Figure 4. Investigation of MetQ as a vaccine candidate.

(A) Mouse sera antibody titres to recombinant His-tagged MetQ after intraperitoneal immunisation with His₆-MetQ. Target protein (His₆-MetQ or the negative control SBP His₆-LivJ) and IgG class are labelled along the X axis, and results were obtained using serum from His₆-MetQ vaccinated mice with the exception of the filled triangles which represent results for serum from control mice (labelled alum). Filled symbols represent titres for individual mice for the total IgG titre, open circles for IgG1, and open diamonds for IgG2A titres. Bars represent median values. (B) Development of fatal disease in mice vaccinated with His₆-MetQ (square symbols) and control (given alum and PBS alone, diamonds) mice after IP inoculation of 10⁴ CFU of D39 (n = 20). There were no statistical differences in survival (log rank test). (C) Phagocytosis of representative S. pneumoniae vaccine serotypes. Key: bacteria opsonised with: grey bars, HBSS; solid bars, serum from alum immunised mice; dark grey bars, polyclonal anti-MetQ sera from MetQ vaccinated mice.