Evaluation of recombinant BCG expressing rotavirus VP6 as an anti-rotavirus vaccine
Division of Medical Virology, Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town 7925, South Africa; Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Cape Town, 7925, South Africa; Initiative for Vaccine Research, World Health Organization, 20 Appia Avenue, CH-1211 Geneva, Switzerland; Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Cape Town, 7925, South Africa; National Health Laboratory Service, Groote Schuur Hospital, Observatory, Anzio Road, Cape Town, 7925, South Africa
Recombinant BCG expressing rotavirus VP6 was explored as an anti-rotavirus vaccine in a mouse model. Three promoters and five ribosome-binding sites were used in episomal and integrative E. coli-mycobacterium shuttle vectors to express VP6 in BCG. The VP6 gene was configured for accumulation within the BCG cytoplasm, secretion from the BCG cell or targeting to the BCG cell membrane. Vectors were assessed in terms of stability, levels of antigen production, immunogenicity and protection in mice. Gross instability occurred in episomal vectors utilizing the hsp60 promoter. However, three integrative vectors using the same expression system and two episomal vectors using inducible promoters were successfully recovered from BCG. Growth rates of the former were not detectably reduced. Growth rates of the latter were considerably reduced, implying the existence of a significant metabolic load. In the absence of selection, loss rate of these plasmids was high. VP6 production levels (0.04-1.78% of total cytoplasmic protein) were on the lower end of the range reported for other rBCG. One episomal and one integrated vaccine reduced viral shedding in intraperitoneally vaccinated mice challenged with rotavirus. Compared to controls, infection-associated faecal shedding of virus was reduced by 66% and 62%, respectively. These protective vectors differ in promoter, ribosome-binding site and antigen production level, but both link the VP6 protein to the 19 kDa lipoprotein signal sequence, suggesting that transport of VP6 to the BCG membrane is important for induction of a protective immune response. Protection occurred in the absence of detectable anti-rotavirus antibody in serum or faeces, implicating cellular immunity in protection. © 2007 Elsevier Ltd. All rights reserved.
BCG vaccine; cytoplasm protein; heat shock protein 60; lipoprotein; protein VP6; recombinant vaccine; rotatex; Rotavirus vaccine; unclassified drug; animal cell; animal experiment; animal model; article; binding site; cell membrane; controlled study; cytoplasm; drug mechanism; drug stability; episome; Escherichia coli; female; gene expression regulation; growth rate; immunity; immunogenicity; mouse; nonhuman; nucleotide sequence; plasmid; priority journal; promoter region; protein expression; protein secretion; protein transport; ribosome; Rotavirus; shuttle vector; signal transduction; target cell; virus infection; virus load; virus shedding; Animals; Antigens, Viral; Capsid Proteins; Female; Genetic Vectors; Mice; Mice, Inbred BALB C; Mycobacterium bovis; Rotavirus; Rotavirus Infections; Rotavirus Vaccines; Transformation, Genetic; Vaccines, Synthetic