An antigen fragment encompassing the AD2 domains of glycoprotein B from two different strains is sufficient for differentiation of primary vs. recurrent human cytomegalovirus infection by ELISA

Primary human cytomegalovirus (HCMV) infection during pregnancy is a freque nt cause of fatal damage in populations with low prevalence of HCMV. Differ entiation of primary vs. recurrent HCMV infection is an important issue in prenatal counseling. Antibodies specific for viral glycoproteins become det ectable only with considerable delay with relation to HCMV infection or IgG seroconversion. Thus, lack of glycoprotein specific (gp-specific) antibodi es can serve as a convenient indicator to identify those pregnant women tha t bear an elevated risk for HCMV transplacental transmission and fetal sequ elae. In the opposite case, presence of gp-specific antibodies virtually ex cludes HCMV primary infection several weeks before sampling. However, no st andardized screening assay for HCMV gp-specific antibodies had been availab le thus far. For this reason, an ELISA based on procaryotically expressed f ragments of HCMV glycoprotein B (gB; gpUL56) was developed. Small fragments of gB from two different laboratory strains, encompassing the antigenic do main 2 (AD2) sufficed for sensitive and specific detection of gp-specific a ntibodies. The gB-ELISA titers correlated with titers of virus neutralizing antibodies in serum samples from primary or recurrent HCMV infections. Ser oconversion kinetics of the gB-ELISA in samples from patients with primary HCMV infection closely paralleled the delay in seroconversion of gp-specifi c antibodies as determined by neutralization assay. Thus this assay provide s a diagnostic tool that is easy to perform and can significantly add to av ailable methods for the timely identification of primary HCMV infection dur ing pregnancy. In addition, the gB-ELISA may be helpful in other clinical s ettings for the differentiation of primary HCMV infection from diseases cau sed by other pathogens. (C) 2001 Wiley-Liss, Inc.