Uptake and processing of a Vibrio anguillarum bacterin in Artemia franciscana measured by ELISA and immunohistochemistry

Nauplii of Artemia franciscana were incubated in two different concentrations (undiluted and 1:9 in autoclaved sea water) of a divalent bacterin composed of two different serovars of Vibrio anguillarum. In order to investigate uptake and further processing of a bacterin in the live feed organism A. franciscana, immunohistochemistry was applied, visualising the presence of whole bacterial cells and antigens from the bacterin in individual nauplii. By using ELISA, it was shown that approximately 1.5-2-5 x 10(5) cells were incorporated into each Artemia under the conditions used. Maximum incorporation of cells was measured after 30 min, whereas after 60 min there was a decline to levels of 0.9-1.6 x 10(5) cells per Artemia. Immediately after incubation in the bacterin solution, the nauplii were transferred to a culture of the alga Isochrysis galbana, in order to simulate transfer of the nauplii to rearing tanks for fish larvae. From the ELISA, it could be concluded that the incorporated bacterial cells were excreted from the Artemia nauplii rapidly, however a large variation among different nauplii could be visualised by immunohistochemistry.