Immunostimulative effect of lactic acid bacteria of bovine origin in intestinal tract of calves

FRIZZO, L.S.; SOTO, L.P.; SALVETTI, N.R.; ZBRUN, M.V.; SEQUEIRA, G.J.; ORTEGA, H.H.; ROSMINI, M.R.

San Miguel de Tucumán, Tucumán, Argentina

Simposio; III Simposio Internacional de II Bacterias Lácticas. Segundo Encuentro de la Red Argentina de Bacterias Lácticas (Red-BAL); 2009

CERELA-CONICET

Lactobacillus spp. are used as probiotics in calves, either as single species or in mixed cultures with other bacteria. A property attributed to probiotics is modulation of the host´s immune response. Some of their effects have been attributed to an increase in the immune response; however, the mechanisms through which these bacteria, orally administered, influence the gut immune system are still unknown. The aim of the work was to evaluate the effect of lactose and a lactic acid bacteria inoculum of bovine origin on IgA-producing cells in jejunum of young calves. Twenty four calves with an age of 10 days (average), were fed ad libitum with balanced feed. Also, milk substitute (4 l/d, 11% DM to 38 ºC) and water were given 2 times daily. The lactose was administered with the milk substitute in quantities of 50 and 100 g. Three bacteria of bovine origin were administered daily: Lactobacillus casei DSPV 318T, L. salivarius DSPV 315T and Pediococcus acidilactici DSPV 006T, all isolated from healthy calves and identified by molecular biology techniques. A factorial design in complete blocks at random was used. Four blocks were built with 6 calves and they were distributed in 6 proposed treatments. The assay was performed during 35 d. The effect of probiotic and lactose factors and interaction between both was evaluated. Data were analyzed using ANOVA and Duncan´s test. Necropsies were performed at the end of experiment to 2 calves in each experimental group. Jejunum were dissected and fixed in 10% buffered formalin during 6 h at room temperature and processed by histological techniques. Serial sections of 4 µm in thickness were obtained. On the sections was carried out the immunohistochemical technique to detect IgA-producing cells (monoclonal Anti-IgA, Serotec, 1:150). Immunostaining was made by streptavidin-peroxidase method; it was used 3.3-diaminobenzidine as chromogen. The Immunohistochemical Stained Area (IHCSA) was calculated as a percentage of total area evaluated through the colour segmentation analysis, which extracts objects by locating all objects of the specific colour (brown stain). Immunohistochemical analysis of the preparations was performed using the software Image Pro-Plus 3.0.1. Intense cytoplasmic marking in cells of the intestinal mucosa and submucosa was observed. The positive reaction showed a specific immunostaining in all cell and in the mucus. Moreover, immunostaining was observed in the secretion of the glands of the mucosa. An increase in the number of IgA-producing cells in jejunum of animals inoculated with lactic acid bacteria in comparison with control animals was observed. The increase in the expression of IgA could be due to a stimulation of the immune system and this could play an essential role in protecting animals against intestinal diseases.