title: Saliva of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) inhibits classical and alternative complement pathways.
abstract: Rhipicephalus (Boophilus) microplus is the main ectoparasite affecting livestock worldwide. For a successful parasitism, ticks need to evade several immune responses of their hosts, including the activation of the complement system. In spite of the importance of R. microplus, previous work only identified one salivary molecule that blocks the complement system. The current study describes complement inhibitory activities induced by R. microplus salivary components and mechanisms elicited by putative salivary proteins on both classical and alternative complement pathways.
  
  
  
  We found that R. microplus saliva from fully- and partially engorged females was able to inhibit both pathways. Saliva acts strongly at the initial steps of both complement activation pathways. In the classical pathway, the saliva blocked C4 cleavage, and hence, deposition of C4b on the activation surface, suggesting that the inhibition occurs at some point between C1q and C4. In the alternative pathway, saliva acts by binding to initial components of the cascade (C3b and properdin) thereby preventing the C3 convertase formation and reducing C3b production and deposition as well as cleavage of factor B. Saliva has no effect on formation or decay of the C6 to C8 components of the membrane attack complex.
  
  
  
  The saliva of R. microplus is able to inhibit the early steps of classical and alternative pathways of the complement system. Saliva acts by blocking C4 cleavage and deposition of C4b on the classical pathway activation surface and, in the alternative pathway, saliva bind to initial components of the cascade (C3b and properdin) thereby preventing the C3 convertase formation and the production and deposition of additional C3b.
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Naylene C S
authors: NC
authors: Silva
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.|Laboratório de Simulídeos e Oncocercose, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brazil.
authors: Vladimir F
authors: VF
authors: Vale
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Paula F
authors: PF
authors: Franco
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.|Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, 21941-591, Brazil.
authors: Nelder F
authors: NF
authors: Gontijo
authors: Vector Molecular Biology Section, LMVR, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD, USA.
authors: Jesus G
authors: JG
authors: Valenzuela
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.|Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, 21941-591, Brazil.
authors: Marcos H
authors: MH
authors: Pereira
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Mauricio R V
authors: MR
authors: Sant'Anna
authors: Empresa de Pesquisa Agropecuária de Minas Gerais, Fazenda Experimental Santa Rita, Rodovia MG 424 km 64, Caixa Postal 295, Prudente de Morais, 35701-970, MG, Brazil.
authors: Daniel S
authors: DS
authors: Rodrigues
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors: Walter S
authors: WS
authors: Lima
authors: Departamento de Patologia, Universidade Federal do Espírito Santo, Vitória, MG, Brazil.
authors: Blima
authors: B
authors: Fux
authors: Departamento de Parasitologia, Laboratório de Fisiologia de Insetos Hematófagos, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. rnaraujo@icb.ufmg.br.|Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, 21941-591, Brazil. rnaraujo@icb.ufmg.br.
authors: Ricardo N
authors: RN
authors: Araujo
mesh_terms: D000818:Animals; D003169:Complement Inactivator Proteins / Q000378:metabolism*; D003170:Complement Pathway, Alternative / Q000187:drug effects*; D003171:Complement Pathway, Classical / Q000187:drug effects*; D057131:Immune Evasion; D007108:Immune Tolerance; D048494:Rhipicephalus / Q000276:immunology*; D012463:Saliva / Q000378:metabolism*
chemical_list: D003169:Complement Inactivator Proteins
keywords: Alternative pathway; Classical pathway; Complement inhibition; Rhipicephalus (Boophilus) microplus; Saliva