Decreased dipeptidyl peptidase IV enzyme activity of plasma soluble CD26 and its inverse correlation with HIV-1 RNA in HIV-1 infected individuals

Human plasma contains soluble CD26/dipeptidyl peptidase IV (sCD26/DPPIV) although its physiological significance remains unclear. To determine whether the plasma sCD26 levels have clinical relevance in HIV-1 infected individuals, the concentration and DPPIV enzyme activity of plasma sCD26 were measured, While there is no significant difference between the plasma levels of sCD26 in 90 HIV-1 infected individuals and in 79 uninfected controls, specific DPPIV enzyme activity of sCD26 was significantly decreased in HIV-1 infected individuals (P < 0.0001). Specific DPPIV enzyme activity was correlated with the levels of CD4(+) T cells (r = 0.247; P < 0.02), CD8(+) T cells (r = 0.236; P < 0.03), and adenosine deaminase (r = 0.227; P < 0.05) and had an inverse correlation with HIV-1 RNA (Spearman's r = 0.474; P = 0.0012). Furthermore, recombinant sCD26 enhanced the in vitro PPD-induced response of lymphocytes from HIV-l infected individuals with decreased specific DPPIV enzyme activity. These results suggest that the specific DPPIV enzyme activity of plasma sCD26 may contribute to the immunopathogenesis of HIV infection. (C) 1999 Academic Press.