A SV_(40) late replacement expression vector containing secreted neuraminidase cDNA was transfected into COS cells. High nenraminidase activity could be detected in the cell culture medium.

• 将含分泌型甲型流感病毒神经氨酸酶cDNA的SV_(40)晚期区段取代载体转染COS细胞后,可在细胞培养液中测出高酶活力。