Rapid diagnosis of Mycobacterium tuberculosis infection in children using interferon-gamma release assays (IGRAs).

Diagnosis of tuberculosis (TB) in children by the tuberculin skin test (TST) poses a diagnostic challenge for physicians due to its low specificity and cross-reactivity with nontuberculous mycobacteria and bacille Calmette-Guerin (BCG). Although interferon-gamma release assays (IGRAs) have been shown as novel TST alternatives for diagnosis of latent TB infection (LTBI) in adults, their effectiveness is less clear in children. The present study examined QuantiFERON-TB Gold (QFT-G) responses and IFN-gamma production capacity of TST-positive children, younger children ≤5 years. A total of 517 children of whom 434 were TST positive ranging in age from 1 month to 18 years were evaluated by the QFT-G. Of the 517 children, 434 (84%) were TST positive, 25 (5.8%) of whom were found to be QFT-G positive and 25 (5.4%) with an indeterminate response. Of the 517 children, 355 (68.7%) were previously BCG immunized and 310/355 (87.3%) were TST positive including 18/27 (66.7%) QFT-positive children. Adequate IFN-gamma production by purified TB peptides or mitogen was observed in 92.8% of children, 29.6% of whom were <5 years. This study shows that the QFT-G assay is useful for diagnosis of LTBI. The finding of 5.8% positive QFT-G in 434 TST-positive children underscores the superior specificity of the QFT-G than the TST and its greater cost effectiveness in preventing unnecessary and potentially toxic treatment in children. The study suggests that the majority of positive TST in children represent false-positive reactions and supports the use of IGRAs for diagnosis of LTBI in children, including those <5 years of age.

Gastrointestinal immunopathology and food allergy.

OBJECTIVE: To review the current data that support the pivotal function of the gastrointestinal immune system in health and disease and its critical role in the pathogenesis of a wide variety of clinical disorders associated with food allergy (FA). DATA SOURCES: Internet-based literature search and our own data. STUDY SELECTION: The studies included in this review were selected based on the expert opinion of the authors. RESULTS: In contrast to the beneficial expressions of gastrointestinal-associated lymphoid tissue, which are seen with relevance to newer methods of delivery of vaccines directly applied to the gastrointestinal mucosal surfaces (eg, oral poliovirus, rotavirus, Salmonella typhi vaccines), the adverse consequences of a mucosal immune response gone astray are evidenced in many diseases such as FA. A classification of clinical disorders associated with FA based on classic mechanisms of immunologic injury is presented, which includes the following: (1) IgE-mediated, (2) non-IgE-mediated, and (3) mixed IgE- and non-IgE-mediated disorders. Our study of immunologic disturbance in patients with non-IgE FA revealed a pattern of increased CD4+ and decreased TH1 cell counts in peripheral blood mononuclear cells in contrast to patients with celiac disease, where a pattern of increased CD8+ and TH1 cell counts in peripheral blood mononuclear cells and increased CD8+ cell counts was seen. CONCLUSIONS: The gastrointestinal immune response thus plays a pivotal role in maintaining protective immunity in health and a critical role in the pathogenesis of a wide variety of clinical disorders associated with FA.

Immunologic studies of specific mucosal and systemic immune responses in Mexican school children after booster aerosol or subcutaneous immunization with measles vaccine.

The purpose of the present study was to compare serum and mucosal immune responses following either aerosol (Aer) or subcutaneous (SQ) measles immunization of Mexican school children. A cohort of 49 children from 6 to 7 years of age received either Aer ( n = 22) or SQ ( n = 27) Edmonston-Zagreb (EZ) measles vaccine. Serum and nasal secretions were collected prior to (Pre), 1 and 3 months (mos) intervals and analyzed for immunoglobulin (Ig) concentrations and measles specific Ig isotype-associated antibody by enzyme immunoassay (EIA). Serum and nasal IgG and IgA antibody responses were stimulated following immunization with live, attenuated EZ measles vaccine administered either by SQ or Aer routes but these responses were significantly greater by the Aer compared to the SQ route. These studies also suggest that the level of antibody in these secretions may serve as an important marker of immunity to measles and lend further support for aerosol immunization as an effective alternative vaccine delivery strategy for measles eradication.

Abnormalities of Th1 function in non-IgE food allergy, celiac disease, and ileal lymphonodular hyperplasia: a new relationship?

BACKGROUND: Non-IgE mechanisms may also be involved food allergy (FA). Our group has been studying the immunopathogenesis clinical entities in children with gastro-intestinal symptoms and in whom biopsies of the terminal ileum show lymphoid tissue masses referred to as ileal lymphonodular hyperplasia. Our more recent studies have demonstrated Th1/Th2 cytokine profiles associated with non-IgE FA and other clinical entities. OBJECTIVE: We investigated 12 subjects with non-IgE FA (group 1) and 4 subjects with celiac disease (group 2). Cytokine profiles and immunologic studies of lymphocytes in peripheral blood and from gastro-intestinal biopsy tissues from patients in groups 1 and 2 were also evaluated. METHODS: Group 1 consisted of 12 children with clinical symptoms of anorexia, diarrhea, and abdominal pain. The diagnosis of non-IgE FA was established by positive double-blind, placebo-controlled food challenge and reduced or negative immediate-type skin testing and negative IgE radioallergosorbent tests. Group 2 consisted of four patients with celiac disease and three adult females with biopsy-proven clinical symptoms of celiac disease. RESULTS: In group 1, peripheral blood CD4 and CD8 lymphocyte distributions were normal, with a predominance of CD4+ cells with a decreased intracellular Th1 cytokine pattern and a normal Th2 intracellular cytokine pattern. In contrast, all four patients in group 2 not only displayed abnormal CD4 and CD8 peripheral blood lymphocyte distributions (CD8 > CD4), but also an abnormal predominance of CD4+ cells with an increased Th1 and a normal Th2 cytokine pattern. A similar abnormal pattern of CD4 > CD8 ratio was observed in intestinal biopsies. All 12 patients in group 1 showed lymphonodular hyperplasia in each of the biopsies and by ileoscopy. CONCLUSIONS: These studies suggest that abnormalities in Th1 function may not only play a role in some patients with non--IgE-mediated FA in whom decreased Th1 function is seen, but also in patients with celiac disease in whom an increased Th1 function is seen. The studies also suggest that lymphonodular hyperplasia may be a hallmark histologic lesion in patients with non--IgE-mediated FA.