TABLE 2.

Summary of experimental design

Expt no.Immunization groupaDosage (μg) of vaccine/birdFrequency of administrationNo. of days (severity) of oral challenge
1VC, Sup, alpha-toxoid, GPD, HP, FBA, and tPFOR20Three times; days 7, 14, and 213 (mild)
2VC, MC, GPD, HP, FBA, and tPFOR40Two times; days 7 and 145 (moderate)
3VC, alpha-toxoid/alpha-toxin,b GPD, HP, tPFOR, and a combination of GPD and HP20Three times; days 7, 14, and 215 (severe)
4AVC and FBA20Three times; days 7, 14, and 213 (mild-moderate)
4BVC, alpha-toxin,c and FBA20Three times; days 7, 14, and 215 (severe)
  • a VC, vehicle-only controls; Sup, crude culture supernatant of virulent C. perfringens, in which the birds received 60 μg/injection of culture supernatant that was processed and concentrated following a protocol described earlier (15); MC, mock-immunized controls, in which the birds were mock immunized with an unrelated protein that was cloned, expressed, and purified from E. coli in the same manner as the C. perfringens-related proteins.

  • b The birds received alpha-toxoid in the first two injections, followed by active alpha-toxin in the third.

  • c The birds received three injections of alpha-toxin, in which the first and the third injections were with 20 μg and the second was reduced to 10 μg.