Functional Leukocyte Administration in Protection against Experimental Neonatal Infection

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Abstract
Summary: Studies have shown that human neonates who develop group B streptococcal sepsis usually lack opsonic antibody (Ab) to their infecting strain and that these neonates may also have unpaired polymorphonuclear leukocyte (PMN) function. The present study was designed to determine the efficacy of administration of PMNs or opsonic Ab-containing serum in protecting against group B streptococcal infection in a newborn rat model. After intraperitoneal (IP) injection of ±5 ± 105 streptococci, animals received separate IP injections of saline, serum lacking opsonic antibody (Ab negative), Ab positive serum or washed adult human PMNs (2 ± 106). The mortality rate in 55 neonatal rats infected with group B streptococci who received saline or Ab negative serum was 91%. In contrast, 40 animals who received adult human PMNs at the time of inoculation had a survival rate of 50% (P ≤0.001). Human serum containing opsonic antibody also provided significant protection against mortality in this model (survival rate 51%, P ≤0.001). Leukocytes from normal term neonates, stressed neonates, or ones pretreated with cytochalasin B offered less protection than did functional adult human cell (P ≤0.001). Speculation: This study provides evidence for polymorphonuclear leukocyte (PMN) dysfunction as another risk factor in group B streptococcal disease and suggests that fully functional PMNs are required for protection. Furthermore, this model involving the administration of human PMNs to an animal appears to have the potential for the in viw evaluation of PMN function in neonates and other compromised hosts.

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