CYSTATIN-C LEVELS IN SERA OF PATIENTS WITH HUMAN-IMMUNODEFICIENCY-VIRUS INFECTION - A NEW AVIDIN-BIOTIN ELISA ASSAY FOR ITS MEASUREMENT

A solid-phase enzyme-linked immunosorbent assay (ELISA) for determining human serum cystatin C is described. In 50 normal samples, cystatin C concentration was 1247 +/- 224-mu-g/L (mean +/- SD) which is in agreement with previously reported levels. Serum levels of cystatin C and beta(2)-microglobulin (beta(2)-M) were investigated in a time-course study during the development of human immunodeficiency virus (HIV) infection. We found a persistent and uniform increase in the beta(2)-M concentration (2762 +/- 1239-mu-g/L). In contrast to beta(2)-M, on the basis of cystatin C levels, we found two distinct populations, one of which demonstrated an increased concentration (1620 +/- 618-mu-g/L). Interestingly a second group (21% of patients) exhibited an initial significant decrease in cystatin C concentration with a mean value of 377 (range 55-850) mu-g/L, followed by an increase. The biphasic pattern of cystatin C serum, a major cysteine proteinase inhibitor, during the course of HIV infection suggests a possible role for these proteinases (or proteinase inhibitors) in the development of this syndrome.