Cloning and characterization of a Loa loa-specific repetitive DNA.

ABSTRACT

A Loa loa EcoRI genomic library in lambda gt11 was screened with 32P-labeled L. loa DNA and 1 repetitive clone, LL20, was isolated. An 800-bp Rsa I fragment of LL20, which is L. loa specific, was subcloned into pUC19 and the recombinant plasmid was designated pRsa4. While the 3.8-kb Eco RI fragment of LL20 cross-hybridized to other filarial DNA under low stringency conditions, the 800-bp fragment of pRsa4 was L. loa specific under the same conditions. Further characterization of the insert of pRsa4 was therefore carried out. Its lower limit of detection is 800 pg of L. loa genomic DNA, it has a low copy number (50-100) and an interspersed distribution in the genome. As a probe it does not distinguish between simian and human L. loa DNA. The nucleotide sequence contains 69% A + T and 31% G + C and shows no notable internal repeats.