Antigens

Toxocara excretory-secretory (TES) products are highly antigenic. The total production per larva has been estimated at 8ng/day and is constant over time (Badley et al. 1987). TES is composed of five major groups of molecules as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), having relative molecular weights of 32, 55, 70, 120, and 400kDa (Maizels et al. 1987,

1993; Maizels and Robertson 1991). By using immunoelectron-microscopy with monoclonal antibodies the internal sites containing antigens has been localized to the oesophageal gland and the midbody secretory gland (Page et al. 1992). The antigens are heavily glycosylated proteins, possessing 40% carbohydrate by weight, with ^-acetylgalactosamine and galactose as the dominant sugar (Meghji and Maizels 1986). In contrast to somatic extracts, TES do not contain phosphoryl-choline (Sugane and Oshima 1983a), a cross-reactive determinant produced by many helminths (Sugane and Oshima 1983b). However, cross-reaction has been observed with other

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helminths (Nicholas et al. 1986; Lynch et al. 1988; Kennedy et al. 1989; Smith 1991). Lately, Loukas et al. (1998) have identified a cystein protease migrating at 30 kDa, in somatic extracts of T. canis larvae. The recombinant protease was expressed in bacteria, used to immunize mice and the subsequent antiserum reacted specifically with the 30kDa native protease in the larval extract. Further studies are in progress to investigate the efficacy of the recombinant protease as a diagnostic antigen.

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