Adjuvant-free immunological manipulation of livestock

Mice and sheep were immunised to growth hormone release inhibiting hormone (GHRIH) using a number of systems which avoided conventional adjuvants. GHRIH was linked directly, or via a horse IgG carrier, to algin or purified protein derivative of tuberculin. A conjugate of GHRIH and flagella from Salmonella dublin was also prepared. Complexes were administered with or without lipopolysaccharide from S typhosa 0901 in a two-injection schedule. Animals receiving conjugates containing purified protein derivative or flagella were preimmunised with live Bacille Calmette-Guérin (BCG) or live S dublin vaccines respectively. Antibody titres to GHRIH, horse IgG and flagella were determined by radioimmunoassay. The system based on tuberculin yielded anti-GHRIH titres in both species which were equivalent to those obtained using Freund's complete adjuvant, while the system based on S dublin produced similar results but only in mice. These data suggest that carrier proteins of bacterial origin may be useful in the development of adjuvant-free autoimmunisation schedules for the practical manipulation of endocrine systems.