Decreased nasal tolerance to allergic asthma in mice fed an amino acid-based protein-free diet.

Intranasal (i.n.) administration of soluble proteins induces a state of specific unresponsiveness to subsequent immunization, known as nasal tolerance. It is thought that newborns are less susceptible to nasal tolerance induction. Recently, we have shown that feeding adult animals with a protein-free diet (Aa) resulted in their arrest at an immature immunological profile. Here, we examined the effects of the Aa diet on the development of nasal tolerance to ovalbumin (OVA) in a murine model of allergic asthma. Nasal OVA administration suppressed almost totally the OVA-induced asthma-like responses (airway eosinophilia, type 2 cytokine production, and OVA-specific IgE antibodies) in chow- or casein-fed BALB/c mice. In contrast, in Aa-fed animals the suppression of asthma-like responses by nasal OVA was partial, being effective in suppressing airway eosinophilia, but not airway type 2 cytokine or OVA-specific IgE response. We conclude that animals fed the Aa diet are more resistant to the induction of nasal tolerance. Our animal model may mimic the features of the immune system of human infants.