PubMed Health⌕ Search

Biomedical subjects

S Fais

Publications and source records attributed to S Fais.

At least 37 records · Page 2Linked to original sources
PubMed1997

U937-SCID mouse xenografts: a new model for acute in vivo HIV-1 infection suitable to test antiviral strategies.

In this study we attempted to develop a new xenochimeric model for HIV infection in SCID mice, characterized by an easy engraftment of target cells, high levels of viremia and long-lasting HIV-1 infection. SCID mice were injected subcutaneously with uninfected human U937 cells and cell-free HIV-1 (IIIB strain) or HIV-1-infected human peripheral blood lymphocytes (PBL). Mice were evaluated for tumor growth, viral infection at the tumor level (DNA-polymerase chain reaction (PCR), RNA-PCR) and immunostaining for the p55/p18 HIV protein) and p24 antigenemia or serum HIV-1 RNA copies. Pretreatment of mice with antibodies to either mouse-IFN alpha/beta or granulocytes resulted in a tumor take and levels of p24 antigenemia higher than in control mice. In mice treated with these antibody preparations, there was a long-lasting HIV infection with the presence of high levels of circulating infectious virus (serum p24 values up to 4000 pg/ml and serum RNA copies up to 5 x 10(7)/ml over 3 months, with the majority of the cells expressing HIV-antigens at the tumor site). Intraperitoneal treatment of SCID mice with AZT (480 mg/kg per day) resulted in a complete inhibition of both p24 and RNA HIV-1 copies in the serum, together with a marked reduction in the number of infected cells and the levels of virus expression at the tumor site. We conclude that some specific features of this model (i.e. easy establishment, high reproducibility, well defined kinetics of virus infection, massive and long persistent viremia) underline the special advantages of its use for testing new antiviral therapies.

Animals↗
PubMed1997

The biological relevance of polykaryons in the immune response.

Peripheral blood monocyte-derived multinucleated giant cells are a well-known feature of chronic inflammatory conditions. Similarly, virus-induced syncytia derived from CD4+ cells are considered to be typical of human immunodeficiency virus infection under culture conditions. Here, Stefano Fais and colleagues summarize recent experimental results comparing the mechanisms underlying the formation and fate of these two different polykaryons, discussing their putative role in the immune response.

CD4-Positive T-Lymphocytes↗
PubMed1996

T-cell dysfunctions in hu-PBL-SCID mice infected with human immunodeficiency virus (HIV) shortly after reconstitution: in vivo effects of HIV on highly activated human immune cells.

The state of activation of the immune system may be an important factor which renders a host more receptive to human immunodeficiency virus (HIV) and more vulnerable to its effects. To explore this issue with a practical in vivo model, we developed a modified protocol of HIV infection in hu-PBL-SCID mice. First, we assessed the time course of activation of human peripheral blood lymphocytes (hu-PBL) in the peritoneal cavity of SCID mice. At 2 to 24 h after the intraperitoneal injection into SCID mice, there was a clear-cut increase in the percentage of hu-PBL expressing early activation markers (CD69), concomitant with the release of soluble intercellular adhesion molecule-1 (sICAM-1) and the soluble interleukin-2 receptor (sIL-2R) and with the accumulation of mRNAs for a number of human cytokines. At 2 weeks, virtually all of the hu-PBL expressed the memory phenotype (CD45RO) and HLA-DR antigens as well. Cells collected from the SCID mouse peritoneum at 2 and 24 h after transplantation were fully susceptible to in vitro infection with HIV type 1 (HIV-1) in the absence of either IL-2 or mitogens. The injection of HIV into hu-PBL-SCID mice at 2 h after reconstitution resulted in a generalized and productive HIV infection of the xenochimeras. This early HIV-1 infection resulted in a dramatic depletion of human CD4+ cells and in decreased levels of sICAM-1 (in the peritoneal lavage fluid) as well as of sIL-2R and immunoglobulins M and A (in the serum). Enzyme-linked immunosorbent assay and/or reverse transcriptase PCR analysis showed higher levels of IL-4, IL-5, and IL-10 in the HIV-infected animals than in control hu-PBL-SCID mice, while gamma interferon levels in the two groups were comparable. When we compared the current model of HIV-1 infection at 2 weeks after the intraperitoneal injection of the hu-PBL in the SCID mice with the model described here, we found that the majority of immune dysfunctions induced in the 2-h infection of the xenochimeras are not inducible in the 2-week infection. This supports the concept that the state of activation of human cells at the moment of the in vivo infection with HIV-1 is a crucial factor in determining the immune derangement observed in AIDS patients. These results show that some immunological dysfunctions induced by HIV infection in AIDS patients can be mimicked in this xenochimeric model. Thus, the hu-PBL-SCID mouse model may be useful in exploring, in vivo, the relevance of hu-PBL activation and differentiation in HIV-1 infection and for testing therapeutic intervention directed towards either the virus or the immune system.

