Purification and evaluation of the integral membrane protein H11 as a protective antigen against Haemonchus contortus.

A detergent extract of adult Haemonchus contortus enriched in the integral membrane protein H11, previously shown to give protective immunity against the parasite, was fractionated by lectin and ion-exchange chromatography. The fractions were evaluated for their ability to immunize Clun Forest and Dorset Horn sheep against experimental haemonchosis. Most of the protective activity was associated with H11. Used in an approximately 95% pure form it gave a mean reduction in parasite egg output of 94.6% and reduced male and female worm numbers by 86.5 and 93.5%, respectively. Level of protection correlated with serum antibody titre to H11.

The potential value of integral membrane proteins in the vaccination of lambs against Haemonchus contortus.

An extract of adult Haemonchus contortus enriched in the parasite's intestinal microvillar membrane protein H11 and other integral membrane proteins but free of the protein contortin was evaluated as a potential vaccine in two breeds of sheep. The worm burdens of Clun Forest sheep injected with the extract and challenged with 25,000 infective larvae were reduced 89% by weight compared to the average for the controls. The worm burdens of Dorset sheep (challenged with 10,000 infective larvae) were reduced 72%. In both breeds the reduction in the number of female worms, 92 and 71.8%, respectively, was greater than the reduction in the males (86.5 and 46%). Parasite egg output, determined only for the Dorsets, was reduced 92% protection correlated with serum antibody titre. Most of the antibodies were directed against H11.

Vaccination of merino lambs against haemonchosis with membrane-associated proteins from the adult parasite.

Groups of South African, farm-reared merino lambs about 4 months old were vaccinated with extracts of adult Haemonchus contortus enriched with H11, an integral membrane protein from the parasite's intestinal microvilli, or with proteins soluble in Tween 20. The lambs were challenged with 5000 infective 3rd-stage larvae. Compared to the adjuvant-injected controls, lambs vaccinated with 350 micrograms/kg liveweight of the H11-enriched extract showed an 89% reduction in parasite egg production and an 88% reduction in total worm burden at post-mortem 35 days post-challenge. The H11-enriched extract contained some protein also present in the Tween 20 extract. Lambs vaccinated with 600 micrograms/kg of protein soluble in Tween 20 showed a 40% reduction in faecal egg counts and 51% reduction in total worm numbers 35 days post-challenge. Animals injected with 20 micrograms/kg of a sub-fraction containing H11 obtained from the H11 extract, showed a 71% reduction in egg output and total worm numbers.

The ultrastructure and possible relationships of four obligate anaerobic chytridiomycete fungi from the rumen of sheep.

Zoospores and vegetative growth phases of three cellulolytic rumen chytridiiomycetes, Piromonas, Sphaeromonas and NF1 have been examined by electron microscopy and compared with published and new data on Neocallimastix. The four genera have some 16 distinctive ultrastructural features in common, which collectively may be used to define the group. Some of the common features may individually be sufficient to distinguish these obligate anaerobes from facultative and aerobic chytridiomycetes. These features are the presence of hydrogenosomes at all stages of the life cycle, the presence in rhizoids and sporangia of characteristic crystals coated with hexagonal arrays of particles, and in zoospores the presence of distinct surface layers on the motility organelles and cell body respectively, the organization of the ribosomes into helical and globular arrays and the structures associated with the kinetosomes.

Vaccination of young lambs by means of a protein fraction extracted from adult Haemonchus contortus.

Lambs aged 48-150 days which had been injected with extracts enriched in a functional antigen (contortin) obtained from adult Haemonchus contortus developed specific circulating antibodies and were less susceptible to haemonchosis when challenged 1 month later with a single dose of 20,000-25,000 infective 3rd-stage larvae. Sera from 18 out of a total of 19 lambs injected with the extract contained precipitating antibodies to 2-5 components of the extract. None of these lambs died. The one extract-injected lamb which did not develop antibodies and 9 of the 13 lambs used as controls died of haemonchosis. The average weight of worms recovered was 1.45 g from the immune lambs and 5.72 g from the non-immune lambs.

Hydrogenosomes in the rumen fungus Neocallimastix patriciarum.

Sedimentable hydrogenase activity was demonstrated in cell-free extracts from both zoospores and vegetative growth of the anaerobic rumen fungus Neocallimastix patriciarum. Electron micrographs of the fraction enriched in hydrogenase activity contained finely granular microbody-like organelles, about 0.5 micron in diameter and having an equilibrium density of about 1.2 g X ml-1 in sucrose, 1.12 g X ml-1 in Percoll and 1.27-1.28 g X ml-1 in Metrizamide. These organelles, which are sedimentable at 10(5) g-min, bear no similarity to mitochondria, but are morphologically similar to hydrogen-evolving organelles possessed by certain anaerobic protozoa and termed 'hydrogenosomes'. Other typical hydrogenosomal enzymes, namely 'malic' enzyme, pyruvate:ferredoxin oxidoreductase and NADPH:ferredoxin oxidoreductase, were enriched in the same particle fraction as hydrogenase. The synthesis of pyruvate:ferredoxin oxidoreductase was found to be suppressed when the organism was cultured under an atmosphere of CO2, and an alternative pathway is proposed for growth under these conditions.

Endotube-brush border complexes dissected from the intestines of Haemonchus contortus and Ancylostoma caninum.

A procedure for the blunt dissection of the syncytial intestine of Haemonchus contortus to separate the endotube-brush border complex is described. A similar complex can be obtained from the partially cellular intestine of Ancylostoma caninum. The structural features of the complexes from the two sources are compared. The main differences are in the retention of terminal bars by the endotube from A. caninum and in the extent and organization of the microfilaments associated with the basal side of the endotubes.