Neurocysticercosis: utilizing the cystic fluid antigen from Taenia solium metacestodes for diagnosis by IgG-ELISA.

Cystic fluid, which has antigenic properties of whole Taenia solium cysticerci, was used to discriminate neurocysticercosis cases and other parasitic infections, especially helminthiases. Twenty-one neurocysticercosis and several kinds of 22 different parasitic infections, including HIV cases (n=234) evaluated a 90.48% sensitivity and 86.32% specificity of indirect ELISA as follows: a low antigen concentration of 5 microg/ml. serum dilution of 1:400, conjugate dilution of 1:2,000 and a cut-off value of 0.349. Eight different helminthic infections (n = 25); echinococcosis (8/10), gnathostomiasis (6/8), strongyloidiasis (5/14), hookworm infection (1/18), angiostrongyliasis (2/25), opisthorchiasis (1/18), onchocercosis (1/3) and toxocariasis (1/6) were cross-reactive with this antigen. No serum antibody from other brain infections in the study gave a reaction with the antigen. In this study, the cystic fluid antigen gave high sensitivity of the test. However, the antigen contains various antigenic molecules able to bind with antibodies from several of the above helminthic sera, especially echinococcosis and gnathostomiasis. In Thailand, gnathostomiasis is one of the more famous tropical diseases but echinococcosis is quite rare. Cystic fluid antigen should be further investigated for its specific finding in diagnosis.

Use of delipidized antigens of Taenia solium metacestodes in IgG-ELISA for detection of neurocysticercosis.

The development of IgG-ELISA for detecting neurocysticercosis is aimed at the routine laboratory, and requires a particular antigen preparation, an acceptable number of serum samples to be tested (both homologous and heterologous) and patients with a diversity of helminthic infections to rule out cross-reactions. This study characterizes IgG-antibodies from cases of neurocysticercosis by assaying the sera against ether-delipidized antigens (5 microg/ml) prepared from metacestodes of Taenia solium. The test had a sensitivity of 90% and a specificity of 83%. IgG-antibodies from heterologous serum samples elicited a number of false positives (25/147) from six different helminthic infections, ie paragonimiasis, echinococcosis, opisthorchiasis, ascariasis, taeniasis and fascioliasis. In additional tests to detect antibody levels to these stage-related antigens, one of three serum samples from T. solium-infected cases gave negative at OD value of 0.187 while the others yielded 0.472 and 0.576. Conversely, assays of all serum samples from neurocysticercosis cases reacted against antigens from Echinococcus granulosus cystic fluid, Paragonimus heterotremus and Opisthorchis viverrini adult worms. In comparison, the antigens from these three species yielded higher mean OD values when assayed against the corresponding infected serum samples. Furthermore, neurocysticercosis cases yielded OD values that are separate and distinct from those of paragonimiasis cases.