RESUMO
BACKGROUND: OM-85 is an immunostimulant bacterial lysate, which has been proven effective in reducing the number of lower airways infections. We investigated the efficacy of the bacterial lysate OM-85 in the primary prevention of a murine model of asthma. METHODS: In the first phase of our study the animals received doses of 0.5ìg, 5ìg and 50ìg of OM-85 through gavage for five days (days −10 to −6 of the protocol), 10 days prior to starting the sensitisation with ovalbumin (OVA), in order to evaluate the results of dose-response protocols. A single dose (5ìg) was then chosen in order to verify in detail the effect of OM-85 on the pulmonary allergic response. Total/differential cells count and cytokine levels (IL-4, IL-5, IL-13 and IFN-ã) from bronchoalveolar lavage fluid (BALF), OVA-specific IgE levels from serum, lung function and lung histopathological analysis were evaluated. RESULTS: OM-85 did not reduce pulmonary eosinophilic response, regardless of the dose used. In the phase protocol using 5ìg/animal of OM-85, no difference was shown among the groups studied, including total cell and eosinophil counts in BALF, serum OVA-specific IgE, lung histopathologic findings and lung resistance. However, OM-85 decreased IL-5 and IL-13 levels in BALF. CONCLUSIONS: OM-85, administered in early life in mice in human-equivalent doses, does not inhibit the development of allergic pulmonary response in mice
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