pYA3493减毒沙门氏菌表达载体-BioVector NTCC质粒载体菌种细胞基因保藏中心

pYA3493 vector减毒沙门氏菌表达载体

-BioVector NTCC质粒载体菌种细胞基因保藏中心

Attenuated Salmonella enterica serovar Typhimurium expressing recombinant antigens from other pathogens

elicits primarily a Th1-type dominant immune response to both recombinant and Salmonella antigens. The

immunogenicity and appropriate subcellular location of the recombinant antigen in the Salmonella vaccine

strain may contribute to augmenting immune responses by facilitating adequate exposure of recombinant

antigen to antigen-presenting cells for processing. To allow for secretion from gram-negative bacteria and

overexpression of antigen, a DNA fragment encoding a highly antigenic
-helical region of PspA (pneumococcal

surface protein A) was subcloned downstream from the -lactamase signal sequence in the multicopy

Asd pYA3493 vector to create pYA3494. pYA3493 was derived from a class of Asd vectors with reduced

expression of Asd to minimize selective disadvantage and enhance immunization of expressed recombinant

antigens. The S. enterica serovar Typhimurium vaccine strain was constructed by the introduction of deletion

mutations crp-28 and asdA16. Approximately 50% of the recombinant PspA (rPspA) expressed in a Salmonella

strain harboring pYA3494 was detected in the combined supernatant and periplasmic fractions of

broth-grown recombinant Salmonella. After a single oral immunization in BALB/c mice with 109 CFU of the

recombinant Salmonella vaccine strain carrying pYA3494, immunoglobulin G (IgG) antibody responses were

stimulated to both the heterologous antigen rPspA and Salmonella lipopolysaccharide (LPS) and outer membrane

proteins (OMPs). About half, and even more at later times after immunization, of the antibodies induced

to rPspA were IgG1 (indicating a Th2-type response), whereas 60 to 70% of the antibodies to LPS and 80 to 90%

of those to OMPs were IgG2a (indicating a Th1-type response). A sublethal infection with Streptococcus

pneumoniae WU2 boosted PspA antibody levels and maintained IgG2a/IgG1 ratios similar to those seen before

the challenge. Oral immunization with Salmonella-PspA vaccine protected 60% of immunized mice from death

after intraperitoneal challenge with 50 times the 50% lethal dose of virulent S. pneumoniae WU2.

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