Combinations of gene deletions for live attenuated shigella vaccine strains
Inventors
Venkatesan, Malabi • Ranallo, Ryan • Barnoy, Shoshana
Assignees
Walter Reed Army Institute of Research
Publication Number
US-9320789-B2
Publication Date
2016-04-26
Expiration Date
2028-04-25
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
Shigella vaccine strains whose primary attenuating feature is deletion of the virG(icsA) gene and additional two or more deletions in setAB(shET1), senA(shET2), senB(shET2-2), stxAB, and msbB2 genes. Thus, the vaccine strain will have three or more deletions in the identified genes, will be safer, and will reduce or eliminate symptoms of fever and diarrhea in humans. The following specific vaccine strains have been constructed: WRSS3 (ΔsenA, ΔsenB, ΔvirG, ΔmsbB2), WRSf2G15 (ΔvirG, ΔsetAB, ΔsenA, ΔsenB, ΔmsbB2), and WRSd5 (ΔvirG, ΔstxAB, ΔsenA, ΔsenB, ΔmsbB2).
Core Innovation
The invention relates to live attenuated Shigella vaccine strains primarily characterized by a deletion of the virG(icsA) gene combined with additional deletions in two or more genes selected from setAB(shET1), senA(shET2), senB(shET2-2), stxAB, and msbB2. This combination results in vaccine strains with three or more gene deletions, enhancing the vaccine safety profile by reducing or eliminating symptoms of fever and diarrhea in humans.
The problem solved by the invention stems from current live vaccines based on virG(icsA) gene deletion, such as SC602 and WRSS1, which, while safe and protective at low doses, nevertheless cause unacceptable reactogenic symptoms including mild diarrhea and fever in 15-25% of vaccinated volunteers. Prior art shows that deletions of the enterotoxin genes setAB and senA ameliorate such symptoms but are insufficient alone. The invention addresses this by combining deletions of virG(icsA) with multiple enterotoxin genes and the msbB2 gene associated with LPS toxicity to attenuate the strain further without compromising immunogenicity or invasiveness.
Specific vaccine strains constructed under this invention include WRSS3 (ΔsenA, ΔsenB, ΔvirG, ΔmsbB2), WRSf2G15 (ΔvirG, ΔsetAB, ΔsenA, ΔsenB, ΔmsbB2), and WRSd5 (ΔvirG, ΔstxAB, ΔsenA, ΔsenB, ΔmsbB2). These strains demonstrate invasive properties, do not form plaques in epithelial cell monolayers, do not induce keratoconjunctivitis in guinea pigs, elicit protective immune responses, and are efficiently excreted in nonhuman primate models. They are formulated to induce mucosal immune responses effectively with low doses (104 to 106 CFU) and can be combined for multivalent vaccines against multiple Shigella serogroups and other enteric pathogens.
Claims Coverage
The patent includes one independent claim detailing a Shigella vaccine strain with specific gene deletions, from which dependent claims elaborate on strain characteristics, formulations, and methods of administration.
Combination gene deletions in Shigella vaccine strains
The vaccine strain consists of a deletion or inactivation of the virG(icsA) gene combined with deletions or inactivations of senA(shET2) and senB(shET2-2) genes.
Vaccine strain serogroup specificity
The strain is virulent from one of four serogroups: S. flexneri, S. sonnei, S. dysenteriae, or S. boydii, with specific claims to S. flexneri 2a and S. dysenteriae 1 strains.
Phenotypic characterization of vaccine strains
The strains are characterized by traits including invasiveness in epithelial cells, lack of plaque formation in epithelial cell monolayers, and absence of keratoconjunctivitis in guinea pig eyes.
Immunogenic composition and live invasive vaccine formulation
Formulations contain the claimed strains with pharmaceutically acceptable carriers and are live and invasive vaccines.
Kits for inducing immunoprotective responses
Kits comprise one or more containers each containing individual vaccine strains from the claimed group for treatment by inducing an immunoprotective response.
Methods of administration and dosing
Administration of an effective amount of the vaccine strains in doses ranging from 104 to 106 CFU, including single oral doses, sufficient to induce protective immunity against Shigella spp.
The claims cover Shigella vaccine strains defined by a specific combination of gene deletions including virG(icsA), senA, and senB, their serogroup variants, phenotypic traits, formulations for immunization, kits, and administration methods delivering effective doses to induce protective immune responses.
Stated Advantages
The vaccine strains are safer with reduced or eliminated reactogenicity symptoms such as fever and diarrhea in human volunteers compared to prior virG(icsA)-based vaccines.
The multiple gene deletions do not compromise the protective immune response or invasive properties of the strains.
Lower doses (104 to 106 CFU) are effective for immunization, reducing vaccine dosage requirements compared to prior art.
The strains enable development of multivalent vaccine formulations covering multiple Shigella serotypes and combinations with vaccines against other enteric pathogens such as ETEC.
Documented Applications
Protection against dysentery and diarrhea caused by Shigella flexneri, Shigella sonnei, Shigella dysenteriae, and Shigella boydii.
Use in mixtures of live attenuated polyvalent vaccines containing two or more Shigella serotypes.
Combination with live attenuated vaccines against enterotoxigenic E. coli (ETEC) for broader protection against diarrheal diseases.
Prime-boost immunization strategies involving initial live vaccine dosing followed by subunit vaccine administration against Shigella.
Use as carriers of antigens from other diarrheal pathogens such as Campylobacter.
Use as mucosal delivery vectors for other prokaryotic or eukaryotic antigens or as carriers of immune modulators such as cytokines.
Interested in licensing this patent?