THE POTENTIAL USE OF TOMATO LECTIN FOR ORAL-DRUG DELIVERY .4. IMMUNOLOGICAL CONSEQUENCES

Previously, it has been shown that the non-toxic tomato lectin (TL) may have potential for oral drug delivery as both an intestinal bioadhesive and a drug carrier - it binds specifically to glycoproteins on the enterocyte surface, resulting in increased uptake of TL in vitro, and exhibits resistance to digestion in the gastrointestinal tract in vivo. In this study, the potential immunological consequences of the uptake of TL by the intestine were investigated by examining the ability of TL to be recognised by TL-specific antibodies after uptake in vitro and to elicit immune responses after uptake in vivo. After incubation in an improved everted gut sac system, TL or TL fragments were found to be able to react with anti-TL antibodies in an ELISA after intestinal processing and transfer into the serosal fluid. Feeding microgram quantities of TL to mice in vivo elicited high specific serum IgG responses and, to a lesser extent, specific intestinal IgA responses. The responses were dose-dependent. Preincubating TL with competing sugar gave measurable reductions in specific serum IgG and intestinal IgA levels. Whilst these results may limit the use of TL as an oral drug carrier for chronic delivery, the possibility is raised of using TL to promote immunization by the oral route.