Distribution of different cells in the blood of infected mice at 5 DPI.

a,b,c<p>The statistical significance of different comparisons (p<0.05) are represented by letters: a) uninfected mice vs. ZH-infected mice; b) RVFV-infected mice vs. RVFV+SGE infected mice; and c) healthy mice vs. RVFV+SGE infected mice. Ten mice were tested in each group.</p

Comparison of RVFV dissemination at D6 in various organs for the two routes of injection.

<p>Six C57Bl/6 mice were infected ID or IP with 10³ pfu, sacrificed at D6 post-infection and the viral titers were determined by plaque assay. The white bars correspond to the IP route and black bars to the ID route. Data are from 3 independent experiments. * indicates significant differences in viral titers between the two sets of data as determined by Mann-Withney test (** p<0.01); *** p<0.001).</p

Weight curves of mice bitten by RVFV-exposed <i>Aedes aegypti</i>.

<p>Ten C57Bl/6 mice were anesthetized and exposed to bites of mosquitoes collected at D19 after virus exposure. The blue and violet curves correspond to mice bitten by 6 mosquitoes (6 of 6 and 4 of 6 mosquitoes were infected respectively). The yellow curve represents a mouse bitten by 8 mosquitoes (3 of 8 mosquitoes were infected). The red curve corresponds to a mouse bitten by 3 (3 of 3 mosquitoes were infected). The black curve corresponds to 7 mosquito bites (4 of 7 mosquitoes were infected) and the green curve corresponds to 9 mosquito bites (3 of 9 mosquitoes were infected). The red arrow indicates the death of the mouse. Two other mice were bitten by 6 mosquitoes (6 of 6 and 4 of 6 mosquitoes were infected respectively) and did not die after 11 days of observation (dark red and light blue curves). Mosquitoes did not feed on 2 mice (brown and turquoise curves).</p

Histological sections of liver at D5 post-infection.

<p>Five C57Bl/6 mice were injected with RVFV at 10³ pfu/mouse. Images A and C correspond to the livers of mice infected in the presence of 1 SGP and viewed at 4X and 10X magnification, respectively (inset in C is 40X). The arrow head in A and C identify inflammatory foci. The arrow in the inset of C identifies a necrotic hepatocyte, and the asterisk identifies neutrophil infiltration. Panel B and D correspond to the livers of mice infected in the absence of SGE at 4X and 10X magnification, respectively. The arrows in the inset in D show a necrotic hepatocyte foci.</p

Survival curves of mice.

<p>Ten C57Bl/6 mice per group were injected with several doses of RVFV ranging from 10 to 10⁴ pfu/mouse (respectively A to D), in the absence (yellow curve) or presence of 1 SGP (red curve).</p

Weight curves of mice infected by ID and bitten by non-infected mosquitoes.

<p>Three lots (A, B and C) of 5 C57Bl/6 anesthetized mice were used for each experiment. They were injected ID with 50 pfu of RVFV before being exposed to the bites of 20 mosquitoes contained in cardboard boxes. After 15 minutes, blood-fed mosquitoes were collected and counted. After exposure, the weight of each mouse was recorded every day. Each curve corresponds to one mouse and the number of non-infected bites is indicated in the legend on the figure. Death occurred at the end of each curve.</p

Viral titers of major target organs at D5 post-infection.

<p>Three lots of <b>5 C57Bl/6 mice</b> were infected by ID injection of 10³ pfu RVFV with or without 1 SGP. RVFV titer was determined by plaque assay on E6 cells at D5 post-infection. Results are presented as box-and-whisker, indicating inside the box the median titer value and the bottom and top of the box being the 25th and 75th percentile. Whiskers correspond to the lowest and largest values of the titers. Mann-Withney test was employed to analyze the difference between sets of data for each organ. * p<0.05; ** p<0.01.</p

Molecular identity of <i>T. vivax</i> IL 1392.

<p>Full lengh of <i>ILDat1.2 VSG</i> gene (A). Initiation and stop codons are underlined. The specific <i>T. vivax</i> 20-amino acids sequence at the N-terminal end of the gene is depicted in red (positions 64 to 123). Forward and reverse primers used in this experiment are in italics. DNA was extracted from <i>T. vivax</i> bloodstream forms and amplified by PCR using <i>VSG-1.2</i>F and <i>VSG-1.2</i>R primers. A fragment of 148 bp was obtained and the resulting sequence aligned with the Y486 reference strain (B). Two point mutations are squared. Blood smears of a mouse infected with <i>T. vivax</i> were fixed and stained with Giemsa (C and D); k = kinetoplast, f = flagellum. The high number of circulating parasites at the peak of parasitemia can be evaluated in the picture (E).</p

Effect of host background on parasite load and fate.

<p>BALB/c, C57BL/6 or Outbred mice were injected i.p. with 1×10² bloodstream forms of <i>T. vivax</i> and the mean parasitemia recorded individually during infection (A, B, C). Mean mortality (D) is depicted compared to BALB/c mice. Results are given as arithmetic means ± standard deviations of at least three independent experiments. Cumulative mortality was recorded over time for all groups and Kaplan-Meir survival curves plotted for the three mouse strains (D); Comparison between survival curves was performed using Log-rank Mantel-Cox test: * p<0.028, ** p<0.0018, when compared with BALB/c survival.</p

<i>T. vivax</i> induces major perturbations in hematological parameters and causes severe thrombocytopenia.

<p>8-week-old Outbred (white symbols) or C57BL/6 (black symbols) mice were injected i.p. with 1×10² bloodstream forms of <i>T. vivax</i>. Blood samples were collected individually every 2–3 days and red blood cell counts (RBC, A), hematocrit (HCT, B), hemoglobin concentrations (HGB, C), leukocytes (WBC, D) and platelets (PLA, E), were determined. Results are given for days 5, 10, 15 and 20 as arithmetic means ± standard deviations of at least three different experiments with 3–5 mice per time point/experimental group. *** p<0.001, ** p<0.01, * p<0.05, when compared with samples from day 0. $ = not determined on day 10 for C57BL/6 mice.</p