A novel live attenuated anthrax spore vaccine based on an acapsular Bacillus anthracis Sterne strain with mutations in the htrA, lef and cya genes.
We recently reported the development of a novel, next-generation, live attenuated anthrax spore vaccine based on disruption of the htrA (High Temperature Requirement A) gene in the Bacillus anthracis Sterne veterinary vaccine strain. This vaccine exhibited a highly significant decrease in virulence in murine, guinea pig and rabbit animal models yet preserved the protective value of the parental Sterne strain. Here, we report the evaluation of additional mutations in the lef and cya genes, encoding for the toxin components lethal factor (LF) and edema factor (EF), to further attenuate the SterneΔhtrA strain and improve its compatibility for human use. Accordingly, we constructed seven B. anthracis Sterne-derived strains exhibiting different combinations of mutations in the htrA, cya and lef genes. The various strains were indistinguishable in growth in vitro and in their ability to synthesise the protective antigen (PA, necessary for the elicitation of protection). In the sensitive murine model, we observed a gradual increase (ΔhtrA<ΔhtrAΔcya<ΔhtrAΔlef<ΔhtrAΔlefΔcya) in attenuation - up to 108-fold relative to the parental Sterne vaccine strain. Most importantly, all various SterneΔhtrA derivative strains did not differ in their ability to elicit protective immunity in guinea pigs. Immunisation of guinea pigs with a single dose (109spores) or double doses (>107spores) of the most attenuated triple mutant strain SterneΔhtrAlefMUTΔcya induced a robust immune response, providing complete protection against a subsequent respiratory lethal challenge. Partial protection was observed in animals vaccinated with a double dose of as few as 105spores. Furthermore, protective immune status was maintained in all vaccinated guinea pigs and rabbits for at least 40 and 30weeks, respectively.
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel. Electronic address: theodorc@iibr.gov.il.
Theodor
T
Chitlaru
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Ma'ayan
M
Israeli
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Shahar
S
Rotem
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Uri
U
Elia
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Erez
E
Bar-Haim
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Sharon
S
Ehrlich
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Ofer
O
Cohen
Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.
Avigdor
A
Shafferman
D000818:Animals; D000881:Anthrax / Q000276:immunology* / Q000517:prevention & control; D022122:Anthrax Vaccines / Q000235:genetics / Q000276:immunology*; D000907:Antibodies, Bacterial / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology; D001408:Bacillus anthracis / Q000235:genetics / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D001427:Bacterial Toxins / Q000235:genetics / Q000276:immunology; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics* / Q000276:immunology; D006168:Guinea Pigs; D006801:Humans; D051379:Mice; D008813:Mice, Inbred ICR; D009154:Mutation / Q000235:genetics / Q000276:immunology; D011817:Rabbits; D012697:Serine Endopeptidases / Q000235:genetics* / Q000276:immunology; D013171:Spores, Bacterial / Q000235:genetics / Q000276:immunology*; D014611:Vaccination / Q000379:methods; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology*; D014774:Virulence / Q000235:genetics / Q000276:immunology
D022122:Anthrax Vaccines; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D014613:Vaccines, Attenuated; C030325:anthrax toxin; D012697:Serine Endopeptidases; C545478:htrA protein, Bacillus anthracis
Anthrax; Anthrax toxins; Bacillus anthracis; HtrA; Live attenuated vaccine