TABLE 1.

Comparative titers of biologically active particles and HAP in subpopulations of different isolates of influenza virus maintained by LM passages in embryonated eggs

IsolateTiter (per ml)a
PFPbTotal CKPcniCKPdDIPeHAPf
TK/OR/71 -NS1(1-230) clone 1 (H7N3)5.8 × 10820 × 10814 × 10848 × 108193 × 108
TK/OR/71 -NS1(1-230) clone 2 (H7N3)4.7 × 10818 × 10813 × 10848 × 108193 × 108
TK/WI/68 (H5N9)0.45 × 1086.5 × 1086.1 × 10824 × 10896 × 108
CK/PA/13609/93 (H5N2)0.83 × 1085.6 × 1084.8 × 10822 × 108203 × 108
TK/OR/71 -NS1(1-230) (H7N3)3.2 × 10822 × 10819 × 1088.6 × 108307 × 108
CK/CT/73/03 (H7N2)0.7 × 1083.8 × 1083.5 × 1088.6 × 108102 × 108
PR/8/34 (H1N1)16 × 10816 × 108<0.1 × 108*2.0 × 108393 × 108
rgPR/8/34 (H1N1)2.7 × 1083.4 × 1080.7 × 108<0.1 × 108*203 × 108
TK/OR/71 -delNS1(1-124) (H7N3)6.9 × 1086.9 × 108<0.1 × 108*<0.1 × 108*203 × 108
  • a *, Less than the level of detection by the assay.

  • b Assayed on primary chicken embryo kidney cells.

  • c Measured by clonogenic assay (29).

  • d niCKP = total CKP − PFP.

  • e Assayed as described for Fig. 2.

  • f Calculated from absolute HA assays with chicken red blood cells (see Materials and Methods).