Laurence Huang

Comparison of the Respiratory Microbiome in Healthy Nonsmokers and Smokers

RATIONALE Results from 16S rDNA-encoding gene sequence-based, culture-independent techniques have led to conflicting conclusions about the composition of the lower respiratory tract microbiome. OBJECTIVES To compare the microbiome of the upper and lower respiratory tract in healthy HIV-uninfected nonsmokers and smokers in a multicenter cohort. METHODS Participants were nonsmokers and smokers without significant comorbidities. Oral washes and bronchoscopic alveolar lavages were collected in a standardized manner. Sequence analysis of bacterial 16S rRNA-encoding genes was performed, and the neutral model in community ecology was used to identify bacteria that were the most plausible members of a lung microbiome. MEASUREMENTS AND MAIN RESULTS Sixty-four participants were enrolled. Most bacteria identified in the lung were also in the mouth, but specific bacteria such as Enterobacteriaceae, Haemophilus, Methylobacterium, and Ralstonia species were disproportionally represented in the lungs compared with values predicted by the neutral model. Tropheryma was also in the lung, but not the mouth. Mouth communities differed between nonsmokers and smokers in species such as Porphyromonas, Neisseria, and Gemella, but lung bacterial populations did not. CONCLUSIONS This study is the largest to examine composition of the lower respiratory tract microbiome in healthy individuals and the first to use the neutral model to compare the lung to the mouth. Specific bacteria appear in significantly higher abundance in the lungs than would be expected if they originated from the mouth, demonstrating that the lung microbiome does not derive entirely from the mouth. The mouth microbiome differs in nonsmokers and smokers, but lung communities were not significantly altered by smoking.

HIV Infection and Risk for Incident Pulmonary Diseases in the Combination Antiretroviral Therapy Era

RATIONALE In aging HIV-infected populations comorbid diseases are important determinants of morbidity and mortality. Pulmonary diseases have not been systematically assessed in the combination antiretroviral therapy (ART) era. OBJECTIVES To determine the incidence of pulmonary diseases in HIV-infected persons compared with HIV-uninfected persons. METHODS We analyzed data from the Veterans Aging Cohort Study Virtual Cohort, consisting of 33,420 HIV-infected veterans and 66,840 age, sex, race and ethnicity, and site-matched HIV-uninfected veterans. Using Poisson regression, incidence rates and adjusted incidence rate ratios were calculated to determine the association of HIV with pulmonary disease. The Virtual Cohort was merged with the 1999 Veterans Large Health Survey to adjust for self-reported smoking in a nested sample (14%). MEASUREMENTS AND MAIN RESULTS Incident chronic obstructive pulmonary disease, lung cancer, pulmonary hypertension, and pulmonary fibrosis, as well as pulmonary infections, were significantly more likely among HIV-infected patients compared with uninfected patients in adjusted analyses, although rates of asthma did not differ by HIV status. Bacterial pneumonia and chronic obstructive pulmonary disease were the two most common incident pulmonary diseases, whereas opportunistic pneumonias were less common. Absolute rates of most pulmonary diseases increased with age, although the relative differences between those with and without HIV infection were greatest in younger persons. Chronic obstructive pulmonary disease and asthma, as well as pulmonary infections, were less likely in those with lower HIV RNA levels and use of ART at baseline. CONCLUSIONS Pulmonary diseases among HIV-infected patients receiving care within the Veterans Affairs Healthcare System in the combination ART era reflect a substantial burden of non-AIDS-defining and chronic conditions, many of which are associated with aging.

Epidemiology and Clinical Significance of Pneumocystis Colonization

Pneumocystis pneumonia has long been recognized as a cause of morbidity and mortality in immunocompromised populations, particularly those with HIV infection. Pneumocystis colonization-that is, detection of the organism or its DNA, without signs or symptoms of pneumonia-has recently been described, and accumulating evidence suggests that it may be an important clinical phenomenon. Sensitive molecular techniques such as polymerase chain reaction are frequently used to identify Pneumocystis colonization. Low levels of Pneumocystis in the lungs may stimulate pulmonary inflammation and may play a role in the development of lung diseases such as chronic obstructive pulmonary disease. In this review, we discuss evidence for the occurrence of Pneumocystis colonization in animals as well as the epidemiology and risk factors for Pneumocystis colonization in various human populations. We also evaluate the clinical significance of Pneumocystis colonization and its relationship to lung disease.

Interferon-gamma release assays for the diagnosis of latent tuberculosis infection in HIV-infected individuals: a systematic review and meta-analysis.

