Cytokine Profile of T lymphocytes from Peripheral Blood and Bronchoalveolar Lavage Fluid in Patients with Active Pulmonary Tuberculosis

Role of flexible bronchoscopy in patients with sputum-negative pulmonary tuberculosis

BACKGROUND

Pulmonary tuberculosis is one of the major health concerns in the developing countries. Isolation of acid-fast bacilli (AFB) or tuberculosis bacilli from the sputum is required for the diagnosis. A proportion of suspected pulmonary tuberculosis (PTB) cases either clinically or radiologically will not produce sputum or will have sputum negative for AFB. These subsets of cases pose a diagnostic challenge to the treating clinicians. In this study, we present our experience and outcomes with flexible bronchoscopy in patients with sputum-negative pulmonary tuberculosis.

MATERIALS AND METHODS

This was a prospective cross-sectional study, conducted at SDS Tuberculosis research Centre and Rajiv Gandhi Institute of Chest Diseases, Bengaluru, India, from 2010 to 2016. A total of 1095 flexible bronchoscopies were done during this period, out of which 180 were patients with sputum negative for AFB, but were strongly suspected to have pulmonary tuberculosis on clinical examination or radiologically. There were 106 males and 74 females. The age ranged between 11 and 68 years. All patients underwent complete evaluation of the tracheobronchial tree followed by bronchoalveolar lavage (BAL). Microbiological studies used were Ziehl-Neelsen (ZN) staining and culture in Lowenstein-Jensen (LJ) medium. Mucosal lesions suspected of tuberculosis were subjected to biopsy and histopathological confirmation. The data was analyzed.

RESULTS

Out of 180 patients, 106 (58.88%) cases had positive AFB smear on BAL. The culture confirmed the diagnosis of pulmonary tuberculosis in 120 cases (66.66%). Histopathology showed caseous granuloma in 38 (42.22%) cases, nonspecific inflammation in 40 (44.44%) cases, and malignancy in 12 (13.33%) cases out of 90 cases, who underwent biopsy. There were no post-procedural complications.

CONCLUSION

Bronchoscopy is the useful tool in the diagnosis of pulmonary tuberculosis in patients with sputum-negative pulmonary tuberculosis. It is also helpful in differentiating conditions having the clinical picture that mimics pulmonary tuberculosis.

Pulmonary tuberculosis in Asian elephants (Elephas maximus): histologic lesions with correlation to local immune responses

Although Mycobacterium tuberculosis infection is an important health concern for Asian elephants (Elephas maximus), no studies have evaluated the associated local immune responses or histologic lesions. In primates including humans, latent tuberculosis is distinguished by well-organized granulomas with TH1 cytokine expression, whereas active disease is characterized by poorly organized inflammation and local imbalance in TH1/TH2 cytokines. This study examined archival, formalin-fixed, paraffin-embedded lung samples from 5 tuberculosis-negative and 9 tuberculosis-positive Asian elephants. Lesions were assessed by light microscopy, and lymphoid infiltrates were characterized by CD3 and CD20 immunolabeling. Expression of TH1 (interferon [IFN]-γ, tumor necrosis factor [TNF]-α) and TH2 (interleukin [IL]-4, IL-10, transforming growth factor [TGF]-β) cytokines was determined using in situ hybridization. In 6 of 9 samples, inflammation was similar to the pattern of primate active disease with low to moderate numbers of lymphocytes, most of which were CD20 positive. In 1 sample, inflammation was most similar to latent tuberculosis in primates with numerous CD3-positive lymphocytes. Expression of IFN-γ was detected in 3 of 8 tuberculosis-positive samples. Expression of TNF-α was detected in 3 of 8 positive samples, including the one with latent morphology. Low-level expression of IL-4 was present in 4 of 8 positive samples. Only single positive samples displayed expression of IL-10 and TGF-β. Tuberculosis-negative samples generally lacked cytokine expression. Results showed heterogeneity in lesions of elephant tuberculosis similar to those of latent and active disease in primates, with variable expression of both TH1 and TH2 cytokines.

Harnessing local and systemic immunity for vaccines against tuberculosis

The lung is the portal of entry for Mycobacterium tuberculosis (Mtb) and animal experimental evidence indicates that local immune defense mechanisms are crucial for protective immunity. Immunization via the lower respiratory tract efficiently induces a dividing, activated, antigen-dependent, lung-resident, memory T-cell population, which is partly recoverable by bronchoalveolar lavage. These cells can inhibit the growth of Mtb in the lungs immediately after infection. Delivery of appropriate signals to the lung innate immune system is critical for induction of effective local immunity. In contrast after parenteral immunization, antigen-specific cells may be found in lung tissue but few are recoverable by lavage and inhibition of mycobacterial growth is delayed. Harnessing both local and systemic immunity can provide highly effective protection in animal models and the evidence suggests that taken in aggregate, multiple animal models may predict the success of novel vaccine strategies in humans.

Use of a T cell interferon gamma release assay in the investigation for suspected active tuberculosis in a low prevalence area

Background

In settings with low background prevalence of tuberculosis (TB) infection, interferon-γ release assays (IGRA) could be useful for diagnosing active TB. This study aims to evaluate the performance of QuantiFERON^®-TB Gold (QFT-G) in the investigation for suspected active TB, with particular attention to patients originating in high-incidence countries. Furthermore, factors associated with QFT-G results in patients with active TB were assessed.

Methods

From patients investigated for clinically suspected active TB, blood was obtained for QFT-G testing, in addition to routine investigations. Positive (PPV) and negative (NPV) predictive values for QFT-G were calculated, comparing patients with confirmed TB and those with other final diagnoses. QFT-G results in TB patients originating from countries with intermediate or high TB incidence were compared with QFT-G results from a control group of recently arrived asymptomatic immigrants from high-incidence countries. Factors associated with QFT-G outcome in patients with confirmed TB were assessed.

Results

Among 141 patients, 41/70 (58.6%) with confirmed TB had a positive QFT-G test, compared to 16/71 (22.6%) patients with other final diagnoses, resulting in overall PPV of 71.9% and NPV of 67.6%. For patients with pulmonary disease, PPV and NPV were 61.1% and 67.7%, respectively, and 90.5% and 66.7% for subjects with extrapulmonary manifestations. Comparing patients from high-incidence countries with controls yielded a PPV for active TB of 76.7%, and a NPV of 82.7%. Patients with confirmed TB and positive QFT-G results were characterized by a lower median peripheral white blood cell count (5.9 × 10⁹/L vs. 8.8 × 10⁹/L; P < 0.001) and a higher median body mass index (22.7 vs. 20.7; P = 0.043) as compared to QFT-G-negative TB patients.

Conclusion

The overall PPV and NPV of QFT-G for identifying active TB were unsatisfactory, especially for pulmonary disease. Thus, the usefulness of QFT-G for this purpose is questionable. However, a high PPV was observed for extrapulmonary TB and QFT-G might be considered in the diagnostic process in this situation. The PPV and NPV for identifying active TB among persons originating from regions with high-and intermediate TB incidence was similar to that observed in subjects originating in the low-incidence region.