Can orally fed antigen prime for a systemic immune response?
We adopted a classical protocol for OVA feeding in conjunction with skin immunization to explore the possibility that the choice of adjuvant and route of vaccination8 might be important in how a tolerogenic OVA-fed antigen may be seen by the immune system as an immunogenic signal. In these experiments, 6–8-week-old C57BL mice were each fed three doses of OVA on alternate days. The OVA was administered by intragastric intubation at a high (20 mg per dose) or low (200 g per dose) dose to two groups of mice (n = 6). Unfed control mice were not fed any OVA. A week later, mice were injected twice intradermally, 7 days apart, with OVA (100 g) adjuvanted in the form of immune-stimulating complexes or ISCOM.9 The experiment was replicated in three sets so that immune responses in high-dose OVA-fed mice (HDOV), low-dose OVA-fed mice (LDOV) and unfed controls could be determined at 7 days post-feeding (PF), at 7 days after one vaccination (post-vaccination 1 or PV1) and, finally, at 7 days after
