The role of N-linked carbohydrates in the antigenicity of Taenia solium metacestode glycoproteins of 12, 16 and 18 kD.

The glycoproteins of 12-28 kD from Taenia solium metacestodes provide a high specificity and sensitivity for the serological diagnosis of the central nervous system infection, neurocysticercosis. Their widespread use as antigens for routine serological assays will require their production in large and reproducible amounts. Prior to determining the ideal strategy to produce these antigens at a large scale, it is important to determine the contribution of the carbohydrates to the antigenicity of these molecules, given the uncertainty of reproducing saccharidic epitopes in recombinant expression systems. In this study we examined this issue. The chemical oxidation of the carbohydrates of the 12-28 kD glycoproteins with sodium metaperiodate, reduced the antigenicity of the molecules to variable extents, with the more notable changes being detected for the 18 and 28 kD antigens. This approach was complemented by purification of the 12, 16 and 18 kD antigens, followed by the enzymatic deglycosylation of their abundant N-linked oligosaccharides. Silver-stained SDS-PAGE analysis indicated that the three deglycosylated antigens now migrated as 7 kD products, suggesting a protein backbone with a similar size, but different extents of glycosylation. By Western blot, the antigenicity of these antigens was diminished. This was more notable for the 18 kD antigen, which is more heavily glycosylated than the 12 or 16 kD glycoproteins. These data suggest that the antigenicity of the glycoproteins of T. solium is due to a combination of carbohydrate and protein epitopes.

Characterisation of the carbohydrate components of Taenia solium metacestode glycoprotein antigens.

Human neurocysticercosis is caused by Taenia solium metacestodes. It usually affects the central nervous system of humans and can be confused with other brain pathologies. The Lens culinaris-binding glycoproteins from this parasite have been shown to be ideal targets for the development of a highly specific immunoassay for the diagnosis of neurocysticercosis. In the present study we characterised the carbohydrates associated with five antigenic glycoproteins of T. solium metacestodes in the range of 12-28 kilodaltons. Lectin-affinities and enzymatic deglycosylations suggested that each of the five antigens contain various glycoforms of asparagine-linked carbohydrates of the hybrid, complex and probably high mannose type. These carbohydrates accounted for at least 30-66% of the apparent molecular mass of the glycoconjugates. In contrast, there was no evidence for the presence of O-linked carbohydrates. Lectin affinity patterns suggested that the sugars are short and truncated in their biosynthetic route, and that some contain terminal galactose moieties. Elucidating the precise structure of the carbohydrates and establishing their role in antigenicity will be essential to design strategies to produce them in large and reproducible amounts for the development of improved immunoassays.

The 1,2,3-benzothiadiazoles. A new type of compound acting on coupling site I, in rat liver mitochondria.

1. In rat liver mitochondria, 6-chloro-1,2,3-benzothiadiazole inhibited ADP phosphorylation and Ca2+-transport when the energy required for these processes came from the oxidation of NAD-linked substrates. The inhibition was characterized by substantial reduction in oxygen consumption, H+-movement and disappearance of acceptor control ratio. 2. When the substrate oxidized was succinate, depending on the 6-chloro-1,2,3-benzothiadiazole concn., little or no effect was observed on ADP phosphorylation and Ca2+-transport. 3. The results suggest that 6-chloro-1,2,3-benzothiadiazole can block site I at low concn., but at higher concn. can affect site I and site II, although site I is always more affected.