Effect of preparations of protein Yop encoded by Yersinia pestis calcium-dependence plasmid on mice

The impact of the preparations of Y. pestis secreted proteins Yop (YopH-M, YopB, YopD-N, YopE) on mice immunized with 3 s.c. injections was studied. Though these proteins failed to protect the animals from plague, they stimulated the immunobiological transformation in the immunized animals. YopB and YopD-N were found to have the highest immunobiological activity with respect to mice. The preparation of YopB induced the production of the highest titers of specific antibodies and stimulated cell-mediated immune response. The injection of YopD-N to mice led to a considerable decrease in the proliferative capacity of splenocytes in vitro in response to stimulation with nonspecific mitogen ConA, as well as to pathological changes in the kidneys.