Placental transfer of naturally acquired, maternal cytomegalovirus antibodies in term and preterm neonates

Maternal antibodies may protect the fetus and neonate against severe forms of CMV-caused disease, therefore this study investigated the efficiency of the placental transfer of naturally acquired, maternal total anti-cytomegalovirus (CMV) IgG and neutralizing antibodies at different gestational ages. The study was conducted on 182 healthy CMV-seropositive Brazilian mothers and their 196 infants who were not infected congenitally with CMV, as determined by CMV detection in urine. The study groups were composed of 44 infants aged 28-30 weeks; 51 infants aged 31-33 weeks; 62 infants aged 34-36 weeks, and 39 infants of gestational age > or = 37 weeks. Quantitative detection of total CMV IgG was carried out using EIA and virus neutralizing titers were determined by a microneutralization assay in sera from mothers and infants. CMV IgG levels and neutralizing titers of the infants correlated with maternal levels (r=0.873 and r=0.841, respectively). The efficiency of placental transfer of these antibodies was enhanced significantly as gestation progressed until 34-36 weeks, when values similar to those of full-term infants (90-100%) were found. Transfer ratios were significantly higher for neutralizing compared to total CMV IgG antibodies at gestational age 31-33 weeks (100% vs. 84%, respectively) and at gestational age 28-30 weeks (75% vs. 60%, respectively). We conclude that placental transfer of naturally acquired maternal CMV neutralizing and total CMV IgG antibodies are similarly efficient above 34 weeks of gestational age. At less than 34 weeks of gestational age, transfer of neutralizing antibodies may be favored and these antibodies reach the neonatal serum of 99% of these premature infants.