We investigated the prophylactic effect of Ubenimex on mice with ascending pyelonephritis induced by Pseudomonas aeruginosa (G-group). This experimental model was established by a two course administration of cyclophosphamide, so that it kept the mice in a neutropenic status (around 2000 white blood cells/mm³) from the time of infection to the time of sacrifice.
The cyclophosphamide-treated group increased their susceptibility more than the control group. In the cyclophosphamide-treated group, the prophylactic administration of Ubenimex (100μg/ day/mouse) did not produce significant decreases of infection-induced motality rate, but yielded a lower incidence of infection than of saline alone.
Administration of Ubenimex was not able to increase the number of neutrophils during the experiment. An investigation of the bactericidal capacity of peritoneal exudating neutrophils revealed that Ubenimex prophylactic administration accelerated its capacity, although cyclophosphamide alone did not.
These results suggest that Ubenimex has a prophylactic effect on bacterial infection in neutropenic mice, and that this effect, in part, depends upon the acceleration of bactericidal capacity of neutrophils produced by Ubenimex.