An ELISA using recombinant proteins for the detection of neutralizing antibodies against human cytomegalovirus

Two prokaryotically expressed fusion proteins encompassing amino acids 484-650 (AD-1) and 27-100 (AD-2) of glycoprotein gp58/116 of human cytomegalovirus (HCMV) were purified from E. coli lysates and used in ELISA to determine antibody levels in human sera. The specificity of the test was established by comparison of 116 randomly selected sera with commercially available HCMV-ELISA tests. The recombinant polypeptides were then used for the analysis of antibody titers in 112 human sera and were compared to the capacity to neutralize HCMV. A strong correlation between the neutralization titer and antibody levels against AD-1 and a weaker correlation for AD-2 was observed. Of 29 sera with a high neutralization titer (> 1:128), 96% and 62% were positive for AD-1 and AD-2, respectively, while 44% and 19% were positive in sera with low neutralization titer (< 1:8). Serum pools prepared from human sera selected on the basis of recognition of the recombinant antigens had a 10-fold higher neutralization capacity than pools prepared from sera with a high titer in commercially available HCMV tests. A synchronous increase in neutralization capacity and titer against recombinant antigens was observed in transplant patients.