Studies on nematode secretory antigens in immunodiagnosis with special reference to toxocariasis
Inmunodiagnosis of nematode infections in man and animals is often inaccurate and unreliable. A rationale is presented for a novel serologic approach which uses in vitro cultivation of the relevant parasitic stages to isolate in vitro released secretory antigens for use in irrrnunoenzymatic assays....
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| Format: | Thesis |
| Language: | English |
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1980
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| Online Access: | https://researchonline.lshtm.ac.uk/id/eprint/4656674/ https://researchonline.lshtm.ac.uk/id/eprint/4656674/1/de%20Savigny-1980-Studies_on_nematode_secretory_antigens%20.pdf |
| Summary: | Inmunodiagnosis of nematode infections in man and animals is often inaccurate and unreliable. A rationale is presented for a novel serologic approach which uses in vitro cultivation of the relevant parasitic stages to isolate in vitro released secretory antigens for use in irrrnunoenzymatic assays. The rationale was tested in the toxocariasis model in man and experimental animals and found to be valid. An in vitro cultivation system is described for the maintenance, in synthetic medium. of actively metabolizing Toxocara canis infective larvae producing 200 pg of antigen per larva per day. Toxocaral secretory antigen was shown to be a simple mixture of at least three genus specific, protein antigens with a major component molecular weight of 42 k daltons and isoelectric point of pI = 9.5. An enzyme-linked immunosorbent assay designed to quantitate anti-toxocaral responses was validated in assays of over 1000 sera from human subjects and experimental animals. Results indicated an advance from existing methodologies. The assay was further evaluated in practice for the serodiagnosis of visceral and ocular toxocariasis. In man. these forms exhibited distinct serological patterns. A realistic model of experimental ocular toxocariasis was developed in the rhesus monkey (Macaca mulatta), and results indicated that intraocular toxocaral larvae are capable of inducing retinal pathology in animals sensitized by a previous toxocaral infection, but not in animals which are Toxocara naïve. Seroepidemiologic studies demonstrated that Iceland and Sudan are non-endemic. England is endemic and Czechoslovakia and Ghana are hyperendemic for toxocariasis. Within these areas subpopulations were identified with higher prevalence of infection. Seroepidemiology in naturally infected dogs revealed that tolerance to toxocaral secretions may occur in pups less than six months of age. The studies indicate that in vitro derived, nematode secretory antigens, used in enzyme-linked immunosorbent assays can provide highly sensitive, genus specific, and reliable immunodiagnostic and seroepidemiologic data on a basis that is both economical and practical. It is proposed that this approach might be applied to the diagnosis of other tissue-invasive nematode infections. |
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