Animals↗
PubMed1996

Human immunodeficiency virus type 1 induces cellular polarization, intercellular adhesion molecule-1 redistribution, and multinucleated giant cell generation in human primary monocytes but not in monocyte-derived macrophages.

In this study, we evaluated the effects of human immunodeficiency virus type 1 (HIV-1) on some morphologic and functional changes in cultured human monocytes/macrophages at different stages of differentiation. Freshly isolated monocytes infected with HIV-1 24 hours after seeding exhibited marked morphologic changes such as uropod formation, polarization of intercellular adhesion molecule-1 (ICAM-1) on the cytoplasmic projection, the redistribution of alpha-actinin on cell-membrane dots, and an increased release of soluble ICAM-1. These changes preceded the increase in monocyte-monocyte fusion and the formation of multinucleated giant cells. In contrast, HIV-1 infection did not affect monocyte-derived macrophages in terms of either cellular polarization or multinucleated giant cell formation. Immunocytochemistry showed that HIV-1 matrix protein was present mostly in bi- and trinucleated cells, which suggests that multinucleated giant cells may represent a long-lived and highly productive cellular source of HIV. The treatment of the HIV-1-infected monocytes with azidodeoxythymidine virtually abolished all viral-induced morphofunctional changes. On the whole, these results indicate that blood monocytes and differentiated macrophages may be affected differently by HIV infection, as monocytes seem to be much more prone to polarize, undergo homotypic fusion, and form multinucleated giant cells. These changes may confer to HIV-infected monocytes an increased ability to transmigrate through endothelia into tissues, whereas differentiated macrophages may have a predominant role as a widespread reservoir of HIV.

Adolescent↗
PubMed1995

The SCID mouse reaction to human peripheral blood mononuclear leukocyte engraftment. Neutrophil recruitment induced expression of a wide spectrum of murine cytokines and mouse leukopoiesis, including thymic differentiation.

In this study, we describe the kinetics of host immune reactions occurring in mice with severe combined immunodeficiency (SCID) at different times after the intraperitoneal injection of human peripheral blood mononuclear leukocytes (huPBL). At 24 hr, a massive neutrophil recruitment and an induced expression of a wide spectrum of murine cytokine mRNA (i.e., interleukin [IL]-1 beta, IL-4, IL-6, IL-10, IL-12, tumor necrosis factor [TNF]-alpha and interferon [IFN]-gamma) occurred in the huPBL-SCID mouse peritoneal cavity. By using ELISAs specific for mouse cytokines, large amounts of IL-1-alpha, TNF-alpha, IL-6, and IFN-gamma were detected in the peritoneal washings of huPBL-SCID mice 1 day after intraperitoneal injection. IL-6 and IFN-gamma production persisted for up to 2 weeks after PBL transplantation. Medullary and extramedullary expansion of the SCID mouse hematopoietic cells also occurred in the chimeras as early as 1 week after injection, together with a marked thymic differentiation (murine CD4+/CD8+ cells) at 10-12 weeks after transplantation. On the whole, these results indicate that, after huPBL injection, SCID mice mount a complex multistage immune response. These host reactions should be taken into consideration for any accurate interpretation of results obtained using the huPBL-SCID model. The control of responses (by means of specific antibodies to murine cytokines and to granulocytes or through the use of anti-inflammatory drugs) may be helpful in improving the engraftment of huPBL in SCID mice and in furthering our knowledge of the T and B cell-independent natural immune reactions.

Animals↗
PubMed1995

Antibody to ICAM-1 mediates enhancement of HIV-1 infection of human endothelial cells.

Human umbilical vein endothelial cells (HUVEC) can be abortively infected with HIV-1, but virus production is rescued by the addition of T cells. Monoclonal antibody (Mab) to ICAM-1, but not its Fab' fragment or MAbs to LFA-1 and PECAM-1, increases HIV-1 infection of HUVEC by enhancing HIV-1 absorption. Enhancement by anti ICAM-1 is probably due to a bridging effect different from the ADE mediated by anti-gp120 that involves FcR or CR-mediated capture of the virus-antibody complex. Since antibodies to cell membrane molecules are present in HIV-1 infected patients, the ADE mediated by such a mechanism can be important in AIDS pathogenesis.

