[Show abstract][Hide abstract] ABSTRACT: In vitro studies show that Leishmania infection decreases the adhesion of inflammatory phagocytes to connective tissue by a mechanism dependent on the modulation of integrin function. However, we know little about the influence of this reduction in leukocyte adhesion on parasite dissemination from the infection site.
[Show abstract][Hide abstract] ABSTRACT: Most inbred strains of mice, like the BALB/c strain, are susceptible to Leishmania amazonensis infections and resistant to Leishmania braziliensis infections. This parasite-related difference could result from the activity of an L. amazonensis-specific virulence factor. In agreement with this hypothesis, it is shown here that the intravenous injection of BALB/c mice with L. amazonensis amastigote extract (LaE) but not the L. braziliensis extract confers susceptibility to L. braziliensis infection. This effect was associated with high circulating levels of IgG1 anti-L. amazonensis antibodies and with an increase in interleukin-4 (IL-4) production and a decrease in gamma interferon production by draining lymph node cells. Moreover, the effect was absent in IL-4-knockout mice. The biological activity in the LaE was not mediated by amphiphilic molecules and was inhibited by pretreatment of the extract with irreversible serine protease inhibitors. These findings indicate that the LaE contains a virulence-related factor that (i) enhances the Leishmania infection by promoting Th2-type immune responses, (ii) is not one of the immunomodulatory Leishmania molecules described so far, and (iii) is either a serine protease or has an effect that depends on that protease activity. In addition to being Leishmania species specific, the infection-enhancing activity was also shown to depend on the host genetic makeup, as LaE injections did not affect the susceptibility of C57BL/6 mice to L. braziliensis infection. The identification of Leishmania molecules with infection-enhancing activity could be important for the development of a vaccine, since the up- or downmodulation of the immune response against a virulence factor could well contribute to controlling the infection.
Infection and immunity 03/2011; 79(3):1236-43. · 4.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This report describes the characterisation of a monoclonal antibody (mAb), AB6, which recognises specifically a cluster of canine leukocyte surface molecules. The immunogen used for obtaining the AB6 mAb was a lysate of canine peripheral blood mononuclear cells (PBMC). This novel mAb belongs to the IgG2a isotype, and reacted in Western blot with four different canine leukocyte glycoproteins with apparent molecular weights of 180, 190, 205 and 220 kDa. The AB6 mAb recognised the majority of canine peripheral blood leukocytes as determined by flow cytometry (97%). It also exhibited a broad reactivity pattern against lymphoid and myeloid cells, inhibited the proliferation of mitogen-stimulated canine PBMC and did not recognise human PBMC and murine splenocytes. The biochemical properties, cell and tissue specificity, and in vitro biological activity of the AB6 mAb indicate that it recognises a canine CD45 homologue. The mAb could become a valuable diagnostic and research tool for the evaluation of immune functions in dogs.
The Veterinary Journal 02/2007; 173(1):158-66. · 2.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Leishmania spp. are intracellular parasites that cause lesions in the skin, mucosa, and viscera. We have previously shown that Leishmania infection reduces mononuclear phagocyte adhesion to inflamed connective tissue. In this study, we examined the role of adhesion molecules and chemokines in this process. Infection rate (r = -0.826, P = 0.003) and parasite burden (r = -0.917, P = 0.028) negatively correlated to mouse phagocyte adhesion. The decrease (58.7 to 75.0% inhibition, P = 0.005) in phagocyte adhesion to connective tissue, induced by Leishmania, occurred as early as 2 h after infection and was maintained for at least 24 h. Interestingly, impairment of cell adhesion was sustained by phagocyte infection, since it was not observed following phagocytosis of killed parasites (cell adhesion varied from 15.2% below to 24.0% above control levels, P > 0.05). In addition, Leishmania infection diminished cell adhesion to fibronectin (54.1 to 96.2%, P < 0.01), collagen (15.7 to 83.7%, P < 0.05), and laminin (59.1 to 82.2%, P < 0.05). The CD11b(hi) subpopulation was highly infected (49.6 to 97.3%). Calcium and Mg(2+) replacement by Mn(2+), a treatment that is known to induce integrins to a high state of affinity for their receptors, reverted the inhibition in adhesion caused by Leishmania. This reversion was completely blocked by anti-VLA4 antibodies. Furthermore, expression of CCR4 and CCR5, two chemokine receptors implicated in cell adhesion, was found to be downregulated 16 h after infection (2.8 to 4.1 times and 1.9 to 2.8 times, respectively). Together, these results suggest that mechanisms regulating integrin function are implicated in the change of macrophage adhesion in leishmaniasis.
Infection and Immunity 08/2006; 74(7):3912-21. · 4.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The production and partial characterization of a monoclonal antibody, the IgG1 IH1, which recognizes an antigen distributed in canine monocytes/macrophages, is reported here. The distribution and apparent molecular weight of the antigen recognized by the IH1 MAb was determined in peripheral blood leukocytes, peripheral blood monocyte-derived macrophages and tissue sections of spleen, liver and skin, using Western blotting, immunocytochemistry, immunohistochemistry and flow cytometry. The IH1 MAb-recognized antigen was detected in Western blotting under non-reducing conditions spread out as a large band covering the position corresponding to the migration of molecules with molecular weights from 55 to 73 kDa. The IH1 MAb labeled blood monocytes, tissue macrophages in lymph nodes, and in the mantle zone of the spleen, and Kupffer cells in the liver. It did not react with human cells. In flow cytometric analysis, the IH1 MAb reacted with a subpopulation of monocytes. The MAb described herein may become a valuable tool for diagnosis and research on canine diseases.