In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization

Prickett, S; Gray, PM; Colpitts, SL; Scott, P; Kaye, PM; Smith, DF; (2006) In vivo recognition of ovalbumin expressed by transgenic Leishmania is determined by its subcellular localization. Journal of immunology (Baltimore, Md, 176 (8). pp. 4826-33. ISSN 0022-1767

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: The importance of the site of Ag localization within microbial pathogens for the effective generation of CD8+ T cells has been studied extensively, generally supporting the view that Ag secretion within infected target cells is required for optimal MHC class I-restricted Ag presentation. In contrast, relatively little is known about the importance of pathogen Ag localization for the activation of MHC class II-restricted CD4+ T cells, despite their clear importance for host protection. We have used the N-terminal targeting sequence of Leishmania major hydrophilic acylated surface protein B to generate stable transgenic lines expressing physiologically relevant levels of full-length OVA on the surface of metacyclic promastigotes and amastigotes. In addition, we have mutated the hydrophilic acylated surface protein B N-terminal acylation sequence to generate control transgenic lines in which OVA expression is restricted to the parasite cytosol. In vitro, splenic dendritic cells are able to present membrane-localized, but not cytosolic, OVA to OVA-specific DO.11 T cells. Strikingly and unexpectedly, surface localization of OVA is also a strict requirement for recognition by OVA-specific T cells (DO.11 and OT-II) and for the development of OVA-specific Ab responses in vivo. However, recognition of cytosolic OVA could be observed with increasing doses of infection. These data suggest that, even under in vivo conditions, where varied pathways of Ag processing are likely to operate, the site of Leishmania Ag localization is an important determinant of immunogenicity and hence an important factor when considering the likely candidacy of vaccine Ags for inducing CD4+ T cell-dependent immunity.<br/>

Item Type: Article
Keywords: Mexicana-infected macrophages, dendritic cell subsets, helper t-cells, antigen presentation, cross-presentation, trypanosoma-cruzi, surface, protein, gene family, activation, parasites, Animals, Animals, Genetically Modified, Antigen Presentation, Base Sequence, CD4-Positive T-Lymphocytes, immunology, CD8-Positive T-Lymphocytes, immunology, Cell Line, DNA, Protozoan, genetics, Gene Expression, Leishmania major, genetics, immunology, Mice, Mice, Inbred BALB C, Mice, Knockout, Mice, SCID, Mice, Transgenic, Ovalbumin, genetics, immunology, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Subcellular Fractions, immunology
Faculty and Department: Faculty of Infectious and Tropical Diseases > Dept of Immunology and Infection
Research Centre: Leishmaniasis Group
PubMed ID: 16585577
Web of Science ID: 238769000043


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