Production of monovalent antisera by induction of immunological tolerance for capsular typing of Streptococcus pneumoniae

Hyperimmune and high‐titered polyclonal pneumococcal antisera, specific for cross‐reactive types within groups, were produced in adult rabbits. Purified capsular polysaccharide was injected intravenously into adult rabbits. One week later, these rabbits were given multiple intravenous injections of formalin‐inactivated pneumococci of the cross‐reactive type by an established method. Each of the resultant antisera were specific for the cross‐reactive type indicating that the previous injection of the polysaccharide had induced epitope‐specific tolerance. This method was successful for production of antisera against pneumococcal types 6A, 6B, 9N, 9V, 19F and 19A. Polyclonal rabbit pneumococcal antisera have some advantages over murine monoclonal antibodies for serologic studies and this method should be applicable for producing type‐specific antibodies to cross‐reactive polysaccharides of clinical interest. Further, this method is simpler and generally produces higher titered monovalent (factor) reagents than absorbed antisera.