Specific IgE antibody responses to somatic and excretory-secretory antigens of third stage G. spinigerum larvae in human gnathostomiasis.

Specific IgE antibody levels in the serum of patients with proven gnathostomiasis and in those with intermittent cutaneous migratory swelling (CMS) were determined by the enzyme-linked immunosorbent assay (ELISA) using somatic extract and excretory-secretory (ES) products of Gnathostoma spinigerum infective larvae as antigens. The third stage larval used were obtained from naturally infected eels. There was an increase in specific IgE antibody to both antigens in these patients. The mean levels of these specific IgE antibodies were significantly higher than that of the healthy control (P<0.01). Comparison between using somatic extract and ES products in the test showed, a positive result in the group of suspected patients with gnathostomiasis or CMS was significantly higher when using ES products (81.81%) than somatic extract (59.09%) as the antigens (P<0.05). However, both somatic and ES antigens cross-reacted with other parasitic sera. The overall sensitivity of the ELISA for these IgE antibodies detection were 71.87 per cent and 87.50 per cent with somatic and ES antigens, respectively. The specificity was 57.53 per cent when somatic antigen was used and increased to 69.86 per cent when ES antigen was used. The positive and negative predictive values of the test were 42.59 per cent and 82.35 per cent by using somatic antigen. Both of these values, were also increased to 56.00 per cent and 92.72 per cent by using the ES antigen. It is obvious that more potential components may be present in ES products than those in the somatic extract. The ES antigen may have to be further purified and may be suitable for evaluation of the effectiveness of chemotherapy. As such, the antibody responses to secreted products are more closely related to active infection than the anti-whole worm antibody that may persist following the death of the parasites. However, in this disease, the effect of the IgE antibody on its pathophysiology it is still not known.