Proinflammatory cytokine synthesis by mucosal fibroblasts from mouse colitis is enhanced by interferon-gamma-mediated up-regulation of CD40 signalling.

Gut mesenchymal fibroblasts form complex phenotypical and functional populations. They participate actively in homeostatic maintenance of the extracellular matrix, epithelial barrier function, repair mechanisms and leucocyte migration. In inflammation, they become activated, change matrix expression and synthesize proinflammatory mediators. Subpopulations of mucosal fibroblasts express CD40 and the aim of this study was to define its role in their proinflammatory function. Stable primary fibroblast lines derived from normal mouse colon and inflamed colon from CD4(+) CD45RB(high)-transplanted SCID mice were used as models to explore the role of mucosal fibroblast CD40 in the inflammatory process. Phenotype correlated with in situ fibroblast phenotype in the tissues of origin. Lines from both sources co-expressed CD40 and Thy1.2 independently of alpha-smooth muscle actin. A subpopulation of CD40(+) fibroblasts from normal colon expressed CD40 at high levels and expression was enhanced by interferon (IFN)-gamma treatment, whereas all CD40(+) fibroblasts from colitis expressed at low levels and expression was unaffected by IFN-gamma treatment. Despite lower-level expression of CD40 by cells from colitis, they secreted constitutively interleukin (IL)-6 and C-C chemokine (CCL)2. Ligation of CD40 enhanced secretion of these mediators and induced secretion of CCL3. CD40 in cells from colitis was more responsive to ligation than CD40 on cells from normal tissue and this sensitivity was amplified selectively by the action of IFN-gamma. We conclude that the inflammatory milieu in colitis induces long-lasting changes in phenotype and proinflammatory function in colonic fibroblasts. In particular, proinflammatory signalling from fibroblast CD40 is amplified synergistically by the Th1 effector T cell cytokine, IFN-gamma.

Systemic administration of the chemokine macrophage inflammatory protein 1alpha exacerbates inflammatory bowel disease in a mouse model.

INTRODUCTION: Exacerbations of inflammatory bowel disease are thought to be related to concurrent infections. As infections are associated with elevated local and serum concentrations of chemokines, we have determined whether systemic administration of the CC chemokine macrophage inflammatory protein 1alpha (MIP-1alpha) exacerbates colitis in a mouse model. METHODS: Colitis was induced in Balb/c mice using trinitrobenzene sulfonic acid (TNBS). Starting four days later, animals received daily intraperitoneal injections of recombinant MIP-1alpha. On day 7, mice were killed and pieces of colon taken for immunohistology and polymerase chain reaction analysis. The direct effects of MIP-1alpha on mucosal T cells and fibroblasts in vitro were also investigated. RESULTS: Systemic administration of MIP-1alpha markedly enhanced colitis with mice developing large transmural ulcers filled with granulation tissue. Treatment resulted in increased numbers of CD4 cells infiltrating the colonic lamina propria, increased interferon gamma (IFN-gamma) levels, and increased transcripts for tumour necrosis factor alpha (TNF-alpha) and matrix metalloproteinase 3 (MMP3). Isolated lamina propria lymphocytes from mice with TNBS colitis contained increased numbers of IFN-gamma and TNF-alpha transcripts when stimulated with MIP-1alpha in vitro. Colonic lamina propria fibroblasts also responded to MIP-1alpha with increased proliferation and decreased collagen 1 synthesis but fibroblast proliferation was not seen in vivo. CONCLUSIONS: These experiments show that increasing serum concentrations of a chemokine, MIP-1alpha, exacerbates immune mediated colitis. The effect seems to be due to the ability of MIP-1alpha to boost Th1 responses in the gut wall. Our findings also suggest a potential pathway by which peripheral infections can exacerbate inflammatory bowel disease.

Transforming growth factor-beta messenger RNA and protein in murine colitis.

