Effects of route and time of administration of antiserum on protection of mice from lethal infection due to group B Streptococcus type III

Abstract

The present study examines a mouse model of infection due to group B Streptococcus serotype III (GBS-III) as to the route and timing of antiserum administration for protection and quantitation of bacteremia with and without antiserum. Data for these parameters are contrasted with those after challenge with serotype Ia of group B Streptococcus (GBS-Ia). An intraperitoneal injection of GBS organisms and protective antiserum from a single syringe can be used to create an animal model of disease. Intraperitoneal injection of GBS-III resulted in bacteremia at 0.5 h both in animals who did not receive antiserum (17.4 X 10(2) +/- 7.6 X 10(2) colony-forming units per ml of blood samples) and in animals who received antiserum (19.3 X 10(1) +/- 6.8 X 10(1) colony-forming units per ml). Although intraperitoneal injection of GBS-Ia also resulted in bacteremia evident by 0.5 h in unprotected animals (30.1 X 10(2) +/- 3.8 X 10(2) colony-forming units per ml), no bacteremia occurred in protected recipients of this organism. Bacteremia due to GBS-Ia and GBS-III logarithmically increased until at least 7 h. Bacteremia due to GBS-III in protected animals was cleared by 24 h. Protection against GBS disease did not require simultaneous or proximate administration of the organism and the antiserum. Mice could be protected from death after intraperitoneal challenge with GBS-III or GBS-Ia by antiserum administered intravenously or intraperitoneally from 6 h before to 2.5 h after challenge.

Mouse protection assay for group B streptococcus type III

“…It would be of interest to compare mouse protection levels with the results of an IgG-specific ELISA test on the same sera. ELISA has also been used to detect antibody in the sera of recipients of a purified polysaccharide vaccine to GBS by Resavy was obtained in the present study, as well as in previous studies using mice (6,16,20).…”

“…When the 2-h sampling period to a level of 106 to 10. protection was defined according to Stanton et No further samples were taken until 20 h after al. (16) as a survival rate of greater than 50%o injection, at which time 13 of 16 of the GBS-when the unprotected controls had a survival broth-treated and 15 of 16 of the GBS-mucinrate of less than 20%o, then the titer of this sera treated mice had died. Bacteria were not recov-could be assessed at 100.…”

“…Since the virulence of the reference strain SS620, (Lancefield D136C) is not enhanced by normal human serum, it may be more useful in evaluating protective antibody in animal model systems. In addition, the Stanton et al (16) definition of protection can be used to eliminate the reservations concerning the mouse protection test by clarifying the endpoint for protection: greater than 50o survival in animals with the test sera when the control animals show less than 20% survival. Obviously, individuals with low levels of antibody could be identified as vaccine candidates by such a process.…”

“…bacterial challenge. Yet, Stanton et al (16) obtained partial protection against serotype III when the antiserum was given i.m. at 3 to 6 h before the bacterial challenge.…”

“…The laboratory reference strain (D136C) was not virulent in the blood-broth murine model. Stanton et al (16) studied the effect of time and route of administration of the antisera in a protection test using the blood-broth model. Intramuscular (i.m.)…”