Immunity to histotropic ascariasis in guinea pigs due to inoculation of metabolic products of larval ascaris suum

Abstract

Excretory- secretory (ES) products elaborated into ambient culture medium during axenic cultivation of Ascaris suum through second larval molt were injected into guinea pigs to evaluate their antigenic properties in inducing functional immunity to histotropic ascariasis. Culture medium which had supported developing larvae of A. suum was concentrated by dialysis and injected subcutaneouslyinto guinea pigs- two injection equivalent to 25,000 and 50,000 infective larvae respectively, were given fourteen days apart. Fourteen days following the second injection immunity was tested by orally administering 10,000 infective eggs of A. suum to each animal. Guinea pigs which had received two previous oral immunizing inoculations of infective eggs at fourteen day intervals as above (Immunized Group) and non-treated animals (Control Group) were challenged simultaneously with the ES Antigen Injected Group. Injection of ES antigen reduced the number of worms migrating (average total 578.7, 733.3, and 2641.7 for ES Antigen Injected, Immunized and Controls respectively); inhibited growth rate (average size of worms were 1.13mm, 0.53mm, and 1.61mm in the ES Antigen Injected, Immunized and Controls respectively); slowed migration rate ( 0.61, 0.69, and 0.16 in the ES Antigen Injected, Immunized and Controls respectively); and reduced pathology. Clinical, histologic and hematologic findings further affirm the immunizing properties of ES antigen. These findings support the supposition of others who have concluded that metabolic products of worms serve as antigens to induce functional immunity in vertebrate hosts (Soulsby 1962, Taffs 1964b,Guerrero, 1969).