Background: Schistosomes are trematode worms that dwell in their definitive host’s blood vessels, where females lay eggs that need to be discharged into the environment with host excreta to maintain their life cycle. Both worms and eggs require type 2 immunity for their maturation and excretion, respectively. However, immune molecules that orchestrate such immunity remain unclear. IL-33 is one of the epithelium-derived cytokines that induce type 2 immunity in tissues. This study aimed at determining its role in the maturation, reproduction, and excretion of S. mansoni eggs, and in the maintenance of egg-induced pathology in the intestines of mice.
Methods: Using S. mansoni-infected IL-33-deficient (IL-33-/-) and wild-type (WT) mice, the morphology of worms and the number of eggs in intestinal tissues were studied at different time points of infection. IL-5 and IL-13 production in spleens and mesenteric lymph nodes were measured. Tissue histology was performed on the terminal ilea of infected and non-infected mice.
Results: Morphology-wise, worms from IL-33-/- and WT mice at the fourth and sixth weeks of infection did not differ. The number of eggs in intestinal tissues did not differ much between IL-33-/- and WT mice. In the sixth week of infection, IL-33-/- mice presented impaired type 2 immunity in intestines, characterized by decreased production of IL-5 and IL-13 in mesenteric lymph nodes and fewer inflammatory infiltrates with fewer eosinophils in the ilea. Otherwise there was no difference between IL-33-/- and WT mice in the levels of IL-25 and thymic stromal lymphopoietin (TSLP) in intestinal tissues.
Conclusions: Despite its ability to initiate type 2 immunity in tissues, IL-33 alone seems dispensable for S. mansoni maturation and its absence may not affect much the accumulation of eggs in intestinal tissues. The transient impairment of type 2 immunity observed in the intestines, but not spleens, highlights the importance of IL-33 over IL-25 and TSLP in initiating, but not maintaining, locally-induced type 2 immunity in intestinal tissues during schistosome infection. Further studies are needed to decipher the role of each of them in schistosomiasis and clarify the possible interactions that might exist between them.
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This is a list of supplementary files associated with this preprint. Click to download.
Additional file 2: Figure S2. Oviposition in S. mansoni infection induces intestinal production of IL-25 and TSLP but not of IL-33. Female WT BALB/c mice (3 animals per time point) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed weekly from week zero (non-infected) to week four, then fortnightly to week 12 of infection. Small intestines were homogenized with gentleMACS Octo Dissociator and the cytokines were measured in the homogenate supernatants by ELISA. Data are presented as mean with SD. Cytokines were measured in only one mouse at 12 wpi.
Additional file 1: Figure S1. IL-33 deficiency does not affect the number of eggs produced per S. mansoni worm pair and the liver egg burden in infected mice Female IL-33-/- and WT BALB/c mice (4-8 animals per group) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed at six, nine and 12 weeks of infection to determine the number of worm pairs and assess the number of liver tissue eggs. (a) Number of eggs per worm pair. (b) Number of eggs per gram of liver tissue. Experiments were replicated at least three times. Data are representative of 2 independent experiments with similar results and are presented as mean with SEM. Groups were compared using unpaired two-tail t-test with Welch’s correction at p<0.05 significance. wpi=week post-infection.
Additional file 2: Figure S2. Oviposition in S. mansoni infection induces intestinal production of IL-25 and TSLP but not of IL-33. Female WT BALB/c mice (3 animals per time point) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed weekly from week zero (non-infected) to week four, then fortnightly to week 12 of infection. Small intestines were homogenized with gentleMACS Octo Dissociator and the cytokines were measured in the homogenate supernatants by ELISA. Data are presented as mean with SD. Cytokines were measured in only one mouse at 12 wpi.
Additional file 1: Figure S1. IL-33 deficiency does not affect the number of eggs produced per S. mansoni worm pair and the liver egg burden in infected mice Female IL-33-/- and WT BALB/c mice (4-8 animals per group) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed at six, nine and 12 weeks of infection to determine the number of worm pairs and assess the number of liver tissue eggs. (a) Number of eggs per worm pair. (b) Number of eggs per gram of liver tissue. Experiments were replicated at least three times. Data are representative of 2 independent experiments with similar results and are presented as mean with SEM. Groups were compared using unpaired two-tail t-test with Welch’s correction at p<0.05 significance. wpi=week post-infection.
