Production and evaluation of the recombinant antigen TES-30 of Toxocara canis for the immunodiagnosis of toxocariasis.

INTRODUCTION: Toxocara canis is a pathogenic nematode of canines which can be accidentally transmitted to humans. Although serology is the most important diagnostic tool for this zoonosis, diagnostic kits use crude excretion/secretion antigens, most of them being glycoproteins which are not species-specific and may cross-react with antibodies generated against other parasites.  OBJECTIVES: To produce the rTES-30 recombinant antigen of Toxocara canis and evaluate it in the immunodiagnosis of toxocariasis.  MATERIALS AND METHODS: The gene that codes for TES-30 was cloned in the expression vector pET28a (+) using single-stranded oligonucleotides united by PCR. The protein rTES-30 was purified by Ni2+ affinity chromotography. Seroreactivity of rTES-30 was evaluated by immunoblot. Given that there is no gold standard test, the behaviour of the antigen was compared with the method that is routinely used to immunodiagnose toxocariasis, i.e., the conventional ELISA technique using excretion/secretion antigens.  RESULTS: The rTES-30 was produced from an Escherichia coli LB culture which yielded 2.25 mg/L of the antigen with a purity of 95%. The results obtained showed 73% (46/63) concordance of reactivity between the rTES-30 immunoblot and the conventional ELISA, and 100% concordance with the nonreactive sera (21). Nineteen of the 21 sera positive for other parasitoses reacted with ELISA, while only seven of these were positive with the rTES-30 immunoblot. Concordance between the ELISA and the immunoblot was moderate (kappa coefficient: 0.575; 95% CI: 0.41- 0.74).  CONCLUSIONS: The data presented show the potential of the rTES-30 inmunoblot for confirmation of possible ELISA positives, not only in epidemiological studies, but also as a candidate for the development of diagnostic tests for ocular toxocariasis in Colombia.

Clinical characteristics of ocular toxocariasis patients on the first attendance / 中华眼底病杂志

Objective To investigate the clinical characteristics of 40 patients with ocular toxocariasis (OT) on the first attendance.Methods A total of 40 consecutive patients who were clinically and serologically diagnosed with OT were retrospectively reviewed.Results The mean age of patients was (12.12±10.42) years.There were 29 males and 11 females.29 cases presented with decreased vision,4 children with leukocoria,2 cases with strabismus and 5 cases was found abnormal during regular eye examination.Initially 8 eyes (20％) were misdiagnosed as retinoblastoma (1 eye),Coat' s disease (1 eye),cataract (2 eyes),iridocyclitis (2 eyes) and retinal detachment (2 eyes).23 eyes had retinal detachment,19 eyes had cataract.OT was the initial diagnosis for 15 patients (37.5％).The best corrected visual acuity (BCVA) were NLP to 0.7.Ultrasound biomicroscopy (UBM) were performed in 29 eyes,and identified peripheral granulomas in 23 eyes and adjacent tractional retinal detachment in 12 eyes.We also identified 17 cases (68.0％) with elevated IgE level among 25 patients with positive serological antibody test.Conclusions Tractional retinal detachment,vitreous opacities and cataract are the common clinical findings at the first attendance of OT patients.The adjunctive test of serum total IgE level may be helpful for the diagnosis.The application of UBM and specific IgG detection in serum and intraocular fluid,can also improve the diagnosis.