpha and vascular endothelial growth factor] in the plasma of 12 healthy tuberculin skin test-positive community controls and 20 human immunodeficiency virus-negative patients with active tuberculosis (TB) and identified potential biomarkers for early treatment response. We showed differences in the level of circulating cytokines between healthy controls and TB patients, but also between fast responders and slow responders to anti-tuberculosis treatment. The general discriminant analysis based on pre-treatment and week 1 measurements identified 10 sets of three-variable models that could classify fast and slow responders with up to 83% accuracy. Overall, this study shows the potential of cytokines as indicators of anti-tuberculosis treatment response.

Clinical utility of serum beta-D-glucan and KL-6 levels in Pneumocystis jirovecii pneumonia

OBJECTIVE

New serum markers (1-->3) beta-D-glucan (beta-D-glucan) and KL-6 are reported to be useful for the clinical diagnosis of Pneumocystis jirovecii pneumonia (PCP). However, the utility of these markers in PCP with HIV infection (HIV PCP) and without HIV (non-HIV PCP) is unknown. This study was aimed to evaluate the utility of beta-D-glucan and KL-6 for the diagnosis of PCP in patients with HIV infection (HIV PCP) and non-HIV PCP.

METHODS

Retrospective study.

PATIENTS

We reviewed the medical records of consecutive 35 patients. The serum levels of beta-D-glucan and KL-6 in HIV PCP and non-HIV PCP were comparatively evaluated. We evaluated these markers in survivors and non survivors.

RESULTS

The detection rates of serum beta-D-glucan and KL-6 levels in non-HIV PCP were lower than those in HIV PCP (88% vs. 100%, 66% vs. 88%, respectively). The false positive rates of these markers in both groups were similar (12%, 37%, respectively). Oxygenation index, serum albumin, and mechanical ventilation were the variables which were significantly associated with poor outcome in the univariate analysis.

CONCLUSION

In conclusion, beta-D-glucan was a reliable diagnostic marker for PCP. However, the detection rate of beta-D-glucan and KL-6 in non-HIV PCP was lower than in HIV PCP. Neither beta-D-glucan nor KL-6 was associated with the outcome of PCP.

Increased synthesis of anti-tuberculous glycolipid immunoglobulin G (IgG) and IgA with cavity formation in patients with pulmonary tuberculosis

Tuberculous glycolipid (TBGL) antigen is a cell wall component of Mycobacterium tuberculosis and has been used for the serodiagnosis of tuberculosis. We investigated correlations between the levels of anti-TBGL antibodies and a variety of laboratory markers that are potentially influenced by tuberculous infection. Comparisons between patients with cavitary lesions and those without cavitary lesions were also made in order to determine the mechanism underlying the immune response to TBGL. Blood samples were obtained from 91 patients with both clinically and microbiologically confirmed active pulmonary tuberculosis (60 male and 31 female; mean age, 59 +/- 22 years old). Fifty-nine patients had cavitary lesions on chest X-rays. Positive correlations were found between anti-TBGL immunoglobulin G (IgG) and C-reactive protein (CRP) (r = 0.361; P < 0.001), between anti-TBGL IgA and soluble CD40 ligand (sCD40L) (r = 0.404; P < 0.005), between anti-TBGL IgG and anti-TBGL IgA (r = 0.551; P < 0.0000005), and between anti-TBGL IgM and serum IgM (r = 0.603; P < 0.00000005). The patients with cavitary lesions showed significantly higher levels of anti-TBGL IgG (P < 0.005), anti-TBGL IgA (P < 0.05), white blood cells (P < 0.01), neutrophils (P < 0.005), basophils (P < 0.0005), natural killer cells (P < 0.05), CRP (P < 0.0005), KL-6 (sialylated carbohydrate antigen KL-6) (P < 0.0005), IgA (P < 0.05), and sCD40L (P < 0.01). The observed positive correlations between the anti-TBGL antibody levels and inflammatory markers indicate the involvement of inflammatory cytokines and NKT cells in the immunopathogenesis of pulmonary tuberculosis.

Simultaneous measurements of KL-6 and SP-D in patients undergoing thoracic radiotherapy

PURPOSE

Radiation pneumonitis (RP) is a serious complication in patients undergoing thoracic radiotherapy (TRT). Serum KL-6 and SP-D have been shown to increase in several kinds of interstitial pneumonia. To evaluate their clinical usefulness in detecting RP, we serially measured them in patients receiving TRT.

