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A worm's best friend: recruitment of neutrophils by Wolbachia confounds eosinophil degranulation against the filarial nematode Onchocerca ochengi.

Hansen RD, Trees AJ, Bah GS, Hetzel U, Martin C, Bain O, Tanya VN, Makepeace BL - Proc. Biol. Sci. (2010)

Bottom Line: In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine.In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability.Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response.

View Article: PubMed Central - PubMed

Affiliation: Liverpool School of Tropical Medicine, School of Veterinary Science and Institute of Infection and Global Health, University of Liverpool, , Liverpool L69 7ZJ, UK.

ABSTRACT
Onchocerca ochengi, a filarial parasite of cattle, represents the closest relative of the human pathogen, Onchocerca volvulus. Both species harbour Wolbachia endosymbionts and are remarkable in that adult female worms remain viable but sessile for many years while surrounded by host cells and antibodies. The basis of the symbiosis between filariae and Wolbachia is thought to be metabolic, although a role for Wolbachia in immune evasion has received little attention. Neutrophils are attracted to Wolbachia, but following antibiotic chemotherapy they are replaced by eosinophils that degranulate on the worm cuticle. However, it is unclear whether the eosinophils are involved in parasite killing or if they are attracted secondarily to dying worms. In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine. In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability. Eosinophil degranulation increased significantly only in the oxytetracycline group; whereas nodular gene expression of bovine neutrophilic chemokines was lowest in this group. Moreover, intense eosinophil degranulation was initially associated with worm vitality, not degeneration. Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response.

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Related in: MedlinePlus

Histopathology of O. ochengi onchocercomata at 12 weeks. (a) Untreated onchocercoma with typical accumulations of neutrophils (open arrowheads) and Splendore-Hoeppli (SH) deposits (yellow arrows) on the worm cuticle. A cross section of an adult female worm shows the hypodermis (closed arrowhead) and microfilariae (black arrows) in the paired uteri. (b) A nodule from the melarsomine (MEL) group, displaying abundant neutrophils (open arrowheads) between the cuticles of three worm sections (black arrows). (c) A MEL-treated nodule with eosinophils (open arrowheads) and degranulating eosinophils (DE; closed arrowhead) some distance from a worm section. The worm has accumulated SH deposits (yellow arrow) and the uteri are empty (black arrows). (d) A nodule from the oxytetracycline (OXY) group shows numerous DE clusters (open arrowheads) around the cuticle, SH phenomenon (yellow arrow) and empty uteri (black arrows). (e) A higher power image from an OXY-treated nodule reveals DE and free granules (open arrowheads) in contact with the worm cuticle (black arrow) overlaying the hypodermis (closed arrowhead). (f) Phase-contrast image of a section from an OXY-treated nodule displaying eosinophil granules (open arrowheads) embedded in SH deposits (yellow arrow); filarial nuclei are also visible in the hypodermis (closed arrowheads). All sections were stained with Giemsa. Scale bars: (a—d) 20 µm; (e,f) 10 µm.
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RSPB20102367F2: Histopathology of O. ochengi onchocercomata at 12 weeks. (a) Untreated onchocercoma with typical accumulations of neutrophils (open arrowheads) and Splendore-Hoeppli (SH) deposits (yellow arrows) on the worm cuticle. A cross section of an adult female worm shows the hypodermis (closed arrowhead) and microfilariae (black arrows) in the paired uteri. (b) A nodule from the melarsomine (MEL) group, displaying abundant neutrophils (open arrowheads) between the cuticles of three worm sections (black arrows). (c) A MEL-treated nodule with eosinophils (open arrowheads) and degranulating eosinophils (DE; closed arrowhead) some distance from a worm section. The worm has accumulated SH deposits (yellow arrow) and the uteri are empty (black arrows). (d) A nodule from the oxytetracycline (OXY) group shows numerous DE clusters (open arrowheads) around the cuticle, SH phenomenon (yellow arrow) and empty uteri (black arrows). (e) A higher power image from an OXY-treated nodule reveals DE and free granules (open arrowheads) in contact with the worm cuticle (black arrow) overlaying the hypodermis (closed arrowhead). (f) Phase-contrast image of a section from an OXY-treated nodule displaying eosinophil granules (open arrowheads) embedded in SH deposits (yellow arrow); filarial nuclei are also visible in the hypodermis (closed arrowheads). All sections were stained with Giemsa. Scale bars: (a—d) 20 µm; (e,f) 10 µm.

