IMMUNOMODULATION OF Lactobacillus reuteri CRL1324 ON GROUP B Streptococcus VAGINAL COLONIZATION IN A MURINE EXPERIMENTAL MODEL

DE GREGORIO PRISCILLA ROMINA; NADER-MACÍAS MARÍA ELENA FÁTIMA; JUÁREZ TOMÁS MARÍA SILVINA

San Miguel de Tucumán, Tucumán.

Simposio; SIBAL 2016 - V Simposio Internacional de Bacterias Lácticas.; 2016

Centro de Referencia para Lactobacilos

Group B Streptococcus (GBS) is an opportunistic pathogen of high clinical relevance mainly in pregnant women. Maternal GBS colonization is one of the higher risk factors for developing disease in newborns, which is also promoted by the increasing antibiotic resistance. One of the most promising strategies is to modulate the vaginal defense mechanisms to increase the host?s ability to avoid microbial colonization or combat infection. The use of beneficial vaginal lactobacilli (BVL) with antibacterial and immune modulatory properties is suggested as a novel and adequate alternative. The inhibitory effect on GBS murine vaginal colonization after the intravaginal (i.va.) inoculation of a BVL (Lactobacillus reuteri CRL1324) was previously demonstrated in our research group. The aim of this work was to evaluate the effect of the i.va. L. reuteri CRL1324 inoculation on different immune cellular populations, cytokines and immunoglobulin isotypes of the vaginal tract, in order to determine if the decrease in the number of viable GBS is a consequence of the modulation of the immune system. Female BALB/c mice in a pseudo-estrous condition were randomly assigned to five experimental groups: (i) Lactobacillus (Lb)+pathogen (Pt)-treated mice (i.va. inoculated seven times with 108 CFU of L. reuteri CRL1324 and later i.va. challenged with a single dose of 107 CFU of GBS NH17), (ii) Pt-challenged mice (i.va. inoculated seven times with saline and later i.va. challenged with107 CFU of GBS NH17), (iii) Lb-treated mice (i.va. inoculated seven times with 108 CFU of L. reuteri CRL1324 and later with saline), (iv) hormone control mice (inoculated only with saline), and (v) agarized peptone control mice (inoculated only with agarized peptone, the media used for lactobacilli inoculation). On the days 1, 5 and 7 post-Pt challenge, flow cytometry was applied to identify: a) specific immune cell populations (neutrophils, macrophages, B and T lymphocytes) from vaginal tissue, and b) cytokines (TNF-α, IFN-γ, IL-6, IL-10, IL-2, IL-17, and IL-4) and antibodies (IgM, IgA, IgE, and IgG subclasses: IgG1, IgG2a, IgG2b, IgG3) from vaginal washing. Data were analyzed using ANOVA (general linear model). The inoculation of L. reuteri CRL1324 previous to the GBS challenge showed an immunomodulatory effect on the mediators and cells of innate immunity, inhibiting the TNF-α production and neutrophil recruitment induced by the pathogen, and increasing the IFN-γ and IL-10 levels and the activated macrophages population. These events could have exerted some type of effect on the increase of the IL-6 levels, B-lymphocytes, IgA and IgG subclasses (IgG1 and IgG2a) observed in the vagina of mice inoculated with L. reuteri CRL1324 before the GBS challenge. Our results indicate that L. reuteri CRL1324 shows a protective effect against GBS colonization that was mediated by the modulation of the innate immune response.