To gain further insights into the kinetics of viral neutralization in vivo, 4 mice from each group were euthanized on day 4 p.c. and viral titer was determined in whole lung tissues. PN-SIA49 significantly reduced virus titer in the lungs of mice infected with WS33 by approximately 2,000 fold at 10 mg/kg and about 700 fold at 1 mg/kg ( Figure 1E ). A 10-fold reduction in pulmonary virus titer was noted in mice challenged with VN04 virus that received PN-SIA49 at 10 mg/kg ( Figure 1F ).