CMV DNA in blood donors with IgM and IgG CMV antibodies.

Strategies for preventing posttransfusion CMV infections include testing for CMV antibodies, CMV DNA, and/or WBC reduction of blood components. 1,2 Early studies with molecular methods produced conflicting results. Nevertheless, recent investigations show that improved CMV PCR assays do not necessarily increase detection of CMV DNA in healthy CMV-seronegative blood donors. 3,4 We confirm these findings in a study of 244 plasma and WBC fractions and 176 serum samples from 420 donors in the Vienna, Austria, region (384 randomly selected and 36 samples selected for IgM anti-CMV reactivity). We tested for IgM and IgG CMV antibodies in serum or plasma with two ELISAs (Enzygnost anti-CMV IgM and Enzygnost anti-CMV IgG, Dade Behring, Marburg, Germany). Results were interpreted to be positive if the corrected absorbance values ( D A = [A antigen – A control antigen ] ¥ correction factor) were greater than the cutoff of 0.2 OD, negative if the absorbance values were less than the cutoff of 0.1 OD, and equivocal if the absorbance values were between 0.1 and 0.2 OD in the first test and in retesting. CMV PCR screening was performed on serum, plasma, and WBC samples with a 5 ¢ -nuclease real-time PCR assay, which targets the polymerase gene region of the virus. PCR-reactive samples were retested and confirmed with a second real-time assay amplifying a sequence stretch in the major immediate early region. In serial dilutions of the quantitated plasma sample VQC 1999/6, the 95 percent cutoff value of the screening assay had been estimated to be four copies per PCR (192 copies/mL). CMV DNA was reproducibly detected and confirmed in the WBC fraction from one donor and a serum sample from another donor. CMV DNA was not detected in the plasma or whole blood corresponding to the CMV DNApositive WBCs. We interpret these results to indicate that this sample was most probably from a latently infected individual. The viral loads in these samples were approximately 10 times lower (approx., 100 copies/mL) than the positive control for the assay (1000 copies/mL). The above findings correlate well with those of Roback and colleagues. 4 In their study, 10 to 99 CMV geq per 250,000 WBCs were detectable in 2 of 1000 whole blood samples. Both samples were reactive for anti-CMV but there was no differentiation between IgM and IgG reactivity. We also found our positive DNA results only in seropositive samples, in the strict sense restricted to IgG-positive and either IgM-equivocal or IgM-negative seroreactivity (Table 1). It is unclear whether CMV DNA detected in the serum sample showing an IgM-equivocal result and IgG antibody positivity corresponds to a late phase of primary CMV infection, a reinfection, or a reactivation of a latent infection. Because Drew and colleagues 3 did not detect CMV DNA in 488 plasma samples from 60 persistently seropositive individuals, but observed plasma CMV DNA in a small percentage of seroconverting blood donors, the first explanation seems to be more probable. In conclusion, our results confirm that CMV DNA is rarely detected in asymptomatic CMV-seropositive blood donors and is absent in CMV-seronegative individuals. If CMV NAT is to have a role in donor screening, it will most probably be limited to the detection of CMV-seronegative window-phase donations. Barbara Glock, DSc Blood Donation Center for Vienna, Lower Austria and Burgenland Austrian Red Cross Nordportalstrasse 248 A-1020 Vienna, Austria e-mail: [email protected] Elisabeth Schistal, MD Blood Donation Center for Vienna, Lower Austria and Burgenland Austrian Red Cross Wiedner Hauptrasse 32 A-1040 Vienna, Austria Wolfgang R. Mayr, MD Blood Donation Center for Vienna, Lower Austria and Burgenland Austrian Red Cross Wiedner Hauptrasse 32 A-1040 Vienna, Austria University Clinic for Blood Group Serology and Transfusion Medicine Waehringer Guertel 18-20 A-1090 Vienna, Austria TABLE 1. Results of CMV PCR testing, correlated with CMV antibody reactivity