AJP - Gastrointestinal and Liver Physiology, Vol 270, Issue 4 554-G564, Copyright © 1996 by American Physiological Society
Transport of an influenza virus vaccine formulation (iscom) in Caco-2 cells
L. Lazorova, P. Artursson, A. Engstrom and A. Sjolander
Department of Pharmaceutics, Uppsala University, Sweden.
The influenza virus envelope glycoproteins hemagglutinin and neuraminidase
were administered to the apical or basolateral sides of Caco-2 monolayers
either as native protein micelles (mic-ag) or after incorporation into the
orally active adjuvant formulation, immune stimulating complexes (iscoms)
(isc-ag). Biotin-conjugated isc-ag were localized in intracellular vesicles
as early as 2 min after administration to the apical side at 37 degrees C.
Ten minutes after administration, both intracellular vesicles and
intercellular spaces were labeled, and extracellular labeling was observed
on the basolateral side of the cells, indicating that isc-ag were
transported across the epithelium within 10 min of exposure. Transport of
125I-labeled isc-ag and mic-ag in the apical-to-basolateral and
basolateral-to-apical directions across Caco-2 monolayers was comparable at
37 degrees C. Gel chromatography analysis revealed that only 0.55-3.1% of
transported isc-ag and mic-ag had a molecular weight of > 5,000, while
21.0-42.3% was eluted at a position corresponding to peptides of
approximately 10 amino acids. Although isc-ag and mic-ag were transported
and degraded by Caco-2 monolayers in comparable amounts, only transported
isc-ag induced a dose-dependent proliferative response in vitro of T cells
primed with influenza virus antigen. High-performance gel chromatography
and reverse-phase high-performance liquid chromatography indicated that
transported antigenic isc-ag consisted of hydrophobic peptides with a
molecular weight of < or = 3,000. These results indicate that antigens
incorporated into the orally active adjuvant formulation iscom are degraded
to antigenic peptides during transport across the intestinal epithelium.