MATERIALS AND METHODS

Thirty-nine patients, who received TRT for lung cancer between July 1999 and April 2004, were prospectively studied. Serum levels of KL-6 and SP-D were measured using enzyme-linked immunosorbent assays. Patients were followed up until August 2004 or their deaths.

RESULTS

During the period, RP occurred in 19 patients. In five patients with diffuse RP extended outside the radiation field, serum KL-6 levels increased, reaching more than 1,000 U/mL. Serum KL-6 levels at 40 Gy in patients who developed RP were higher than those without it (p = 0.0363, Mann-Whitney U test). In addition, serum KL-6 levels at 40 Gy in patients who developed RP were higher than those of pretreatment (p = 0.0126, Wilcoxon signed rank test). On the other hand, there were no statistical differences between sp-d at 40 Gy and those before TRT (P = 0.1165).

CONCLUSIONS

Increased KL-6 at 40 Gy compared with those before treatment in patients undergoing TRT may be of clinical significance. KL-6 proved to be a useful indicator for estimating RP, while usefulness of SP-D was not confirmed in this study.

The role of serum KL-6 measurement in common pediatric respiratory infections

KL-6 is a useful marker for interstitial pneumonia of various origins. However, the role of KL-6 in common pediatric respiratory infections is largely unknown. In order to determine whether the KL-6 level is elevated during respiratory infection, and whether KL-6 is a useful biomarker for the disease activity, we evaluated serum KL-6 levels in 132 children with various respiratory infections. KL-6 levels were significantly higher in patients with measles, influenza, or respiratory syncytial virus infection than in the control subjects. On the other hand, KL-6 levels in patients with bacterial infections such as mycoplasma, chlamydia, or pertussis were comparable to the control values. In patients with viral infections, high KL-6 levels, as defined by the mean plus 2 standard deviations of the control group, significantly correlated with low SpO(2) or days of O(2) administration, but did not correlate with C-reactive protein or white blood cell counts. These results indicate that measurement of serum KL-6 levels is helpful for the management of common pediatric respiratory infections.

KL-6 and surfactant proteins A and D in serum and bronchoalveolar lavage fluid in patients with acute eosinophilic pneumonia

OBJECT

The serum levels of KL-6, surfactant protein A (SP-A), and SP-D are useful biomarkers and prognostic factors for the activity of interstitial pneumonias. The aim of this study was to determine the clinical roles of the levels of KL-6, SP-A, and SP-D in the serum and bronchoalveolar lavage fluid (BALF) of patients with acute eosinophilic pneumonia (AEP).

MATERIALS AND METHODS

We researched 5 cases of AEP. The levels of KL-6, SP-A, and SP-D in the sera and BALF of those patients were measured by enzyme-linked immunosorbent assay.

RESULTS

KL-6 levels in BALF did not differ between AEP patients and the healthy control group, while SP-A and SP-D levels in BALF were significantly higher in the AEP patients than in the healthy control group. In sera, AEP patients had significantly higher than normal levels of SP-A and SP-D, but not of KL-6. Only in sera there was a positive correlation between SP-A and SP-D, but no apparent correlations in BALF and also between KL-6 and the others. Furthermore, the BALF levels of SP-D, but not of SP-A or KL-6, statistically correlated with the concentration of albumin in BALF. After clinical improvement, the elevated levels of serum SP-A or SP-D in AEP patients decreased until normal levels were reached within 2 months.

CONCLUSION

These results suggest that the serum or BALF levels of SP-D appear to be more sensitive than those of SP-A or KL-6 at reflecting the inflammatory response in AEP lungs.

Serum biomarkers in interstitial lung diseases

The use of biomarkers in medicine lies in their ability to detect disease and support diagnostic and therapeutic decisions. New research and novel understanding of the molecular basis of the disease reveals an abundance of exciting new biomarkers who present a promise for use in the everyday clinical practice. The past fifteen years have seen the emergence of numerous clinical applications of several new molecules as biologic markers in the research field relevant to interstitial lung diseases (translational research). The scope of this review is to summarize the current state of knowledge about serum biomarkers in interstitial lung diseases and their potential value as prognostic and diagnostic tools and present some of the future perspectives and challenges.

