Excretory secretory
proteins produced in vitro by Anisakis simplex larvae incubated in Medium 199 or
phosphate buffered saline with
dextrose are similar with respect to
protein content and
biological activity. Analysis by
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis suggested that the molecular weight of the component(s) responsible for inhibition of
mitogen induced lymphocyte blastogenesis is between 66,000 and 95,000. In vitro production of excretory secretory
protein, approximately 1 microgram/24 hr by a single larva, was sufficient to inhibit lymphocyte blastogenesis. Serum from a human
anisakiasis patient reacted with these
proteins in immunoblots, indicating that, during invasion of the gastric mucosa, enough of them are produced in vivo to induce an immune response. The excretory secretory
proteins significantly inhibited proliferation of transformed mammalian cell lines of lymphoid (P3/X63-Ag8) and epithelioid (HeLa) origin. As in
mitogen stimulated lymphocytes, the inhibitory effect was
cytostatic rather than cytotoxic. These findings suggest that, in addition to being potent immunogens, larval excretory secretory
proteins are produced in sufficient quantity to modulate the host response in
anisakiasis.