Kinetics of peptide uptake and tissue distribution following a single intranasal dose of peptide.

We have previously used intranasal (i.n.) peptide application to induce mucosal tolerance in experimental autoimmune encephalomyelitis (EAE). This strategy, however, appeared to give rise to similar phenomena of tolerance observed as a result of systemic administration of soluble antigenic peptide. We were interested, therefore, in the uptake and tissue distribution of peptide following i.n. treatment. In the H-2u mouse model of EAE, the highly tolerogenic peptide analogue Ac1-9[4Y] of myelin basic protein (MBP) displays high affinity binding to Au MHC class II. For the purpose of the present study this peptide was synthesised to contain a tritiated acetyl group and a protocol was developed to recover radioactivity in solubilised tissues taken at various times after [3H]Ac1-9[4Y] i.n.. Radiolabel loads of the lung and gastro-intestinal tract were initially high but declined rapidly. Radiolabel uptake by blood and lymphoid tissues followed similar kinetics with peak levels around 2.5-4 hours after i.n. administration. Concentrations were high in the draining cervical lymph nodes (CLN) but also reached significant levels in the spleen and 'nondraining' inguinal lymph nodes. The presence of intact antigenic peptide was demonstrated in spleens and CLN from Ac1-9[4Y] i.n. treated mice. Cell suspensions prepared from these tissues at selected time points after peptide i.n. were able to stimulate peptide-specific T cell lines up to at least one day after peptide i.n., suggesting long lasting formation of stable Au-Ac1-9[4Y] complexes in vivo.