FIG. 6.

Replication tropism of NA stalk deletion viruses in chickens. White Leghorn chickens were infected with 5 × 10⁶ EID₅₀/ml of either RG mall/178, RG qa-mall/178, RG ch-qa/178, or the 7:1 reassortant Mall:Ch_NA or Qa:Ch_NA. Lung homogenates and swabs (tracheal or cloacal) were collected 3 dpi and were titrated in embryonated chicken eggs by EID₅₀ (indicated by a superscript “a”). No swabs were collected for chickens infected with either Mall:Ch_NA or Qa:Ch_NA (ND, not done). The asterisk above the RG qa-mall/178 lung bar indicates that only one lung sample was positive for virus. Replication of recombinant viruses was also tested in DF1 cells. Supernatants were collected at 3 dpi and were titrated using the 50% tissue culture infective dose (TCID₅₀) (indicated by a superscript “b”). Titers are expressed in either log₁₀ EID₅₀/ml or log₁₀ TCID₅₀/ml, as indicated. The origins of the HA and NA surface genes, the presence or absence of transmission, and the route of transmission are given below the bar graph. F-O, fecal-oral transmission; Resp., respiratory transmission.