A recombinant multi-antigen vaccine with broad protection potential against avian pathogenic Escherichia coli

PLoS One. 2017 Aug 24;12(8):e0183929. doi: 10.1371/journal.pone.0183929. eCollection 2017.

Abstract

Chickens are a major source of protein worldwide, yet infectious diseases continue to threaten the poultry industry. Avian pathogenic Escherichia coli (APEC), a subgroup of extraintestinal pathogenic E. coli (ExPEC), causes colibacillosis in chickens resulting in economic loss because of treatment, condemnation of products, and death. In this study, we evaluated a recombinant antigens (rAg) vaccine combining common ExPEC surface proteins EtsC, OmpA, OmpT, and TraT for broad protective potential against APEC infections in chickens. The specific objectives were to evaluate antibody (serum) and cytokines (lymphoid organs) responses to vaccination; in vitro bactericidal ability of serum and splenocytes against multiple APEC serotypes; and in vivo protection against APEC challenge in chickens. Groups of four-day old chickens (N = 10) were vaccinated twice (two-week interval) subcutaneously with rAgs alone or in combination and CpG adjuvant or PBS (control). IgY antibody in the serum and mRNA expression of IL-1β, IL-6, IL-18, IFN-γ, IL-4, IFN-β, and IL-8 in bursa, spleen, and thymus were measured using ELISA and RT-qPCR, respectively. Serum and splenocytes were tested for their bactericidal ability in vitro against multiple APEC isolates. Vaccinated and non-vaccinated chickens were challenged with 108 CFU of APEC-O2 via air sac at 31 days post first vaccination. Vaccine protection was determined by the decrease of bacterial loads in blood and organs (lung, heart, spleen, and liver), as well as gross colibacillosis lesion scores in air sac, heart, and liver. Vaccination significantly (P < 0.05) elicited IgY against specific antigens, induced immune related mRNA expression in the spleen and bursa, reduced in vitro growth of multiple APEC serotypes, and decreased bacterial loads in the heart and spleen, and gross lesion scores of the air sac, heart and liver in chickens. The vaccine reported may be used to provide broad protection against APEC strains, increasing animal welfare and food production.

MeSH terms

  • Animals
  • Antigens, Bacterial / immunology*
  • Cytokines / genetics
  • Escherichia coli / immunology*
  • Escherichia coli Infections / prevention & control*
  • Escherichia coli Vaccines / immunology*
  • Polymerase Chain Reaction
  • Poultry Diseases / immunology
  • Poultry Diseases / microbiology
  • Poultry Diseases / therapy*
  • RNA, Messenger / genetics
  • Spleen / immunology

Substances

  • Antigens, Bacterial
  • Cytokines
  • Escherichia coli Vaccines
  • RNA, Messenger

Grants and funding

This research was supported by a grant from the U.S. Department of Agriculture National Research Initiative USDA-NIFA-AFRI grant 2011-67005-25080 (https://nifa.usda.gov/) to MM and Iowa State University (http://www.iastate.edu/) start-up funding to MM. The funding sources had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.