MOLECULAR CHARACTERIZATION OF A BRUGIA-MALAYI INTERMEDIATE FILAMENT PROTEIN WHICH IS AN EXCRETORY-SECRETORY PRODUCT OF ADULT WORMS

Filarial parasites release macromolecules into their environment both in vitro and in vivo. These excretory-secretory products (E-S) have be en studied with respect to function, vaccination potential, pathogenic ity, and ability to serve as antigen targets for diagnostic tests. We have recently described monoclonal antibody OV-1 which binds to an int ermediate filament in E-S and circulating antigens of Onchocerca volvu lus. OV-1 also binds to cross-reactive antigens of Brugia malayi. Ther efore, OV-1 was used to immunoscreen a B. malayi adult worm cDNA libra ry in an attempt to clone a homologue (BMIF). BMIF is a 1664-bp full-l ength transcript which codes for 505 amino acids. BMIF has 95% sequenc e homology at the amino-acid level to OV1CF, an O. volvulus intermedia te filament that was also selected with OV-1, and 75% homology to Asca ris intermediate filament A. Southern blot analysis suggests that BMIF is confined to a single location in the genomic DNA of B. malayi. Ant ibodies raised to BMIF identified native antigens in immunoblots of B. malayi adult worms, infective larvae and adult E-S. In addition, the antibody also bound to a 60-kDa antigen in immunoblots of poly(ethylen e glycol)-precipitated immune complexes in sera from B. malayi infecte d patients. Localization studies showed that the antigen encoded by BM IF is present in the hypodermis, developing embryos and muscle of adul t B. malayi. These studies show that BMIF is an E-S product of B. mala yi adult worms which is detectable in sera from patients with brugian filariasis.