Neutralization of seven different influenza virus types and subtypes in MDCK, Caco-2, and Mv1 Lu cells (by days).

<p>Neutralization titers in MDCK (blue solid triangles), Caco-2 (gray open diamonds), and Mv1 Lu (gray solid diamonds) cells were determined by FFA at Day 1 (panel A), and NA activity at Day 3 (panel B) and Day 6 (panel C). Approximately 100 FFU of each virus type/subtype were added to serial 2-fold dilution of normal sheep antiserum (nSheep), sheep anti-HA (aHA), sheep anti-NA (aNA), or ferret polyclonal antiserum (pre- [fPre] or post-immunization [fPost] with the specified virus strain) and incubated at room temperature for 30 min. Serum treated virus was then transferred onto cells and titers were determined by NA activity. Titers were determined based on the log₂ dilution that reduced the NA activity greater than or equal to 50% of that observed in virus control wells. The nSheep serum had a titer of <6.3 when assayed with minimal dilution. The titer reported in this chart is higher due to the starting dilution used in assays that was identical to the dilution used for the hyperimmune anti-HA antisera.