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

Abstract

Human sera were examined by an enzyme-linked immunosorbent assay for immunoglobulin G (IgG) and IgM antibodies to purified type III polysaccharide of group B streptococci. The antigen-binding capacity of a reference human serum was determined by a radioimmunoassay, and the total antibody content was determined by quantitative precipitation. The serum was then depleted of IgM and IgA to determine the effect on the antigen-binding capacity. Duplicate samples of 81 sera were tested by the enzyme-linked assay in comparison with reference standard serum. Although levels of IgG antibody were greater in subjects who had carried type III streptococci during pregnancy, concentrations of this antibody were generally low. Only 2 of 28 sera (7%) from parturient subjects and 7 of 25 sera (28%) from adult volunteers contained .1 ,ug of IgG antibody per ml; the mean levels were 0.13 and 0.53 ,ug/ml, respectively. In contrast, 19 of 28 maternal sera (68%) and 22 of 25 (88%) volunteer adult sera contained .1 ,ug/ml of IgM antibody; mean levels were 1.33 and 1.54 ,ug/ml, respectively. The cord serum levels of IgG antibody were almost identical to maternal serum concentrations, whereas IgM antibody was essentially undetected. Immulon 1 Removawell plates (Dynatech Laboratories, Inc., Alexandria, Va.) and incubated at 37°C for 2 h. The wells were then washed three times with PBS containing 0.05% Tween 20 (Fisher Scientific Co., Pittsburgh, Pa.). Human or rabbit serum (100 Rl) diluted in PBS-Tween was added to duplicate wells and incubated at 37°C for 30 min (human and rabbit serum) or at 4°C overnight (human serum only). The IgG fraction of goat anti-human IgG, IgM, or IgA was conjugated with bovine intestinal alkaline phosphatase 98

Seroepidemiology of group B streptococcus type II antibody specificity

“…Levels were somewhat higher in maternal but not cord sera, probably because IgM and IgA antibodies were also being detected. In a study of naturally occurring antibodies against GBS type III, IgM was found to be the major isotype of antibodies in maternal sera (Anthony et al 1984).…”

Streptococcal Infections

“…This concept is based on the finding that few infants with group B streptococcal disease have antibodies to the offending type, and that antibodies are protective against bacterial challenge in animal models. (144) Naturally occurring antibodies in mothers are often of the IgM class and do not readily cross the placenta, (145) and less IgG antibody is transferred to the premature than to the full-term fetus. Despite the presumed importance of antibodies, it should be pointed out that the prevalence of group B streptococcal antibodies is generally low, with about 6% of cord sera having >2 J.1g/ml against types la, Chapter 34 • Streptococcal Infections 697 II, and III in a defined population.…”