Immune responses associated with homologous protection conferred by commercial vaccines for control of avian pathogenic Escherichia coli in turkeys

Abstract

Avian pathogenic Escherichia coli (APEC) infections are a serious impediment to sustainable poultry production worldwide. Licensed vaccines are available, but the immunological basis of protection is ill-defined and a need exists to extend cross-serotype efficacy. Here, we analysed innate and adaptive responses induced by commercial vaccines in turkeys. Both a live-attenuated APEC O78 ΔaroA vaccine (Poulvac® E. coli) and a formalin-inactivated APEC O78 bacterin conferred significant protection against homologous intra-airsac challenge in a model of acute colibacillosis. Analysis of expression levels of signature cytokine mRNAs indicated that both vaccines induced a predominantly Th2 response in the spleen. Both vaccines resulted in increased levels of serum O78-specific IgY detected by ELISA and significant splenocyte recall responses to soluble APEC antigens at post-vaccination and post-challenge periods. Supplementing a non-adjuvanted inactivated vaccine with Th2-biasing (Titermax® Gold or aluminium hydroxide) or Th1-biasing (CASAC or CpG motifs) adjuvants, suggested that Th2-biasing adjuvants may give more protection. However, all adjuvants tested augmented humoral responses and protection relative to controls. Our data highlight the importance of both cell-mediated and antibody responses in APEC vaccine-mediated protection toward the control of a key avian endemic disease.

Evaluation of the efficacy of an autogenous Escherichia coli vaccine in broiler breeders

“…it has been suggested that Poulvac® induced immunity probably does not depend on the production of circulating antibodies (as assessed through the presence of B lymphocytes) but is linked to the presence of CD4 + TCRVβ1 + (Fernandes et al, 2013) . This statement, however, conflicts with the finding by Sadeyen et al( 2015b), who showed that both Poulvac® and an inactivated culture of the same strain as included in the Poulvac® vaccine (APEC O78) stimulated a cell-mediated as well as a pronounced humoral response in an intra-airsac model of acute colibacilliosis in turkey poults. Yet, another study demonstrated that a protective effect of Poulvac® vaccines strictly requires a cyclophosphamidesensitive cell population that includes B cells (Sadeyen et al, 2015a).…”

“…In such cases, control of E. coli infections relies on efficient vaccination strategies. The licensed vaccine, Poulvac® is indicated for protection in young birds (broilers or chicks to become broiler breeders or layers) against septicaemia, peritonitis and perihepatitis, and has proven effective in several experimental evaluations (Fernandes et al, 2013;Mombarg et al, 2014;Sadeyen et al, 2015b). For Poulvac®, the therapeutic indications do not include long-term protection beyond the 5-6 weeks of the life of broilers.…”

A cyclophosphamide-sensitive cell compartment is essential for homologous protection conferred by licensed vaccines for the control of avian pathogenic Escherichia coli in chickens

“…In chickens given Poulvac ® E. coli [2] or an independent aroA-based live-attenuated APEC vaccine [3], significant induction of cellular responses was detected relative to modest humoral responses implying antibody may be playing a subtle role. In contrast, our recent studies in turkeys showed an association of antibody with homologous protection after vaccination with Poulvac ® E. coli or an inactivated vaccine [4], with innate responses indicative of a slight Th2 bias and evidence that protection may be improved via use of Th2-biasing adjuvants. In contrast, inactivated vaccines are believed to confer protection largely via specific antibody [5][6][7].…”

“…The use of Cy to derive B cell-deficient birds is well-established in chickens [14][15][16][17]. (EC34195nal R ) used in this study have previously been described [4]. Vaccination and challenge studies were conducted according to the requirements of the Animal (Scientific Procedures) Act 1986 (licence no.…”

“…Specified pathogen-free Brown Leghorn chickens, bred at The Pirbright Institute, were housed in wire colony cages with free access to water and feed. Vaccines were administered to 10 day-old chickens per group according to the regimen previously described [4], then challenged with 10 7 colony-forming units (CFU) of EC34195nal R via the left caudal airsac at 41 days of age and monitored for clinical signs. Post-mortem analysis, enumeration of tissue-associated bacteria and ELISAs for APEC-specific IgY were conducted as previously described [4].…”