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Bac protein based recombinant peptides as possible means for vaccine development against GBS infection

Abstract number: 902_p1057

Meringova L.

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Objectives:

Group B streptococci (GBS) being the main cause of infection pathology of the newborns can also cause serious infections in adults. Construction of the recombinant vaccine against GBS infection might be important for the several risk groups including pregnant women. Several recombinant peptides based on the GBS IgA binding protein Bac were used for vaccination of mice in order to evaluate their immunogenicity and possible protection against GBS infection.

Materials and methods:

GBS strain 219, type IIbc was used as source of DNA for cloning. Bac gene fragments corresponding to the 3' portion of the gene were obtained by PCR and cloned in E. coli expression vectors. Recombinant proteins P1, P5, P6 (26, 24, 35 kD) were purified by affinity chromatography and used for subcutaneous immunisation of mice. Immunisation was accomplished in three doses of the antigens (5, 10 and 20 mg) two times each dose with interval of 4 weeks. ELISA monitored antibody titres starting from the 21st day until the 150th day from the beginning of immunisation. Constant of association (Ka) of the antibodies was estimated employing computer software package ‘Polyconst’. Protection studies were accomplished in mice infected intraperitoneum by GBS with doses 106 and 107 cells per mice.

Results:

Three Bac based recombinant peptides were used for immunisation of mice. Largest peptide P6 generated the highest titres of antibodies (1 × 106) on the 69th day of experiment. That titre was not changed till the end of the study. Ka of the antibodies to the P6 peptide varied from 108 to 1013 M-1 with the 50% share of high affinity IgG. Immunisation with peptides P1 and P5 reached maximum on the 41st or 48th day of the experiment with titres 1:50 000 or 1:12 000, respectively, with gradual decrease till the end of the study. Affinity of IgG to those peptides also varied between 106 and 1012 M-1. Share of high affinity IgG was 10–30%. Cross-absorbtion of the antibodies to the peptides demonstrated the homology between anti-P6 and anti-P1 and differences with anti-P5. The most immunogenic peptide P6 was used for mice protection study. It was shown that mice with IgG titre against P6 equal to 1:100 000 were protected against GBS infection and GBS was eliminated from blood and peritoneum.

Conclusion:

Bac based peptides P6 and P1 can be considered as possible vaccine components against GBS infection. Perspectives of GBS vaccine development and epitop organisation of Bac proteins are discussed.

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Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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