Use of an electronic nose to diagnose Mycobacterium bovis infection in badgers and cattle

It is estimated that more than 50 million cattle are infected with Mycobacterium bovis worldwide, resulting in severe economic losses. Current diagnosis of tuberculosis (TB) in cattle relies on tuberculin skin testing, and when combined with the slaughter of test-positive animals, it has significantly reduced the incidence of bovine TB. The failure to eradicate bovine TB in Great Britain has been attributed in part to a reservoir of the infection in badgers (Meles meles). Accurate and reliable diagnosis of infection is the cornerstone of TB control. Bacteriological diagnosis has these characteristics, but only with samples collected postmortem. Unlike significant wild animal reservoirs of M. bovis that are considered pests in other countries, such as the brushtail possum (Trichosurus vulpecula) in New Zealand, the badger and its sett are protected under United Kingdom legislation (The Protection of Badgers Act 1992). Therefore, an accurate in vitro test for badgers is needed urgently to determine the extent of the reservoir of infection cheaply and without destroying badgers. For cattle, a rapid on-farm test to complement the existing tests (the skin test and gamma interferon assay) would be highly desirable. To this end, we have investigated the potential of an electronic nose (EN) to diagnose infection of cattle or badgers with M. bovis, using a serum sample. Samples were obtained from both experimentally infected badgers and cattle, as well as naturally infected badgers. Without exception, the EN was able to discriminate infected animals from controls as early as 3 weeks after infection with M. bovis, the earliest time point examined postchallenge. The EN approach described here is a straightforward alternative to conventional methods of TB diagnosis, and it offers considerable potential as a sensitive, rapid, and cost-effective means of diagnosing M. bovis infection in cattle and badgers.

Serum KL-6 and Surfactant Proteins A and D in Pediatric Interstitial Lung Disease

OBJECTIVE

To determine if serum KL-6, surfactant protein A (SP-A), and surfactant protein D (SP-D) levels are elevated in pediatric interstitial lung disease (ILD) and associated with pulmonary function and disease severity score.

METHODS

Serum KL-6, SP-A, and SP-D levels were measured by enzyme-linked immunosorbent assay in 10 children with ILD and in 10 healthy volunteers. In the ILD group, FEV1 percentage of predicted, FVC percentage of predicted, and ILD disease severity score were measured and correlated with serum KL-6, SP-A, and SP-D levels.

RESULTS

For the ILD and control groups, respectively, mean serum KL-6 was 4,523 U/mL and 206 U/mL (p = 0.007), mean serum SP-A was 133 ng/mL and 21 ng/mL (p = 0.003), and mean serum SP-D was 304 ng/mL and 75 ng/mL (p = 0.004). There was an inverse relationship between SP-A and FVC (p = 0.05), and between SP-D and FEV1 (p = 0.05). There was a direct relationship between SP-D and ILD score (p = 0.05).

CONCLUSIONS

Serum KL-6, SP-D and SP-D levels are elevated in children with ILD. SP-A and SP-D levels appear to correlate with some measures of disease severity.

Role of KL-6 in evaluating the disease severity of rheumatoid lung disease: comparison with HRCT

OBJECTIVE

To determine the role of KL-6 (Krebs von den Lungen-6) in evaluating the disease severity of pulmonary lesions in rheumatoid arthritis (RA) compared with high resolution computed tomography (HRCT) findings.

METHODS

Fifty serum KL-6 levels and HRCT images were prospectively obtained from 47 RA patients. Eight HRCT findings were classified into five grades. Patients were also divided into two groups according to the KL-6 threshold level and HRCT findings were evaluated.

RESULTS

There was a positive correlation between the serum KL-6 level and the total CT score (r = 0.83). Reticular opacity most closely related to the serum KL-6 levels (r = 0.84). In the high KL-6 group (n = 10), the average CTscore was markedly increased (64.6 points) and severe honeycombing expanded into the whole lung. One case revealed diffuse ground glass opacity. In 12 of 40 cases in the normal KL-6 group, CT scores mildly increased compared with the other cases (over 20 points). The predominant finding of these cases could be classified into four types: (1) narrow spread honeycombing; (2) subtle fibrosis; (3) airway diseases; and (4) dense consolidation.

CONCLUSION

KL-6 is a useful marker to detect severe RA lung disease. It is also useful to distinguish non-fibrosis from fibrosis predominant cases. However, it sometimes could not detect early stage RA lung disease.