Using a CD4+ T-cell-transplanted SCID mouse model of colitis, we have analyzed TGF-beta transcription and translation in advanced disease. By in situ hybridization, the epithelium of both control and inflamed tissues transcribed TGF-beta1 and TGF-beta3 mRNAs, but both were expressed significantly farther along the crypt axis in disease. Control lamina propria cells transcribed little TGF-beta1 or TGF-beta3 mRNA, but in inflamed tissues many cells expressed mRNA for both isoforms. No TGF-beta2 message was detected in either control or inflamed tissues. Immunohistochemistry for latent and active TGF-beta1 showed that all cells produced perinuclear latent TGF-beta1. The epithelial cell basal latent protein resulted in only low levels of subepithelial active protein, which co-localized with collagen IV and laminin in diseased and control tissue. Infiltrating cells expressed very low levels of active TGF-beta. By ELISA, very low levels (0-69 pg/mg) of soluble total or active TGF-beta were detected in hypotonic tissue lysates. TGF-beta1 and TGF-beta3 are produced by SCID mouse colon and transcription is increased in the colitis caused by transplantation of CD4+ T-cells, but this does not result in high levels of soluble active protein. Low levels of active TGF-beta may be a factor contributing to unresolved inflammation.

The role of up-regulated serine proteases and matrix metalloproteinases in the pathogenesis of a murine model of colitis.

Proteinases are important at several phases of physiological and pathological inflammation, mediating cellular infiltration, cytokine activation, tissue damage, remodeling, and repair. However, little is known of their role in the pathogenesis of inflammatory bowel disease. The aim of this study was to assess the role of tissue proteases in a mouse model of colitis. Proteolytic activity was analyzed, using gel and in situ zymography, in colonic tissues from severe combined immunodeficient mice with colitis induced by transfer of CD4(+) T lymphocytes. Serine proteinase levels increased in colitic tissue, with major species of 23 kd, 30 kd, and 45 kd. Co-migration and inhibition studies indicated that the 23-kd proteinase was pancreatic trypsin and that the 30-kd species was neutrophil elastase. Matrix metalloproteinase (MMP)-9 expression, and MMP-2 and MMP-9 activation, was elevated in colitic tissues. Proteinase levels followed a decreasing concentration gradient from proximal to distal colon. Proteolysis was localized to infiltrating leukocytes in diseased severe combined immunodeficient mice. Transmural inflammation was associated with serine proteinase and MMP activity in overlying epithelium and with marked subepithelial proteolytic activity. The results demonstrate a clear elevation in the levels and activation of proteases in colitis, potentially contributing to disease progression through loss of epithelial barrier function.

Mucosal immunization with experimental feline immunodeficiency virus (FIV) vaccines induces both antibody and T cell responses but does not protect against rectal FIV challenge.

Feline immunodeficiency virus (FIV) is a natural lentiviral pathogen of cats which can be experimentally transmitted via rectal and vaginal routes--the major routes of human immunodeficiency virus type 1 transmission in man. An important objective for lentiviral research is the development of vaccine strategies which generate good mucosal immune responses capable of giving protection from a mucosal virus challenge. The experimental vaccines employed in this study were based on (a) a peptide from the third variable region of the FIV envelope glycoprotein and (b) fixed whole FIV, Glasgow-8 strain. Adjuvants used were Quil A and cholera toxin for mucosal administration and incomplete Freund's adjuvant and immune stimulating complexes for subcutaneous injection. Mucosal immunization was given by rectal and intranasal routes. Both antibody and proliferative responses were elicited by mucosal immunization and cholera toxin was found to be a good mucosal adjuvant. The addition of a lipo thioester to the FIV peptide improved IgG and IgA responses upon parenteral administration. However, no protection from a rectal FIV challenge was achieved.

Tumour necrosis factor-alpha (TNF-alpha) transcription and translation in the CD4+ T cell-transplanted scid mouse model of colitis.

The adoptive transfer of activated CD4+ alpha/beta T cell blasts from the spleens of immunocompetent C.B-17+/+ or BALB/cdm2 mice into C.B-17scid/scid (scid) mice induces a colitis in the scid recipient within 8 weeks, which progresses to severe disease within 16 weeks. T cells isolated from recipient colon show a Th1 cytokine phenotype. We have examined the relationship between the phenotype of the cellular infiltrate and the transcription and translation of the proinflammatory cytokine TNF-alpha. The techniques of double indirect immunohistology and in situ hybridization using digoxigenin-labelled riboprobes were used. The prominent myeloid cell infiltrate in diseased tissues comprised F4/80+, Mac-l+ macrophages, neutrophils, dendritic cells and activated macrophages. TNF-alpha transcription and translation were associated with activated macrophages in the lamina propria. Activated macrophages transcribing and translating TNF-alpha were clustered in areas of tissue destruction. Crypt epithelium of inflamed tissues transcribed TNF-alpha at a very early stage of the disease process, but translation of TNF-alpha protein could only be found in advanced epithelial dysplasia. This indicates differential post-transcriptional control of TNF-alpha in activated macrophages and the epithelium.

