INHIBITION OF IN-VITRO REPLICATION OF THE OYSTER PARASITE PERKINSUS-MARINUS BY THE NATURAL IRON CHELATORS TRANSFERRIN, LACTOFERRIN, AND DESFERRIOXAMINE

The mammalian iron-binding proteins transferrin and lactoferrin, the b actericidal peptide lactoferricin B, and the bacterial siderophore des ferrioxamine were tested for their ability to inhibit the in vitro rep lication of the oyster parasite Perkinsus marinus. All three chelators were effective in reducing the parasite proliferation in a dose-depen dent manner. Lactoferricin B, a peptide of lactoferrin that exhibits b actericidal properties unrelated to iron chelation, had no inhibitory activity on the parasite. When the chelators were partially or complet ely saturated with the appropriate iron equivalents, their inhibitory effects on the parasite proliferation were diminished or abolished acc ordingly, confirming that this activity was related to the chelator's capacity for iron sequestration. Our results indicate that the parasit e has a strong requirement for soluble iron and its growth rates are c orrelated with iron availability. We propose that excess iron accumula tion in the host Crassostrea virginica promotes parasite proliferation . P. marinus may avoid oxidative damage that would compromise its intr acellular survival by exhaustion the host's intracellular selected iro n pools required for superoxide and hydroxyl radical production.