Combined use of Quantiferon and HBHA-based IGRA supports tuberculosis diagnosis and therapy management in children.

OBJECTIVES: Interferon-γ release assays (IGRA) are designed for diagnosis of tuberculosis (TB) infection, and do not discriminate latent TB infection (LTBI) from active TB. Heparin-binding hemagglutinin antigen (HBHA) emerged as a promising antigen for TB diagnosis when used in IGRA format. Aim of this study was to prospectively evaluate the performance of an HBHA-based IGRA to support TB diagnosis and TB therapy monitoring in children with TB infection or active TB disease. METHODS: Following clinical, microbiological and radiological assessment, children (0-14 years old) were tested by the QuantiFERON TB-Gold In tube (QFT) assay and an aliquot of whole-blood was stimulated with HBHA and IFNγ evaluated only in QFT-positive subjects. RESULTS: Among the 550 children tested, 486 (88.4%) scored negative and 64 (11.6%) positive. None of the QFT-negative had active TB. Among the QFT-positive, 45 were with LTBI and 19 active TB. HBHA-IGRA scored positive in 41/45 children (91.1%) with LTBI and in 6/19 active TB children (31.6%) at diagnosis (p = 0.001); remarkably, 5 of these 6 children with active TB scoring HBHA-positive were asymptomatic. Moreover, following TB-specific therapy, most of the non-HBHA-responding children, gained an HBHA-positive response. CONCLUSIONS: HBHA-based IGRA is a useful support in TB diagnosis and TB-therapy monitoring in children.

Accuracy of QuantiFERON-TB Gold Test for Tuberculosis Diagnosis in Children.

OBJECTIVES: To evaluate the accuracy of the QuantiFERON-TB Gold assay (QFT-IT) in children with suspected active or latent TB infection (LTBI). METHODS: A retrospective study was conducted on 621 children (0-14 years old) evaluated for TB infection or disease. Following clinical assessment, children were tested with the QFT-IT assay. RESULTS: Among the 140 active TB suspects, we identified 19 cases of active disease. The overall sensitivity for active TB was 87.5%, ranging from 62.5% in children 25-36 months old to 100% in children older than 49 months. The overall specificity for active TB was 93.6%. Among the 481 children tested for LTBI screening, 38 scored positive and all but 2 had at least one risk factor for TB infection. Among the 26 children with indeterminate results, bacterial, viral or fungal pneumonia were later diagnosed in 11 (42.3%) cases and non-TB related extra-pulmonary infections in 12 (46.1%). CONCLUSIONS: Our results indicate that the children's response to QFT-IT associates to active TB and risk factors for LTBI. Moreover, we show that mitogen response is also found in children of 1 year of age, providing support for QFT-IT use also in young children.

Functional dissection of protein domains involved in the immunomodulatory properties of PE_PGRS33 of Mycobacterium tuberculosis.

PE_PGRSs are a large family of proteins identified in Mycobacterium tuberculosis complex and in few other pathogenic mycobacteria. The PE domain of PE_PGRS33 mediates localization of the protein on the mycobacterial cell surface, where the PGRS domain is available to interact with host components. In this study, PE_PGRS33 and its functional deletion mutants were expressed in M. smegmatis, and in vitro and in vivo assays were used to dissect the protein domains involved in the immunomodulatory properties of the protein. We demonstrate that PE_PGRS33-mediated secretion of TNF-α by macrophages occurs by extracellular interaction with TLR2. Our results also show that while the PGRS domain of the protein is required for triggering TNF-α secretion, mutation in the PE domain affects the pro-inflammatory properties of the protein. These results indicate that PE_PGRS33 is a protein with immunomodulatory activity and that protein stability and localization on the mycobacterial surface can affect these properties.

A twenty-year retrospective study of pediatric tuberculosis in two tertiary hospitals in Rome.

BACKGROUND: Tuberculosis (TB) is among the top 10 causes of child death worldwide. Nevertheless, childhood disease has been neglected by tuberculosis control programs. METHODS: This was a retrospective study of patients < 16 years of age diagnosed with active TB in 2 tertiary hospitals in Rome (Italy), between 1990 and 2009. RESULTS: Two hundred fourteen cases of active tuberculosis were identified (132 definite, 82 probable). Pulmonary involvement was the most common form (75.5%), followed by lymphadenopathy (15.4%) and central nervous system TB (11%). Fever (51.86%) and cough (40%) were the most common presenting symptoms. A total of 23.4% of children were asymptomatic on admission. Sensitivities of the tuberculin skin test and the quantiferon test were 93.4% and 97%, respectively. Both tests performed in 52 children agreed in 49 cases (94%). Sensitivities for culture, Ziehl-Neelsen staining and polymerase chain reaction were 58%, 25% and 66.3%, respectively. The adult source case was identified in 28% of cases. History of contact with a patient with active TB was associated with pulmonary TB (P = 0.0014), whereas negative history of contact was associated with lymph node (P = 0.0064) and central nervous system TB (P = 0.05). CONCLUSIONS: Our study emphasizes the difficulty in managing children with suspected TB, because the absence of constitutional symptoms cannot exclude TB, and bacteriologic confirmation is the exception. Immunologic diagnosis can be a valuable tool to identify TB-infected children because the quantiferon test showed high sensitivity in all age groups. This is of primary importance because early identification of children with latent tuberculous infection and appropriate chemoprophylaxis represent, to date, the most important tool to reduce the burden of TB.