title: A worm's best friend: recruitment of neutrophils by Wolbachia confounds eosinophil degranulation against the filarial nematode Onchocerca ochengi.
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.
authors.affiliation: Liverpool School of Tropical Medicine, School of Veterinary Science and Institute of Infection and Global Health, University of Liverpool, , Liverpool L69 7ZJ, UK.
authors.forename: Rowena D E
authors.initials: RD
authors.lastname: Hansen
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Trees
authors.forename: Germanus S
authors.initials: GS
authors.lastname: Bah
authors.forename: Udo
authors.initials: U
authors.lastname: Hetzel
authors.forename: Coralie
authors.initials: C
authors.lastname: Martin
authors.forename: Odile
authors.initials: O
authors.lastname: Bain
authors.forename: Vincent N
authors.initials: VN
authors.lastname: Tanya
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Makepeace
mesh_terms: D000818:Animals; D001152:Arsenicals / Q000494:pharmacology* / Q000627:therapeutic use; D002163:Cameroon; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology*; D015550:Cell Degranulation / Q000187:drug effects / Q000502:physiology*; D004804:Eosinophils / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D006652:Histological Techniques; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009854:Onchocerca / Q000382:microbiology*; D009855:Onchocerciasis / Q000188:drug therapy / Q000662:veterinary*; D010118:Oxytetracycline / Q000494:pharmacology* / Q000627:therapeutic use; D014227:Triazines / Q000494:pharmacology* / Q000627:therapeutic use; D020577:Wolbachia / Q000187:drug effects / Q000276:immunology / Q000502:physiology*
chemical_list: D001152:Arsenicals; D014227:Triazines; C076253:melarsomine; D010118:Oxytetracycline