An enzyme linked immunoassay using recombinant antigens for differentiation of primary from secondary or past CMV infections in pregnancy

Background: As primary cytomegalovirus (CMV) infection in pregnancy may be associated with severe fetal outcome, the serological differentiation of primary infection from recurrent or previous infection is of major importance. Objectives: This differentiation was attempted with a CMV IgG enzyme immunoassay (EIA), which investigated the differential IgG immune response to recombinant proteins p52 and pp150. To express the IgG reactivity to either protein a ratio was calculated by OD p52/OD pp150. Study design: Serial samples from groups of pregnant women with primary infection ( n=18) were compared to those with recurrent ( n=7) or previous CMV infection ( n=189). Results: In primary infected women a predominant IgG response to p52 (p52 alone or ratio ≥1.5) was observed in early sera less than 4 weeks after seroconversion, whereas the IgG response to recombinant protein pp150 was delayed and appeared after 2–7 weeks. Women with secondary and those with past infection had either IgG antibodies to pp150 alone or a ratio of less than 1.5 in 85 and 89.1% respectively with no remarkable change of ratio over time. Conclusions: The IgG recombinant EIA was shown to be a useful supplementary assay for differentiation of primary up to 8 weeks after seroconversion from recurrent or past infections.