Evidence for oral ingestion as the principal route ofantigen entry in bath-immunized fish

The uptake of bovine serum albumin by the skin of bath-immunised rainbow troutOncorhynchus mykiss

“…Recently, Robohm & Koch (1995) suggested that the intestine was the principal site of antigen uptake, because plugging fish oesophagi with a dental-impression compound reduced the uptake of botulinum toxin nearly sixfold in bath treatment. However, their suggestion seems to be inapplicable to ordinary bath immunisation for the following two reasons.…”

“…In contrast, later studies reported that the gill is the main site of antigen uptake (Bower & Alexander, 1981;Alexander et al, 1981), and this is generally accepted at present (Smith, 1982;Tatner et al, 1984;Zapata et al, 1987;Kawahara & Kusuda, 1988). The intestine has also been proposed as a site of antigen uptake (Robohm, 1986;Rombout et al, 1985;Tatner, 1987;Robohm & Koch, 1995). Thus, the primary site responsible for antigen uptake has been a controversial topic with several organs having been implicated.…”

Particulate antigen uptake during immersion immunisation of fish: The effectiveness of prolonged exposure and the roles of skin and gill

“…Robohm and Koch (1995) showed that plugging the oesophagi of fish swimming in water containing a lethal dose of a soluble toxin significantly reduced mortality relative to untreated control fish. Although some uptake of soluble antigen may occur (Rombout et al, 1986), there is no evidence for significant uptake of antigen in particulate form through the gastrointestinal tract.…”

“…The step of antigen entry is likely a critical factor limiting the success of this delivery method. Qualitative and some quantitative evidence has shown that antigen enters through the skin (Smith, 1982;Tatner et al, 1984), and the gill (Tatner et al, 1984;Zapata et al, 1987) and is present in the gastrointestinal tract as a result of swallowing during exposure (Tatner, 1987;Robohm & Koch, 1995). Nevertheless the relative contributions of these tissues and optimal delivery parameters remain unclear due to di$culties in quantifying uptake.…”

Different prevalences of Renibacterium salmoninarum detected by ELISA in Alaskan chinook salmon Oncorhynchus tshawytscha spawned from freshwater and seawater

“…Again, the soluble antigen would be extremely diluted by ambient water but bioaccumulation of low levels in kidney tissues that are detectable by our ELISA (220 ng ml-'; Meyers et al 1993b) is feasible during continual exposure of fish for several weeks. Fish rapidly adsorb (Smith 1988) certain Gram-negative and Gram-positive bacterial antigens from ambient water through the gills (Alexander et al 1981, Smith 1982 or by drinking water containing the antigens (Robohm & Koch 1995). These antigens accumulate in various fish tissues including the kidney (Nelson et al 1985).…”