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Infection and Immunity, November 2001, p. 6604-6611, Vol. 69, No. 11
Departments of
Microbiology1 and Oral
Biology,2 University of Alabama at Birmingham,
Birmingham, Alabama 35294
Received 2 May 2001/Returned for modification 3 July 2001/Accepted 3 August 2001
Attenuated Salmonella enterica serovar Typhimurium
has been used for targeted delivery of recombinant antigens to gut- and nose-associated lymphoid tissues. Contradictory reports have described the effect of preexisting immunity to the antigen delivery vehicle. We
decided to examine this discrepancy by studying the effect of
immunizing mice by the intranasal (i.n.) route with
Salmonella expressing an insoluble protein and to study
the ability to augment recall responses by boosting with either
Salmonella-expressed protein or purified soluble protein
alone. The glucan-binding domain (GLU) of the enzyme
glucosyltransferase (GTF), which is an important virulence factor of
Streptococcus mutans, was recombinantly expressed in the
insoluble phase in S. enterica serovar Typhimurium, and the immunogenicity of this construct was studied in mice. We
examined the induction of primary immune responses by insoluble GLU
polypeptide delivered in Salmonella at week 1 (groups 1 and 2) and recall responses after a week 15 boost with either
Salmonella expressing GLU (group 1) or purified GLU
polypeptide (groups 2 and 3). Group 4 served as the control and
received phosphate-buffered saline alone by the i.n. route. Significant
anti-GLU serum immunoglobulin G (IgG) levels were seen in groups 1, 2, and 3 at week 18 (P < 0.001), i.e., 3 weeks after
the booster immunization. Mice in group 2, who received
Salmonella followed by GLU, had the highest GLU-specific
IgG levels among all groups. The serum IgG levels persisted in all
responding groups for at least 7 weeks after the boost (week 22). The
IgG2a/IgG1 subclass ratio of serum anti-GLU antibodies in group 1 significantly increased after the boost. These results support the
induction of a type 1-like immune response to GLU after primary and
booster immunizations with Salmonella expressing GLU. On
the other hand, group 2 mice, which received Salmonella
expressing GLU as the primary dose and soluble protein as the booster
dose, exhibited a shift from a type 1-like to a more type 2-like immune
response to GLU following the boost. These results indicate that
S. enterica serovar Typhimurium is an excellent delivery
vehicle for the insoluble and recombinantly expressed GLU of GTF and
that this construct was especially effective in priming the host for a
secondary response to soluble GLU polypeptide.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.11.6604-6611.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Effect of Attenuated Salmonella
enterica Serovar Typhimurium Expressing a Streptococcus
mutans Antigen on Secondary Responses to the Cloned
Protein

and
*
Corresponding author. Mailing address: Department of
Microbiology, University of Alabama at Birmingham, 845 S. 19th, BBRB 258, Birmingham, AL 35294-2170. Phone: (205) 934-3470. Fax: (205) 934-1426. E-mail: suemich{at}uab.edu.
Present address: Department of Oral Biology, State University of
New York at Buffalo, Buffalo, NY 14214.
Present address: Departments of Microbiology and Oral Biology,
State University of New York at Buffalo, Buffalo, NY 14214.
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