Leptotrichia buccalis hemagglutination in cell binding and salivary inhibition studies

The characteristic hemagglutination (HA) of Leptotrichia buccalis was used for measuring its attachment to various human cells and for determining if saliva contained hemagglutination inhibition (HI) factors. The microbial strain utilized displayed the characteristic EM morphology of L. buccalis. Sonicated preparations of the organism were tested for HA activity before and after adsorption with human cells. Buccal epithelial cells, red blood cells (RBC), HeLa and embryonic kidney cells all bound the HA fragments of the organisms. The bacterial fragments on the cells could be observed by fluorescent antibody testing. The fragments were released from the cells used for adsorption with chelators and upon addition of CaCl2 the HA activity returned. Whole saliva displayed hemagglutination inhibition activity in a manner suggesting a binding site interaction. The similarity of the HA activity of F. nucleatum is discussed as are the relationships of cell binding to colonization of the organisms and immunopathology to host cells.