Polymorphism in the Dirofilaria immitis immunodominant antigen gene.

Dg2, a gene encoding a 34 kDa immunodominant antigen of Dirofilaria immitis was cloned and demonstrated to be specifically expressed in the larval stage. In this study, a newly constructed genomic DNA library was screened by hybridization with Dg2. One of the resulting positive clones was similar to Dg2 in the structure of its exonic regions but different in number, position, size and sequence of introns. This was designated DgK. Full-length cDNA was isolated using the rapid amplification of cDNA ends (RACE) method to study the transcript corresponding to DgK. Sequence analysis revealed that the mRNA corresponding to DgK is trans-spliced during post-transcriptional processing because the 5' end of the amplified cDNA contains seven nucleotides of the nematode-spliced leader (SL) sequence.