Improved survival after pneumococcus in splenectomized and nonsplenectomized mice with Corynebacterium parvum
J. C. Hebert, R. L. Gamelli, R. S. Foster Jr, B. J. Chalmer and J. H. Davis
Splenectomy increases the susceptibility to infections with certain
bacteria, particularly Streptococcus pneumoniae. Because the
immunomodulator Corynebacterium parvum expands the phagocytic cell
compartment and enhances reticuloendothelial function, we tested the effect
of C parvum in mice challenged with aerosolized pneumococci. Mice
splenectomized seven days before pneumococcal challenge and treated
intraperitoneally with 700 micrograms of C parvum immediately after
exposure were protected when compared with splenectomized or sham-operated
saline-injected controls. Analysis of proportional hazards showed the risk
of dying in order of greatest to least as follows: splenectomy/saline,
sham/saline, splenectomy/C parvum and sham/C parvum. The benefits of an
intact spleen and C parvum seemed to be additive in their protective
effects after aerosol pneumococcal challenge. After intravenous challenge,
bloodstream clearance was improved in sham-operated mice at three days
after C parvum injection compared with saline-injected sham-operated
controls and C parvum-injected splenectomized mice. A significant
improvement in bacterial clearance did not occur until seven days after C
parvum treatment in splenectomized mice. The results demonstrate the value
of a nonspecific immunomodulator for enhancing the defense mechanisms of
both normal and splenectomized animals.