Assessment by flow cytometry of peripheral blood leukocyte enzymatic activities in HIV patients

Leukocyte enzymatic activities are important in non-specific protection aga inst bacterial infections, but traditional methods for the detection of int racellular enzymatic activities rely on cumbersome and complex assays. The development of specific substrates, which become fluorescent upon degradati on of the biomolecule after its passive entry into intact cells, permits a simplified evaluation of leukocyte enzymatic activities. We have used this method to assess intracellular elastase, collagenase and cathepsin D activi ties of peripheral brood leukocytes using flow cytometry in a series of HIV patients and healthy controls. Monocytes displayed the highest enzymatic a ctivities for the three proteases tested. In HIV-infected patients, the col lagenase and cathepsin D activities of monocytes wa e significantly lower, whereas the elastase and cathepsin D activities of polymorphonuclear cells were elevated. Slightly higher elastase activity was detected in the lympho cytes of patients. This study demonstrates the feasibility of this new meth od for the study of intracytoplasmic enzymatic activities. Significant vari ations were observed in the peripheral blood of HIV-infected patients and d ifferent patterns were especially evident in monocytes and polymorphonuclea r cells. (C) 2001 Elsevier Science B.V. All rights reserved.