Comparison of two Cobas Core enzyme immunoassays with other test systems for the detection of cytomegalovirus-specific IgG and IgM antibodies

Evaluation of the indirect and IgM-capture anti-human cytomegalovirus IgM ELISA methods as confirmed by cytomegalovirus IgG avidity

Primary cytomegalovirus (CMV) infection during pregnancy often results in congenital CMV infection with severe clinical complications. IgM antibodies are one of the indices of primary infection. The IgG avidity index (AI) is also known to remain low for 3 months after primary infection. Here, we evaluated and compared the performance of CMV IgM and IgG avidity assays. Because sensitivity and specificity reportedly differ between CMV IgM kits, CMV IgM detection was compared between the two commercially available ELISA kits that are most commonly used in Japan. Sera for CMV IgM were first screened using a traditional indirect ELISA kit. Selected samples were then tested for CMV IgM and CMV AI using a CMV IgM-capture ELISA kit and a CMV IgG avidity assay, respectively. The rate of concordance between the IgM kits was 89% (42/47), indicating the absence of any significant difference. Most of the CMV IgM-positive plasma samples showed high CMV IgG AI; however, 18 commercially available plasma samples with low CMV IgG AI were all CMV IgM-positive. One plausible explanation for this discrepancy is that the duration of low IgG AI is shorter than that of IgM positivity. Alternatively, CMV IgM tests may generate pseudo-positive readouts in cases of congenital infection. Nevertheless, our study confirms that CMV IgG AI can be a reliable indicator of CMV primary infection.

Perinatal or early-postnatal cytomegalovirus infection in preterm infants under 34 weeks gestation born to CMV-seropositive mothers within a high-seroprevalence population

In a prospective study, we evaluated the frequency, correlates, and clinical significance of perinatal or early-postnatal cytomegalovirus (CMV) infection in <34-week-gestation infants (n=95) born to CMV-seropositive mothers. None had congenital CMV infection. Overall, 21 (22.1%; 95% CI=14.2-31.8) infants were found to be infected; 10 excreted CMV at <60 days, and 11 had later excretion. Blood transfusion, birth weight, and vaginal delivery were not associated factors. Receiving natural breast milk within the first 30 days (OR=4.5, P=.02) or for >30 days (OR=7.9, P <.01) was associated with infection. Only one (4.8%) of the infected infants was symptomatic. For <34-week-gestation infants, frequency of perinatal and early-postnatal CMV infection is high. Early or prolonged exposure to breast milk is an associated factor. However, most infections are asymptomatic, indicating that CMV infection in preterm infants within such a population is a serious problem infrequently.

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.

Congenital cytomegalovirus infection in preterm and full-term newborn infants from a population with a high seroprevalence rate

BACKGROUND

Cytomegalovirus (CMV) is the most frequent cause of congenital infections in humans. Prematurity occurs in as many as 34% of infants with symptomatic congenital CMV infection.

OBJECTIVE

To determine the clinical presentation and frequency of congenital CMV infection among preterm infants and full-term infants from a population with a high seroprevalence rate.

DESIGN/METHODS

A total of 289 preterm infants (median gestational age, 34 weeks; median birth weight, 1,757 g) and 163 term infants (median gestational age, 39 weeks; median birth weight, 3,150 g) sequentially born were included in the study. Serum IgG antibodies to CMV were measured in all mothers. One urine sample was collected within the first 7 days of age from all newborns. Virus isolation in urine samples was performed by tissue culture, and viral DNA was detected by a multiplex PCR. CMV infection was diagnosed in infants with virus excretion detected by both methods on at least two occasions within the first 3 weeks of life.

RESULTS

Maternal CMV seropositivity rate was 95.7%. Congenital CMV infection was detected in 6 of 289 (2.1%) (95% confidence interval, 0.84 to 4.68) preterm infants and in 3 of 163 term infants (1.8%) (95% confidence interval, 0.48 to 5.74) (P > 0.05). Four of 6 preterm infants with congenital CMV infection were symptomatic, but none of the term infants was symptomatic (P = 0.16).

CONCLUSION

The frequency of congenital CMV infection in preterm newborn infants from mothers with a high seropositive rate was similar to that found in term infants. No significant difference was found between the proportion of symptomatic infants among preterm and term infants. Our finding of symptomatic congenital CMV infection underscores the need of further evaluation of correlates of congenital symptomatic infection in highly immune populations.