Comparative study of KL-6, surfactant protein-A, surfactant protein-D, and monocyte chemoattractant protein-1 as serum markers for interstitial lung diseases

KL-6, surfactant protein (SP)-A, SP-D, and monocyte chemoattractant protein-1 (MCP-1) are reported to be sensitive markers for interstitial lung diseases (ILD). However, each marker has been studied independently. The aim of this study was a comparative analysis of the diagnostic values of these markers. Subjects consisted of 33 patients with ILD (21 cases of idiopathic pulmonary fibrosis and 12 associated with collagen vascular diseases) and 82 control subjects (12 cases of bacterial pneumonia and 70 healthy volunteers). Receiver operating characteristic curves revealed that KL-6 was superior to the other markers. The cut-off levels for these markers that resulted in the highest diagnostic accuracy were determined to be 465 U/ml for KL-6, 48.2 ng/ml for SP-A, 116 ng/ml for SP-D, and 1080 pg/ml for MCP-1. The sensitivity, specificity, and diagnostic accuracy were 93.9%, 96.3%, and 95.7% for KL-6; 81.8%, 86.6%, and 85.2% for SP-A; 69.7%, 95.1%, and 87.8% for SP-D; and 51.5%, 92.7%, and 80.9% for MCP-1; respectively. The serum levels of SP-A and SP-D, but not of KL-6, were significantly higher in patients with bacterial pneumonia than in healthy volunteers. These results suggest that of the markers studied, KL-6 is the best serum marker for ILD.

Serum KL-6 in adult patients with polymyositis and dermatomyositis

OBJECTIVE

To determine the serum levels of KL-6, a mucin-like high-molecular-weight glycoprotein, in polymyositis/dermatomyositis (PM/DM) patients.

METHODS

Serum samples from 42 adult PM/DM patients and 38 healthy control subjects were examined using specific enzyme-linked immunosorbent assay (ELISA) systems.

RESULTS

The serum levels of KL-6 in the PM/DM patients were significantly higher than those of the healthy controls. The elevated serum KL-6 levels correlated with the presence of interstitial lung disease (ILD) and decreased percentage diffusing capacity of carbon monoxide (%DLco) in the PM/DM patients. The serum KL-6 levels inversely correlated with %DLco and percentage vital capacity. Additionally, the serum KL-6 levels were elevated in five of the seven DM patients with malignant neoplasia.

CONCLUSIONS

These results suggest that the serum KL-6 level might be a useful serum marker for ILD and internal malignancy in PM/DM.

Partitioning lung and plasma proteins: circulating surfactant proteins as biomarkers of alveolocapillary permeability

1. The alveolocapillary membrane faces an extraordinary task in partitioning the plasma and lung hypophase proteins, with a surface area approximately 50-fold that of the body and only 0.1-0.2 micron thick. 2. Lung permeability is compromised under a variety of circumstances and the delineation between physiological and pathological changes in permeability is not always clear. Although the tight junctions of the epithelium, rather than the endothelium, are regarded as the major barrier to fluid and protein flux, it is becoming apparent that the permeability of both are dynamically regulated. 3. Whereas increased permeability and the flux of plasma proteins into the alveolar compartment has dire consequences, fortuitously the flux of surfactant proteins from the airspaces into the circulation may provide a sensitive means of non-invasively monitoring the lung, with important implications for treatment modalities. 4. Surfactant proteins are unique in that they are present in the alveolar hypophase in high concentrations. They diffuse down their vast concentration gradients (approximately 1:1500-7000) into the circulation in a manner that reflects lung function and injury score. Surfactant proteins vary markedly in size (approximately 20-650 kDa) and changes in the relative amounts appear particularly diagnostic with regard to disease severity. Alveolar levels of surfactant proteins remain remarkably constant despite respiratory disease and, unlike the flux of plasma proteins into the alveolus, which may reach equilibrium in acute lung injury, the flux of surfactant proteins is unidirectional because of the concentration gradient and because they are rapidly cleared from the circulation. 5. Ultimately, the diagnostic usefulness of surfactant proteins as markers of alveolocapillary permeability will demand a sound understanding of their kinetics through the vascular compartment.

Circulating KL-6 predicts the outcome of rapidly progressive idiopathic pulmonary fibrosis

Searching for early predictive markers of the therapeutic effects of high-dose corticosteroids ("pulse therapy") on patients with rapidly progressing idiopathic pulmonary fibrosis (IPF), we evaluated 14 such patients, who had received weekly pulse therapy for at least 3 wk. Eight patients responded to the treatment and survived. However, six patients failed to respond, and all of them died within 3 mo after treatment. Serum levels of KL-6 (MUC1 mucin), neutrophil elastase (NE), and lactate dehydrogenase (LDH) were measured before, and at 1 wk and 3 wk after treatment. Levels of KL-6 decreased significantly in patients who lived, whereas KL-6 levels tended to increase in patients who died. The values of NE did not change significantly. LDH levels decreased significantly at 1 wk, and tended to decrease at 3 wk in patients who lived. However, in patients who died, they did not significantly change. At the first cycle of treatment when clinical effects may not be evident, the decrease in KL-6 but not LDH levels was significantly related to a favorable outcome, whereas their increase was related to a poor outcome. Results suggest that monitoring with KL-6 may contribute to early clinical decisions for alternative therapy in the management of rapidly progressing IPF.

