Streptococcal H2O2 inhibits IgE-triggered degranulation of RBL-2H3 mast cell/basophil cell line by inducing cell death.

Mast cells and basophils are central players in allergic reactions triggered by immunoglobulin E (IgE). They have intracellular granules containing allergic mediators (e.g., histamine, serotonin, inflammatory cytokines, proteases and ß-hexosaminidase), and stimulation by IgE-allergen complex leads to the release of such allergic mediators from the granules, that is, degranulation. Mast cells are residents of mucosal surfaces, including those of nasal and oral cavities, and play an important role in the innate defense system. Members of the mitis group streptococci such as Streptococcus oralis, are primary colonizers of the human oral cavity. They produce hydrogen peroxide (H2O2) as a by-product of sugar metabolism. In this study, we investigated the effects of streptococcal infection on RBL-2H3 mast cell/basophil cell line. Infection by oral streptococci did not induce degranulation of the cells. Stimulation of the RBL-2H3 cells with anti-dinitrophenol (DNP) IgE and DNP-conjugated human serum albumin triggers degranulation with the release of ß-hexosaminidase. We found that S. oralis and other mitis group streptococci inhibited the IgE-triggered degranulation of RBL-2H3 cells. Since mitis group streptococci produce H2O2, we examined the effect of S. oralis mutant strain deficient in producing H2O2, and found that they lost the ability to suppress the degranulation. Moreover, H2O2 alone inhibited the IgE-induced degranulation. Subsequent analysis suggested that the inhibition of degranulation was related to the cytotoxicity of streptococcal H2O2. Activated RBL-2H3 cells produce interleukin-4 (IL-4); however, IL-4 production was not induced by streptococcal H2O2. Furthermore, an in vivo study using the murine pollen-induced allergic rhinitis model suggested that the streptococcal H2O2 reduces nasal allergic reaction. These findings reveal that H2O2 produced by oral mitis group streptococci inhibits IgE-stimulated degranulation by inducing cell death. Consequently, streptococcal H2O2 can be considered to modulate the allergic reaction in mucosal surfaces.

Bacteriotherapy for preventing recurrent upper respiratory infections in children: a real-world experience.

Background Recurrent upper respiratory infections (RURI) constitute a social problem for both their pharmaco-economic impact and the burden for the family. Bacteriotherapy could be an interesting preventive option. Objective The aim of this study was to evaluate the preventive effects of RURI in children. Design The study was designed as spontaneous, and was conducted in real-life seting. Globally, 80 children (40 males, mean age 5.26 (2.52) years) with RURI were enrolled. Children were treated with Streptococcus salivarius 24SMB and Streptococcus oralis 89a: nasal spray 2 puffs per nostril twice/day for a week for 3 monthly courses. Number of URI, and school and work absences were evaluated and compared with the past year. Results Bacteriotherapy significantly halved the mean number of URI episodes being 5.98 (2.30) in the past year and 2.75 (2.43) after the treatment (p<0.0001). Bacteriotherapy also induced an over 35% reduction both in the number of school days and in the number of working days missed per month from 4.50 (2.81) to 2.80 (3.42) and from 2.33 (2.36) to 1.48 (2.16) respectively (p<0.0001). Conclusions This and real-life study provides the first evidence that Streptococcus salivarius 24SMB and Streptococcus oralis 89a nasal spray could be effective in preventing RURI in children.