Novel use of anaerobically induced promoter, dmsA, for controlled expression of fragment C of tetanus toxin in live attenuated Salmonella enterica serovar Typhi strain CVD 908-htrA

摘要

The anaerobically induced promoter dmsA (P-dmsA) was adapted to optimize in vivo expression of foreign antigens in attenuated Salmonella enterica serovar Typhi live vector vaccines CVD 908-htr. P-dmsA from Escherichia coli and two derivatives, P-dmsA2 and P-dmsA3 were cloned into a plasmid driving the expression of a gene encoding tetanus toxin fragment C. Expression of fragment C varied from a low level induced by pTETdmsA, to moderate and high levels induced, respectively, by pTETdmsA2 and pTETdmsA3. Mice were immunized intranasally with CVD 908-htrA harboring pTET(dmsA2) or pTET(dmsA3), and the serum antitoxin response was compared to that elicited by CVD 908-htrA(pTETnir 15) (P-nir15 is a benchmark anaerobically activated promoter). S. Typhi carrying pTETdmsA2 elicited modest tetanus antitoxin titers while S. Typhi harboring pTETdmsA3 generated elevated titers (GMT = 55 384) that were higher than elicited by pTETnir15 (GMT = 4354) (P = 0.007). Mice immunized with CVD 908-htrA carrying pTETdmsA3 and pTETnir15 survived tetanus toxin challenge. P-dmsA derivatives are attractive promoters for in vitro expression of foreign genes in attenuated live vector vaccines.