• Vaccine Name: S. flexneri Invaplex 50 Subunit Vaccine
• Target Pathogen: Shigella
• Target Disease: Shigellosis
• Vaccine Ontology ID: VO_0011468
• Type: Subunit vaccine
• Status: Research
• Antigen: IpaB, IpaC, and IpaD, and LPS (Turbyfill et al., 2000).
• ipaB gene engineering:
  • Type: Recombinant protein preparation
  • Description:
  • Detailed Gene Information: Click Here.
• IpaC gene engineering:
  • Type: Recombinant protein preparation
  • Description:
  • Detailed Gene Information: Click Here.
• ipaD gene engineering:
  • Type: Recombinant protein preparation
  • Description:
  • Detailed Gene Information: Click Here.
• Preparation: A novel method has been developed for isolating a macromolecular complex containing the major known virulence factors and immunogens from intact, viable, virulent shigellae. This structure was referred as the invasin complex, or invaplex. It has been possible to isolate two forms of the invaplex, called invaplex 24 and invaplex 50, by FPLC ion-exchange chromatography from S. flexneri 2a and S. flexneri 5. Both forms contain the invasins (IpaB, IpaC, and IpaD) and LPS, but IpaA and VirG, a truncated form of VirG, were found only in Invaplex 50. Other unidentified proteins were also present in both invaplex preparations (Turbyfill et al., 2000).
• Immunization Route: Intranasally
• Description: Isolated invasin complex (invaplex), which contains the major antigens of virulent Shigella, is shown to be immunogenic when delivered by a mucosal route without the need for any additional adjuvant. Western blot analysis of the complex indicates that all of the major virulence antigens of Shigella, including IpaB, IpaC, and IpaD, and LPS are components of this macromolecular complex.

Mouse Response

• Host Strain: BALB/cByJ
• Vaccination Protocol: The ability of the invaplex fractions to promote an immune response in BALB/cByJ mice was tested in groups of five mice. Each mouse was immunized intranasally with 5 μg of invaplex 24 or invaplex 50 from S. flexneri 2a or S. flexneri 5 on days 0, 14, and 28. Saline was used to immunize control animals. A total antigen volume of 25 μl was delivered in 5 to 6 small drops applied to the external nares with a micropipette (Turbyfill et al., 2000).
• Challenge Protocol: Three weeks after the final immunization with either S. flexneri 2a invaplex 24, invaplex 50, or saline, mice (15 per group) were challenged intranasally with a lethal dose of S. flexneri 2a 2457T (107 CFU/30 μl) as described for the mouse lung model (18). The mouse challenge dose was prepared from a frozen lot of S. flexneri 2a that had been harvested during the log phase of growth, which is the time of optimal invasiveness for shigellae, and then stored in liquid nitrogen (Turbyfill et al., 2000).
• Efficacy: A significant level of protection against lethal challenge was achieved in mice immunized with S. flexneri 2a invaplex 50. Invaplex-immunized mice lost weight upon challenge, but by days 3 to 4 they began to recover and gain weight whereas control mice soon died. Similar levels of protection were afforded by invaplex 50 (10 of 15 mice survived) (Turbyfill et al., 2000).