OPSONOPHAGOCYTIC AND BACTERICIDAL ACTIVITY MEDIATED BY PURIFIED IGG SUBCLASS ANTIBODIES AFTER VACCINATION WITH THE NORWEGIAN GROUP-B MENINGOCOCCAL VACCINE

To study how the different immunoglobulin (Ig)G subclass antibodies ma y confer protection against systemic meningococcal disease, we isolate d IgG1, IgG2 and IgG3 antibodies from plasma from vaccinees immunized with the Norwegian meningococcal outer membrane vesicle vaccine. Four IgG1, one IgG2 and four IgG3 preparations were purified. The IgG2 and IgG3 subclass preparations were free from contaminating subclasses, wh ereas the IgG1 preparations contained from 0 to 14% of IgG2 and/or IgG 3. Immunoblotting against whole-cell meningococcal antigens showed bro ad specificities of the various preparations, both within and between subclasses. These subclass preparations were tested for opsonophagocyt ic and bactericidal activity. As targets we used two different variant s of the meningococcal vaccine strain, with low (44/76-SL) and high (4 4/76-1) expression of the outer membrane protein Ope. Using polymorpho nuclear leucocytes as effector cells in the presence of human compleme nt, all three IgG subclass preparations revealed high, and similar, op sonophagocytic activities against 44/76-SL, whereas against 44/76-1 th e IgG2 preparation showed a reduced activity and most IgG3 preparation s were slightly more active than the IgG1 preparations. Regarding bact ericidal activity, all the three subclasses were highly active against 44/76-SL. Against 44/76-1 the bactericidal activities were somewhat m ore varied: all IgG1 and three IgG3 preparations exhibited higher acti vities than against 44/76-SL. Due to the low concentration in the 1gG2 preparations, only a weak activity was seen against 44/76-1. One IgG3 preparation that was highly opsonophagocytic revealed no bactericidal activity against either of the two bacterial variants examined. In co nclusion, we have shown that the IgG subclass effector functions diffe r from person to person, but that antibodies of IgG1, IgG2 and IgG3 su bclasses, judged by their behaviour in the functional tests, may all c ontribute to protection against meningococcal disease.