A single volume element (voxel) in a medical image may be composed of a mixture of multiple tissue types. The authors call voxels which contain multiple tissue classes mixels. A statistical mixel image model based on Markov random field (MRF) theory and an algorithm for the classification of mixels are presented. The authors concentrate on the classification of multichannel magnetic resonance (MR) images of the brain although the algorithm has other applications. The authors also present a method for compensating for the gray-level variation of MR images between different slices, which is primarily caused by the inhomogeneity of the RF field produced by the imaging coil.

Understanding functional interactions between DCs and antigens is necessary for achieving an optimal and desired immune response during vaccine development. Here, we identified and characterized protein Rv2299c (heat-shock protein 90 family), which effectively induced DC maturation. The Rv2299c-maturated DCs showed increased expression of surface molecules and production of proinflammatory cytokines. Rv2299c induced these effects by binding to TLR4 and stimulating the downstream MyD88-, MAPK- and NF-κB-dependent signaling pathways. The Rv2299c-maturated DCs also showed an induced Th1 cell response with bactericidal activity and expansion of effector/memory T cells. The Rv2299c-ESAT-6 fused protein had greater immunoreactivity than ESAT-6. Furthermore, boosting BCG with the fused protein significantly reduced hypervirulent Mycobacterium tuberculosis HN878 burdens post-challenge. The pathological study of the lung from the challenged mice assured the efficacy of the fused protein. The fused protein boosting also induced Rv2299c-ESAT-6-specific multifunctional CD4+ T-cell response in the lungs of the challenged mice. Our findings suggest that Rv2299c is an excellent candidate for the rational design of an effective multiantigenic TB vaccine.

The failure of Mycobacterium bovis BCG as a TB vaccine against TB reactivation suggests that latency-associated proteins should be included in alternative TB vaccine development. Further, antigens known to generate protective immunity against the strong Th1 stimulatory response to reactivated TB should be included in novel vaccine design. Recent studies have emphasized the importance of Rpfs from Mycobacterium tuberculosis in the reactivation process and cellular immunity. However, little is known about how RpfB mediates protective immunity against M. tuberculosis. Here, we investigated the functional roles and signaling mechanisms of RpfB in DCs and its implications in the development of T cell immunity. DCs treated with RpfB displayed features of mature and functional status, with elevated expression of cell surface molecules (CD80, CD86, and MHC class I and II) and proinflammatory cytokine production (TNF-α, IL-1β, IL-6, and IL-12p70). Activation of DCs was mediated by direct binding of RpfB to TLR4, followed by MyD88/TRIF-dependent signaling to MAPKs and NF-κB signaling pathways. Specifically, we found that the RpfB G5 domain is the most important part in RpfB binding to TLR4. RpfB-treated DCs effectively polarized naïve CD4(+) and CD8(+) T cells to secrete IFN-γ and IL-2. Importantly, RpfB induced the expansion of memory CD4(+)/CD8(+)CD44(high)CD62L(low) T cells in the spleen of M. tuberculosis-infected mice. Our data suggest that RpfB regulates innate immunity and activates adaptive immunity through TLR4, a finding that may help in the design of more effective vaccines.

Mycobacterium tuberculosis heparin-binding hemagglutinin (HBHA), a virulence factor involved in extrapulmonary dissemination and a strong diagnostic antigen against tuberculosis, is both surface-associated and secreted. The role of HBHA in macrophages during M. tuberculosis infection, however, is less well known. Here, we show that recombinant HBHA produced by Mycobacterium smegmatis effectively induces apoptosis in murine macrophages. DNA fragmentation, nuclear condensation, caspase activation, and poly (ADP-ribose) polymerase cleavage were observed in apoptotic macrophages treated with HBHA. Enhanced reactive oxygen species (ROS) production and Bax activation were essential for HBHA-induced apoptosis, as evidenced by a restoration of the viability of macrophages pretreated with N-acetylcysteine, a potent ROS scavenger, or transfected with Bax siRNA. HBHA is targeted to the mitochondrial compartment of HBHA-treated and M. tuberculosis-infected macrophages. Dissipation of the mitochondrial transmembrane potential (ΔΨm) and depletion of cytochrome c also occurred in both macrophages and isolated mitochondria treated with HBHA. Disruption of HBHA gene led to the restoration of ΔΨm impairment in infected macrophages, resulting in reduced apoptosis. Taken together, our data suggest that HBHA may act as a strong pathogenic factor to cause apoptosis of professional phagocytes infected with M. tuberculosis.

Reciprocal induction of the Th1 and Th17 immune responses is essential for optimal protection against Mycobacterium tuberculosis (Mtb); however, only a few Mtb antigens are known to fulfill this task. A functional role for resuscitation-promoting factor (Rpf) E, a latency-associated member of the Rpf family, in promoting naïve CD4+ T-cell differentiation toward both Th1 and Th17 cell fates through interaction with dendritic cells (DCs) was identified in this study. RpfE induces DC maturation by increasing expression of surface molecules and the production of IL-6, IL-1β, IL-23p19, IL-12p70, and TNF-α but not IL-10. This induction is mediated through TLR4 binding and subsequent activation of ERK, p38 MAPKs, and NF-κB signaling. RpfE-treated DCs effectively caused naïve CD4 + T cells to secrete IFN-γ, IL-2, and IL-17A, which resulted in reciprocal expansions of the Th1 and Th17 cell response along with activation of T-bet and RORγt but not GATA-3. Furthermore, lung and spleen cells from Mtb-infected WT mice but not from TLR4 −/− mice exhibited Th1 and Th17 polarization upon RpfE stimulation. Taken together, our data suggest that RpfE has the potential to be an effective Mtb vaccine because of its ability to activate DCs that simultaneously induce both Th1-and Th17-polarized T-cell expansion. Keywords: Mycobacterium tuberculosis Dendritic cell Resuscitation-promoting factor E (RpfE) Th1 polarization Th17 polarization TLRAdditional supporting information may be found in the online version of this article at the publisher's web-site IntroductionTuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains one of the major infectious diseases worldwide. Mtb infecCorrespondence: Prof. Sung Jae Shin e-mail: sjshin@yuhs.ac; hjukim@cnu.ac.kr tions result in close to two million deaths annually, indicating an urgent need for improved treatment and prevention strategies [1]. Although the Mycobacterium bovis BCG vaccine (Bacille CalmetteGuerin) is safe and cost effective and is efficacious in protecting * These authors contributed equally to this work.C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu1958 Han-Gyu Choi et al. Eur. J. Immunol. 2015. 45: 1957-1971 children against the early manifestations of TB [2,3], its limited efficacy against adult pulmonary TB has been repeatedly reported [3][4][5]. Recently, the reciprocal induction of Th1 and Th17 cellular responses has been shown to play an important role in establishing protective immunity against TB [6]. In general, protection from Mtb is dependent on a robust Th1 response through IFN-γ secretion by antigen-specific CD4 + T cells; however, recent studies have emphasized the importance of the Th17 response in protective immunity against Mtb infection [7][8][9]. Hence, understanding the balance between the Th1 and Th17 responses during infection [10] and identifying novel proteins that simultaneously induce the Th1 and Th17 immune responses are crucial for the development of efficacious vaccines. The induction of protective immunity against ...