title: Inhibition of the classical pathway of the complement system by saliva of Amblyomma cajennense (Acari: Ixodidae).
abstract: Inhibition of the complement system during and after haematophagy is of utmost importance for tick success in feeding and tick development. The role of such inhibition is to minimise damage to the intestinal epithelium as well as avoiding inflammation and opsonisation of salivary molecules at the bite site. Despite its importance, the salivary anti-complement activity has been characterised only in species belonging to the Ixodes ricinus complex which saliva is able to inhibit the alternative and lectin pathways. Little is known about this activity in other species of the Ixodidae family. Thus, the aim of this study was to describe the inhibition of the classical pathway of the complement system by the saliva of Amblyomma cajennense at different stages of the haematophagy. The A. cajennense saliva and salivary gland extract (SGE) were able to inhibit the complement classical pathway through haemolytic assays with higher activity observed when saliva was used. The anti-complement activity is present in the salivary glands of starving females and also in females throughout the whole feeding process, with significant higher activity soon after tick detachment. The SGE activity from both females fed on mice or horses had no significant correlation (p > 0.05) with tick body weight. The pH found in the intestinal lumen of A. cajennense was 8.04 ± 0.08 and haemolytic assays performed at pH 8.0 showed activation of the classical pathway similarly to what occurs at pH 7.4. Consequently, inhibition could be necessary to protect the tick enterocytes. Indeed, the inhibition observed by SGE was higher in pH 8.0 in comparison to pH 7.4 reinforcing the role of saliva in protecting the intestinal cells. Further studies should be carried out in order to identify the inhibitor molecule and characterise its inhibition mechanism.
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Paula F
authors.initials: PF
authors.lastname: Franco
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Naylene C S
authors.initials: NC
authors.lastname: Silva
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil; Laboratório de Simulídeos e Oncocercose, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brazil.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Fazito do Vale
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Jéssica F
authors.initials: JF
authors.lastname: Abreu
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Vânia C
authors.initials: VC
authors.lastname: Santos
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Nelder F
authors.initials: NF
authors.lastname: Gontijo
authors.affiliation: Vector Molecular Biology Section, LMVR, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA.
authors.forename: Jesus G
authors.initials: JG
authors.lastname: Valenzuela
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Marcos H
authors.initials: MH
authors.lastname: Pereira
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Mauricio R V
authors.initials: MR
authors.lastname: Sant'Anna
authors.affiliation: Instituto de Ciências Biológicas e da Saúde, Pontifícia Universidade Católica de Minas Gerais, PUC Minas, MG, Brazil.
authors.forename: Alessandra P S
authors.initials: AP
authors.lastname: Gomes
authors.affiliation: Laboratório de Fisiologia de Insetos Hematófagos, Departamento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. Electronic address: rnaraujo@icb.ufmg.br.
authors.forename: Ricardo N
authors.initials: RN
authors.lastname: Araujo
mesh_terms: D000818:Animals; D001835:Body Weight; D003171:Complement Pathway, Classical / Q000276:immunology*; D005260:Female; D006461:Hemolysis / Q000276:immunology; D006734:Horse Diseases / Q000469:parasitology; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000737:chemistry; D026863:Ixodidae / Q000033:anatomy & histology / Q000276:immunology*; D008297:Male; D051379:Mice; D012463:Saliva / Q000276:immunology; D013984:Tick Infestations / Q000469:parasitology / Q000662:veterinary
keywords: Amblyomma cajennense; Anti-complement; Classical pathway; Haematophagy; Saliva