Fig 2. Pre-existing CD4+ T cell immunity to epitopes contained within the core of liposomal vaccine particles enhances the antibody response to non-cognate target antigens on the particle surface.
Mice (n = 4) were pre-vaccinated with either PBS or OVA323-339 in TMG at week 0 and week 2, prior to vaccination with CSP(OVA323-339) liposomes at week 4. The effect of this pre-existing immunity to OVA323-339 on anti-CSP antibody responses was measured over weeks 4 to 8 and compared using two-way ANOVA with Bonferroni’s post-test. Asterisks indicate the statistical significance of the difference between OVA323-339 + TMG (black circles, solid black line) and PBS + TMG (grey squares, solid grey line) pre-vaccinated groups. This difference was found reproducibly in multiple experiments and a typical result is shown (b). Anti-OVA323-339 responses were also measured in both PBS and OVA323-339 pre-vaccinated mice administered CSP(OVA323-339) liposomes (c). The effect of liposomal particle dose was examined by vaccinating mice (n = 4) with five-fold dilutions of CSP(OVA323-339) vaccine (the highest concentration containing 50 μg of CSP and 10 μg of OVA323-339). Anti-CSP responses were compared using a one-way ANOVA with Tukey’s post-test for multiple comparisons (d). Pre-vaccination with PBS or OVA323-339 in TMG was then performed either intramuscularly or subcutaneously. Subsequently, CSP(OVA323-339) liposomal vaccines were then administered either subcutaneously (e) or intramuscularly (f) and mean anti-CSP responses were compared over time using two-way ANOVA with Bonferroni’s post test. Asterisks indicate the difference between groups shown in blue and grey groups at the indicated time points.