Figure 6.

IgG Ab response in immunized mice, and blood-stage parasitemia with the homologous and heterologous prime-boost regimens. In the homologous prime-boost regimen (PPP), groups of 6- to 8-week-old female C57BL/6 mice were immunized subcutaneously (s.c.) with 10 µg of each recombinant protein and Poly (I:C) (50 µg/dose). In the heterologous prime-boost regimen (AdPP), groups of 6- to 8-week-old female BALB/c mice were immunized intramuscularly (i.m.) with AdHu5 or AdC68 at a dose of 10⁸ infection units, and boosted twice with 10 µg of each recombinant protein and Poly (I:C) (50 µg/dose). Twenty-one days after third dose, mice were challenged with 2,000 Pb/PvVK210 spz. or with 2,000 Pb/PvVK247 spz, alternatively. Protection is indicated by the time predicted to reach 1% blood-stage parasitemia using a linear regression model. Blood-stage parasitemia was monitored from day 3 post-challenge until mice reach 1% parasitemia. Titres of IgG Abs against yPvCSP-All_CT and yPvCSP-All_FL were measured by ELISA. Serum was collected after the third dose. (a) and (d). IgG Ab titres of the immunized mice using a homologous (PPP) or heterologous prime-boost regimen (AdPP), respectively. (b) and (c). Time to 1% blood-stage parasitemia post-challenge with Pb/PvVK210 spz (n = 6 per group) or Pb/PvVK247 spz (n = 6 per group) after PPP regimen. (e) and (f). Time to 1% blood-stage parasitemia post-challenge with Pb/PvVK210 spz (n = 6 per group) or Pb/PvVK247 spz (n = 6 per group) after AdPP regimen. For IgG Ab titre, two independent assays were performed. The results are expressed as the arithmetic mean titres of each group (log₁₀ ± SEM) and were compared by one-way ANOVA followed by Tukey’s Multiple Comparison Test. Significant differences between groups are denoted on the graph: ***P < 0.001 and for time to reach 1% of parasitemia, two independent assays were performed. Significant value of ***P < 0.001 was determined by one-way ANOVA with Mantel-Cox test.