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Infection and Immunity, May 2000, p. 2775-2782, Vol. 68, No. 5
OraVax, Inc., Cambridge, Massachusetts
02139,1 and Research Department, Pasteur
Merieux Connaught, 69280 Marcy l'Etoile, France2
Received 1 July 1999/Returned for modification 22 September
1999/Accepted 4 February 2000
The heat-labile toxin (LT) of Escherichia coli is a
potent mucosal adjuvant that has been used to induce protective
immunity against Helicobacter felis and Helicobacter
pylori infection in mice. We studied whether recombinant LT or
its B subunit (LTB) has adjuvant activity in mice when delivered with
H. pylori urease antigen via the parenteral route. Mice
were immunized subcutaneously or intradermally with urease plus LT,
recombinant LTB, or a combination of LT and LTB prior to intragastric
challenge with H. pylori. Control mice were immunized
orally with urease plus LT, a regimen shown previously to protect
against H. pylori gastric infection. Parenteral
immunization using either LT or LTB as adjuvant protected mice against
H. pylori challenge as effectively as oral immunization and
enhanced urease-specific immunoglobulin G (IgG) responses in serum as
effectively as aluminum hydroxide adjuvant. LT and LTB had adjuvant
activity at subtoxic doses and induced more consistent antibody
responses than those observed with oral immunization. A mixture of a
low dose of LT and a high dose of LTB stimulated the highest levels of
protection and specific IgG in serum. Urease-specific IgG1 and IgG2a
antibody subclass responses were stimulated by all immunization
regimens tested, but relative levels were dependent on the adjuvant
used. Compared to parenteral immunization with urease alone, LT
preferentially enhanced IgG1, while LTB or the LT-LTB mixture
preferentially enhanced IgG2a. Parenteral immunization using LT or LTB
as adjuvant also induced IgA to urease in the saliva of some mice.
These results show that LT and LTB stimulate qualitatively different
humoral immune responses to urease but are both effective parenteral
adjuvants for immunization of mice against H. pylori infection.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Parenteral Adjuvant Activities of Escherichia
coli Heat-Labile Toxin and Its B Subunit for Immunization of
Mice against Gastric Helicobacter pylori
Infection
*
Corresponding author. Mailing address: OraVax, Inc., 38 Sidney St., Cambridge, MA 02139. Phone: (617) 494-1339. Fax: (617) 494-0927. E-mail: rweltzin{at}oravax.com.
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