Abstract
BackgroundDuring the last two decades research on animal filarial parasites, especially Onchocerca ochengi, infecting cattle in savanna areas of Africa revealed that O. ochengi as an animal model has biological features that are similar to those of O. volvulus, the aetiological agent of human onchocerciasis. There is, however, a paucity of biochemical, immunological and pathological data for O. ochengi. Galectins can be generated by parasites and their hosts. They are multifunctional molecules affecting the interaction between filarial parasites and their mammalian hosts including immune responses. This study characterized O. ochengi galectin, verified its immunologenicity and established its immune reactivity and that of Onchocerca volvulus galectin.ResultsThe phylogenetic analysis showed the high degree of identity between the identified O. ochengi and the O. volvulus galectin-1 (ß-galactoside-binding protein-1) consisting only in one exchange of alanine for serine. O. ochengi galectin induced IgG antibodies during 28 days after immunization of Wistar rats. IgG from O. ochengi-infected cattle and O. volvulus-infected humans cross-reacted with the corresponding galectins. Under the applied experimental conditions in a cell proliferation test, O. ochengi galectin failed to significantly stimulate peripheral blood mononuclear cells (PBMCs) from O. ochengi-infected cattle, regardless of their parasite load.ConclusionAn O. ochengi galectin gene was identified and the recombinantly expressed protein was immunogenic. IgG from Onchocerca-infected humans and cattle showed similar cross-reaction with both respective galectins. The present findings reflect the phylogenetic relationship between the two parasites and endorse the appropriateness of the cattle O. ochengi model for O. volvulus infection research.
Highlights
During the last two decades research on animal filarial parasites, especially Onchocerca ochengi, infecting cattle in savanna areas of Africa revealed that O. ochengi as an animal model has biological features that are similar to those of O. volvulus, the aetiological agent of human onchocerciasis
O. ochengi galectin was identified in all studied worm stages: microfilariae, infective third-stage larvae, adult males and females
Galectin from cDNA which originated from RNA isolated from adult female O. ochengi was cloned and expressed in Escherichia coli
Summary
During the last two decades research on animal filarial parasites, especially Onchocerca ochengi, infecting cattle in savanna areas of Africa revealed that O. ochengi as an animal model has biological features that are similar to those of O. volvulus, the aetiological agent of human onchocerciasis. Antioxidants and orthologues of host cytokines and lectins [15, 16] contribute to the establishment of infection in various ways: They are involved in vital biological processes such as proliferation, cells differentiation or immune cell responses Such molecules can be collected as excretory-secretory products (ESPs) from worms kept in vitro [17, 18] and constitute potential targets for the development of new control intervention strategies [19, 20]. Galectins have been considered useful targets for the development of an antiparasitic vaccine or for therapy [23, 24] They are capable of down-regulating protective Th1 immunity, enabling survival of the parasite within the host [23, 13]. Secreted by all stages of the worms, galectins may be essential for survival of Onchocerca filariae in their definitive hosts [30]
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