Induction of protective immunity to Trichostrongylus colubriformis in neonatal merino lambs.
The premise that any bias of immune reactivity in neonatal lambs towards T-helper (TH)2 responses could benefit the induction of protection against gastrointestinal nematodes was investigated. In two trials, lambs were either trickle-immunised with 2000 infective larvae of Trichostrongylus colubriformis (TcL3), 3 times weekly from the day of birth for 6 weeks or inoculated with a recombinant T. colubriformis 17 kDa antigen in incomplete Freund's adjuvant (IFA). In trial 1, trickle immunised and control neonates challenged at 7 weeks of age had similar worm counts 10 days after challenge, but from 25 days, significant reductions (P<0.01) in mean faecal egg count and worm count in excess of 75% were displayed by the immunised lambs. The results of a second, similar trial, gave 85-91% reductions in parasitism in trickle immunised neonates (P<0.001) and around 50% protection in neonates vaccinated with recombinant 17 kDa antigen. Parasitism in immunised neonates in Trial 2 was significantly reduced (P<0.001) compared to that in 4-month-old animals. Antibody responses in trickle-immunised (protected) and challenge control (infected) neonates were almost exclusively of the IgG1 isotype compared to vaccinated animals which exhibited increased levels of anti-17kD IgG2. Trichostrongylus colubriformis infection, but not specific vaccination, induced interleukin-5 production by mesenteric lymph node cells. The results offer the tantalising prospect of generating protective immunity to gastrointestinal parasites prior to weaning in sheep; this was most effectively generated by viable parasites in this investigation.
Emery
D L
DL
CSIRO Animal Production, McMaster Laboratory, Blacktown, NSW, Australia. d.emery@anprod.csiro.au
McClure
S J
SJ
Davey
R J
RJ
Bendixsen
T
T
D000818:Animals; D000831:Animals, Newborn; D000909:Antibodies, Helminth / Q000097:blood*; D000947:Antigens, Helminth / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D007074:Immunoglobulin G / Q000097:blood; D007411:Intestinal Diseases, Parasitic / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D008213:Lymphocyte Activation; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000469:parasitology / Q000517:prevention & control; D014253:Trichostrongylosis / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D014254:Trichostrongylus / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D014611:Vaccination / Q000662:veterinary*; D014614:Vaccines, Synthetic / Q000276:immunology
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D007074:Immunoglobulin G; D014614:Vaccines, Synthetic