Immune response to DosR and Rpf antigens from Mycobacterium tuberculosis (Mtb) seems to be important for latency maintenance. Little is known about the dynamics of the immune response to these... Show moreImmune response to DosR and Rpf antigens from Mycobacterium tuberculosis (Mtb) seems to be important for latency maintenance. Little is known about the dynamics of the immune response to these antigens in an endemic community. Thus, the IFN gamma response and cytokine production in response to PPD, Esat6-Cfp10 (E6-C10), DosR and Rpf antigens in healthy HHC of tuberculosis (TB) patients over a 12 (T-12) months period (short-term, stLTBI) was investigated. This response was compared with a group of LTBI, who have remained healthy for 5-7 years (long-term, ItLTBI). According to the IFN gamma response, two groups of HHCs were identified in stLTBI in response to E6-C10. At T-12, E6-C10(+) HHCs displayed a decrease in the IFN gamma levels and a generalized decrease in cytokines production. The E6-C10(-) HHC showed an increase in the IFN gamma response and cytokine levels. In stLTBI, the responses to E6-C10, DosR, and Rpf may be interpreted as a protective immune response controlling Mtb infection and may be leading to a state of latent infection. Comparing the response of stLTBI and ItLTBI, we observed significant changes in the proportions of CD45RO(+)CD27(+) T cells to specific DosR and Rpf, which may indicate a persistent immune response to Mtb antigens in ItLTBI. (c) 2016 Elsevier Ltd. All rights reserved. Show less
This thesis focuses on cellular immunity against mycobacteria during latency with the aim to contribute to improved immunodiagnosis of latent TB and to gain insight into immune responses which play... Show moreThis thesis focuses on cellular immunity against mycobacteria during latency with the aim to contribute to improved immunodiagnosis of latent TB and to gain insight into immune responses which play a role in controlling latent infection. Several new highly M. tuberculosis-specific peptides mixtures were identified to optimize the sensitivity of immunodiagnostic assays. The performance of interferon-gamma-release-assays (IGRA) for detection of latent TB were evaluated. Two short-incubation IGRA, QuantiFERON-TB Gold and T-SPOTTM.TB, were found to correlate better to the level of exposure to M. tuberculosis than the tuberculin skin test (TST), indicating that these assays are very sensitive for detection of recent infections. However, short-incubation IGRA are less sensitive than prolonged-incubation IGRA and TST for detection of latent TB acquired in the past. The search for proteins that are specifically targeted by the immune system during latency led to the identification of several antigens encoded within the DosR-regulon. This set of genes of M. tuberculosis is strongly upregulated by during in vitro models of latency. These antigens, including 16kDa _-crystallin, were preferentially recognized by latently infected individuals, which suggest that T-cell responses to latency antigens are associated with natural protection against reactivation of TB, warranting their further study as vaccine candidates. Show less
