Immunogenicity of a Glycoconjugate from Hydrazine-Detoxified Lipopolysaccharide of Vibrio cholerae O139.

A glycoconjugate (dLPS-CBSA) from hydrazine-detoxified lipopolysaccharide (LPS) of Vibrio cholerae O139 and BSA was used for immunization of BALB/c mice. The immunogenicity (concentration of induced IgG antibodies) of the conjugate was determined by enzyme-linked immunosorbent assay. The highest level of LPS-specific IgGs was found in sera collected 2 weeks after the third immunization. Both IgM and IgG antibodies present in the anti-V. cholerae O139-specific sera showed long-lasting vibriocidal activity. The glycoconjugate also stimulated production of IL-4, IL-6, IFNγ, TNFα and IL-10. Immunization with the conjugate induced significant production of both Th1 and Th2 cytokine sets, indicating balanced Th1/Th2 immune response polarization. The quantitative analysis of total and LPS-specific IgM and IgG antibodies production by B lymphocytes (from both the spleen and the bone marrow) was performed by ELISPOT assay. From the analysis of antibodies produced directly by B lymphocytes in the bone marrow (of dLPS-CBSA immunized mice), we were able to identify the IgM-IgG switch in the antibodies produced.