Antibodies, Monoclonal↗
PubMed1995

Host cell antigenic profile acquired by HIV-1 is a marker of its cellular origin.

HIV-1 acquires cell membrane proteins during budding. The cell membrane proteins (CMP) profile of laboratory HIV-1 strains grown in different host cells was established, by using an immobilized antibody capture (IAC), to verify whether CMPs present on HIV-1 correlate with its host cell origin. HIV-1 grown in different cell lines incorporates cell markers such as CD3, CD19, CD14, CD31 and IL 2-R, according to the distinctive expression of these antigens on the host cells. Furthermore, also T-tropic and monocytotropic HIV-1 strains display host cell specific markers, supporting the hypothesis that virus associated CMPs are a marker of host cell origin.

Antigens, CD↗
PubMed1995

Peripheral monocyte and naive T-cell recruitment and activation in Crohn's disease.

BACKGROUND & AIMS: Transmural perivascular mononuclear cell infiltrates are a feature of Crohn's disease. The aim of this study was a molecular characterization of the mechanisms leading to the formation of these infiltrates. METHODS: Endothelial cell and leukocyte expression of the adhesion molecules directing leukocyte transendothelial migration were studied in situ by immunohistochemical analysis of 10 samples from patients with Crohn's disease and 10 samples from normal controls. Double-staining methods were used to characterize the cells forming the infiltrates. RESULTS: CD11a+ and L-selectin-positive mononuclear cells seemed to be the major component of perivascular infiltrates. The vast majority of these cells were CD68+, CD31+ monocytes/macrophages surrounded by CD3+, L-selectin-positive, CD31+, CD45RA+, and/or CD45RO+ T lymphocytes. T lymphocytes within the vessels expressed both CD45RA and CD45RO markers. Endothelial cells were intercellular adhesion molecule 1 positive and mostly CD34+. Strong adhesion between L-selectin-positive and CD11a+ intravascular mononuclear cells and CD34+ and intercellular adhesion molecule 1-positive endothelial cells were observed. CONCLUSIONS: Data indicate that peripheral mononuclear cells are actively recruited in the submucosa of Crohn's disease tissue; endothelial cells express adhesion molecules highly permissive for transendothelial migration of monocytes and both naive and memory T cells contributing to infiltrates generation; and close membrane contact between migrated macrophages and naive T cells leads to the T-cell transition from naive to memory phenotype within Crohn's disease.

CD3 Complex↗
PubMed1995

HIV type 1 grown on interferon gamma-treated U937 cells shows selective increase in virion-associated intercellular adhesion molecule 1 and HLA-DR and enhanced infectivity for CD4-negative cells.

Cellular adhesion molecules, such as ICAM-1, -2, and -3; LFA-1; and HLA class I and II are incorporated into HIV-1 virions during budding from infected cells. These virion-associated molecules can be involved in the adsorption to susceptible cells displaying the corresponding counterligands. A number of cytokines have been shown to upregulate the cellular expression of adhesion molecules, such as ICAM-1 and HLA-DR. In this study we investigated the effects of IFN-gamma on the incorporation of ICAM-1, LFA-1, and HLA-DR into mature HIV-1 progeny from chronically infected cells. The ability of such virus progeny to infect either CD4-positive or -negative cells was also investigated. The results indicate that IFN-gamma stimulates the expression of ICAM-1 and of HLA-DR on HIV-1-infected cells, whereas LFA-1 expression is unaffected. The same modifications were also observed on virus progeny, because specific MAbs to ICAM-1 and HLA-DR captured infectious HIV-1 from IFN-treated cells with higher efficiency as compared to virus from control cells, whereas virus binding to anti LFA-1 MAb was unchanged. Moreover, the HIV-1 progeny released from IFN-treated cells showed an increased ability to bind to and to infect CD4-negative cells, whereas the infectivity was basically unchanged for CD4-positive cells. Our results suggest that cytokines, as well as other soluble factors, may expand the host cell range of HIV-1, possibly through modifications of the cell-derived surface molecules on the virions.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4 Antigens↗
PubMed1995

Regulation of U-937 monocyte adhesion to cultured human mesangial cells by cytokines and vasoactive agents.

