Early interactions between lung dendritic cells (LDCs) and Mycobacterium tuberculosis, the etiological agent of tuberculosis, are thought to be critical for mounting a protective anti-mycobacterial immune response and for determining the outcome of infection. However, these interactions are poorly understood, at least at the molecular level. Here we show that M. tuberculosis enters human monocyte-derived DCs after binding to the recently identified lectin DC-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN). By contrast, complement receptor (CR)3 and mannose receptor (MR), which are the main M. tuberculosis receptors on macrophages (Mφs), appeared to play a minor role, if any, in mycobacterial binding to DCs. The mycobacteria-specific lipoglycan lipoarabinomannan (LAM) was identified as a key ligand of DC-SIGN. Freshly isolated human LDCs were found to express DC-SIGN, and M. tuberculosis–derived material was detected in CD14−HLA-DR+DC-SIGN+ cells in lymph nodes (LNs) from patients with tuberculosis. Thus, as for human immunodeficiency virus (HIV), which is captured by the same receptor, DC-SIGN–mediated entry of M. tuberculosis in DCs in vivo is likely to influence bacterial persistence and host immunity.

We have obtained bulk samples of the graphite intercalation compound, CaC6, by a novel method of synthesis from highly oriented pyrolytic graphite. The crystal structure has been completely determined showing that it is the only member of the MC6, metal-graphite compounds that has rhombohedral symmetry. We have clearly shown the occurrence of superconductivity in the bulk sample at 11.5 K, using magnetization measurements.

An acute exacerbation of Th1 responses against mycobacterial antigens appears to cause IRS in patients co-infected with HIV and TB. This key event provides new evidence valuable for the diagnosis and treatment of IRS.

Interactions between dendritic cells (DCs) andMycobacterium tuberculosis, the etiological agent of tuberculosis, most likely play a key role in anti-mycobacterial immunity. We have recently shown that M. tuberculosis binds to and infects DCs through ligation of the DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and that M. tuberculosis mannose-capped lipoarabinomannan (ManLAM) inhibits binding of the bacilli to the lectin, suggesting that Man-LAM might be a key DC-SIGN ligand. In the present study, we investigated the molecular basis of DC-SIGN ligation by LAM. Contrary to what was found for slow growing mycobacteria, such as M. tuberculosis and the vaccine strain Mycobacterium bovis bacillus CalmetteGué rin, our data demonstrate that the fast growing saprophytic species Mycobacterium smegmatis hardly binds to DC-SIGN. Consistent with the former finding, we show that M. smegmatis-derived lipoarabinomannan, which is capped by phosphoinositide residues (PI-LAM), exhibits a limited ability to inhibit M. tuberculosis binding to DC-SIGN. Moreover, using enzymatically demannosylated and chemically deacylated ManLAM molecules, we demonstrate that both the acyl chains on the ManLAM mannosylphosphatidylinositol anchor and the mannooligosaccharide caps play a critical role in DC-SIGN-ManLAM interaction. Finally, we report that DC-SIGN binds poorly to the PILAM and uncapped AraLAMcontaining species Mycobacterium fortuitum and Mycobacterium chelonae, respectively. Interestingly, smooth colony-forming Mycobacterium avium, in which ManLAM is capped with single mannose residues, was also poorly recognized by the lectin. Altogether, our results provide molecular insight into the mechanisms of mycobacteria-DC-SIGN interaction, and suggest that DC-SIGN may act as a pattern recognition receptor and discriminate between Mycobacterium species through selective recognition of the mannose caps on LAM molecules.The interaction between Mycobacterium tuberculosis and host dendritic cells (DCs) 1 is thought to be critical for mounting a protective anti-mycobacterial immune response and for determining the outcome of infection (1-4). However, the molecular bases of DC infection by mycobacteria remain poorly understood. We have recently shown that M. tuberculosis, as well as the vaccine strain Mycobacterium bovis bacillus CalmetteGuérin (BCG), use the DC-specific intercellular adhesion molecule-3 (ICAM-3)-grabbing nonintegrin (DC-SIGN) to bind to and enter human DCs (5), a feature that may allow the bacillus to persist within a unique immature compartment of the cells (6). DC-SIGN/CD209 is a calcium-dependent (C-type) transmembrane lectin that contains a single carbohydrate recognition domain at its extracellular C-terminal end. It is expressed on DCs as well as on some macrophage (M) subsets, including alveolar Ms (7,8). DC-SIGN has been described initially as a receptor for ICAM-3 and ICAM-2, as well as for human and simian immunodeficiency viruses, enabling the trans infection of susceptible CD4 ϩ T lympho...

