(1) Host Pathogenesis. Chronic lung infections associated with nontuberculous mycobacteria (NTM) often occur in the setting of known structural lung disease such as COPD or bronchiectasis associated with cystic fibrosis. Our observational cohort study serves as the backbone for pathogenesis research focused on patients with idiopathic nodular bronchiectasis associated with NTM infection occurring predominantly in older women. We have used the overlapping features of known genetic diseases such as cystic fibrosis and Marfan syndrome to probe underlying pathophysiologic pathways and genetic risks (Ann Am Thorac Soc 2016). Collaborative work, using genetic data obtained from previous whole exome sequencing (WES) of our familial and spontaneous cohorts of idiopathic bronchiectasis associated with pulmonary NTM infections, looked at the significance of heterozygous mutations in macrophage expressed gene 1 (MPEG1) which encodes for the highly conserved pore forming protein perforin-2. Neutrophils, macrophages, and B cells from 4 patients in our cohort with these mutations had impaired killing of M. avium complex relative to healthy control cells. In addition, CRISPR mutagenesis validated the deleterious impact of these mutations on antibacterial activity suggesting that haploinsufficiency of perforin-2 may be a risk factor for NTM susceptibility (JCI Insight. 2017). Re-analysis of WES from this cohort using genome-wide variant-level linkage analysis of 4,328 independent common variants identified a significant 20-cM region on chromosome 6q12-6q16 (HLOD=3.9). Using the collapsed haplotype pattern method to perform a gene-level linkage analysis of all genes on chromosome 6, collaborators at Johns Hopkins identified the TTK protein kinase (TTK) gene as the most significant (HLOD=3.38). The TTK gene, which encodes a protein kinase essential for mitotic checkpoints in DNA damage response, and other genetic loci identified in this study may play a role in pulmonary NTM disease pathogenesis (Am J Respir Crit Care Med. 2017). These and other phenotype-genotype correlations are being further addressed by our lab in multi-site Rare Disease Clinical Research Network cross-sectional study which completed enrollment last year. (2) Epidemiology. In 2008 our lab along with extramural academic partners developed a US Bronchiectasis Research Registry that has been administered by the COPD Foundation. This Registry has enrolled over 2000 patients in the US and is being used as a source of participants in clinical trials and for epidemiologic research. An initial assessment of 1,826 bronchiectasis patients (79% women, 89% white, 60% never smokers, and mean age of 64 14 years) enrolled in the Registry from 13 academic centers compared patients with NTM (63%) to those without NTM. Patients with NTM were older, more predominantly women, had bronchiectasis diagnosed at a later age, more commonly had diffusely dilated airways and tree-in-bud abnormalities, and less commonly Pseudomonas and Staphylococcus aureus isolated than patients with NTM (Chest 2017). A collaborative study using the Registry to examine 1,250 bronchiectasis patients with immunoglobulin levels recorded at the time of Registry entry revealed a prevalence of untreated hypogammaglobulinemia of 1.4% which was slightly higher in bronchiectasis patients with NTM (1.6%) than those without (1.3%) (Ann Allergy Asthma Immunol. 2017). The Registry was queried to look at pharmacotherapy and found that inhaled steroids were used commonly, despite asthma and COPD reported in a relatively small number of patients, and relatively few patients were taking suppressive antibiotics (Chest 2017). We published two studies looking at the geographic distribution and associated characteristics of pulmonary NTM disease. The first expanded on our prior work showing an independent increased risk of NTM among Asian/Pacific Islanders and an exceedingly high prevalence of NTM in the state of Hawaii among Medicare beneficiaries. Using electronic records from Kaiser Permanente Hawaii from 2005-2013, we found the period prevalence of pulmonary NTM was highest among Japanese, Chinese, and Vietnamese patients (>300/100,000 persons) and lowest among Native Hawaiians and Other Pacific Islanders (50/100,000). There were ethnic associations by mycobacterial species with Japanese patients twice as likely as all other racial/ethnic groups to have Mycobacterium abscessus but much less likely to have Mycobacterium tuberculosis (no cases) compared with (>50/100,000) among Filipino, Korean, and Vietnamese patients. These substantial differences in the epidemiology of pulmonary NTM by race/ethnicity, suggest behavioral and biologic factors affecting disease susceptibility (Emerg Infect Dis 2017). The PremierTM Healthcare Database including nearly 6 million unique patients hospitalized over a 5-year period was used to examine the geographic distribution of mycobacterial species in the US. Of the nearly 8000 patients with positive NTM cultures (0.13%), Mycobacterium avium complex ranged from 61% to 91% of isolates and was most frequently seen in the South and Northeast regions; M. abscessus/M. chelonae ranged from 2% to 18% of isolates and was most frequently recovered in the West; and other species, including M. fortuitum and M. kansasii, ranged from 7% to 26% and were also most frequently noted in the West. These significant differences in geographic distribution of species suggests possible variation in environmental or climatic risk factors (Ann Am Thorac Soc 2017). (3) Microbial pathogenesis. Detecting NTM when it is present in the lung, distinguishing active disease from transient colonization, determining timing of treatment and assessing response to treatment are all reliant, in part on recovery and identification of NTM in sputum or other more difficult to obtain respiratory specimens. Development of serum based assays that have adequate sensitivity, specification, and meaningful quantitation that relates to disease activity has been elusive. Promising new technology developed by collaborators using antibody-labeled and energy-focusing porous discoidal silicon nanoparticles (nanodisks) and high-throughput mass spectrometry (MS) to rapidly quantify serum concentrations of mycobacteria-specific peptide fragments with enhanced sensitivity and specificity (relative to sputum and other specimen cultures) for TB may also prove useful for NTM disease (Proc Natl Acad Sci USA 2017). Work over the past year has focused on developing laboratory based models such as amoeba and zebrafish to assess genomic changes in serial clinical isolates of M. abscessus obtained from patients over the course of their disease to identify host adaptation factors of the mycobacterial that may relate to virulence and serve as targets for therapeutic intervention. (4) Drug development. The treatment of PNTM disease requires prolonged, multi-drug, poorly tolerated regimens of limited efficacy. A recent multi-site Phase 2 trial, designed and led by our research group, of a liposomal amikacin (LAI) for inhalation (Insmed, Inc) demonstrated a greater proportion of early and sustained mycobacterial culture conversion relative to placebo added to a background failing drug regimen in patients with treatment refractory M. avium or M. abscessus lung disease. Microbiologic response correlated with functional improvement as demonstrated by increased distance achieved on the 6-minute walk test (Am J Respir Crit Care Med 2017). The completion and success of the Phase 2 trial has led to increased focus on drug development and trial design for NTM disease by the FDA and increased interest among biotech and pharmaceutical companies for directing relevant drugs in development toward this indication.
Showing the most recent 10 out of 53 publications
