Preliminary Studies on the Prevention of the Ovalbumin-Induced Allergic Response by <i>Enterococcus faecalis</i> CECT7121 in Mice

Abstract

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.

Treatment with &lt;i&gt;Enterococcus faecalis&lt;/i&gt; CECT7121 Is Not Effective as Therapy in Mice with an Established Allergy Status

“…This probiotic also decreased the proliferation of splenocytes and the secretion of Th2 cytokines [23]. In the latter model, we have demonstrated that the previous implantation of E. faecalis CECT7121 in the intestinal mucosa prevents the development of the allergic status.…”

“…Previously, our group has demonstrated that the i.g. administration of Enterococcus faecalis CECT7121, prior to the sensitization induced by the administration of OVA, can prevent the establishment of the allergic response [23].…”

“…OVA immunization [10 μg OVA and 1 mg Al(OH) 3 ] was performed on days 0, 7 and 21 by s.c. injection (0.2 ml) on the back of each mouse ( Figure 1). An E. faecalis CECT7121 suspension (3 × 10 8 CFU/ml, prepared as previously described [23] was administrated by the i.g. route (0.2 ml/mice/day) with a gavage needle on three doses: days 1, 2 and 3; days 13, 14 and 15 and on days 28, 29 and 30.…”

“…Baker) as previously described [23]. One hundred microlitres of spleen cell suspension (4 × 10 6 cells/ml) were cultured with 100 μl of ulture medium alone or with 100 μl of OVA (1 mg/ml; Sigma-Aldrich) in quadruplicate at 37˚C in presence of 5% CO 2 .…”

“…Specific anti-OVA IgE and IgG antibody levels were measured by indirect ELISA in individual serum samples, employing OVA as coating antigen at 10 μg/ml in phosphate-buffered saline (PBS). A biotinylated anti-mouse IgE antibody (BD Biosciences) followed by an avidine-HRP solution or a HRP-conjugated anti-mouse IgG serum (Cappel) or a HRP-conjugated anti-mouse IgG1 or a HRP-conjugated anti-mouse IgG2a sera (Bethyl) were used as secondary antibodies [23]. To determine the titre of each serum sample, two-fold serial dilutions were performed.…”