| Part 1 Study on immunodiagnosis of latent Mycobacterium tuberculosis infection among IMID patients in BCG-vaccinated areaObjective:To evaluate a new interferon gamma release assay (TSPOT.TB assay) and conventional tuberculin skin test (TST) for detecting latent tuberculosis infection (LTBI) among patients with immune mediated inflammatory diseases (IMID) prior to initiation of anti-TNF alpha therapy in BCG-vaccinated area. Methods:Two hundred and ninety-four IMID patients and 48 Healthy controls from Eastern China were enrolled. The TSPOT.TB assay and TST were performed on all subjects simultaneously. The positive rates, odds ratio of risk factors and M.tb antigen-specific immune responses were anylyzed among different subgroups. Results:The positive rate of TSPOT.TB assay was 27.2% and that of TST was 51.4% (cut-off?5mm) or 38.4% (cut-off?10mm) among IMID patients. In healthy controls, the TSPOT.TB positive rate was 20.8% and TST positive rate was 64.6% (cut-off?5mm) or 50.0% (cut-off?10mm). Either in IMID patients or in Healthy controls, the TST positive rates were both significantly higher than that of TSPOT.TB assay (both P<0.0001). TST positive rate in IMID patients was lower than that in Healthy controls, while TSPOT.TB positive rate in IMID patients was higher than that in Healthy controls. Comparing to healthy individuals, IMID patients were more likely to be misdiagnosed as LTBI by TST. Among IMID patients, BCG vaccination and immunosuppressive therapy significantly affected TST results among IMID patients (odds ratio was 2.05 and 0.56, respectively, both P<0.05), but had no influence on the performance of TSPOT.TB assay. The variance of M.tb antigen-specific immune responses among different IMID subgroups was consistant with the difference of positive rates and odds ratio of risk factors. It was suggested that TST induration diameters?10mm should be a better cut-off value for TST positive when preliminary screening LTBI by TST among IMID patients in BCG-vaccinated area. Conclusion:TSPOT.TB assay is a more reliable and sensitive tool for screening latent tuberculosis infection among IMID patients in BCG-vaccinated area, especially for those on immunosuppressive therapy. Part 2 Study on immunodiagnosis of latent Mycobacterium tuberculosis infection among HIV-infected individuals in BCG-vaccinated areaObjective:To investigate the disease burden of HIV with active or latent tuberculosis coinfection in Southwestern China and to evaluate the diagnostic power of enzyme-linked immunospot (ELISPOT)-based IFN-?release assay and conventional tuberculin skin test (TST) in detecting active and latent tuberculosis infection among HIV-infected individuals in BCG-vaccinated area. Methods:A total of 100 HIV-infected individuals who had HIV infection only (HIV+TB-), HIV with latent tuberculosis coinfection (HIV+LTB), or HIV with active tuberculosis coinfection (HIV+ATB) were recruited from Yunnan Province. The TSPOT.TB assay and TST were performed on all recruited subjects simultaneously. Results:The prevalence of latent tuberculosis coinfection in HIV-infected individuals with no clinical evidence of active tuberculosis was 67.6%. In HIV-infected patients with or without active tuberculosis, TSPOT.TB positive rate in subjects with TST induration<5 mm were 66.7%(16/24) or 47.5%(19/40), respectively. In HIV-infected patients with CD4+ T cells<500/?l and co-infected with or without active TB, the positive rate of TSPOT.TB assay was significantly higher than that of TST (66.7% vs.23.8%,55.6% vs.22.2% and 44.4% vs.11.1%,69.2% vs.42.3%, respectively, both P?0.0001). In addition, the TSPOT positive rate in HIV+ATB group increased to>85% in patients with TB treatment for less than 1 month and CD4+ T cells?200/?l, while in patients with TB treatment for more than 3 months and CD4+ T cells<200/?l, the TSPOT positive rate decreased to only 33.3%. Among HIV-infected individuals without active TB, the TSPOT positive rate was not significantly affected by CD4 cell count (P>0.05). In contrast, the TST positive rate was dramatically decreased in HIV-infected individuals with CD4 cell counts less than 200/?l (P<0.05). Conclusion: The prevalence of latent TB coinfection in HIV-infected individuals without active TB is very high in China. TSPOT.TB assay is more sensitive and rapid than TST for diagnosing TB infection among HIV-infected individuals in BCG-vaccinated area. The performance of TSPOT.TB assay is independent of CD4 cell count. It could be an effective tool for guiding isoniazid preventive therapy in HIV and latent TB co-infected patients and for TB control in China. Part 3 Study on immunopathogenesis of latent Mycobacterium tuberculosis infection progressing to active tuberculosis among HIV-infected individuals in BCG-vaccinated areaObjective:To investigate cellular immune responses of M.tb antigen peptide-specific CD4+ and CD8+ T cells and nonpeptide-specific V?2V?2+ T cells during clinical quiescence of latent tuberculosis coinfection among HIV-infected individuals in BCG-vaccinated area. Methods:One hundred HIV-infected individuals who had HIV infection only (HIV+TB-), HIV with latent tuberculosis coinfection (HIV+LTB), or HIV with active tuberculosis coinfection (HIV+ATB) were recruited from Yunnan Province to measure M.tb purified protein derivative (PPD)-specific IFN?+ CD4+ and IFN?+CD8+ T cells, and phosphoantigen HMBPP-specific IFN?+V?2V?2+ T cells using enzyme-linked immunospot and intracellular cytokine staining assays. Results: Both HIV+ATB and HIV+LTB groups had low levels of PPD-specific IFN?+CD4+ T cells regardless of CD4+ peripheral blood lymphocyte counts. However, numbers of PPD-specific IFN?+CD8+ T cells in the HIV+LTB group were significantly greater than those in the HIV+ATB group. Surprisingly, numbers of phosphoantigen HMBPP-specific IFN?+V?2V?2+ T cells in the HIV+LTB group were much greater than those in the HIV+ATB group (P?0.0001). This difference was present in the subgroups of HIV+LTB with CD4 cell counts more than 200/?l or less than 200/?l. Numbers of HMBPP-specific IFN?+V?2V?2+ T cells were even seven times greater than those of PPD-specific IFN?+CD8+ T cells within the HIV+LTB group. Conclusion:Potent immune responses of HMBPP-specific IFN?+V?2V?2+ T cells and PPD-specific IFN?+CD8+ T cells were detected in HIV+LTB individuals but not HIV+ATB patients. The robust immune responses of V?2V?2+ and CD8+ T effector cells were associated with the latent stage of Mycobacterium tuberculosis coinfection among HIV-infected population in BCG-vaccinated area. |
PDF Full Text Request