MURINE IMMUNE RESPONSE TO INTRANASAL IMMUNIZATION WITH VIRB7 PROTEIN FROM BRUCELLA ABORTUS

FLORENCIA MUÑOZ GONZALEZ ; MARÍA SOLEDAD HIELPOS; PABLO CÉSAR BALDI; IVÁN ALONSO PAIVA; JULIANA FALIVENE; ANDREA GISELLE FERNÁNDEZ; MARIANA CRISTINA FERRERO

Mar del Plata

Congreso; LXIV Reunión anual de la Sociedad Argentina de Inmunología; 2016

Sociedad Argentina de Inmunología

Brucellosis is frequently transmittedto humans through mucosae. Currently, there are no human vaccines against thisdisease. Using a murine model we evaluated VirB7, a virulence factor fromBrucella, as a potential component of an acellular vaccine against brucellosis.Six week-old Balb/c mice were weeklyimmunized for 3 weeks with VirB7 (10ug) plus cholera toxin (CT, 2ug), CT alone orsaline. One week after last immunization serum, saliva, feces, bronchoalveolar (BAL)and vaginal lavage fluids, lung homogenates and spleens were obtained. Levelsof VirB7-specific antibodies were measured by indirect ELISA in all samples. Invitro production of gamma interferon (IFN-γ), interleukin2 (IL-2) and IL-5 by spleen cells stimulated with VirB7 (1 or 10 µg), ConA orRPMI was determined. Other mice (VirB7 plus CT) were injected intradermally in oppositefootpads with VirB7 or saline to evaluate DTH (24 to 72 h).Immunized mice showed increasedserum levels of total antibodies against VirB7 (p<0.0001), and of specificIgA in saliva, feces and BAL (p<0.01; p<0.05; p<0.001) compared withcontrols. IgA titers in lungs and serum were 80 and 9600, respectively. Serum titersof IgG1 were higher than those of IgG2a (16000 vs. 3840). The IgG1/IgG2a ratiowas 6. A specific DTH response was detected at all times evaluated. Splenocytesfrom immunized mice secreted high levels of IFN-γ (mean 34677 pg/mland 50270 pg/ml for 1 ug and 10 µg VirB7, p<0.01 and p<0.001 vs RPMI), IL-2(187 pg/ml and 395 pg/ml, p<0.05 and p<0.001) andIL-5 (504 pg/ml and 700 pg/ml, p<0.05 and p<0.01). No significantdifferences versus RPMI were found in the control group for any cytokine.Intranasal administration of VirB7 plusCT induced a systemic and mucosal (lung and gut) specific immune response,which may contribute to prevent the mucosal entry of Brucella and itsdissemination. The activated cellular immune response, shown by DTH reactions andhigh levels of IFN-γ, may be crucial for this protectiveeffect.