Tissue localization of excretory-secretory antigens of larval Toxocara canis in acute and chronic murine toxocariasis.

The distribution of excretory-secretory antigens of larval Toxocara canis (TEX) in tissue was studied in cases of both acute and chronic experimental murine toxocariasis. Liver samples were collected from BALB/c BYJ mice killed either 2 days (acute) or 8 months (chronic) after intragastric inoculation with infective T. canis eggs. Cryostat sections of liver were stained using biotin-conjugated, rabbit anti-TEX antibody with an avidin-fluorescein isothiocyanate indicator. In both acute and chronic infections larval sections were brightly fluorescent. The patterns of antigen deposition in acute infections were indicative of larval migration. In tissue sections from chronic infections, antigens were observed mainly within the core of granulomas centered around larvae and within the inner rim of the collagen capsule of granulomas in which a larva or larval remnant was not detected. When present within the collagenous capsule, TEX appeared to be extracellular. These findings suggest that an accurate histopathological diagnosis of larval toxocariasis may be possible in biopsy or autopsy material lacking an obvious etiological agent.