Encephalitis associated with giant cells in a cat with naturally occurring feline immunodeficiency virus infection demonstrated by in situ hybridization.

This report describes the clinical, pathological, immunocytochemical, and in situ hybridization characteristics of encephalitis associated with feline immunodeficiency virus (FIV) infection in a 4-year-old domestic cat. Lesions were identified throughout the brain, affecting the cerebrum, medulla, and cervical spinal cord. Perivascular lymphocytic cuffing, gliosis, and white matter vacuolation were most severe in the cerebrum, affecting the white matter and the deep laminae of the grey matter. Gemistocytes were prominent, and many bizarre cells with large, sometimes multinucleate, hyperchromatic nuclei were evident. Immunostaining with antibody specific for FIV p24 nucleocapsid protein produced staining in the gemistocytes and glial cells of the white matter. In situ hybridization with a 327-base pair fragment of the FIV gag gene produced staining that was most intense in the white matter and gemistocytes of the deep laminae of the grey matter. These findings indicated localization of FIV infection within the cerebrum, and the detection of FIV RNA by in situ hybridization confirms the infection as active.

Vaccination with fixed feline immunodeficiency virus (FIV) infected cells: protection, breakthrough and specificity of response.

Infection of cats with feline immunodeficiency virus (FIV), a naturally occurring lentivirus infection of cats which causes an AIDS-like disease, has generated considerable interest as an animal model for HIV vaccination. This paper reports on experiments performed to examine the potential of a fixed infected cell vaccine to confer protection against intraperitoneal challenge with cell-free FIV. The cell vaccine was highly immunogenic and elicited antibody responses to virus core antigen, p24, high virus neutralizing (VN) antibody titres, and antibodies which recognized cellular components of the vaccine. Whilst protection, assessed by the inability to detect infectious virus by virus isolation or polymerase chain reaction, against homologous but not heterologous FIV isolates was apparent up to week 12 post-challenge, when cats were monitored longer up to week 50 post-challenge a breakthrough in vaccine protection against homologous virus was observed. Protection could not be correlated with levels of antibody to p24 or VN antibody titres. In contrast with simian immunodeficiency virus vaccine studies in macaques there was no clear evidence that antibodies recognizing cellular components of the vaccine, including MHC class I and II antigens, conferred any protective effect following challenge. These results indicate that long-term post-challenge monitoring for infection is essential in lentivirus vaccine trials.

Vaginal and rectal infection of cats with feline immunodeficiency virus.

The objective of this study was to examine the potential of vaginal and rectal mucosal routes for feline immunodeficiency virus (FIV) uptake and infection, as a model of mucosal HIV infection, and to determine the fate of virus at these mucosal sites following transmission of infection. SPF cats were exposed to FIV isolates (PET, GL-8, T637), administered as either cell-associated or cell-free inocula, via the rectum or vagina. Establishment of infection was confirmed by isolation of infectious FIV from peripheral blood mononuclear cells (PBMC), and by presence of FIV proviral DNA in PBMC using a nested polymerase chain reaction. Fate of virus in tissue taken at necropsy from cats infected for 6-48 weeks was assessed by localizing FIV core and envelope proteins, p24 and gp41, using a biotin-streptavidin linked immunoperoxidase (IP) technique. Cells susceptible to infection were identified by an in situ hybridization technique for FIV viral DNA and RNA. Cell-free, as well as cell-associated, virus was infectious across intact vaginal and rectal mucosal surfaces. Transmission was most successful using cell-associated inocula, and via the rectal route. Cells infected with FIV were detected by IP staining in the colon of 6/9 rectally challenged cats and 1/5 vaginally challenged cats. Virus was predominantly localized within the epithelium at the base of the colonic crypts associated with lymphoid aggregates (follicle associated epithelium; FAE), and within the lymphoid follicle itself. Occasional infected cells were also noted within the lamina propria. The distribution of FIV DNA positive cells in the colon was similar to that for FIV antigen whilst FIV RNA positive cells were found more extensively, including within the lamina propria and lymphoid follicle. FIV infected cells were not detected within the vagina, or colonic and ileac lymph nodes. Similar patterns of infected cells were seen in all of the positive cats, indicating that colonic tissues remain persistently actively infected with FIV. We conclude that the FIV/cat model of rectal and vaginal mucosal infection should prove useful for characterizing the mechanism by which HIV infects mucosal surfaces and as a challenge system for the design of vaccines effective at preventing HIV infection via rectal and vaginal routes.

