Intraperitoneal fluid accumulation induced by Clostridium perfringens alpha-toxin (phospholipase C)

We report that the intraperitoneal injection of Clostridium perfringens alpha-toxin into mice induces ascites. This phenomenon was monitored by measuring fluid volume and analyzing hematologic data. The mouse toxicity test provides a simple and useful model for examining C. perfringens alpha-toxin-induced vascular permeability.     

Reduced expression of STAT4 and IFN-gamma in macrophages from BALB/c mice

BALB/c mice have been shown to easily induce Th2 type responses in several infection models. In this study, to examine the mechanisms of Th2 dominant responses in BALB/c mice, we assessed several macrophage functions using C3H/HeN, C57BL/6, and BALB/c mouse strains. Peritoneal macrophages from three strains of mice equally produced IL-12 by stimulation with LPS plus IFN-gamma. However, IFN-gamma production in response to IL-12 or IL-12 plus IL-18 was much lower in macrophages from BALB/c mice than other strains. IFN-gamma produced by activated macrophages induced IL-12R mRNA expression in T cells and macrophages themselves depending on their amount of IFN-gamma; namely, macrophages from BALB/c mice induced lower expression of IL-12R. Intracellular levels of STAT4 were much lower in macrophages from BALB/c mice. However, other STATs, such as STAT1 or STAT6, were expressed similarly in the three mouse strains. STAT4 and IFN-gamma production by other cell types such as T cells and B cells were equal in C3H/HeN and BALB/c mice. These results indicate that macrophages from Th2-dominant BALB/c mice have different functional characters compared with other mouse strains; that is, STAT4 expression and IFN-gamma production are reduced, which is one of the causes to shift to Th2-type responses.     

Solution structure of the DFF-C domain of DFF45/ICAD. A structural basis for the regulation of apoptotic DNA fragmentation

DFF45/ICAD has dual functions in the final stage of apoptosis, by acting as both a folding chaperone and a DNase inhibitor of DFF40/CAD. Here, we present the solution structure of the C-terminal domain of DFF45, which is essential for its chaperone-like activity. The structure of this domain (DFF-C) consists of four alpha helices, which are folded in a novel helix-packing arrangement. The 3D structure reveals a large cluster of negatively charged residues on the molecular surface of DFF-C. This observation suggests that charge complementation plays an important role in the interaction of DFF-C with the positively charged catalytic domain of DFF40, and thus for the chaperone activity of DFF45. The structure of DFF-C also provides a rationale for the loss of the chaperone activity in DFF35, a short isoform of DFF45. Indeed, in DFF35, the amino acid sequence is truncated in the middle of the second alpha helix constituting the structure of DFF-C, and thus both the hydrophobic core and the cluster of negative charges are disrupted.     

X-Linked inhibitor of apoptosis protein is involved in mutant SOD1-mediated neuronal degeneration

Mutations in the superoxide dismutase 1 (SOD1) gene cause the degeneration of motor neurons in familial amyotrophic lateral sclerosis (FALS). An apoptotic process including caspase-1 and -3 has been shown to participate in the pathogenesis of FALS transgenic (Tg) mouse model. Here we report that IAP proteins, potent inhibitors of apoptosis, are involved in the FALS Tg mouse pathologic process. The levels of X-linked inhibitor of apoptosis protein (XIAP) mRNA and protein were significantly decreased in the spinal cord of symptomatic G93A-SOD1 Tg mice compared with littermates. In contrast, the levels of cIAP-1 mRNA and protein were increased in symptomatic G93A-SOD1 Tg mice, whereas the levels of cIAP-2 mRNA and protein were unchanged. In situ hybridization showed that the expression of XIAP was remarkably reduced in the motor neurons of Tg mice, and the expression of cIAP-1 was strongly increased in the reactive astrocytes of Tg mice. Overexpression of XIAP markedly inhibited the cell death and caspase-3 activity in the neuro2a cells expressing mutant SOD1. Deletional mutant analysis revealed that the N-terminal domain of XIAP, the BIR1-2 domains, was essential for this inhibitory activity. These results suggest that XIAP plays a role in the apoptotic mechanism in the progression of disease in mutant SOD1 Tg mice and holds therapeutic possibilities for FALS.     

Elicitation of simian immunodeficiency virus-specific cytotoxic T lymphocytes in mucosal compartments of rhesus monkeys by systemic vaccination

Since most human immunodeficiency virus (HIV) infections are initiated following mucosal exposure to the virus, the anatomic containment or abortion of an HIV infection is likely to require vaccine-elicited cellular immune responses in those mucosal sites. Studying vaccine-elicited mucosal immune responses has been problematic because of the difficulties associated with sampling T lymphocytes from those anatomic compartments. In the present study, we demonstrate that mucosal cytotoxic T lymphocytes (CTL) specific for simian immunodeficiency virus (SIV) and simian HIV can be reproducibly sampled from intestinal mucosal tissue of rhesus monkeys obtained under endoscopic guidance. These lymphocytes recognize peptide-major histocompatibility complex class I complexes and express gamma interferon on exposure to peptide antigen. Interestingly, systemic immunization of monkeys with plasmid DNA immunogens followed by live recombinant attenuated poxviruses or adenoviruses with genes deleted elicits high-frequency SIV-specific CTL responses in these mucosal tissues. These studies therefore suggest that systemic delivery of potent HIV immunogens may suffice to elicit substantial mucosal CTL responses.     

