IDEHU   05542
INSTITUTO DE ESTUDIOS DE LA INMUNIDAD HUMORAL PROF. RICARDO A. MARGNI
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Immunization with VirB7 from Brucella abortus, a modulator of macrophage functions, protects mice from virulent challenge
Autor/es:
POLLAK C; DELPINO MV,; FOSSATI, CA; BALDI PC,
Lugar:
Buenos aires
Reunión:
Congreso; First French-Argentine Immunology Congress. LVIII Reunión Anual de la Sociedad Argentina de Inmunología; 2010
Resumen:
Brucella survival inside macrophages depends on the type IV
secretion system (T4SS) encoded by virB
genes. We evaluated in vitro the
modulation of macrophage functions by T4SS structural proteins located in Brucella external membrane (VirB7 and
VirB9). Monocytic human THP-1 cells were preincubated with recombinant VirB7 or
VirB9 proteins and stimulated for 24 h with agonists of TLR4 (LPS), TLR2
(Pam3Cys) or TLR5 (flagellin), and TNF-α and IL-1β levels were measured in
culture supernatants. Only VirB7-pretreated cells showed a significant decrease
of LPS- or flagellin-stimulated IL-1β secretion (>77% and >81%,
respectively), and of LPS-, Pam3Cys- or flagellin-stimulated TNF-α secretion
(62%, 63% and 90% respectively). In view of these results we decided to
evaluate if immunization with VirB proteins awards protection to Brucella challenge. BALB/c mice were
immunized twice with either VirB7, VirB9 or PBS mixed with Freund's adjuvant.
As positive vaccination control a group received a dose of heat-killed B. melitensis H38. One month after the
last dose half of the animals were challenged with B. abortus 544 and the other half was used for immune response
studies. One month after challenge animals were sacrificed and spleens were
extracted for bacterial counts. Specific anti-VirB7 IgG1 titers were higher
than IgG2, and the opposite was true for anti-VirB9. In cellular response tests
both proteins specifically stimulated IFN-γ secretion (VirB7, 3223.03 ± 873.39
pg/ml vs. 83,89 ± 80.56 pg/ml in PBS control; VirB9, 477.81 ± 235.42 pg/ml vs.
30,98 ± 34,31 pg/ml). VirB proteins did not stimulate IL-4 secretion. Splenic
bacterial loads after B. abortus
challenge were significantly lower in mice immunized with VirB proteins than in
the PBS group. These results suggest that VirB7 modulates human macrophages
functions, contributing to Brucella
survival inside these cells. In addition, VirB7 and VirB9 are potentially
useful for developing acellular vaccines against Brucella