Ai. Fattom et al., A STAPHYLOCOCCUS-AUREUS CAPSULAR POLYSACCHARIDE (CP) VACCINE AND CP-SPECIFIC ANTIBODIES PROTECT MICE AGAINST BACTERIAL CHALLENGE, Infection and immunity, 64(5), 1996, pp. 1659-1665
The efficacy of capsular polysaccharide (CP)-specific antibodies elici
ted by active immunization with vaccines composed of Staphylococcus au
reus types 5 and 8 CP linked to Pseudomonas aeruginosa exoprotein A or
with immune immunoglobulin G (I-IgG) obtained from vaccinated plasma
donors was tested in lethal and sublethal bacterial mouse challenge mo
dels. A dose of 2 x 10(5) CFU of S. aureus type 5 CP per mouse adminis
tered intraperitoneally (i.p.) with 5% hog mucin was found to cause 80
to 100% mortality in BALB/c mice within 2 to 5 days. Mice passively i
mmunized i.p. 24 h earlier or subcutaneously 48 h earlier with 0.5 ml
of I-IgG showed significantly higher average survival rates than anima
ls receiving standard IgG or saline (P < 0.01) following the bacterial
challenge. Animals actively immunized with the monovalent type 5 CP-P
. aeruginosa exoprotein A conjugate showed a survival rate of 73% comp
ared with 13% in phosphate-buffered saline-immunized animals. The prec
hallenge geometric mean titer of type 5 CP antibodies in animals that
died was significantly (P < 0.05) lower than that of animals which sur
vived the challenge (95.7 versus 223.6 mu g/ml, respectively). The IgG
was further evaluated in mice challenged i.p. with a sublethal dose o
f 5 x 10(4) CFU per mouse. Serial blood counts were performed on survi
ving animals at 6, 12, 24, and 48 h. Surviving animals were sacrificed
at 72 h, and bacterial counts were performed on their kidneys, livers
, and peritoneal lavage fluids. Animals receiving I-IgG had lower bact
erial counts in blood samples and lower bacterial densities in kidneys
, livers, and peritoneal lavage samples than mice immunized with stand
ard Ige (P < 0.05). These data suggest that S. aureus type 5 CP antibo
dies induced by active immunization or administered by passive immuniz
ation confer protection against S. aureus infections.