Tissue location of Vibrio antigen delivered by immersion to tiger shrimp (Penaeus monodon)

Using an indirect fluorescent antibody technique, we traced the tissue location of heat-killed Vibrio vulnificus antigen delivered by immersion to tiger shrimp (Penaeus monodon). At selected time intervals (5 min, 3, 6 and 12 h, and 1, 3, 7 and 14 days) following administration, we observed antigen uptake in hemolymph and tissues such as the gills, stomach, hepatopancreas, intestines, hematopoietic tissue and lymphoid organ, but not in the heart. In addition, we found some differences in time of appearance and amount of Vibrio antigen detected among these tissues. Various amounts of antigen were detectable in plasma and hemocytes 1 day following delivery, in the gills up to day 7, in the hepatopancreatic and hematopoietic tissue to day 3, in the stomach and midgut to the end of day 1, in the hindgut for only 6 h, and in the lymphoid organ from 6 h to 7 days; by day 14, the antigen was completely undetectable. According to the immunohistological results, we consider that Vibrio antigen is absorbed through the digestive and circulatory systems. The systemic, rather than local, defense system of tiger shrimp can be enhanced; however, this enhancement is only of short duration.