Mentions: Quantitative analysis revealed striking differences in the nodular eosinophil : neutrophil ratio between treatment groups (figure 1a). In the CON group, neutrophils vastly outnumbered eosinophils (overall median ratio = 0.004) and there was no significant change in the composition of the granulocytic infiltrate over time (Friedman test: χ2 = 5.6, p = 0.507). A modest increase in the eosinophil : neutrophil ratio was observed in the MEL group, culminating in a shift towards eosinophilia in resolving nodules at the termination of the experiment, although this was not statistically significant (figure 1a; Friedman test: χ2 = 6.0, p = 0.473). However, there was a much larger and sustained expansion of the nodular eosinophil population in the OXY group, which peaked in a statistically significant, 275-fold increase in the median eosinophil : neutrophil ratio by 36 wpt (figure 1a; Friedman test: χ2 = 19.3, p < 0.001). Median nodule area gradually reduced during both adulticidal treatments (figure 2b) as the worms were eliminated and this was statistically significant in the MEL group (Friedman test: χ2 = 11.1, p = 0.012), although only a non-significant trend was apparent in the OXY group (Friedman test: χ2 = 10.3, p = 0.096). When DE adjacent to worm sections were analysed separately on a semi-quantitative scale, a clear distinction between the MEL and OXY treatment groups was observed (figure 1c). In the MEL group (in common with the CON group), the median score did not exceed 1 throughout the experiment, and no significant change over time was detected (Friedman test, MEL: χ2 = 4.9, p = 0.605; CON: χ2 = 3.9, p = 0.755). By contrast, there was a marked, statistically significant peak in DE in the OXY group at 12 wpt (figure 1c; Friedman test: χ2 = 11.9, p = 0.042) and the maximum score of 3 (greater than 10 DE per worm section) was only recorded herein.Figure 1.


A worm's best friend: recruitment of neutrophils by Wolbachia confounds eosinophil degranulation against the filarial nematode Onchocerca ochengi.

Hansen RD, Trees AJ, Bah GS, Hetzel U, Martin C, Bain O, Tanya VN, Makepeace BL - Proc. Biol. Sci. (2010)

Histopathology of O. ochengi onchocercomata at 12 weeks. (a) Untreated onchocercoma with typical accumulations of neutrophils (open arrowheads) and Splendore-Hoeppli (SH) deposits (yellow arrows) on the worm cuticle. A cross section of an adult female worm shows the hypodermis (closed arrowhead) and microfilariae (black arrows) in the paired uteri. (b) A nodule from the melarsomine (MEL) group, displaying abundant neutrophils (open arrowheads) between the cuticles of three worm sections (black arrows). (c) A MEL-treated nodule with eosinophils (open arrowheads) and degranulating eosinophils (DE; closed arrowhead) some distance from a worm section. The worm has accumulated SH deposits (yellow arrow) and the uteri are empty (black arrows). (d) A nodule from the oxytetracycline (OXY) group shows numerous DE clusters (open arrowheads) around the cuticle, SH phenomenon (yellow arrow) and empty uteri (black arrows). (e) A higher power image from an OXY-treated nodule reveals DE and free granules (open arrowheads) in contact with the worm cuticle (black arrow) overlaying the hypodermis (closed arrowhead). (f) Phase-contrast image of a section from an OXY-treated nodule displaying eosinophil granules (open arrowheads) embedded in SH deposits (yellow arrow); filarial nuclei are also visible in the hypodermis (closed arrowheads). All sections were stained with Giemsa. Scale bars: (a—d) 20 µm; (e,f) 10 µm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3119012&req=5