Very-low-level methicillin-resistant Staphylococcus aureus (MRSA), or class 1 MRSA, is often misdiagnosed as methicillin-susceptible S. aureus (MSSA). We evaluated the performances of three methods for detection of low-level methicillin resistance: the disk diffusion method using the cephamycin antibiotics cefoxitin and moxalactam, the Vitek 2 system (bioMérieux), and the MRSA-screen test (Denka). Detection of the mecA gene by PCR was considered to be the "gold standard." We also determined the sensitivity of the oxacillin disk diffusion method with 5-and 1-g disks and that of the Oxascreen agar assay with 6 mg of oxacillin liter ؊1 for detection of MRSA. We compared the distributions of MICs of oxacillin and cefoxitin by the E-test (AB Biodisk), and those of moxalactam by dilutions in agar, for MRSA and MSSA isolates. The 152 clinical isolates of S. aureus studied were divided into 69 MSSA (mecA-negative) and 83 MRSA (mecA-positive) isolates, including 63 heterogeneous isolates and 26 class 1 isolates (low-level resistance). The cefoxitin and moxalactam disk diffusion tests detected 100% of all the MRSA classes: cefoxitin inhibition zone diameters were <27 mm, and moxalactam inhibition zone diameters were <24 mm. The Vitek 2 system and the MRSA-screen test detected 94 and 97.6% of all MRSA isolates, respectively. The sensitivities of the 5-and 1-g oxacillin disks were 95.2 and 96.4%, respectively, whereas that of the Oxascreen agar screen assay was 94%. All of the tests except the 1-g oxacillin disk test were 100% specific. For the class 1 MRSA isolates, the sensitivity of the Vitek 2 test was 92.3%, whereas those of the MRSA-screen test and the disk diffusion method with cefoxitin and moxalactam were 100%. Therefore, the cefoxitin and moxalactam disk diffusion methods were the bestperforming tests for routine detection of all classes of MRSA.

Leprosy is a debilitating infectious disease of human skin and nerves. Genetic factors of the host play an important role in the manifestation of disease susceptibility. The human NRAMP1 gene is a leprosy susceptibility candidate locus since its murine homologue Nramp1 (formerly Lsh/Ity/Bcg) controls innate resistance to Mycobacterium lepraemurium. In this study, 168 members of 20 multiplex leprosy families were genotyped for NRAMP1 alleles and 4 closely linked polymorphic markers. Highly informative haplotypes overlapping the NRAMP1 gene were constructed, and the haplotype segregation into leprosy-affected offspring was analyzed. It was observed that the segregation of NRAMP1 haplotypes into affected siblings was significantly nonrandom. This finding is consistent with the hypothesis that NRAMP1 itself is a leprosy susceptibility locus.

If it were possible to promote or suspend the formation of specifically sensitized lymphocytes (activated T cells), the problems of achieving a sustained attack on tumor cells and microbial parasites, or of preventing graft rejection, might be largely overcome. Methods for manipulating the immune response for such purposes have been proposed from time to time (1-3), but progress has been slow because so little is known of how cell-mediated immunity is normally regulated. Although much has been learned about the allied problem cf what controls the formation of antibodies (4), almost nothing is known about the mechanism that regulates the production and function of the cells which mediate delayed-type hypersensitivity (DTH).I While studying the tumor-suppressive activity of Mycobacterium boris BCG it was observed that lymphoid tissues which were under the stimtflatory influence of a BCG infection were capable of a much more vigorous response to a second antigen (5). Both cellular and humoral immunity to sheep red blood cells (SRBC) were augmented, as evidenced by higher and more sustained levels (DTH) and increased numbers of plaque-forming cells (PFC) in responding lymph nodes. Since D T H does not usually appear unless special conditions of immunization are used, these findings suggested that the formation of activated T cells is normally restricted by an inhibitory mechanism that does not operate properly in lymphoid tissues infected with BCG.Miller et al. (5) have shown that mice given a subcutaneous injection of SRBC in saline develop a poorly sustained state of hypersensitivity which conforms to all of the established criteria by which D T H is recognized, including its mediation by 0-bearing lymphocytes. It was therefore possible to study the mechanism which regulates T-cell activity in the absence of any influence from adjuvants such as were used by Nelson and Mildenhall (6) when they, too, showed that mice develop classical D T H in response to SRBC.

Dendritic cells (DCs) are likely to play a key role in immunity against Mycobacterium tuberculosis, but the fate of the bacterium in these cells is still unknown. Here we report that, unlike macrophages (Mφs), human monocyte-derived DCs are not permissive for the growth of virulent M. tuberculosis H37Rv. Mycobacterial vacuoles are neither acidic nor fused with host cell lysosomes in DCs, in a mode similar to that seen in mycobacterial infection of Mφs. However, uptake of the fluid phase marker dextran, and of transferrin, as well as accumulation of the recycling endosome-specific small GTPase Rab11 onto the mycobacterial phagosome, are almost abolished in infected DCs, but not in Mφs. Moreover, communication between mycobacterial phagosomes and the host-cell biosynthetic pathway is impaired, given that &lt;10% of M. tuberculosis vacuoles in DCs stained for the endoplasmic reticulum-specific proteins Grp78/BiP and calnexin. This correlates with the absence of the fusion factor N-ethylmaleimide-sensitive factor onto the vacuolar membrane in this cell type. Trafficking between the vacuoles and the host cell recycling and biosynthetic pathways is strikingly reduced in DCs, which is likely to impair access of intracellular mycobacteria to essential nutrients and may thus explain the absence of mycobacterial growth in this cell type. This unique location of M. tuberculosis in DCs is compatible with their T lymphocyte-stimulating functions, because M. tuberculosis-infected DCs have the ability to specifically induce cytokine production by autologous T lymphocytes from presensitized individuals. DCs have evolved unique subcellular trafficking mechanisms to achieve their Ag-presenting functions when infected by intracellular mycobacteria.