Fig. 7.

Analysis of immune responses to ComP-CPS8 and EPA-CPS8 bioconjugates in mice. a Titers of CPS8 IgG antibodies in mice immunized with CPS8 bioconjugate vaccines. Mouse groups were as follows: EPA (n = 9, mice vaccinated with 5 µg of total protein), ComP-CPS8 (n = 10, mice vaccinated with 5 µg total polysaccharide), and EPA-CPS8 (n = 10, mice vaccinated with 100 ng of total polysaccharide). All mice were immunized with 100 µL of a vaccine diluted 1:1 with Imject Alum Adjuvant on days 1, 14, and 28. Sera were collected on day 4. For the titration, enzyme-linked immunosorbent assay (ELISA) plates were coated with whole-cell serotype 8 pneumococci and incubated with 2-fold serial dilutions of sera. Each dot represents a single vaccinated mouse (n = 10 mice per group). ELISA statistical calculations were performed on sera samples run in technical triplicates. Titers for individual mice are shown, with error bars representing the standard error of the mean. Statistically significant titers compared to the EPA placebo group are denoted with asterisk and were determined using Kruskal–Wallis one-way analysis of variance (ANOVA). **P = 0.0223 and ****P < 0.0001. For analysis and representation purposes, negative titer values (<100) were given an arbitrary value of 10. b Opsonophagocytosis killing of S. pneumoniae serotype 8 by day 42 sera from mice immunized with ComP-CPS8 and EPA-CPS8 bioconjugate vaccines. The same mouse groups described for the IgG titers were employed for the OPA. A 40% (v v⁻¹) sample of serum and bacterial multiplicity of infection (MOI) of 0.01 were added to fresh whole blood from naive mice to perform the assay. Results are expressed as percent bacterial killing for individual mice, with error bars representing the standard deviation of the mean. Statistically significant killing compared to the EPA placebo group is denoted with asterisk and were determined using Kruskal–Wallis one-way ANOVA. **P = 0.0015. Source data are provided as a Source Data file