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Infection and Immunity, December 2001, p. 7493-7500, Vol. 69, No. 12
Max-Planck-Institut für
Infektionsbiologie, Abteilung Molekulare Biologie, D-10117 Berlin,
Germany
Received 18 June 2001/Returned for modification 26 July
2001/Accepted 4 September 2001
Regulated antigen expression can influence the immunogenicity of
live recombinant Salmonella vaccines, but a rational
optimization has remained difficult since important aspects of this
effect are incompletely understood. Here, attenuated Salmonella
enterica serovar Typhimurium SL3261 strains expressing the
model antigen GFP_OVA were used to quantify in vivo antigen levels by
flow cytometry and to simultaneously follow the crucial early steps of
antigen-specific T-cell responses in mice that are transgenic for a
T-cell receptor recognizing ovalbumin. Among seven tested promoters,
PpagC has the highest activity in
murine tissues combined with low in vitro expression, whereas
Ptac has a comparable in vivo and a
very high in vitro activity. Both SL3261 (pPpagCGFP_OVA) and SL3261 (pPtacGFP_OVA) cells can induce potent
ovalbumin-specific cellular immune responses following oral
administration, but doses almost 1,000-fold lower are sufficient for
the in vivo-inducible construct SL3261 (pPpagCGFP_OVA)
compared to SL3261 (pPtacGFP_OVA). This efficacy difference
is largely explained by impaired early colonization capabilities of
SL3261 (pPtacGFP_OVA) cells. Based on the findings of this
study, appropriate in vivo expression levels for any given antigen can
be rationally selected from the increasing set of promoters with
defined properties. This will allow the improvement of recombinant
Salmonella vaccines against a wide range of pathogens.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.12.7493-7500.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Regulated Antigen Expression in Live Recombinant
Salmonella enterica Serovar Typhimurium Strongly Affects
Colonization Capabilities and Specific CD4+-T-Cell
Responses
*
Mailing address: Max-Planck-Institut für
Infektionsbiologie, Abteilung Molekulare Biologie, Schumannstraße
21/22, D-10117 Berlin, Germany. Phone: 49 30 28460 430. Fax: 49 30 28460 401. E-mail: bumann{at}mpiib-berlin.mpg.de.
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