Leukocyte adhesion to kidney cells is an early event in renal inflammation, such as glomerulonephritis. We developed an experimental model of monocyte adhesion to cultured human mesangial cells. U-937 myelomonocytic leukaemia cells, similar to peripheral blood human monocytes, irreversibly bound to mesangial cell monolayers upon 30-180 min coincubations (to a max. of 13,600 +/- 1100/cm2 monolayer), as assessed by cell counting, U-937 labelling with 3H-thymidine, and colorimetry of nuclear staining with crystal violet. Adhesion was enhanced in mesangial cells proliferating in response to 17% fetal bovine serum, indicating expression of a proinflammatory phenotype. E. coli lipopolysaccharide (LPS), tumour necrosis factor-alpha (TNF-alpha) and protein kinase C activation with phorbol myristate acetate (PMA) potentiated monocyte binding during either coincubation or 24-h pretreatment (0.1 microM PMA, +200 +/- 21%). Binding was also promoted by pretreatment with vasoconstrictors, such as the thromboxane A2 mimetic, U-46619 (10 nM-1 microM, max. +35 +/- 3%), or 1 microM angiotensin II (+64 +/- 4%). To elucidate the mechanisms of monocyte adhesion, we analysed the adhesion molecules expressed by human mesangial cells, employing reverse transcription/polymerase chain reaction to detect ICAM-1, VCAM-1 and E-selectin gene expression. Proliferating cells express VCAM-1 and ICAM-1, confirmed by immunocytochemical staining and 79 +/- 3% inhibition of stimulated adhesion by pretreatment of mesangial cells with an anti-ICAM-1 monoclonal Ab. E-selectin transcription was not detectable.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1995

Inability of normal human intestinal macrophages to form multinucleated giant cells in response to cytokines.

Multinucleated giant cells are an important feature of the granulomatous reaction in Crohn's disease (CD) but their cellular origin is poorly understood. The aim of this study was to discover if intestinal macrophages are capable of generating multinucleated giant cells in vitro in response to cytokine stimulation. Human intestinal macrophages were isolated from the intestinal mucosa of CD and uninflamed surgical specimens. Isolated macrophages were cultured in chamber slides with and without exposure to a panel of cytokines and cell activators. Cell fusion, multinucleated giant cells formation, and the expression of adhesion molecules were assessed at various time intervals. In contrast with the autologous peripheral monocytes cell fusion was very poor in cultures of control intestinal macrophages and virtually no multinucleated giant cells were seen. Control intestinal macrophages seemed to poorly express the adhesion molecules required for cell to cell adhesion and fusion, namely ICAM-1 and LFA-1. None of these functions was affected by the exposure to cytokines, including interferon gamma. In cultures of macrophages isolated from CD tissues multinucleated giant cell formation spontaneously occurred as early as three days and was not enhanced by the addition of cytokines. CD macrophages seemed to highly express both ICAM-1 and LFA-1. These data show that human intestinal macrophages are unable to form multinucleated giant cells in response to stimuli and support the concept that they are downregulated in a number of functions. The data also suggest that macrophages participating in the ganulomatous reaction in CD are recruited from the circulation.

Cell Culture Techniques↗
PubMed1995

Unidirectional budding of HIV-1 at the site of cell-to-cell contact is associated with co-polarization of intercellular adhesion molecules and HIV-1 viral matrix protein.

OBJECTIVES: To explore the possibility that HIV-1 budding and cellular adhesion molecules co-polarize at cell-to-cell contact sites. To investigate the incorporation of host-cell-derived adhesion molecules into HIV-1. METHODS: The cellular sites involved in HIV-1 budding were examined by transmission electron microscopy. Single and double immunocytochemistry staining was used to evaluate the cellular distribution of the viral matrix protein and adhesion molecules. Quantitative flow cytometry was used to measure the cellular expression of adhesion molecules. An immunocapture technique was used to measure the presence of cell-derived proteins on HIV-1. The captured virus was measured by a p24 antigen assay. The infectivity of virus captured by monoclonal antibodies was tested by measuring the virus antigen yield in supernatants after the addition of sensitive cells. RESULTS: Released and budding HIV-1 was mainly localized at the cell-to-cell contact regions. This feature was consistent with a polarized staining for the virus matrix protein p18 at cell-to-cell contact regions. Intercellular adhesion molecules (ICAM)-1 in HIV-1-infected cells were polarized on both isolated cells and syncytia, co-localizing with HIV-1 matrix protein. HIV-1 incorporated all the adhesion molecules expressed by the host cells, although without quantitative correlation with their cellular expression. CONCLUSIONS: HIV-1 is released at cell-to-cell membrane contact sites. Both ICAM-1 and virus matrix protein co-polarized on isolated cells and syncytia at the sites involved in the recruitment of uninfected cells. The impressive concentration of ICAM at cell sites where most virions are released may account for the acquisition of these membrane proteins by the HIV-1 progeny, and may be important for the cell-mediated spread.

