The duck EB66® cell substrate reveals a novel retrotransposon

During the establishment of the duck EB66 (R) cell line as a new cell substrate for vaccine production in industry, a very low level of reverse transcriptase (RT) activity was detected in the culture supernatant by product-enhanced RT assay but a whole battery of tests failed to evidence infectious particles. Results from extensive biochemical and physical testing demonstrated that RT activity was associated to an intracellular, non-enveloped and dense structure different from an infectious retroviruses. In silico analysis of Anas platyrhynchos genome revealed that the most likely candidates for encoding a ribonucleoprotein (RNP)-associated RT were nine copies of chicken repeat 1 (CR1)-like elements, belonging to the non-long terminal repeat retrotransposons. The presence of the full length Anas platyrhynchos chicken repeat 1 like sequence (APCR1) was confirmed in EB66 (R) cells and the related ribonucleic acid was present in the RT-containing fraction of EB66 (R) cells.