An O-Antigen Glycoconjugate Vaccine Produced Using Protein Glycan Coupling Technology Is Protective in an Inhalational Rat Model of Tularemia

Figure 3

GtExoA glycoconjugate stimulates memory immunity in vaccinated rats. Groups of F344 rats () were vaccinated three times, two weeks apart with 10 μg of GtExoA coadministered with MF59, or immunised with MF59 alone, and immune responses were measured 28 days after the third immunisation. (a) Quantitation of rat IgG recognising the GtExoA glycoconjugate antigen was determined by ELISA for a serial dilution of sera from GtExoA and respective MF59 adjuvant control rats. The mean OD_450nm (±SEM) response is presented for each dilution for each vaccine group. The use of solid or dotted datapoint connecting lines identifies responses in sera from rats immunised with GtExoA + MF59 or with the MF59 adjuvant only, respectively. Responses in respective groups immunised via the i.p. or s.c. routes are identified using red or blue connecting lines, respectively (see legend). (b) Splenocytes were isolated from rats immunised with either GtExoA administered by i.p. (light blue bars) or s.c. (dark blue bars) routes and from rats immunised with LVS (black bars) or PBS. Splenocytes were cultured in the presence of purified ExoA protein, LVS sonicate, F. tularensis Schu S4 sonicate, Con-A, or medium. The expression of IFNγ in 72-hour culture supernatants was measured by ELISA. The OD_450nm results were normalised by transformation into units of ρg/mL by generating a standard curve using recombinant rat IFNγ. Statistical analysis of differences between groups was determined by one-way ANOVA with Holm-Sidak’s posttests (, , or ). Data validity was tested using Bartlett’s test for equal variance. IFNγ responses are presented as mean response for each group () ±SEM.

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