Adoptive transfer of <i>N. caninum</i> tachyzoite-infected DC in mice and parasite transmission to offspring during pregnancy.

<p><b>A</b>. Kinetics of dissemination of <i>N. caninum</i> in BALB/c mice inoculated i.p. with ∼2.5×10⁶ cfu (experiment 1) or ∼1.5×10⁶ cfu (experiment 2) free Nc-1<i>Luc</i> tachyzoites or Nc-1<i>Luc</i>-infected DC. Progression of <i>N. caninum</i> infection and parasite biomass was assessed by bioluminescence imaging (BLI) using the IVIS Spectrum imaging system. Photon emission (photons s⁻¹ cm⁻²) was assessed for 180 s 10–12 min after i.p. injection of d-luciferin. Images are from two experiments with four mice per group on days 1 and 2 p.i. Colour scales indicate photon emission (photons s⁻¹ cm⁻²) during 180 s exposure time. <b>B</b>. Total photon emission analysis of BALB/c mice inoculated i.p. with free Nc-1<i>luc</i> tachyzoites or Nc-1<i>Luc</i>-infected DC on days 1–5 after inoculation. There was a dramatic increase in the parasite burden in mice inoculated with Nc-1<i>Luc</i>-infected DC compared to free Nc-1<i>Luc</i> on days 1 and 2 p.i. (P<0.05; Student's <i>t</i> test). Compiled data are from two independent experiments (day 1 p.i. n = 11; day 2–5 p.i. n = 8). <b>C</b>. Imaging of infected organs <i>ex vivo</i>. Organs were dissected on day 1 p.i from mice infected with free Nc-1<i>Luc</i> tachyzoites or Nc-1<i>Luc</i> -infected DC, respectively. Parasite load was significantly higher in the Nc1<i>Luc</i>-infected DC group. Signals were observed in images of the testis (T), liver (LV), spleen (S), mesenteric lymph nodes (MLN), lung (L), kidney (K) and brain (CNS). No signal was detected in the heart (H). <b>D</b>. Detection of <i>N. caninum</i> DNA in mouse brains on day 1 p.i. by real-time PCR as indicated under <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032123#s2" target="_blank">Materials and Methods</a>. Y-axis indicates percentage of mice with positive PCR for mice infected with Nc-1<i>Luc</i>-infected DC or free Nc-1<i>Luc</i> tachyzoites, respectively (n = 11; positive 4/11 <i>versus</i> 0/11; P<0.05, Fisher <i>F</i> test). <b>E</b>. Kaplan–Meier survival curves for neonates born to dams inoculated with ∼2.5×10⁶ cfu of free Nc-Spain 7 tachyzoites or Nc-Spain 7-infected DC, 5×10⁶ non-infected DC or PBS buffer. The curves represent the percentage of animals surviving over a period of 30 days post-partum (pp). Vertical steps downward correspond to days pp when a mouse died or was sacrificed. Symbols indicate censored observations. The number of dead mice was registered daily, and the median survival time of the Nc-Spain 7-infected DC group was significantly shorter than that of the free Nc-Spain 7-infected group (P<0.001, Log-rank test). Compiled data are from two independent experiments (n = 7–14 pregnant mice per group). <b>F</b>. Parasite loads in brain from offspring quantified by real-time PCR and expressed in terms of number of parasites per µg of host DNA. Pups born to mice inoculated with Nc-Spain 7-infected-DC displayed significant higher parasite loads than the free Nc-Spain 7-infected group (P<0.01; Student's <i>t</i> test). The data are represented as individual points and horizontal lines correspond to the mean value. Compiled data are from two independent experiments.