OvGalBP, a filarial antigen with homology to vertebrate galactoside-binding proteins.
The increased incidence of "allergic" symptomatology and clinical complications seen in non-endemic individuals with loiasis, as compared to natives of endemic areas, is thought to reflect a heightened immune response to filarial antigens. To identify antigens involved in this hyperresponsiveness, a cDNA library constructed from adult female RNA from the related filarial parasite, Onchocerca volvulus, was screened with serum from a North American who acquired loiasis in West Africa. Sequence analysis of one of the identified clones, OvGalBP, revealed significant homology to the vertebrate S-type lectins, a family of thiol-dependent, metal-independent galactoside binding lectins, which includes an IgE-binding protein thought to be involved in IgE regulation. The 1100-bp insert of OvGalBP contains the entire protein coding region and has a 3' poly(A) tail. The two amino acid consensus sequences (WGxExR and HFNPRF) found in all of the S-type lectins are present. Purified recombinant protein expressed as a fusion with glutathione-S-transferase (OvGalBP-GST) was recognized by sera from a majority of filaria-infected patients but not by putatively immune individuals from an endemic area or by unexposed endemic and non-endemic controls. Interestingly, OvGalBP-GST specifically bound IgE (and not IgG) in a lactose-inhibitable manner, suggesting a potential role for this protein in the pathophysiology of human filarial infection.
Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City 52242.
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D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth / Q000302:isolation & purification; D000947:Antigens, Helminth / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D005260:Female; D005690:Galactose / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D007073:Immunoglobulin E / Q000302:isolation & purification; D008118:Loiasis / Q000276:immunology; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D017181:Onchocerca volvulus / Q000276:immunology*; D009855:Onchocerciasis / Q000276:immunology; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins; C023550:galactose-binding protein; D007073:Immunoglobulin E; D005690:Galactose