Quantitation of in vitro opsonic activity of human antibody induced by a vaccine consisting of the type III-specific polysaccharide of group B streptococcus

Abstract

Human antibody, induced by a vaccine consisting of undegraded and highly purified extracellular type III-specific polysaccharide of group B streptococcus, was shown to increase the rate of phagocyte-mediated killing of bacteria of the homologous type. The bactericidal effect was mediated by type III-specific antibody and was complement dependent. An assay which permitted quantitation of "opsonic activity" was developed. In this assay, loss of CFUs occurred at a constant rate, and the rate constant was used as a measure of opsonic activity of antisera. A linear relationship between type III-specific antibody concentration (40 to 500 ng/ml) and the rate constant of killing was observed. When sets of immune sera were tested, some sera reacted anomalously, mediating significantly higher or lower rates than expected on the basis of their antibody content. Since type III-specific antibody in immune sera was found almost exclusively in the immunoglobulin G class, we hypothesize that differences in immunoglobulin G subclass distribution of specific antibody may have been the source of this variation.were sedimented with dextran (Dextran T500; Pharmacia Fine Chemicals, Piscataway, N.J.), and PMN were isolated from the leucocyte-rich plasma by densi-1155 on August 1, 2020 by guest http://iai.asm.org/ Downloaded from

Progress toward a group B streptococcal vaccine

“…70 GBS-CPS vaccine underwent clinical trials in healthy adults including pregnant women in the 1980s. [71][72][73][74][75] Although tetravalent GBS polysaccharide vaccine with serotypes Ia, Ib, II, and III was shown to be well-tolerated, the proportion of subjects with more than four-fold increase in the serotype-specific Ig titers compared with those in the unvaccinated group was only 33% for serotype Ia, 0% for serotype Ib, 17% for serotype II, and 70% for serotype III. 73 During the PDVAC meeting in 2014, it was concluded that the native CPS vaccine was ineffective due to its poor immunogenicity.…”

Immunoglobulin G and M composition of naturally occurring antibody to type III group B streptococci

“…The serum was centrifuged in a model L analytical ultracentrifuge (Beckman) at 70,000 x g for 30 min to float the lipids and then at 35,000 x g for 60 min to precipitate insoluble protein. Aliquots (1 ml) of undiluted serum were each mixed with 100 RI of 0.2 M Na EDTA buffer (pH 7.0) containing purified type III antigen (and 1,000 U of penicillin G and 1 mg of streptomycin per ml) in conical tubes (10 by 39 mm) with snap tops; 13 doubling quantities of antigen, 0.016 through 64 ,ug, were used. The tubes were closed, kept at 4°C for 1 week, and shaken gently each day.…”

“…However, the human immune response to these bacteria has not been characterized by a solid-phase assay for immunoglobulin classes. Several laboratories are actively evaluating group B streptococcal vaccines (5,12,13), ultimately to stimulate maternal IgG antibody for placental transfer.…”

Liver macrophages and sinusoidal endothelial cells execute vaccine-elicited capture of invasive bacteria

“…Passive protection of immune serum against lethal infection of S. pneumoniae was evaluated as described (67). Briefly, sera from naive (natural) or vaccinated (immune) mice were incubated at 56°C for 30 min for heat inactivation of complement protein (68). Then heat-inactivated serum (10 μl) was pre-incubated with a lethal dose of S. pneumoniae (10 6 CFU in 90 μl) for 5 min before being i.v.…”