Development of Stable Vibrio cholerae O1 Hikojima Type Vaccine Strains Co–Expressing the Inaba and Ogawa Lipopolysaccharide Antigens

Abstract

We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hikojima serotype that co–express the Inaba and Ogawa antigens of O1 lipopolysaccharide (LPS). Mutation of the wbeT gene reduced LPS perosamine methylation and thereby gave only partial transformation into Ogawa LPS on the cell surface. The strains express approximately equal amounts of Inaba– and Ogawa–LPS antigens which are preserved after formalin–inactivation of the bacteria. Oral immunizations of both inbred and outbred mice with formalin–inactivated whole–cell vaccine preparations of these strains elicited strong intestinal IgA anti–LPS as well as serum vibriocidal antibody responses against both Inaba and Ogawa that were fully comparable to the responses induced by the licensed Dukoral vaccine. Passive protection studies in infant mice showed that immune sera raised against either of the novel Hikojima vaccine strains protected baby mice against infection with virulent strains of both serotypes. This study illustrates the power of using genetic manipulation to improve the properties of bacteria strains for use in killed whole–cell vaccines.

Oral cholera vaccines and their impact on the global burden of disease

“…72 Finally, for children and adults, a simpler vaccine consisting of a single inactivated Hikojima strain that expresses Ogawa and Inaba serotypes is in development. 7,73 As the vaccine includes a single strain, the manufacturing costs would likely be less than for current OCVs. This vaccine, Hillchol, has been shown to be safe in a phase 1/2 trial and non-inferior when compared to Shanchol.…”

“…A third serotype, Hikojima, is rarely isolated. 7 To cause disease, V. cholerae colonizes the proximal small intestine and then produces an enterotoxin that induces voluminous diarrhea containing water and electrolytes. The toxin is composed of A and B subunits.…”

Lack of Fc Gamma Receptor IIIA Promotes Rather than Suppresses Humoral and Cellular Immune Responses after Mucosal or Parenteral Immunization with Antigen and Adjuvants

“…To determine serum OVA‐specific total IgG as well as IgG1 and IgG2c antibody titres, enzyme‐linked immunosorbent assays (ELISA) were performed as described previously . Endpoint titres were expressed as the reciprocal log 10 of the extrapolated dilution giving an absorbance at 450 nm of 0.4 above the background after a 20‐min incubation with the enzyme substrate.…”

Delivery strategies to enhance oral vaccination against enteric infections

“…Additionally, novel strains of V. cholerae expressing multiple surface antigens have been generated and hold promise for future trials [104]. The use of WCK genetically modified non-pathogenic bacteria as antigen vectors may improve safety and ease of production while enhancing antigenicity.…”