Surface carbohydrate changes onOnchocerca lienalislarvae as they develop from microfilariae to the infective third-stage inSimulium ornatum

Abstract

Use was made of seven FITC labelled lectins as tools to investigate the surface ofOnchocerca lienalislarvae as they develop through to the infective third-stage in a natural vector,Simulium ornatum. The lectins were derived fromCanavalia ensiformis(Con A),Lens culinaris(lentil),Triticum vulgaris(wheat germ),Arachis hypogaea(peanut),Helix pomatia, Phaseolus vulgaris(kidney bean) andTetragonolobus purpureus(asparagus pea). Between 70 and 100 living parasites were examined for each developmental stage; i.e. skin microfilariae, late first-stages, second-stages, preinfective third-stages and infective third-stages isolated from the mouth parts of the flies. None of the lectins used bound to the surface of the microfilariae. However, progressive binding to the cuticle of the first- and second-stages was observed using Con. A, lentil lectin and wheat germ agglutinin (WGA). Following moulting to the third-stage, binding of these three lectins declined. Furthermore, as these lectins decreased, peanut andHelix pomatialectins progressively increased in their binding, despite the fact that they showed little or no binding to the first- and second-stages; stages at which Con A, lentil and WGA were at their maximum. Asparagus pea and kidney bean lectins failed completely to bind to any of the larvae examined. Carbohydrate inhibition tests showed that the lectin was indeed binding specifically to glycoconjugates on the parasite surface. WGA binding was not inhibited by prior incubation with N-acetyl-D-glucosamine, even at high concentrations, but neuraminic acid did completely inhibit its binding. Judging from the patterns of binding on the nematodes themselves, the carbohydrates may not be vector in origin, but derive from the worms. The lectin specificities indicate that initially mannose/glucose type derivatives are present on the surface. Following moulting to the third-stage these are progressively replaced, or overlaid with galactosamine type derivatives, also present on the infective third-stage as it enters the bovine host. The availability of these surface glycoconjugates to attack mediated by natural insect lectins may be of importance in the parasite regulatory mechanisms of the blackfly. Variability in these surface carbohydrates, and in the response to them could well be a contributing factor in the cytospecific variation inS. damnosumsusceptibility to geographical variants ofO. volvulus.

Surface lectin binding characteristics of developing stages of Brugia in Armigeres subalbatus: I. Brugia pahangi.

“…Similar results were reported with developmental stages of O. lienalis in Simulium (Ham et al, 1988 on both melanized mf and developing larval stages suggest that the larvae may be evading host responses through molecular mimicry. However, there is a possibility that the observed differences in surface lectin binding characteristics were due to larval age differences.…”

“…On the other hand, blood-dwelling mf and fully matured infective larvae showed little or no binding affinity for the lectins tested; apparently the worms response differently in their vertebrate host. Infective stages of O. lienalis obtained from the head also bound less lectins than those from the thorax (Ham et al, 1988). Rao et al (1987c), however, reported that the cuticular surface of L3 of W. bancrofti bound WGA.…”

Use of microarray hybridization to identify Brugia genes involved in mosquito infectivity

“…Į-tocopherol); it also is associated with alkaline phosphatase and calcium-activated ATPase activities (Araujo et al 1993;Sayers et al 1984;Smith et al 1998). Filarial developmental transitions induce changes in the protein, lipid and carbohydrate composition of the cuticle (Hirzmann 2002;Apfel et al 1992;Ham et al 1988;Lewis et al 1999), and our transcriptome data indicate that mature mf differentially produce transcripts involved in cuticular structure, including two encoding cuticular collagens, one (TC2854) that is highly similar to C. elegans col-34, and the other an uncharacterized B. malayi gene (GenBank accession no.…”

The effects of protease inhibitors and sugars on the survival and development of the parasite Onchocerca ochengi in its natural intermediate host Simulium damnosum s.l.

“…However, this is unlikely to be the explanation, because the haemolymph as such is extremely nutritious itself and the killing and clearance of Onchocerca mf occur within a few hours (Lehman et al 1994;Hagen, unpublished observations). Whatever led to improved survival during the short phase of microfilarial migration to the flight muscle of the blackflies must Methyl--d-M, methyl--d-mannopyranoside; N-acetyl-gluc, N-acetyl-d-glucosamine (Ham et al 1988b). Parallel to these developmental changes, the haemolymph lectin composition of the infected blackfly changes also (Smail & Ham 1988).…”

“…. We chose these sugars because they were used for assessing the carbohydrate changes on developing larvae of O. lienalis (Ham et al 1988b).…”