Humoral immunity to cholera toxin and ovalbumin in the brushtail possum (Trichosurus vulpecula)

Abstract

AIM: To compare the humoral immune responses of female possums to ovalbumin (OVA) and cholera toxin (CT) administered using different routes and dosage regimes.

METHODS: Three groups of mature female possums were immunised intragastrically (n=15) orsurgically (intraileal, n=4; Peyer's patches, n=4). Levels of antibodies to OVA and CT in serum, ileal, vaginal, oviduct and uterine secretions were measured by indirect enzyme-linked immunosorbent assay (ELISA). All manipulations were conducted under general anaesthesia.

RESULTS: Antibodies to CT increased significantly in serum (p<0.001) and in lateral vaginal secretions (p<0.05) after intragastric immunisation using 250–1000 µg CT. Simultaneous intragastric administration of CT with 3 mg OVA did not significantly increase antibody levels to OVA. When OVA (3 mg) and CT (250 µg) were injected into the ileum, followed by intragastric administration 4 weeks later, antibody levels to CT were significantly (p<0.05) increased in serum, uterine and medial vaginal secretions, and antibody levels to OVA were significantly (p<0.05) increased in serum and medial vaginal secretions. When OVA (3 mg) with Incomplete Freund's adjuvant was injected directly into Peyer's patches, followed by peritoneal administration 4 weeks later, antibody levels in serum, ileal and reproductive-tract secretions were generally higher than those that resulted from the other immunisation treatments.

CONCLUSIONS: Administration of OVA induced an antibody response in serum and in reproductive and alimentary tract secretions when administered with CT directly into the ileum, or when injected into Peyer's patches and peritoneum. CT was a potent enteric immunogen.

KEYWORDS::

• Possum
• cholera toxin
• ovalbumin
• intragastric immunisation
• Peyer's patches
• mucosal immunity
• antibody