Objective: To determine whether interferon-gamma release assays (IGRAs) improve the identification of HIV-infected individuals who could benefit from latent tuberculosis infection therapy. Design: Systematic review and meta-analysis. Methods: We searched multiple databases through May 2010 for studies evaluating the performance of the newest commercial IGRAs (QuantiFERON-TB Gold In-Tube [QFT-GIT] and T-SPOT.TB [TSPOT]) in HIV-infected individuals. We assessed the quality of all studies included in the review, summarized results in prespecified subgroups using forest plots, and where appropriate, calculated pooled estimates using random effects models. Results: The search identified 37 studies that included 5736 HIV-infected individuals. In three longitudinal studies, the risk of active tuberculosis was higher in HIV-infected individuals with positive versus negative IGRA results. However, the risk difference was not statistically significant in the two studies that reported IGRA results according to manufacturer-recommended criteria. In persons with active tuberculosis (a surrogate reference standard for latent tuberculosis infection), pooled sensitivity estimates were heterogeneous but higher for TSPOT (72%; 95% confidence interval [CI], 62-81%) than for QFT-GIT (61%; 95% CI, 47-75%) in low-/middle-income countries. However, neither IGRA was consistently more sensitive than the tuberculin skin test in head-to-head comparisons. Although TSPOT appeared to be less affected by immunosuppression than QFT-GIT and the tuberculin skin test, overall, differences among the three tests were small or inconclusive. Conclusions: Current evidence suggests that IGRAs perform similarly to the tuberculin skin test at identifying HIV-infected individuals with latent tuberculosis infection. Given that both tests have modest predictive value and suboptimal sensitivity, the decision to use either test should be based on country guidelines and resource and logistic considerations.

Interferon-γ Release Assays for Active Pulmonary Tuberculosis Diagnosis in Adults in Low- and Middle-Income Countries: Systematic Review and Meta-analysis

BACKGROUND The diagnostic value of interferon-γ release assays (IGRAs) for active tuberculosis in low- and middle-income countries is unclear. METHODS We searched multiple databases for studies published through May 2010 that evaluated the diagnostic performance of QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB (T-SPOT) among adults with suspected active pulmonary tuberculosis or patients with confirmed cases in low- and middle-income countries. We summarized test performance characteristics with use of forest plots, hierarchical summary receiver operating characteristic (HSROC) curves, and bivariate random effects models. RESULTS Our search identified 789 citations, of which 27 observational studies (17 QFT-GIT and 10 T-SPOT) evaluating 590 human immunodeficiency virus (HIV)-uninfected and 844 HIV-infected individuals met inclusion criteria. Among HIV-infected patients, HSROC/bivariate pooled sensitivity estimates (highest quality data) were 76% (95% confidence interval [CI], 45%-92%) for T-SPOT and 60% (95% CI, 34%-82%) for QFT-GIT. HSROC/bivariate pooled specificity estimates were low for both IGRA platforms among all participants (T-SPOT, 61% [95% CI, 40%-79%]; QFT-GIT, 52% [95% CI, 41%-62%]) and among HIV-infected persons (T-SPOT, 52% [95% CI, 40%-63%]; QFT-GIT, 50% [95% CI, 35%-65%]). There was no consistent evidence that either IGRA was more sensitive than the tuberculin skin test for active tuberculosis diagnosis. CONCLUSIONS In low- and middle-income countries, neither the tuberculin skin test nor IGRAs have value for active tuberculosis diagnosis in adults, especially in the context of HIV coinfection.

Psychological stress and the subsequent appearance of new brain MRI lesions in MS

Objective: To examine the relationship between stressful life events and psychological distress, and the subsequent development of gadolinium-enhancing (Gd+) brain lesions. Background: It has long been speculated that stressful life events and psychological distress are associated with disease exacerbation in MS. This is the first prospective longitudinal study of the relationship between stressful life events, psychological distress, and disease activity as measured by Gd+ brain MRI. Methods: Thirty-six patients (mean age, 44.4 years; 22 women, 14 men) with relapsing forms of MS were assessed once every 4 weeks for 28 to 100 weeks. Assessments included Gd+ MRI, the Social Readjustment Rating Scale (SRRS), the Hassles Scale, and the Profile of Mood States. The SRRS was altered in the following manner: 1) three items that confounded with MS were eliminated, 2) endorsed items were rated for intensity, and 3) the scale was divided into three subscales: major negative events, conflict and disruption in routine, and positive life events. Data were analyzed using mixed-effects logistic regression to account for intrasubject correlations. Stress and distress measures were used to predict concurrent and future MRI activity. Results: For the total sample of patients, increased conflict and disruption in routine was followed by increased odds of developing new Gd+ brain lesions 8 weeks later (odds ratio, 1.64; p = 0.00083). There was no strong evidence of a relationship between psychological stress or distress and clinical exacerbation. Conclusions: These data provide support for the notion that conflict and disruption in routine are related to subsequent disease activity in MS. However, this relationship is not sufficiently robust to predict clinical exacerbations reliably in individual patients.

