Cloning and characterization of two novel Taenia solium antigenic proteins and applicability to the diagnosis and control of taeniasis/cysticercosis.

摘要

Infections due to Taenia solium in humans (taeniasis/cysticercosis) remain a complex health problem, particularly in developing countries where pigs and humans live in close contact. Neurocysticercosis, an infection of the human central nervous system by the larval stage, is the most important cause of seizures and is now recognized as the single major cause of acquired epilepsy in the world.;Two oncosphere proteins that might protect the porcine intermediate host against cysticercosis were characterized by two-dimensional gel-electrophoresis and micro-sequencing. The first protein of approximately 31.5 kD in the crude oncosphere extract (Tso31) has four variants at the cDNA level. The predicted protein presents 253 amino acids, one putative N-glycosylation site, two fibronectin type III domains, and one C terminal transmembrane domain.;The second protein was identified after micro-sequencing of protein spots corresponding to a molecular size of 22.5 kD. At the cDNA level the protein presents a putative molecular weight of 42.7 kD and the sequence identified by micro-sequencing seems to be a fragment of this protein.;Only two pigs out of eight vaccinated with a recombinant Tso31 protein fused to GST were protected and although the total median number of cysts decreased in vaccinated pigs compared to controls this decrease was not statistically significant (P=0.09).;The N terminal fragment of the 42 kD protein was cloned and expressed, fused to GST and tested as a diagnostic antigen for the detection of human cysticercosis alone and in combination with the Tso31 protein. When the combination was used in an ELISA format the sensitivity and the specificity of the assay were 85% and 65% respectively.;Based on the genomic sequence of the Tso31 protein a nested PCR assay was developed for the specific diagnosis of taeniasis due to T. solium using DNA directly extracted from fecal samples. Samples collected and preserved in a 2% potassium dichromate solution were washed and DNA was directly purified using the FastDNARTMSPINRTMKit for Soil. Under field conditions the assay had a 100% sensitivity and specificity. The nested PCR described here might be a useful tool for the early diagnosis and prevention of taeniasis/cysticercosis.