Study of immune responses in Mus musculus after oral administration of Bacillus halotolerans and Bacillus subtilis

In recent years, there has been increased interest in developing vaccine platforms that may be quickly adapted to combat various viruses. In this regard, there is a prospect of developing a recombinant oral vaccine based on enteroinvasive bacteria of the genus Bacillus for the control of infectious diseases in farming. The microorganism Bacillus halotolerans which is able to withstand extreme environmental conditions and has antagonistic activity may also become a promising biological agent. The effect of enteroinvasive strains on the induction of proinflammatory shifts in the blood picture and in the wall of the middle section of the small intestine (Intestinum jejunum) in laboratory animals was studied on ICR (CD-1) mice. To evaluate immunological responses, the expression of genes involved in the formation of an inflammatory immune response such as Vegf-A, Foxp3, Tgf-β1 in samples of the jejunum, spleen and lungs was studied by PCR. In our previous studies, B. halotolerans was characterized by invasiveness and was isolated from the liver upon oral administration, and also stimulated the formation of antibodies to its autoantigens. In this study, we showed that B. halotolerans, when administered orally to mice of the Mus musculus species, led to a significant shortening of the jejunal villi, indicating the presence of proinflammatory reactions in the intestine. However, it did not affect the depth of intestinal crypts and did not cause changes in blood composition. The absence of a proinflammatory response did not statistically significantly correlate with increased expression of the Vegf-A, Foxp3, and Tgf-β1 genes in the intestinal wall.