The immune enhancement of a novel lecithin/B-glucans-based adjuvant on native Neospora caninum tachyzoites extract vaccine

MANSILLA, FLORENCIA; FRANCO MAHECHA, OLGA LUCÍA; LAVORIA, MARÍA DE LOS ÁNGELES; DADÍN PRANDO MOORE; WILDA, MAXIMILIANO; ALEJANDRA CAPOZZO

MAR DEL PLATA

Congreso; IX Congreso Argentino de Protozoología y Enfermedades Parasitarias; 2011

Sociedad Argentina de Protozoología

Neospora caninum is an intracellular protozoan of the phyllum Apicomplexa that causes abortion in cattle. Protective immunity against neosporosis involves T-cell responses and IFN-y. Currently there is no effective vaccine for controlling neosporosis. The objective of this study was to evaluate the effect of a new adjuvant (Providean-AVEC®) formulated with whole soluble-native tachyzoite lysate (sNcAg) using the BALB/c validated model The vaccine antigen was selected based on its capacity to activate dendritic cells (DC). DC were stimulated with soluble and insoluble fractions of tachyzoite lysate and inactivated tachyzoites, and the production of pro-inflammatory cytokines was determined by flow cytometry. Killed tachyzoites and sNcAg induced IL-6, TNFα and IL-12p70. sNcAg was selected as vaccine antigen because it was the most efficient in inducing pro-inflammatory cytoquines. Vaccines containing 4 y 0,4 µg of sNcAg were formulated with Providean-AVEC®, ISCOMs o Alum Hydroxide (Alum) and evaluated in the mouse model. Animals were immunized twice at two-weeks-intervals, challenged (1x106 tachyzoites/animal) 38 days post-vaccination and euthanized 21 days post-infection. Matched groups were euthanized at 38 dpv. Blood samples, spleen and brain were collected for ELISA, ELISPOT and PCR analysis, respectively. Animals immunized with 4µg de sNcAg+Providean-AVEC® seroconverted after the first dose, while the other groups needed a booster dose. Vaccination with 4µg of sNcAg+Alum elicited specific serum IgG1 and a Th2 cytokine profile, which controlled parasites during the acute phase but failed to limit the establishment of chronic infection. Mice immunized with 4µg sNcAg+ISCOM or with either 0,4 or 4µg of sNcAg Providean-AVEC® formulations elicited higher IgG2a than IgG1 serum levels, and IFN-γ anamnestic responses, with a cytokine-Th1 biased profile. These animals were protected against both acute and chronic infection; with no signs of brain parasite burden. Vaccines with 0,4 µg sNcAg formulated with ISCOM or Alum were not protective. These results show that Providean-AVEC® vaccine formulations can protect against Neosporosis even with a ten times lower antigen payload than vaccines prepared with other adjuvants. The rational formulation of vaccines with antigens capable to stimulate dendritic cells and an adjuvant that promotes serum IgG2a and IFN-y synthesis can induce protective responses against N. caninum.