RSPB20102367F2: Histopathology of O. ochengi onchocercomata at 12 weeks. (a) Untreated onchocercoma with typical accumulations of neutrophils (open arrowheads) and Splendore-Hoeppli (SH) deposits (yellow arrows) on the worm cuticle. A cross section of an adult female worm shows the hypodermis (closed arrowhead) and microfilariae (black arrows) in the paired uteri. (b) A nodule from the melarsomine (MEL) group, displaying abundant neutrophils (open arrowheads) between the cuticles of three worm sections (black arrows). (c) A MEL-treated nodule with eosinophils (open arrowheads) and degranulating eosinophils (DE; closed arrowhead) some distance from a worm section. The worm has accumulated SH deposits (yellow arrow) and the uteri are empty (black arrows). (d) A nodule from the oxytetracycline (OXY) group shows numerous DE clusters (open arrowheads) around the cuticle, SH phenomenon (yellow arrow) and empty uteri (black arrows). (e) A higher power image from an OXY-treated nodule reveals DE and free granules (open arrowheads) in contact with the worm cuticle (black arrow) overlaying the hypodermis (closed arrowhead). (f) Phase-contrast image of a section from an OXY-treated nodule displaying eosinophil granules (open arrowheads) embedded in SH deposits (yellow arrow); filarial nuclei are also visible in the hypodermis (closed arrowheads). All sections were stained with Giemsa. Scale bars: (a—d) 20 µm; (e,f) 10 µm.
Mentions: Quantitative analysis revealed striking differences in the nodular eosinophil : neutrophil ratio between treatment groups (figure 1a). In the CON group, neutrophils vastly outnumbered eosinophils (overall median ratio = 0.004) and there was no significant change in the composition of the granulocytic infiltrate over time (Friedman test: χ2 = 5.6, p = 0.507). A modest increase in the eosinophil : neutrophil ratio was observed in the MEL group, culminating in a shift towards eosinophilia in resolving nodules at the termination of the experiment, although this was not statistically significant (figure 1a; Friedman test: χ2 = 6.0, p = 0.473). However, there was a much larger and sustained expansion of the nodular eosinophil population in the OXY group, which peaked in a statistically significant, 275-fold increase in the median eosinophil : neutrophil ratio by 36 wpt (figure 1a; Friedman test: χ2 = 19.3, p < 0.001). Median nodule area gradually reduced during both adulticidal treatments (figure 2b) as the worms were eliminated and this was statistically significant in the MEL group (Friedman test: χ2 = 11.1, p = 0.012), although only a non-significant trend was apparent in the OXY group (Friedman test: χ2 = 10.3, p = 0.096). When DE adjacent to worm sections were analysed separately on a semi-quantitative scale, a clear distinction between the MEL and OXY treatment groups was observed (figure 1c). In the MEL group (in common with the CON group), the median score did not exceed 1 throughout the experiment, and no significant change over time was detected (Friedman test, MEL: χ2 = 4.9, p = 0.605; CON: χ2 = 3.9, p = 0.755). By contrast, there was a marked, statistically significant peak in DE in the OXY group at 12 wpt (figure 1c; Friedman test: χ2 = 11.9, p = 0.042) and the maximum score of 3 (greater than 10 DE per worm section) was only recorded herein.Figure 1.

Bottom Line: In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine.In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability.Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response.

View Article: PubMed Central - PubMed

Affiliation: Liverpool School of Tropical Medicine, School of Veterinary Science and Institute of Infection and Global Health, University of Liverpool, , Liverpool L69 7ZJ, UK.

ABSTRACT
Onchocerca ochengi, a filarial parasite of cattle, represents the closest relative of the human pathogen, Onchocerca volvulus. Both species harbour Wolbachia endosymbionts and are remarkable in that adult female worms remain viable but sessile for many years while surrounded by host cells and antibodies. The basis of the symbiosis between filariae and Wolbachia is thought to be metabolic, although a role for Wolbachia in immune evasion has received little attention. Neutrophils are attracted to Wolbachia, but following antibiotic chemotherapy they are replaced by eosinophils that degranulate on the worm cuticle. However, it is unclear whether the eosinophils are involved in parasite killing or if they are attracted secondarily to dying worms. In this study, cattle infected with Onchocerca ochengi received adulticidal regimens of oxytetracycline or melarsomine. In contrast to oxytetracycline, melarsomine did not directly affect Wolbachia viability. Eosinophil degranulation increased significantly only in the oxytetracycline group; whereas nodular gene expression of bovine neutrophilic chemokines was lowest in this group. Moreover, intense eosinophil degranulation was initially associated with worm vitality, not degeneration. Taken together, these data offer strong support for the hypothesis that Wolbachia confers longevity on O. ochengi through a defensive mutualism, which diverts a potentially lethal effector cell response.

Show MeSH
Related in: MedlinePlus