Selection of an intravenous immune globulin for the immunoprophylaxis of cytomegalovirus infections: an in vitro comparison of currently available and previously effective immune globulins.

In an attempt to select an i.v. immune globulin to be used for the immunoprophylaxis of cytomegalovirus (CMV) infections in recipients of allogeneic bone marrow transplants, we conducted an in vitro comparison of three newly available commercial i.v. immune globulins with two CMV hyperimmune globulin products shown to be efficacious in previous CMV immunoprophylaxis studies. We compared these products for both CMV immunoreactive antibody titer by enzyme-linked immunosorbent assay (ELISA) and for in vitro functional activity by virus neutralization using both standard laboratory and wild clinical isolates of CMV. All five products had high titers of CMV-specific IgG when assayed by ELISA, ranging from 1:1600 to 1:25,600; the two hyperimmune products had the highest titers as expected. However, both hyperimmune products, despite having much higher CMV-IgG titers by ELISA, had CMV neutralizing antibody titers only equivalent to those found in two of the three standard i.v. immune globulin products tested (mean of 1:500-1:1000). One of the three commercial immune globulins tested had a lower mean neutralizing antibody titer in lots assayed compared to the other products (mean of 1:50). There was thus no direct or predictable correlation in any of the products tested between the quantity of CMV-IgG as measured by ELISA and in vitro functional activity as measured by virus neutralization. We also noted marked variation between different lots of the same product in all three commercially available immune globulin products. To insure that both current and future CMV immunoprophylaxis trials are standardized, the quantity as well as the functional activity of CMV-specific antibodies in products used need to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)