Protective Anti-RVFV NP Responses in Mice p,0.01) (Figure 2e–f). At 120 hours p.i. IFNb expression remained upregulated in control mice liver. The challenge virus was first detected in the tissues of adjuvant control mice at 24 hours p.i. and, subsequently, at high titers in adjuvant and PBS controls at 72 and 120 hours p.i. Low titer of the virus was detected in liver of recNP-immunized mice only at 72 hours p.i. (10,000 fold lower than control mice). Surprisingly the virus replicated to relatively higher titers in the spleen of recNP-immunized mice, but only at 72 hours and still 100 fold lower compared to control mice (Figure 3a–b). The expression of genes involved in B- and T-cell immunity and other immune functions at 72 hours The expression of an array of 84 genes involved in B- and T-cell immunity, and other immune functions, were analyzed in the liver and spleen tissues of recNP-immunized, and non-immunized adjuvant and PBS control mice at 72 hours post infection relative to an age related normal control group. The list of genes tested, fold change values for different groups and P-values are shown in Table S1. Only five genes were significantly upregulated and one down- regulated in the liver of recNP-immunized mice, compared to 34 upregulated and nine downregulated in non-immunized adjuvant control mice, and 37 upregulated and eight downregulated in non- immunized PBS control mice (Table S1). There was an almost 100% overlap between the up- or downregulated genes in liver of non-immunized adjuvant and PBS control mice, with only a few genes not consistent between these two groups, most likely as a result of the fold change in some of these genes being on the borderline of the cut-off fold-change value, indicating that mock Figure 3. (a–b). Mean viral loads in livers and spleens of RVFV infected mice. Groups, consisting of 3 mice per group per time point, are indicated as: RecNP immunized (–N–), adjuvant control (–o–) and PBS control mice (–m–). Livers are indicated in panel a, and spleens in panel b. doi:10.1371/journal.pone.0025027.g003 PLoS ONE | www.plosone.org 4 September 2011 | Volume 6 | Issue 9 | e25027