PRIMARY STRUCTURE OF AND IMMUNOGLOBULIN-E RESPONSE TO THE REPEAT SUBUNIT OF GP15 400 FROM HUMAN LYMPHATIC FILARIAL PARASITES/

We have isolated and sequenced clones encoding the repeated subunit of the surface-associated glycoprotein gp15/400 from the two nematode sp ecies predominantly responsible for lymphatic filariasis in humans: Br ugia malayi and Wuchereria bancrofti. The amino acid sequence of the 1 5-kDa subunit, derived from the nucleotide sequence of the gene fragme nt from B. malayi, is identical to that previously reported for B. pah angi, whereas the derived W. bancrofti protein sequence differs in onl y 7 of 132 residues. The identity of the protein in the two Brugia spe cies allowed us to use a recombinant from B. pahangi to examine the se rological response of adult Indonesian subjects infected with B. malay i. The polymerase chain reaction-amplified subunit was expressed in Es cherichia coli via the pDS56/RBS11 plasmid and purified by nickel-chel ating chromatography. A significant proportion of individuals produced antigen-specific immunoglobulin E (IgE). This was most pronounced in the individuals with elephantiasis, with 14 of 15 showing elevated tit ers and a mean of 3.2 ng of specific IgE ml-1. Only 2 of 15 microfilar emic individuals possessed elevated titers of specific IgE, with a mea n of 0.045 ng ml-1 for the group as a whole. Asymptomatic amicrofilare mic residents showed approximately equal numbers of responders (define d as having a value in the radioimmunoassay greater than two standard deviations above controls) and nonresponders, with a group mean of 1.2 ng of antigen-specific IgE ml-1.