Differential control of major histocompatibility complex class II I-Ek alpha protein expression in the epithelium and in subsets of lamina propria antigen-presenting cells of the gut.

In the gut, both the villus epithelium and cells of macrophages and dendritic cell lineages of the lamina propria and Peyer's patches express major histocompatibility complex (MHC) class II glycoproteins and have the potential to present soluble protein antigen. Using mice transgenic for the X and Y promoter deletion mutants of the gene encoding the I-Ek alpha class II protein we have shown: that an intact promoter is essential for expression of I-Ek alpha on the epithelium and lamina propria macrophages; that only the Y box is essential for expression by lamina propria dendritic cells; and that dendritic cells in Peyer's patches are phenotypically more restricted than in the lamina propria and express I-Ek alpha under different regulatory control mechanisms. The results show that different inductive mechanisms exist for class II in distinct mucosal cell populations and provide a model for the analysis of differential antigen handling in the gut mucosa.

Induction of MHC class II gene products in rat intestinal epithelium during graft-versus-host disease and effects on the immune function of the epithelium.

The induction of major histocompatibility complex (MHC) class II expression in the epithelium of the small intestine of the rat during graft-versus-host disease (GVHD) and the effect of this process on the capacity of isolated epithelial cells to present antigen has been investigated. By immunohistology, increased class II (I-A) was noted in lamina propria cells and villus epithelium and de novo expression in crypt epithelium by Day 7 after transfer of parental spleen cells into irradiated hybrid rats. This increased expression reached a maximum by Day 9 or 10. The kinetics of induction of I-E products paralleled those of I-A in villus epithelium, but I-E was not seen in crypt epithelium. Direct radioimmunoassay of class II in isolated villus and crypt epithelial cells revealed a minor peak of class II, particularly in villus cells, very soon after cell transfer which waned and then increased to a second peak at Days 7-9. Assay of presentation of ovalbumin by isolated enterocytes to primed T cells at the peak of class II induction showed that increased class II expression by villus cells mediated enhanced antigen-presenting activity, whereas increases in crypt cell class II did not enable these cells to present ovalbumin.

An immunoassay for the quantitation of cell membrane MHC class II antigen.

A method is described for the quantitative assay of cellular MHC class II proteins. The assay has been developed for special use with epithelial cells isolated from the intestine, but has been successfully used with other cell types. It comprises a competitive immunoassay of anti-class II activity in cell lysates, using IgG-coated Sephacryl S300 as the solid phase and is sensitive over the range 1 ng-1 microgram.

Antigen processing by isolated rat intestinal villus enterocytes.

The processing of ovalbumin by isolated rat enterocytes and by splenic adherent cells (SAC) was compared. Paraformaldehyde fixation blocked presentation of ovalbumin to T cells by both cell types when given before, but not after, an antigen pulse. Presentation of ovalbumin by both cell types was blocked by treatment with chloroquine, ammonium chloride or monensin before the antigen pulse. Leupeptin treatment before the antigen pulse inhibited presentation by SAC, but not by enterocytes. Ovalbumin processed by enterocytes was not presented by fixed SAC. Radiolabelled ovalbumin was degraded to small molecular weight fragments by SAC, but not by enterocytes. It is suggested that, compared to the degradative processing seen in macrophages. B cells and dendritic cells, processing of ovalbumin by enterocytes comprises a more subtle, non-degradative mechanism.