Elevated serum levels of mucin-associated antigen in patients with acute respiratory distress syndrome

Increased serum levels of mucin-associated antigen have been previously demonstrated in patients with cystic fibrosis (CF) and interstitial pneumonia, and in lung-transplant recipients. The present study assessed the serum airway mucin levels in patients with acute respiratory distress syndrome (ARDS). An enzyme-linked immunosorbent assay (ELISA) method with a human-airway-mucin-specific monoclonal antibody (17Q2) was used to measure serum mucin levels in normal subjects, chronic smokers, patients with chronic bronchitis and other pulmonary diseases, patients with acute cardiogenic lung edema, and patients with ARDS. The serum mucin levels measured 9.9 +/- 0.8 ng/ml (mean +/- SEM, n = 59) in normal subjects, 12.7 +/- 1.6 ng/ml (n = 29) in chronic smokers, 21.8 +/- 1.9 ng/ml (n = 28) in patients with chronic bronchitis and other pulmonary diseases, 9.0 +/- 3.1 ng/ml (n = 5) in patients with acute cardiogenic lung edema. The serum mucin level was 53.8 +/- 6.6 ng/ml (n = 13) in patients with ARDS (p < 0.05, as compared with the four other groups). Serial measurements of serum mucin levels were obtained in patients with ARDS. Statistical analysis showed an inverse correlation of serial measurements of serum mucin with static respiratory-system compliance (p = 0.021), an inverse correlation of sequential serum mucin levels and log(Pa(O2)/Fl(O2)) (p = 0.016), and a positive correlation of sequential serum mucin levels and lung injury score (LIS) (p = 0.019). Gel-filtration analysis showed that mucin-associated antigens in ARDS sera were polydispersed and smaller than the antigens in normal sera. This study indicates that an increasing amount of degraded mucin occurs in patients with ARDS.

KL-6, a human MUC1 mucin, is chemotactic for human fibroblasts

KL-6 in serum and bronchoalveolar lavage fluid has been reported to be a sensitive marker indicating the activity of fibrosing lung diseases. The molecule is clustered in MUC1 mucin according to the findings of immunohistochemical and cytometric studies. To elucidate the pathogenic role of KL-6 in fibrosing lung disease, we characterized its biochemical properties and examined whether purified KL-6 is chemotactic for human fibroblasts in vitro using modified Boyden chambers. Biochemical properties of purified KL-6 were similar to those of other MUC1 mucins previously reported. KL-6 promoted the migration of 5 of 5 human lung fibroblasts and 3 of 4 human skin fibroblasts. Checkerboard analysis revealed that KL-6 was chemotactic as well as chemokinetic. Though platelet-derived growth factor, fibroblast growth factor, or fibronectin were also chemotactic for fibroblasts in the experimental system, only fibronectin augmented KL-6-induced chemotaxis. These observations indicate that KL-6 is one of the chemotactic factors for most fibroblasts and that the increased KL-6 in the epithelial lining fluid in small airways may cause the intra-alveolar fibrosis in fibrosing lung diseases.

Pulmonary epithelial cell injury and alveolar-capillary permeability in berylliosis

Inhaled beryllium induces specific sensitization and nonspecific effects leading to chronic beryllium disease (CBD). It is not known whether beryllium induces epithelial cell injury and increases alveolar-capillary leak. We hypothesize that lung injury is an early event in this disease and that markers of lung injury reflect severity of CBD. We measured serum and bronchoalveolar lavage fluid (BALF) KL-6 level, a marker of epithelial cell injury, and BALF/serum albumin, a marker of alveolar-capillary permeability, in 26 patients with CBD, 15 beryllium-sensitized subjects without disease (BeS), and 32 control subjects (Ctrl). We examined the association of these markers, BAL cellularity, pulmonary function, gas exchange, serum angiotensin-converting enzyme, chest radiograph, the effects of glucocorticoid therapy, and clinical course. BALF/serum albumin and serum KL-6 increased in CBD and were discriminative markers for CBD. BALF KL-6 and BALF/serum albumin reflected mainly lung cellular and granulomatous inflammation. Serum KL-6, like and BALF KL-6, was associated with permeability change and reflected functional and radiologic abnormalities. Serum KL-6 detected early lung injury in BeS. Epithelial injury and permeability changes occur early in CBD, indicating disease severity. Monitoring of these events with serum KL-6 may be useful for management of CBD.