Cleavage of the xylosyl serine linkage between a core peptide and a glycosaminoglycan chain by cellulases

We previously found that endo-beta-xylosidase from Patinopecten is an endo-type glycosidase that cleaves the xylosyl serine linkage between a glycosaminoglycan chain and its core protein (Takagaki, K., Kon, A., Kawasaki, H., Nakamura, T., Tamura, S., and Endo, M. (1990) J. Biol. Chem. 265, 854-860). Screening for endo-beta-xylosidase activity in several cellulases detected this activity in the enzymes from Aspergillus niger, Penicillium funiculosum, Trichoderma reesei, Trichoderma viride, and Irpex lacteus. The cellulase derived from A. niger was purified, and its molecular weight was determined to be 26,000 by SDS-PAGE. Examination of the specificity of the cellulase revealed that 1) the enzyme acts on the linkage region (xylosyl serine) between a core peptide and a glycosaminoglycan chain; 2) enzymatic activity is greater with shorter glycosaminoglycan chains; 3) the enzyme readily hydrolyzes the linkage in glycosaminoglycan peptides, but intact proteoglycan is cleaved only slowly; and 4) the activity is unaffected by the glycosaminoglycan component (chondroitin sulfate, dermatan sulfate, and heparan sulfate). Judging from these enzymatic characteristics, this cellulase is different from the endo-beta-xylosidase of Patinopecten. We believe that this cellulase will become a useful tool in the further development of glycotechnology, because, like the endo-beta-xylosidase of Patinopecten, it enables the release of intact glycosaminoglycans from glycosaminoglycan peptides.     

CD1 molecules efficiently present antigen in immature dendritic cells and traffic independently of MHC class II during dendritic cell maturation

Upon exposure to Ag and inflammatory stimuli, dendritic cells (DCs) undergo a series of dynamic cellular events, referred to as DC maturation, that involve facilitated peptide Ag loading onto MHC class II molecules and their subsequent transport to the cell surface. Besides MHC molecules, human DCs prominently express molecules of the CD1 family (CD1a, -b, -c, and -d) and mediate CD1-dependent presentation of lipid and glycolipid Ags to T cells, but the impact of DC maturation upon CD1 trafficking and Ag presentation is unknown. Using monocyte-derived immature DCs and those stimulated with TNF-alpha for maturation, we observed that none of the CD1 isoforms underwent changes in intracellular trafficking that mimicked MHC class II molecules during DC maturation. In contrast to the striking increase in surface expression of MHC class II on mature DCs, the surface expression of CD1 molecules was either increased only slightly (for CD1b and CD1c) or decreased (for CD1a). In addition, unlike MHC class II, DC maturation-associated transport from lysosomes to the plasma membrane was not readily detected for CD1b despite the fact that both molecules were prominently expressed in the same MIIC lysosomal compartments before maturation. Consistent with this, DCs efficiently presented CD1b-restricted lipid Ags to specific T cells similarly in immature and mature DCs. Thus, DC maturation-independent pathways for lipid Ag presentation by CD1 may play a crucial role in host defense, even before DCs are able to induce maximum activation of peptide Ag-specific T cells.     

Induction of CD1-restricted immune responses in guinea pigs by immunization with mycobacterial lipid antigens

Group 1 CD1 molecules have been shown to present lipid and glycolipid Ags of mycobacteria to human T cells. However, a suitable animal model for the investigation of this component of antimycobacterial immunity has not yet been established. Previously, we found that guinea pigs express multiple isoforms of group 1 CD1 proteins that are homologous to human CD1b and CD1c. In this study, we show that CD1-restricted T cell responses can be generated in guinea pigs following immunization with lipid Ags from Mycobacterium tuberculosis. Splenic T cells from lipid Ag-immunized guinea pigs showed strong proliferative responses to total lipid Ags and partially purified glycolipid fractions from M. tuberculosis. These lipid Ag-reactive T cells were enriched in CD4-negative T cell fractions and showed cytotoxic activity against CD1-expressing guinea pig bone marrow-derived dendritic cells pulsed with M. tuberculosis lipid Ags. Using guinea pig cell lines transfected with individual CD1 isoforms as target cells in cytotoxic T cell assays, we found that guinea pig CD1b and CD1c molecules presented M. tuberculosis glycolipid Ags to T cells raised by mycobacterial lipid immunization. These results were confirmed using a T cell line derived from M. tuberculosis lipid Ag-immunized guinea pigs, which also showed CD1-restricted responses and cytolytic activity. Our results demonstrate that CD1-restricted responses against microbial glycolipid Ags can be generated in vivo by specific immunization and provide support for the use of the guinea pig as a relevant small animal model for the study of CD1-restricted immune responses to mycobacterial pathogens.     

Prior vaccination increases the epitopic breadth of the cytotoxic T-lymphocyte response that evolves in rhesus monkeys following a simian-human immunodeficiency virus infection

Although recent evidence has confirmed the importance of cytotoxic T-lymphocyte (CTL) responses in controlling human immunodeficiency virus type 1 and simian immunodeficiency virus replication, the relevance of the epitopic breadth of those CTL responses remains unexplored. In the present study, we sought to determine whether vaccination can expand CTL populations which recognize a repertoire of viral epitopes that is greater than is typically generated in the course of a viral infection. We demonstrate that potent secondary CTL responses to subdominant epitopes are rapidly generated following a pathogenic simian-human immunodeficiency virus challenge of rhesus monkeys vaccinated with plasmid DNA or recombinant modified vaccinia virus Ankara vaccines. These data indicate that prior vaccination can increase the breadth of the CTL response that evolves after an AIDS virus infection.