Passive and active immunotherapy for experimental pneumococcal pneumonia by polyvalent human immunoglobulin or F(ab')2 fragments administered intranasally.

Experimental pneumococcal pneumonia in leukopenic BALB/c mice enabled evaluation of passive immunotherapy with human polyvalent intravenous immune globulin (IVIG) given intravenously or intranasally and with F(ab')2 fragments administered intranasally. For intravenous and intranasal IVIG, the respective effective doses were < 5 but > 0.5 mg/kg and < 250 but > 2.5 micrograms/kg. For F(ab')2 fragments, the effective dose was < 500 but > 2.5 micrograms/kg. Assessment of the acquired immune responses of passively protected mice and convalescing controls 3 weeks after primary infection showed that antibody responses to whole bacteria were serotype-specific in all mice. Mice protected with IVIG and F(ab')2 fragments had more antibodies to pneumolysin than did controls. In addition, treated mice acquired greater resistance to reinfection than untreated survivors. Thus, local passive immunotherapy may be an effective means of treating pneumococcal pneumonia and may promote acquired resistance to reinfection.