PRODUCTION, BINDING CHARACTERISTICS AND PROTECTIVE IMMUNITY OF MONOCLONAL-ANTIBODY TO PNEUMOCOCCAL TYPE-9V CONJUGATE

A monoclonal antibody (MAb) to pneumococcal type-9V polysaccharide (PS ) was produced using PS conjugated to inactivated pneumolysin as the i mmunogen, The MAb to 9V PS was of the IgG(1) subclass, The antigen-ant ibody reaction increased rapidly at low concentrations and reached a p lateau at 10 mu g PS/ml as measured by nephelometry of the group 9 PS against 9V MAb binding, In contrast, the binding of group 9 PS against rabbit 9V antiserum (AS) increased proportionally and continued to in crease up to the highest concentration of PS tested (20 mu g PS/ml), T he 9V MAb reacted with all group 9 PSs (9A, 9L, 9N and 9V) by immunodi ffusion, In the homologous 9V Ag-MAb reaction, there were marked diffe rences in the inhibition of binding by the cross-reactive 9L PS (19.2% inhibition) and the 9N PS (0.2%), In contrast, inhibition of the homo logous 9V Ag-rabbit AS binding by cross-reactive 9L and 9N PSs ranged from 57.8 to 62.7%, Removal of the O-acetyl group from 9V PS by alkali hydrolysis resulted in decreased binding with rabbit 9V AS, However, the binding reaction with 9V MAb was less affected by the loss of O-ac etyl content, The 9V MAb was both opsonic and passively protected youn g mice against challenge with type-9V pneumococci.