Antigens, CD↗
PubMed1994

Vasoactive intestinal polypeptide modulates the in vitro immunoglobulin A production by intestinal lamina propria lymphocytes.

BACKGROUND/AIMS: Vasoactive intestinal polypeptide (VIP) modulates the immunoglobulin (Ig) synthesis in the peripheral blood of humans and in various lymphoid organs of other species. Because VIP receptors have been shown on lamina propria mononuclear cells (LPMC), the effects of graded doses of VIP on the in vitro Ig production by normal human LPMC was investigated. METHODS: Colonic LPMC were cultured with or without graded doses of VIP (1 pmol/L-1 mumol/L). The concentrations of Ig A, G, and M in the 12 days supernatants were quantitated by an enzyme-linked immunosorbent assay, and the effects of VIP were characterized by limiting dilution analysis (LDA). RESULTS: The addition of VIP was associated with a significant increase in the production of IgA, whereas IgG levels were significantly reduced. Both these effects were restricted to LPMC. LDA showed that the IgA-enhancing effect was associated with an increase in the number of IgA-producing precursor cells and with variation in the regulatory phenomena involved in IgA production. CONCLUSIONS: In humans, a major function of the mucosal immune system (i.e., the synthesis of IgA) is modulated by VIP. Data suggest that VIP may either act as an indirect switch factor or increase the clone size of pre-committed cells.

Cells, Cultured↗
PubMed1994

Inhibitory effect of somatostatin-14 and some analogues on human natural killer cell activity.

The effect of somatostatin-14 (SST) and the SST analogues SMS and RC160 on human natural killer (NK) activity mediated by large granular lymphocytes (LGL), as well as on IL-2- and/or anti-CD16 monoclonal antibody (mAb)-induced activation of these cells, was investigated. The NK activity of LGL was studied by the release of 51Cr by the erythroleukemia-derived cell line K562, whereas 51Cr release by the P815 murine mastocytoma-derived cell line, for which lysis was redirected by the use of an anti-CD16 mAb, was used to study the cytolytic potential of these cells. IL-2 was used at the final concentration of 100 IU and was incubated overnight with LGL. SST and the analogues, added to these systems at final doses ranging from 10(-12) to 10(-5) M, were inhibitory of the NK cell activity to K562, with a dose-response curve starting from 10(-8) M and reaching a significant level at 10(-6) M. On the contrary, no effect was observed on the redirected killing assay to P815 and on the IL-2-induced activation of NK cells. These results provide additional evidence for the immunomodulatory action of somatostatin.

Adult↗
PubMed1994

Interferon expression in Crohn's disease patients: increased interferon-gamma and -alpha mRNA in the intestinal lamina propria mononuclear cells.

The in vivo interferon (IFN) activation in Crohn's disease was evaluated by measuring the relative amounts of IFN-alpha and -gamma mRNA in freshly isolated human lamina propria mononuclear cells (LPMC) from patients with Crohn's disease and controls. Both IFN-gamma and IFN-alpha mRNA, as estimated by dot blot analysis, were increased in Crohn's disease (LPMC), although the relative amounts of IFN mRNA appeared to differ among patients. Appreciable amounts of IFN-gamma mRNA were found in Crohn's disease peripheral blood mononuclear cells (PBMC) extracts, whereas the same cells were negative for IFN-alpha mRNA. Only minute amounts of IFN-gamma RNA were found sporadically in control LPMC while no IFN-alpha was detected. Control PBMC were shown to be virtually negative for both IFN-alpha and IFN-gamma mRNA. These data suggest that IFN induction in the normal human gut is a well-controlled function and that in Crohn's disease tissues, both IFN-gamma and IFN-alpha production are dysregulated. The increased IFN activity may represent a major feature in the induction and perpetuation of the chronic inflammatory process in Crohn's disease.

Crohn Disease↗