Table 3.

Passive protection of infant rats by preincubation of serotype 3 pneumococci in sera of young rats immunized intranasally with killed Rx1AL plus CT or in control sera

Inoculum (CFU/intrathoracic injection)Serum sourceBacteremiaMortality
No. bacteremic/total no. (%)P vs NRSNo. dead/total no. (%)P vs NRS
5NRS9/10 (90)11/11 (100)
Rats immunized with CT alone10/12 (83)1.011/11 (100)1.0
Humans vaccinated with 23-valent PS vaccinea0/11 (0)<0.00010/11 (0)<0.0001
Rats immunized with Rx1/AL− + CT1/11 (9)0.00031/11 (9)<0.0001
50–75NRS12/12 (100)12/12 (100)
Rats immunized with CT alone18/22 (82)0.2722/22 (100)1.0
Humans vaccinated with 23-valent PS vaccinea4/12 (33)0.0014/12 (33)0.001
Rats immunized with Rx1AL + CT14/24 (58)0.01513/24 (54)0.006
  • a Human anticapsular antibody: BPIG (hyperimmune globulin obtained from healthy adult volunteers immunized with 23-valent pneumococcal polysaccharide vaccine).