Preliminary studies on the prevention of the ovalbumin-induced allergic response by Enterococcus faecalis CECT7121 in mice.

Background: Allergic diseases are featured by an increased production of IgE due to an imbalance in the immune response towards a Th2 profile. In this work, the ability of Enterococcus faecalis CECT7121 to regulate this Th2-exaggerated response in a murine model of ovalbumin (OVA)-induced allergy was studied.

Methods: BALB/c mice intragastrically inoculated with E. faecalis CECT7121 before and during a subcutaneous immunization protocol with OVA were studied in comparison with an immunized control group. The allergen-specific immune response (IgE, IgG, IgG1 and IgG2a) was assessed. The proliferative activity of memory splenocytes and the levels of IL-4, IL-5, IL-13, IL-10, IL-12 and IFN-γ were also determined.

Results: Upon treatment with E. faecalis CECT7121 the following effects were observed: (1) a decrease in specific IgE levels, (2) an increase in anti-OVA IgG2a levels, (3) the levels of anti-OVA IgG and IgG1 remained unaltered, (4) a reduction in the proliferation rate of memory cells, (5) a decrease in the levels of the Th2 cytokines IL-4, IL-5 and IL-13, and (6) the secretion of IL-10, IL-12 and IFN-γ remained unchanged. Moreover, the incubation of human basophils with non-viable E. faecalis CECT7121 together with an allergen preparation induced the release of β-hexosaminidase at levels that were lower than control reactions and similar i.g. the spontaneous release.

Conclusions: In this model, the i.g. administration of E. faecalis CECT7121 hampers the establishment of the OVA-induced allergic immune response, suggesting that this strain could be useful for the treatment of IgE-mediated allergic diseases.