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Posted 18 Dec, 2020
On 20 Dec, 2020
Invitations sent on 07 Dec, 2020
On 07 Dec, 2020
Received 07 Dec, 2020
On 06 Dec, 2020
On 06 Dec, 2020
On 06 Dec, 2020
On 06 Nov, 2020
Received 23 Oct, 2020
Received 23 Oct, 2020
On 01 Oct, 2020
On 30 Sep, 2020
Received 07 Sep, 2020
Invitations sent on 25 Aug, 2020
On 25 Aug, 2020
On 13 Aug, 2020
On 13 Aug, 2020
On 12 Aug, 2020
On 12 Aug, 2020
Posted 18 Dec, 2020
On 20 Dec, 2020
Invitations sent on 07 Dec, 2020
On 07 Dec, 2020
Received 07 Dec, 2020
On 06 Dec, 2020
On 06 Dec, 2020
On 06 Dec, 2020
On 06 Nov, 2020
Received 23 Oct, 2020
Received 23 Oct, 2020
On 01 Oct, 2020
On 30 Sep, 2020
Received 07 Sep, 2020
Invitations sent on 25 Aug, 2020
On 25 Aug, 2020
On 13 Aug, 2020
On 13 Aug, 2020
On 12 Aug, 2020
On 12 Aug, 2020
Background: Schistosomes are trematode worms that dwell in their definitive host’s blood vessels, where females lay eggs that need to be discharged into the environment with host excreta to maintain their life cycle. Both worms and eggs require type 2 immunity for their maturation and excretion, respectively. However, immune molecules that orchestrate such immunity remain unclear. IL-33 is one of the epithelium-derived cytokines that induce type 2 immunity in tissues. This study aimed at determining its role in the maturation, reproduction, and excretion of S. mansoni eggs, and in the maintenance of egg-induced pathology in the intestines of mice.
Methods: Using S. mansoni-infected IL-33-deficient (IL-33-/-) and wild-type (WT) mice, the morphology of worms and the number of eggs in intestinal tissues were studied at different time points of infection. IL-5 and IL-13 production in spleens and mesenteric lymph nodes were measured. Tissue histology was performed on the terminal ilea of infected and non-infected mice.
Results: Morphology-wise, worms from IL-33-/- and WT mice at the fourth and sixth weeks of infection did not differ. The number of eggs in intestinal tissues did not differ much between IL-33-/- and WT mice. In the sixth week of infection, IL-33-/- mice presented impaired type 2 immunity in intestines, characterized by decreased production of IL-5 and IL-13 in mesenteric lymph nodes and fewer inflammatory infiltrates with fewer eosinophils in the ilea. Otherwise there was no difference between IL-33-/- and WT mice in the levels of IL-25 and thymic stromal lymphopoietin (TSLP) in intestinal tissues.
Conclusions: Despite its ability to initiate type 2 immunity in tissues, IL-33 alone seems dispensable for S. mansoni maturation and its absence may not affect much the accumulation of eggs in intestinal tissues. The transient impairment of type 2 immunity observed in the intestines, but not spleens, highlights the importance of IL-33 over IL-25 and TSLP in initiating, but not maintaining, locally-induced type 2 immunity in intestinal tissues during schistosome infection. Further studies are needed to decipher the role of each of them in schistosomiasis and clarify the possible interactions that might exist between them.
Figure 1
Figure 1
Figure 1
Figure 1
Figure 1
Figure 1
Figure 1
Figure 1
This is a list of supplementary files associated with this preprint. Click to download.
Additional file 2: Figure S2. Oviposition in S. mansoni infection induces intestinal production of IL-25 and TSLP but not of IL-33. Female WT BALB/c mice (3 animals per time point) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed weekly from week zero (non-infected) to week four, then fortnightly to week 12 of infection. Small intestines were homogenized with gentleMACS Octo Dissociator and the cytokines were measured in the homogenate supernatants by ELISA. Data are presented as mean with SD. Cytokines were measured in only one mouse at 12 wpi.
Additional file 1: Figure S1. IL-33 deficiency does not affect the number of eggs produced per S. mansoni worm pair and the liver egg burden in infected mice Female IL-33-/- and WT BALB/c mice (4-8 animals per group) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed at six, nine and 12 weeks of infection to determine the number of worm pairs and assess the number of liver tissue eggs. (a) Number of eggs per worm pair. (b) Number of eggs per gram of liver tissue. Experiments were replicated at least three times. Data are representative of 2 independent experiments with similar results and are presented as mean with SEM. Groups were compared using unpaired two-tail t-test with Welch’s correction at p<0.05 significance. wpi=week post-infection.
Additional file 2: Figure S2. Oviposition in S. mansoni infection induces intestinal production of IL-25 and TSLP but not of IL-33. Female WT BALB/c mice (3 animals per time point) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed weekly from week zero (non-infected) to week four, then fortnightly to week 12 of infection. Small intestines were homogenized with gentleMACS Octo Dissociator and the cytokines were measured in the homogenate supernatants by ELISA. Data are presented as mean with SD. Cytokines were measured in only one mouse at 12 wpi.
Additional file 1: Figure S1. IL-33 deficiency does not affect the number of eggs produced per S. mansoni worm pair and the liver egg burden in infected mice Female IL-33-/- and WT BALB/c mice (4-8 animals per group) were subcutaneously infected with 50 and 35 S. mansoni cercariae, respectively for nine and 12 weeks and sacrificed at six, nine and 12 weeks of infection to determine the number of worm pairs and assess the number of liver tissue eggs. (a) Number of eggs per worm pair. (b) Number of eggs per gram of liver tissue. Experiments were replicated at least three times. Data are representative of 2 independent experiments with similar results and are presented as mean with SEM. Groups were compared using unpaired two-tail t-test with Welch’s correction at p<0.05 significance. wpi=week post-infection.
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