• Vaccine Name: APEC vaccine using GST-Iss fusion protein
• Target Pathogen: Escherichia coli
• Target Disease: Hemorrhagic colitis
• Tradename: None
• Vaccine Ontology ID: VO_0000454
• Type: Subunit vaccine
• Antigen: APEC protein ISS fused to glutathione S-transferase (GST) (Lynne et al., 2006).
• Iss gene engineering:
  • Type: Recombinant protein preparation
  • Description: Iss fusion proteins were produced for administration as a vaccine (Lynne et al., 2006).
  • Detailed Gene Information: Click Here.
• Preparation: Purification of GST-Iss was achieved by using an affinity matrix. Various doses of GST-Iss were then added to a water-in-oil emulsion (Lynne et al., 2006).
• Virulence: Not noted.
• Description: Colibacillosis, caused by avian pathogenic Escherichia coli (APEC), is a major problem for the poultry industry in the United States resulting in significant annual losses. One of the problems in colibacillosis control is that no single bacterial trait has been identified that can be used as an identifier of virulent avian isolates or as a target of control strategies. Previous work showed that complement resistance may play an important role in APEC virulence, and the increased serum survival gene or iss, which is associated with E. coli complement resistance was found significantly more often in APEC than it was in the E. coli isolates of apparently healthy birds. This strong association between iss and APEC suggested that iss-centric strategies might be useful in colibacillosis control (Lynne et al., 2006).

Chicken Response

• Host Strain: 2-wk-old leghorn chickens obtained from Charles River Laboratories (Boston, MA).
• Vaccination Protocol: One hundred twenty-eight chickens were divided into eight groups of 16. Birds were placed in stainless steel HEPA-filtered negative-pressure isolators 1 wk before vaccination. Each bird was given 0.5 ml of a water-in-oil emulsion containing either 50 μg, 10 μg, or 2 μg of GST-Iss per dose. At 3 wk of age, each chicken in groups 1A, 1B, 2A, 2B, 3A, and 3B received a 0.5-ml dose of the vaccine. Birds in groups 4A and 4B were not vaccinated (nonvaccinated controls). The injections were given in the back of the neck at the midpoint between the head and body (Lynne et al., 2006).
• Persistence: Not noted.
• Immune Response: Birds that received a higher dose of GST-Iss had average antibody titers of 10,000 to 100,000 against GST-Iss, whereas birds that received a lower dose had average titers of 1000 (Lynne et al., 2006).
• Side Effects: Not noted.
• Challenge Protocol: Four weeks following vaccination, each bird was subjected to challenge with an APEC strain. Each bird in each group was given a 1.0-ml i.m. injection of either 108.72 CFUs of APEC-C-O2 or 108.89 CFUs of APEC-C-O78. Birds were observed for 14 days following challenge. Birds that died were necropsied and observed for lesions consistent with colibacillosis; cultures of bone marrow were taken for bacterial isolation on eosin methylene blue agar (Lynne et al., 2006).
  
• Efficacy: Birds immunized with GST-Iss were able to produce antibody titers against GST-Iss and Iss that were significantly different from unimmunized controls. Also, Iss did stimulate an immunoprotective response against heterologous challenge. Paradoxically, lower doses seemed to offer better protection than did higher doses, a result that could not be accounted for (Lynne et al., 2006).
• Description: Iss, the protein encoded by the iss gene, might be useful as an immunogen capable of eliciting a protective response against APEC infection in birds. If Iss could stimulate an immunoprotective response in birds, it might have wide-ranging benefits, because iss is found in APEC of many serogroups and in APEC isolated from various lesion types, avian host species, and forms of colibacillosis. This widespread distribution of iss among APEC suggests that an Iss-based vaccine could provide broad protection to birds against heterologous APEC challenge. Computer analysis of Iss' predicted amino acid sequence has suggested that many portions of Iss are antigenic, and Iss is thought to be exposed on the bacterial surface in intact E. coli, meaning that it is accessible to the host's immune system. Such observations suggest that Iss may have the ability to evoke an immunoprotective response in birds against APEC that would have wide application. GST was selected as a fusion partner in an effort to elicit a stronger immune response (Lynne et al., 2006).