Sulfa or sulfone prophylaxis and geographic region predict mutations in the Pneumocystis carinii dihydropteroate synthase gene.

To determine factors associated with mutations in the Pneumocystis carinii dihydropteroate synthase (DHPS) gene, a prospective study of human immunodeficiency virus (HIV)-infected patients with confirmed P. carinii pneumonia was conducted in Atlanta, Seattle, and San Francisco. Clinical information was obtained from patient interview and chart abstraction. DHPS genotype was determined from DNA sequencing. Overall, 76 (68.5%) of 111 patients had a mutant DHPS genotype, including 22 (81.5%) of 27 patients from San Francisco. In multivariate analysis, sulfa or sulfone prophylaxis and study site were independent predictors of a mutant genotype. Fourteen (53.8%) of 26 patients who were newly diagnosed with HIV infection and had never taken prophylaxis had a mutant genotype. The significance of geographic location as a risk factor for mutant genotype and the high proportion of mutant genotypes among persons never prescribed prophylaxis, including those newly diagnosed with HIV infection, provide indirect evidence that these mutations are transmitted from person to person either directly or through a common environmental source.

Effect of mutations in Pneumocystis carinii dihydropteroate synthase gene on outcome of P carinii pneumonia in patients with HIV-1: a prospective study

BACKGROUND Investigators have reported that patients infected with Pneumocystis carinii containing mutations in the DHPS (dihydropteroate synthase) gene have a worse outcome than those infected with P carinii containing wild-type DHPS. We investigated patients with HIV-1 infection and P carinii pneumonia to determine if DHPS mutations were associated with poor outcomes in these patients. METHODS We compared presence of mutations at the DHPS locus with survival and response of patients to co-trimoxazole or other drugs. FINDINGS For patients initially given co-trimoxazole, nine (14%) of 66 with DHPS mutant died, compared with nine (25%) of 36 with wild type (risk ratio50.55 [95% CI=0.24-1.25]; p=0.15). Ten (15%) of 66 patients with a DHPS mutant did not respond to treatment, compared with 13 (36%) of 36 patients with the wild type (0.42 [0.20-0.86]; p=0.02). For patients aged 40 years or older, four (14%) of 29 with the mutant and nine (56%) of 16 with the wild type died (0.25 [0.09-0.67]; p=0.005). INTERPRETATION These results, by contrast with those of previous studies, suggest that patients with wild-type P carinii do not have a better outcome than patients with the mutant when given co-trimoxazole. Our results suggest that presence of a DHPS mutation should be only one of several criteria guiding the choice of initial drug treatment of P carinii pneumonia in patients with HIV-1 infection.

Dihydropteroate synthase gene mutations in Pneumocystis and sulfa resistance

We review studies of dihydropteroate synthase gene mutations in Pneumocystis jirovecii and summarize the evidence for resistance to sulfamethoxazole and dapsone.

Respiratory symptoms and airway obstruction in HIV-infected subjects in the HAART era.

Background Prevalence and risk factors for respiratory symptoms and airway obstruction in HIV-infected subjects in the era of highly active antiretroviral therapy (HAART) are unknown. We evaluated respiratory symptoms and measured airway obstruction to identify the impact of HAART and other risk factors on respiratory symptoms and pulmonary function. Methodology/Principal Findings Two hundred thirty-four HIV-infected adults without acute respiratory symptoms were recruited from an HIV clinic. All subjects were interviewed and performed spirometry. Multivariate linear and logistic regressions were performed to determine predictors of respiratory symptoms, forced expiratory volume in one second (FEV1) percent predicted, and FEV1/forced vital capacity (FEV1/FVC). Thirty-one percent of subjects reported at least one respiratory symptom. Smoking status (current or former versus never) (odds ratio [OR] = 2.7, 95% confidence interval [CI] = 1.41–5.22, p = 0.003), higher log plasma HIV viral levels (OR = 1.12, 95%CI = 1.02–1.24, p = 0.02), and lower FEV1/FVC (OR = 1.06 for every 0.01 decrease in FEV1/FVC, 95%CI = 1.02–1.14, p = 0.001) were independent predictors of respiratory symptoms. Age (p = 0.04), pack-year smoking history (p<0.001), previous bacterial pneumonia (p = 0.007), and HAART use (p = 0.04) were independent predictors of decreased FEV1/FVC. Conclusions/Significance Respiratory symptoms remain common in HIV-infected subjects, especially in those with a smoking history. Subjects who were older, had a greater pack-year history of smoking, or previous bacterial pneumonia had lower FEV1/FVC ratios. Interestingly, use of HAART was independently associated with a decreased FEV1/FVC, possibly secondary to an immune response to subclinical infections, increased autoimmunity, or other factors associated with HAART use.