An Inhibitor of the Alternative Pathway of Complement in Saliva of New World Anopheline Mosquitoes.
The complement system present in circulating blood is an effective mechanism of host defense, responsible for the killing of pathogens and the production of potent anaphylatoxins. Inhibitors of the complement system have been described in the saliva of hematophagous arthropods that are involved in the protection of digestive tissues against complement system-mediated damage. In this study, we describe albicin, a novel inhibitor of the alternative pathway of complement from the salivary glands of the malaria vector, Anopheles albimanus The inhibitor was purified from salivary gland homogenates by reverse-phase HPLC and identified by mass spectrometry as a small (13.4-kDa) protein related to the gSG7 protein of Anopheles gambiae and Anopheles stephensi Recombinant albicin was produced in Escherichia coli and found to potently inhibit lysis of rabbit erythrocytes in assays of the alternative pathway while having no inhibitory effect on the classical or lectin pathways. Albicin also inhibited the deposition of complement components on agarose-coated plates, although it could not remove previously bound components. Antisera produced against recombinant albicin recognized both the native and recombinant inhibitors and also blocked their activities in in vitro assays. Using surface plasmon resonance and enzymatic assays, we found that albicin binds and stabilizes the C3-convertase complex (C3bBb) formed on a properdin surface and inhibits the convertase activity of a reconstituted C3bBb complex in solution. The data indicate that albicin specifically recognizes the activated form of the complex, allowing more efficient inhibition by an inhibitor whose quantity is limited.
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852; Department of Parasitology, University of Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil; and.
Antonio F
0000-0002-2019-1348
AF
Mendes-Sousa
Department of Parasitology, University of Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil; and.
Daniel C
0000-0002-6607-8818
DC
Queiroz
Department of Parasitology, University of Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil; and Laboratory of Simuliids and Onchocerciasis, Oswaldo Cruz Institute, Fiocruz, Rio de Janeiro 21040-900, Brazil.
Vladimir F
0000-0002-6505-5999
VF
Vale
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852;
José M C
JM
Ribeiro
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852;
Jesus G
JG
Valenzuela
Department of Parasitology, University of Minas Gerais, Belo Horizonte, Minas Gerais 30123-970, Brazil; and.
Nelder F
0000-0003-3357-2497
NF
Gontijo
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852; jandersen@niaid.nih.gov.
John F
JF
Andersen
D000818:Animals; D000852:Anopheles / Q000276:immunology*; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D003170:Complement Pathway, Alternative / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019476:Insect Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013058:Mass Spectrometry; D016133:Polymerase Chain Reaction; D011817:Rabbits; D012463:Saliva / Q000276:immunology*; D012471:Salivary Proteins and Peptides / Q000276:immunology*; D020349:Surface Plasmon Resonance
D019476:Insect Proteins; D012471:Salivary Proteins and Peptides; C000621723:albicin protein, Anopheles albimanus