title: Immune-mediated damage is not essential for the expulsion of Nippostrongylus brasiliensis adult worms from the small intestine of mice.
abstract: Nippostrongylus brasiliensis adult worms are expelled from the rat small intestine during a primary infection by two steps. First, host immune responses cause damage to the worms, and then a nonspecific inflammatory response initiates expulsion. We have tested the two-step expulsion hypothesis in mice infected with N. brasiliensis. After a primary infection in C57BL/6 mice, adult worms started to lay eggs on day 5 postinfection (p.i.) and were expelled around day 9-10 p.i. According to the rat system, 5 day- and 8-day-old worms were assumed to be 'normal' and 'damaged', respectively. When 5 day- and 8 day-old worms obtained from C57BL/6 mice were transferred surgically into the small intestine of naive C57BL/6 mice, both 5 day- and 8 day-old worms were almost simultaneously expelled by day 6 postworm implantation (p.w.i.). In contrast, when 5 day- and 8 day-old worms of mouse origin were implanted into naive Wistar rats, 8 day-old worms were expelled by day 5 p.w.i., while 5 day-old worms were expelled by day 8 p.w.i. Similar results were obtained when BALB/c mice were used. Therefore, mice can expel N. brasiliensis adult worms as rapidly as rats expel 'damaged' worms, regardless of the status of the worms ('normal' or 'damaged'). Stat6-deficient mice were unable to expel implanted 5 day-old worms up to day 10 p.w.i., suggesting that cellular mechanisms depending on Stat6-signalling system are necessary for the expulsion. When N. brasiliensis adult worms obtained from Stat6-deficient mice 5 and 15 days after a primary infection were implanted into Wistar rats, the former established in the recipient rats for approximately 1 week and were then expelled by day 10 p.w.i., whereas the latter were expelled by day 4 p.w.i. These results suggest that immune-mediated damage of N. brasiliensis adult worms (first step) is not a prerequisite for expulsion from the small intestine of mice, although adult worms are actually damaged by Stat6-independent immune mechanisms.
authors.affiliation: Department of Parasitology, Miyazaki Medical College, Kiyotake, Miyazaki, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ishiwata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakao
authors.forename: Fukumi
authors.initials: F
authors.lastname: Nakamura-Uchiyama
authors.forename: Yukifumi
authors.initials: Y
authors.lastname: Nawa
mesh_terms: D000818:Animals; D005243:Feces / Q000469:parasitology; D007421:Intestine, Small / Q000469:parasitology* / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009559:Nippostrongylus / Q000302:isolation & purification / Q000472:pathogenicity*; D010270:Parasite Egg Count; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D017206:Strongylida Infections / Q000276:immunology* / Q000469:parasitology / Q000503:physiopathology*