Histopathological study of mice infected with <i>Trypanosoma vivax</i>.

<p>8-week-old Outbred mice were injected i.p. with 10² bloodstream forms of <i>T. vivax</i> and different lymphoid and non lymphoid organs were harvested for histopathological examination 20 days post-infection. Spleen (A–D): (A) Diffuse lesions characterized by large necrotic foci in the red pulp (black star), associated with lymphoid tissue disorganization in the white pulp (white star). (B) Infiltration of a necrotic focus by activated macrophages (top of the Fig., arrows) and trypanosomes (arrowhead shows very small basophilic points in the inset depicting a higher magnification). (C) Presence of lower density hematopoiesis compared to non-infected mice. (D) Infiltration of the white pulp by activated macrophages and presence of a Mott cell (arrow). Liver (E–G): (E) Multifocal inflammatory lesions centered on portal tracts/centrilobular veins (arrows), and focal necrotic focus (star). (F) Peri-venous inflammatory infiltrate composed of plasma cells (mostly), but also lymphocytes and macrophages. In the inset depicting a higher magnification, arrowhead points to trypanosomes in the vascular spaces. (G) Foci of extramedullary hematopoiesis. Kidney (H–J): (H) Interstitial inflammatory infiltrates (I) mostly composed of plasma cells. (J) Trypanosomes in an arcuate artery (star); in the inset depicting a higher magnification, arrowhead points to trypanosomes in the vascular spaces. Cerebellum (K–M): (K) Multifocal lesions centered on blood vessels (arrows). (L) Blood vessel lumen filled by trypanosomes, proteins and erythrocytes (star), with perivascular edema (arrow) and ischemic neurons (arrowheads). (M) Trypanosomes in a meningeal blood vessel. Hematoxylin-eosin staining, scale bars are indicated at the bottom of each photograph. In the inset depicting a higher magnification, the arrowhead points to trypanosomes.</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

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