THE EFFECT OF
PRIMING AND PREEXISTENCE OF ANTI-CARRIER IMMUNITY ON THE IMMUNE RESPONSES
TO GROUP B STERPTOCOCCUS TYPE B STREPTOCOCCUS TYPE III CAPSULAR
POLYSACCHARIDE-CHOLERA TOXIN B SUBUNIT CONJUGATE AFTER INTRANASANL
IMMUNIZATION
Shen XZ1,2,
, Lagergard T1, Yang YH2, Lindblad M1,
Fredriksson M and Holmgren J1.
1. Department
of Medical Microbiology and Immunology, Göteborg University, Göteborg,
Sweden
2. Beijing
Children ´s Hospital Affiliated to Capital University of Medical Sciences,
Beijing, China
Objectives: To investigate the
effect of priming and boosting with Group B Streptococcus type III capsular
polysaccharide (GBS CPS III), GBS CPS III-recombinant cholera toxin B
subunit (r CTB) conjugate or r CTB on anti-CPS III systemic and mucosal
immune responses to GBS CPS III-r CTB conjugate after intranasal (i.n.)
immunization in mouse model.
Methods: GBS CPS III was
conjugated with rCTB using the reductive amination method. The ratio
(wt/wt) of CPS and rCTB in the conjugate was 0.90:1. The female mice, were
immunizated intranasally with 30ug CPS in conjugate or CPS alone, including
0.5 mg CT as ajuvant. Mice were immunizaed two or
three times at intervals of 12-14 days and sacrificed 7-10 days after the
last immunization. The perfusion extraction method was used to obtain lungs
and vagina specimens for antibody detection. Antibodies to rCTB were
detected by GM1 ELISA. The concentration of antibodies was expressed as
reciprocal sample dilutions (titers), giving an absorbence of 0.4 above the
background level for IgG and 0.2 above the background for IgA.
Results: Priming with pure GBS
CPS III alone or with GBS CPS III-rCTB conjugate induced comparable levels
of specific IgG and IgA in serum, lungs and vagina. However, the
immunization scheme of both priming and boosting with conjugate was
superior to priming with CPS and boosting with conjugate or the reverse, on
inducing strongest anti-CPS responses. All the immunization schemes, except
priming and boosting with CPS, could induce similar high levels of IgG1
antibody responses in serum. The mice primed with CPS III and boosted with
CPS III-rCTB conjugate by i.n. route failed to produce significant levels
of IgG2a, IgG2b and IgG3 in serum, comparing with the levels in mice primed
with the conjugate. Pre-immunization with rCTB did not suppress specific
serum IgG response induced by GBS CPS III-rCTB conjugate intranasally, but
did inhibit IgA responses. Moreover, a strong inhibitory effect on anti-CPS
IgA response in lungs was observed. I.n. immunization with GBS CPS III-rCTB
conjugate could not overcome the inhibition caused by pre-immunization with
rCTB intraperitoneally.
Conclusions: The priming with CPS
affects the distribution of IgG subclasses to GBS CPS and that preexisting
rCTB immunity has an inhibitory effect on the mucosal immune responses
elicit by the conjugate given by i.n. routes.