IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
- Brucella lumazine synthase, a polymeric protein that induces cross-priming and generates a specific cytotoxic response via TLR4
Autor/es:
P BERGUER, V ALZOGARAY, J MUNDIÑANO, I PIAZZON, F GOLDBAUM
Lugar:
Seattle, WA, USA
Reunión:
Simposio; Keystone Symposia, Immunological Mechanisms of Vaccination; 2010
Resumen:
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The
enzyme lumazine synthase from Brucella
spp. (BLS) is a highly immunogenic protein that folds as a stable dimer of
pentamers. It is possible to insert foreign peptides and proteins at its
ten-amino acid termini without disrupting its general folding, and these
chimeras are very efficient to elicit systemic and oral immunity without
adjuvants, which are commonly needed in the formulation of subunit-based
vaccines.
We
showed that BLS stimulates bone marrow dendritic cells from mice in vitro
to up-regulate the levels of costimulatory molecules (CD40, CD80, and CD86) and
major histocompatibility class II Ag. Furthermore, the mRNA levels of several
chemokines are increased, and proinflammatory cytokine secretion is induced
upon exposure to BLS. In vivo, BLS
increases the number of dendritic cells and their expression of CD62L in the
draining lymph nodes of immunized mice. All of the observed effects are
dependent on TLR4. An in vivo
cytotoxicity assay showed that immunization with a BLS chimera displaying 10
copies of ovalbumin peptide 257-264 (OVAp) induces a strong OVAp-specific
effector CTL response even in the absence of adjuvant and that is dependent on
TLR4.
To
test the ability of BLS to induce the cross-priming of CD8+ cells, transgenic
CD8+ cells specific for OVAp were adoptively transferred into normal mice. After
20 h, BLS-OVAp immunization induces the proliferation of OVAp-specific CD8+
lymphocytes and increases the percentage
of OVAp-specific CD8+ cells
expressing CD69. After 5 days, the percentage of OVAp-specific CD8+ cells
expressing high levels of CD44 increases in BLS-OVAp-immunized mice. This cell
subpopulation shows a decreased expression of IL-7Rα, indicating
that BLS-OVAp induces the generation of CD8+ effector cells.
Unlike
other subunit-based vaccines, BLS and BLS chimeras induce rapid activation of dendritic
cells, CTLs and a specific cytotoxic response, making this polymeric protein an
ideal antigen carrier for vaccine development.