Oesophagostomum radiatum: the effect of different adjuvants on vaccination with a partially purified protective antigen.

The components of a soluble extract of adult Oesophagostomum radiatum were separated into four fractions by gel filtration chromatography on a Superose-12 column. The second fraction had a molecular weight range of approximately 60,000-65,000 as judged by SDS gel electrophoresis. Vaccination of calves with this fraction significantly (P < 0.05) reduced faecal egg output after challenge infection. In addition, the packed cell volume of vaccinated calves was higher than that of control calves (P < 0.05). The effect of three adjuvants on the vaccine activity was compared. Fraction 2 presented in dextran sulfate reduced the faecal egg count by 93.6% (P < 0.05), Fraction 2 in Freund's complete adjuvant reduced the faecal egg count by 27% (P = N.S.). Quil A was ineffective as an adjuvant.

The development of a recombinant Babesia vaccine.

Crude extracts of Babesia bovis parasites were shown to induce levels of protection in susceptible cattle equivalent to that resulting from natural infection. The crude material was systematically fractionated and tested in numerous sequential vaccination/challenge experiments in adult cattle. Antigens in protective fractions were then purified by affinity chromatography with monoclonal antibodies. Three highly protective (more than 95% reduction in parasitaemias) antigens were thus identified. None of these antigens was immunodominant; a number of immunodominant antigens were identified and all were immunosuppressive and/or non-protective. The three protective antigens were cloned and expressed as either beta-galactosidase or glutathione-S-transferase (GST) fusion proteins. Two of these, GST-12D3 and GST-11C5, when used in combination were almost as protective as has been previously shown for the commercially available live attenuated vaccine. A short fragment of a third antigen (21B4) has also been shown to be protective. In two of the antigens, repetitive segments have been shown to be non-protective while the third antigen (12D3) does not contain repetitive domains. Homologues of these antigens exist in other Babesia species and it is anticipated that these may be candidate antigens for protective vaccines against those species.

Oesophagostomum radiatum: successful vaccination of calves with high molecular weight antigens.

Extracts of adult Oesophagostomum radiatum were resolved into four fractions by gel filtration chromatography on a Superose 12 column. ELISA assays on these four fractions showed that the antibodies produced by naturally infected calves predominantly reacted with the void volume fraction (VV). Three trials were conducted in which calves were vaccinated with the VV fraction of adult extract. When compared to untreated controls, vaccination with the VV of adult extract significantly (P less than 0.05) reduced worm establishment and faecal egg output after challenge infection relative to untreated controls.

Differential recoveries from faecal cultures of larvae of some gastro-intestinal nematodes of cattle.

Faecal cultures were established using bovine faeces containing known numbers of eggs from either Oesophagostomum radiatum, Haemonchus placei, Cooperia pectinata or a mixture of all three. A substantially greater percentage of larvae was recovered from cultures of O. radiatum and C. pectinata than was recovered from cultures of H. placei. The same pattern was observed in mixed cultures although yields of larvae from all species in mixed cultures were significantly reduced (p less than 0.001). The lower recovery of H. placei was not associated with a lower viability of H. placei eggs. Of the three different methods of harvesting larvae, the jar and mesh recovery technique was the least effective and significantly fewer larvae were recovered with this technique than with the Baermann and inversion techniques (p less than 0.05). The results are discussed with reference to the use of faecal culture and larval differentiation in the diagnosis of mixed species nematode infections of cattle.

Antigenic differences among the life cycle stages of Oesophagostomum radiatum.

Maturation of Oesophagostomum radiatium is characterised by production of different proteins in all the life cycle stages that occur within the bovine host. One-dimensional sodium dodecyl sulphate-polyacrylamide gels stained for total protein, showed that fourth stage larvae (L4) and adult worms have many proteins in common but L4 has a major additional protein (82,000 D); third stage larvae have many different proteins. Analysis of the proteins of each life cycle stage by Western blotting with sera from naturally infected calves showed that each life cycle stage had specific antigenic proteins. The major protein unique to L4 was identified as a developmentally regulated antigen.