E. Lutz et al., MATURATION OF ANTIBODY AVIDITY AFTER PRIMARY HUMAN CYTOMEGALOVIRUS-INFECTION IS DELAYED IN IMMUNOSUPPRESSED SOLID-ORGAN TRANSPLANT PATIENTS, Journal of medical virology, 44(4), 1994, pp. 317-322
An IgG antibody avidity assay which uses urea to modify a commercial e
nzyme-linked immunosorbent assay (ELISA) has been investigated for its
ability to distinguish primary human cytomegalovirus (CMV) from recur
rent or longterm infection. Twenty-four immunosuppressed solid organ t
ransplant patients were studied. The avidity indices for IgG to CMV we
re low for 12 out of 13 patients with primary infection (mean 18%), hi
gh for all 11 patients with long-term infection (mean 85%), and the 1
patient with primary infection showing an intermediate avidity index (
51%) was found to have acquired passively large amounts of CMV immunog
lobulin, presumably of high avidity, during therapy. From the results,
low and high avidity indices were defined as lying between 0-34% and
60-100%, respectively, and it was thus clear that the avidity assay ca
n discriminate between primary and recurrent or long-term CMV infectio
n. The avidity indices of eight of the immunosuppressed organ transpla
nt patients with primary infection were followed in serial serum sampl
es over time and IgG antibody to CMV was found to take at least a year
to mature to high avidity in contrast to the 2-6 months expected for
normal subjects. This finding provides evidence that immunosuppression
has subtle, hitherto unsuspected, effects on humoral immunity to CMV
in addition to the well-known depression of cell-mediated responses. I
t is concluded that this reliable avidity assay will be of importance
in the diagnosis of CMV infection and in elucidating the pathogenesis
of CMV-induced disease in organ transplant recipients. (C) 1994 Wiley-
Liss. Inc.