Modulation of human neutrophil adherence by periodontopathic bacteria: reversal by specific monoclonal antibodies

Previous investigations by us have shown that direct interaction of Fusobacterium nucleatum with polymorphonuclear neutrophils (PMNs) results in the stimulation of PMN adherence whereas direct interaction with Bacteroides gingivalis results in PMN suppression. In the present study, panels of monoclonal antibodies (MAbs) raised against cell wall antigens of F. nucleatum and B. gingivalis were tested to determine their ability to block the modulatory effects of the bacteria in their interactions with PMNs. While no activity was demonstrated for any of the 9 MAbs raised against F. nucleatum, it was found that 2 of 16 MAbs raised against B. gingivalis were able to reverse the suppression of PMN adherence induced by the bacteria. Further studies on these 2 reactive MAbs showed that the effect of MAbs were abrogated by heat treatment as well as by trypsin proteolysis. Investigations into the nature of the reactive epitopes on the bacterial surface showed that they probably contain protein components susceptible to proteolytic attack by subtilisin. In addition, beta-galactose may be a component of the reactive epitopes for one of the MAbs, but sialic acid residues on the bacterial surface are probably not involved as their elimination by neuraminidase did not affect the binding of both MAbs. The results of the present study strongly validate our previous observations that direct specific interaction of B. gingivalis with human PMNs occurs, resulting in the suppression of PMNs.