Unformulated
oligodeoxynucleotides (ODN) containing CpG motifs (
CpG-ODN) have been shown to stimulate the innate immune system against a variety of bacterial, viral, and
protozoan infections in a variety of vertebrate species. We have previously shown that in ovo delivery of unformulated
CpG-ODN was able to significantly protect neonatal broiler chickens against Escherichia coli or Salmonella Typhimurium
infections. The objectives of this study were to examine the safety and immunoprotective effects of
CpG-ODN formulated with 2 types of
carbon nanotubes (CNTs) or 2 types of
lipid-
surfactant (LSC) delivery systems in neonatal broilers against E. coli
septicemia. Embryonated eggs, which had been incubated for 18 days, received either 50 μg of CNT-
CpG-ODN, 50 μg of LSC-
CpG-ODN, 50 μg of unformulated
CpG-ODN, or saline. Four days after exposure to
CpG-ODN (day 1 posthatch), 1 x 10(4) or 1 x 10(5) colony-forming units of a virulent strain of E. coli isolated from a turkey with
septicemia were inoculated subcutaneously in the neck. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for 8 days following challenge with E. coli. Bacterial isolations and pathologic observations were conducted immediately after birds were dead or euthanatized. The survival rate of birds in groups receiving saline following E. coli
infection was 20% to 30%. In contrast, birds receiving
CpG-ODN formulations had a significantly higher survival rate of 60% to 80% (P < 0.01). Bacterial loads and clinical scores were significantly lower (P < 0.05) in groups treated with CNT- or LSC-
CpG-ODN compared to the groups receiving
CpG-ODN or saline. Moreover, there is no evidence of any adverse effects of these formulations in any organs or in growth rates of birds until 42 days of age. This is the first time that
CpG-ODN formulated with CNT and LSC have been demonstrated to have an immunomodulatory effect against an E. coli
infection in neonatal broiler chickens following in ovo delivery.