Colonization by Superantigen Producing <i>Staphylococcus aureus</i> in Mice Enhances the Capacity to Develop Oral Tolerance

Abstract

Microbial stimulation in early childhood may be necessary for proper maturation of the immune system. Infants colonized with Staphylococcus aureus have low risk of developing food allergy. Neonatal exposure to staphylococcal superantigen improves oral tolerance and enhances protection in experimental allergy models. Here, we used three wild-type strains of S. aureus , naturally harboring genes for different superantigens (SElM/SElO alone, or in combination with SEA or TSST-1). We first investigated their in vitro stimulatory capacity of splenocytes from germ-free mice. Secondly, germ-free mice were colonized with the strains and their capacity to develop oral tolerance was tested in a food allergy model. In vitro , S. aureus with only SElM/SElO genes promoted the strongest B-cell stimulation. S. aureus carrying gene for SEA induced the highest proportion of CD4 + FoxP3 + T cells. The proportion of regulatory T cells was inversely correlated to B-cell proliferation, indicating suppressive ability of these cells. All strains were equally able to colonize the germ-free gut, initially achieving 10 10 CFU/g faeces, which decreased to 10 5 over a period of six weeks. Mice colonized with S. aureus carrying genes for SEA or TSST-1 had improved capacity to develop tolerance compared to germ-free mice. These results suggest that colonization by S. aureus producing superantigens may improve active tolerance to gut allergens.