Cloning and characterization of a species-specific repetitive DNA sequence from Loa loa

A genomic DNA library of Loa loa was constructed in lambda gt11 using EcoRI-digested DNA from microfilariae isolated from two West African patients. Screening with labeled L. loa DNA yielded several potential repetitive DNA clones. An MboI fragment of one of these, LL3M9, was identified and characterized. Sequence analysis of LL3M9 revealed an 839-bp fragment with an unusual 356-bp region containing 37 copies of the hexamer CTTAGG, many of which are arranged in repeated motifs of 12, 27 and 63 bp. This region shares many of the characteristics of eukaryotic satellite DNA. A synthetic oligonucleotide corresponding to the 27-bp repeated motif, LL3M9REP, was found to be both sensitive and species-specific by dot hybridization. Species specificity of LL3M9REP was confirmed by amplification of the repetitive region using genomic DNA as a template in the polymerase chain reaction.