title: Tetracycline therapy targets intracellular bacteria in the filarial nematode Litomosoides sigmodontis and results in filarial infertility.
abstract: Intracellular bacteria have been described in several species of filarial nematodes, but their relationships with, and effects on, their nematode hosts have not previously been elucidated. In this study, intracellular bacteria were observed in tissues of the rodent parasite Litomosoides sigmodontis by transmission electron microscopy and by immunohistochemistry using antiendobacterial heat shock protein-60 antisera. Molecular phylogenetic analysis of the bacterial 16S ribosomal RNA gene, isolated by PCR, showed a close relationship to the rickettsial Wolbachia endobacteria of arthropods and to other filarial intracellular bacteria. The impact of tetracycline therapy of infected rodents on L. sigmodontis development was analyzed in order to understand the role(s) these bacteria might play in filarial biology. Tetracycline therapy, when initiated with L. sigmodontis infection, eliminated the bacteria and resulted in filarial growth retardation and infertility. If initiated after microfilarial development, treatment reduced filarial fertility. Treatment with antibiotics not affecting rickettsial bacteria did not inhibit filarial development. Acanthocheilonema viteae filariae were shown to lack intracellular bacteria and to be insensitive to tetracycline. These results suggest a mutualistic interaction between the intracellular bacteria and the filarial nematode. Investigation of such a mutualism in endobacteria-containing human filariae is warranted for a potential chemotherapeutic exploitation.
authors.affiliation: Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany. hoerauf@bni.uni-hamburg.de
authors.forename: A
authors.initials: A
authors.lastname: Hoerauf
authors.forename: K
authors.initials: K
authors.lastname: Nissen-Pähle
authors.forename: C
authors.initials: C
authors.lastname: Schmetz
authors.forename: K
authors.initials: K
authors.lastname: Henkle-Dührsen
authors.forename: M L
authors.initials: ML
authors.lastname: Blaxter
authors.forename: D W
authors.initials: DW
authors.lastname: Büttner
authors.forename: M Y
authors.initials: MY
authors.lastname: Gallin
authors.forename: K M
authors.initials: KM
authors.lastname: Al-Qaoud
authors.forename: R
authors.initials: R
authors.lastname: Lucius
authors.forename: B
authors.initials: B
authors.lastname: Fleischer
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000032:analysis; D004153:Dipetalonema / Q000187:drug effects; D005368:Filariasis / Q000188:drug therapy; D005370:Filarioidea / Q000187:drug effects / Q000382:microbiology*; D007150:Immunohistochemistry; D007246:Infertility; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D051381:Rats; D012281:Rickettsia / Q000187:drug effects*; D013752:Tetracycline / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D013752:Tetracycline