ASSESSING THE SIGNIFICANCE OF REVERSE-TRANSCRIPTASE ACTIVITY IN CHICKCELL-DERIVED VACCINES

A recent publication reported the detection of low levels of the enzym e reverse transcriptase (RTase) in live viral vaccines prepared in chi ck embryo cells. The enzyme was detected using an assay with greatly i ncreased sensitivity compared to more conventional methods. The author s have confirmed the observation of RTase activity and demonstrate tha t the activity is not dependent on the production of viral vaccines in chick cells but is present ubiquitously in chick embryonic fluids. Th e authors have also been unable to transmit the RTase activity from ch ick cells to a wide variety of cells of human, monkey, rabbit and turk ey origin, suggesting that the activity is not associated with an avia n agent capable of infecting these cells. it is concluded that the dat a available present no cause for concern over the safety of vaccines d erived in chick cells and current WHO requirements for such vaccines r emain appropriate. (C) 1997 The International Association of Biologica l Standardization.