Table 1.

Relationship among immunization dose, antibody production, and survival ratea

Immunization dose (EID50)No. of immunizationsNo. of mice
With >400 U of Ab/total no. testedSurvived/total no. tested
0/5 (0.0)0/5 (0.0)
108.9 15/5 (100.0)5/5 (100.0)
107.9 13/6 (50.0)4/6 (66.7)
106.9 14/10 (40.0)4/10 (40.0)
105.9 12/8 (25.0)2/8 (25.0)
104.9 20/10 (0.0)0/10 (0.0)
  • a Female BALB/c mice, 9 weeks old, were immunized with various single doses of PR8 via a stomach tube and with two doses of 104.9 EID50 of PR8 at 2 weeks and at 6 and 2 weeks before nasal inoculation (103.5EID50 of PR8), respectively. After nasal injection of PR8, the mice were observed for survival for 14 days. The numbers in parentheses are the ratios of antibody-enhanced mice to surviving mice.