THREE SALIVARY SERPINS FROM THE CATTLE TICK RHIPICEPHALUS MICROPLUS: INSIGHTS IN TICK-HOST RELATIONSHIP
Autor(es): Lucas Tirloni, Tae Kim, Abid Ali, Adriana Seixas, Carlos Termignoni, Albert Mulenga, Itabajara da Silva Vaz Jr.
THREE SALIVARY SERPINS FROM THE CATTLE TICK RHIPICEPHALUS MICROPLUS: INSIGHTS IN TICK-HOST RELATIONSHIP
» Área de pesquisa: ACAROLOGIA
» Instituição: Universidade Federal do Rio Grande do Sul
» Agência de fomento e patrocinadores: CNPq, CAPES, INCT-Entomologia Molecular, FAPERGS
INTRODUCTION: The cattle tick Rhipicephalus microplus is considered the most harmful cattle parasite in sub-tropical areas of the world. As several hematophagous parasites, its saliva contains bioactive compounds which modulate host defenses in order to have their blood meal. A proteomic analysis revealed R. microplus saliva contains three serpins. Serpins are a superfamily of serine endopeptidase inhibitors with a role in regulating processes such as immunity, inflammation, complement activation and blood clotting in mammals. Since serpins act regulating host defense systems against tick feeding, we are mindful that ticks secrete serpins enhancing its blood meal. MATERIAL AND METHODS: Three R. microplus salivary serpins (RmS-3, RmS-6 and RmS-17) encoding sequences were cloned into pPICZαC to allow recombinant expression in Pichia pastoris. Recombinant proteins were purified and treated with deglucosidases. Inhibitory activity of recombinant serpins against enzymes related to host defense systems were tested. Serum from animals infested with different tick species were used to check cross-reactivity among recombinant serpins by western-blot. RESULTS: The three recombinant proteins are glycosylated, since the treatment with deglucosidases changes they molecular weight. Recombinant serpins were recognized by serum from cattle infested with R. microplus and also were recognized by serum from rabbits infested with Amblyomma americanum and Rhipicephalus sanguineus. These salivary serpins have distinct inhibition profile: rRmS-3 has anti-chymotrypsin, anti-elastase, anti-cathepsin G and anti-chymase activity; rRmS-6 has anti-trypsin, anti-chymotrypsin, anti-plasmin and anti-factor Xa activity; and rRmS-17 has anti-chymotrypsin, anti-trypsin, anti-cathepsin-G and anti-plasmin activity. CONCLUSION: P. pastoris expression system allowed production of active and glycosylated tick recombinant serpins. Since peptidases as trypsin-like, chymotrypsin-like, elastase, cathepsin G and plasmin are involved in immunological processes enhancing inflammation, we suggest these salivary serpins have a role as immunomodulatory proteins during parasitism by R. microplus.
