A natural-based nanoadjuvant enhances humoral and cellular immune response incorporated into an inactivated enterotoxigenic Escherichia coli (ETEC) vaccine

CECCHINI ME; MONTIRONI ID; ARSAUTE S; RAVIOLO J; MAÑAS F; RUIZ MORENO F; MALETTO B; BELLINGERI R; CARIDDI LN

Congreso; LXXI Reunión Científica Anual de la Sociedad Argentina de Inmunología; 2023

In a previous study, we have demonstrated the adjuvant potential of a Minthostachys verticillata essential oil-based nanoemulsion (NEO), an Argentinian plant, into an inactivated enterotoxigenic Escherichia coli (ETEC) vaccine administered subcutaneously in mice. We observed anti-ETEC IgG levels similar to incomplete Freund's adjuvant (IFA), without a granuloma induction in the area of inoculation. In addition, the binding between NEO and ETEC was demonstrated by SEM. The aim of this study was to evaluate the IgG subclasses, the functionality of antibodies and the cytokines profile induced by NEO incorporated in an experimental inactivated vaccine against ETEC. The NEO was synthetized with 20% v/v of EO, 1% v/v of a surfactant mixture (0.75% Tween 80 and 0.25% Span 60) and 79% v/v of distillated water. Experimental vaccines were prepared as follow: a) formaldehyde-inactivated ETEC at 1x109 UFC/mL and saline solution, b) ETEC with NEO (0.5 mg/mL), c) ETEC with incomplete Freund's adjuvant (IFA) (50%), d) ETEC with EO (0,5 mg/mL) and e) ETEC with surfactant mixture (Tween80/Span60 0,5 mg/mL). Mice were divided into six groups of four animals each and vaccines were administrated subcutaneously on days 1, 14, 28 and 42. One group received only saline solution as a negative control. Animals were kept under controlled temperature, provided ad libitum access to food and water and were sacrificed 7 days after the last inoculation. For each group, a pool of sera was obtained and anti-ETEC IgG titers as wells as the IgG1 and IgG2a subclasses were determined through the indirect ELISA method. As in previous study, results showed that IgG titers of the group that received the vaccines formulated with EO as adjuvant were significantly increased compared to group that received ETEC (p˂0.0001), reaching similar values of those in IFA group. All groups vaccinated showed IgG1 levels higher than control group, being IFA the adjuvant that achieved the highest levels (p