TRANSPORT OF AN INFLUENZA-VIRUS VACCINE FORMULATION (ISCOM) IN CACO-2CELLS

The influenza virus envelope glycoproteins hemagglutinin and neuramini dase were administered to the apical or basolateral sides of Caco-2 mo nolayers either as native protein micelles (mic-ag) or after incorpora tion into the orally active adjuvant formulation, immune stimulating c omplexes (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 in tracellular vesicles and intercellular spaces were labeled, and extrac ellular labeling was observed on the basolateral side of the cells, in dicating that isc-ag were transported across the epithelium within 10 min of exposure. Transport of I-125-labeled isc-ag and mic-ag in the a pical-to-basolateral and basolateral-to-apical directions across Caco- 2 monolayers was comparable at 37 degrees C. Gel chromatography analys is 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 i sc-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-p erformance liquid chromatography indicated that transported antigenic isc-ag consisted of hydrophobic peptides with a molecular weight of le ss than or equal to 3,000. These results indicate that antigens incorp orated into the orally active adjuvant formulation iscom are degraded to antigenic peptides during transport across the intestinal epitheliu m.