Determination of anti-p52 IgM and anti-gB IgG by ELISA as a novel diagnostic tool for detection of early and late phase of primary human cytomegalovirus infections during pregnancy

Performance of eight commercial immunoassays for the detection of cytomegalovirus-specific IgM antibodies in pregnancy - no test fits all needs

Detection of cytomegalovirus (CMV)-specific immunoglobulin M (IgM) antibodies as first-line serologic diagnosis plays an important role in identifying CMV primary infection during pregnancy. The performance characteristics of eight commercially available CMV IgM assays were compared. Sensitivity and IgM antibody kinetics were assessed using 100 acute phase and follow-up sera from 39 pregnant women with a well-defined onset of CMV primary infection. Specificity was analyzed using 50 well-characterized serum samples from pregnant women not infected or latently infected with CMV and from patients with other acute infections. Until 12 weeks after the onset of primary infection, four assays showed sensitivities of 100%, whereas the others had individual gaps to detect all primary infections in this time period. All assays showed a time-dependent decrease of IgM levels. More than 12 weeks after the onset of infection, the IgM-positive rates varied considerably between tests. The specificity was between 92% and 98% in all but one assay. The observed differences in the performance characteristics must be taken into account in CMV screening and diagnosis of primary infection during pregnancy.

Efficiency of CMV serodiagnosis during pregnancy in daily laboratory routine

BACKGROUND

Maternal acute primary cytomegalovirus (CMV) infection during the first trimester may cause severe long-term sequelae in newborns. For risk assessment, serological screening is routinely performed in pregnant women based on IgM, IgG and avidity tests using whole-virus antigen. A recent study evaluated the diagnostic value of recombinant protein-based ELISAs as second-line tests in pregnancy CMV screening, including anti-p52 IgM and anti-gB IgG as markers defining the early and late phase of infection, respectively. In the present study, these recombinant ELISAs were used as first-line screening tests in daily laboratory routine and compared to lysate-based assays with respect to [i] the number of conclusive results obtained with the initial sample and [ii] the underlying workload.

METHODS

553 unselected routine serum samples from pregnant women were tested for anti-CMV IgM and IgG antibodies using lysate-based ELISAs and avidity testing. Anti-CMV IgM antibodies against recombinant p52 and anti-CMV IgG antibodies against recombinant glycoprotein B (gB) were also determined by ELISA. All assays were performed and interpreted according to the manufacturer's instructions.

RESULTS

For lysate-based IgM, IgG and avidity testing, 84.6 % of samples yielded conclusive results in a total of 1156 tests, while 15.4 % needed follow-up testing of a consecutive sample. Anti-p52 CMV IgM and anti-gB CMV IgG testing produced conclusive results for 92.8 % of samples in a total of 1026 tests, while 7.2 % samples required follow-up testing.

CONCLUSIONS

The first-line use of ELISAs measuring anti-p52 CMV IgM and anti-gB CMV IgG antibodies to test for maternal CMV infection increases the number of conclusive results derived from an initial serum sample while requiring a considerably lower number of tests compared to the lysate-based approach. For day-to-day routines in a diagnostic laboratory, this high efficiency of the recombinant testing approach has significant practical relevance.

Diagnosis and Stratification of Pseudomonas aeruginosa Infected Patients by Immunochemical Quantitative Determination of Pyocyanin From Clinical Bacterial Isolates

The development of a highly sensitive, specific, and reliable immunochemical assay to detect pyocyanin (PYO), one of the most important virulence factors (VFs) of Pseudomonas aeruginosa, is here reported. The assay uses a high-affinity monoclonal antibody (mAb; C.9.1.9.1.1.2.2.) raised against 1-hydroxyphenazine (1-OHphz) hapten derivatives (PC1; a 1:1 mixture of 9-hydroxy- and 6-hydroxy-phenazine-2-carobxylic acids). Selective screening using PYO and 1-OHphz on several cloning cycles allowed the selection of a clone able to detect PYO at low concentration levels. The microplate-based ELISA developed is able to achieve a limit of detection (LoD) of 0.07 nM, which is much lower than the concentrations reported to be found in clinical samples (130 μM in sputa and 2.8 μM in ear secretions). The ELISA has allowed the investigation of the release kinetics of PYO and 1-OHphz (the main metabolite of PYO) of clinical isolates obtained from P. aeruginosa-infected patients and cultured in Mueller–Hinton medium. Significant differences have been found between clinical isolates obtained from patients with an acute or a chronic infection (~6,000 nM vs. ~8 nM of PYO content, respectively) corroborated by the analysis of PYO/1-OHphz levels released by 37 clinical isolates obtained from infected patients at different stages. In all cases, the levels of 1-OHphz were much lower than those of PYO (at the highest levels 6,000 nM vs. 300 nM for PYO vs. 1-OHphz, respectively). The results found point to a real potential of PYO as a biomarker of P. aeruginosa infection and the possibility to use such VF also as a biomarker for patient stratification[2] and for an effective management of these kinds of infections.

Human cytomegalovirus non-primary infection during pregnancy: antibody response, risk factors and newborn outcome

OBJECTIVES

Human cytomegalovirus (HCMV) non-primary infections can occur in pregnant women and may result in congenital infection. Comprehensive studies investigating the frequency, characteristics, risk factors and immune response of non-primary infection in pregnancy are missing, while rate of vertical transmission is not known.

METHODS

HCMV non-primary infection was investigated prospectively in 250 pregnant women. Blood and urine samples as well as saliva and vaginal swabs were collected at 13, 21 and 31 weeks of gestation and at delivery. HCMV-DNA and specific IgG and IgM levels were determined.

RESULTS

Overall, 105/250 pregnant women (42.0%) developed non-primary infection. HCMV-DNA was detected more frequently in the vaginal secretions (84/250 of the women, 33.6%) than in the urine (35/250, 14.0%), in the saliva (26/250, 10.4%), and in the blood (7/250, 3.0%). The rate of HCMV non-primary infection increased significantly with the progression of pregnancy (from 12.9% in the first trimesters of gestation to 21.9% at delivery, p<0.01). IgM was detected in 25/250 of the women (10.0%), with no association with non-primary infection, while anti-gB IgG was significantly higher (p<0.01) in women with non-primary infection. Age and close contact with children were not associated with non-primary infection. No woman with non-primary infection transmitted the infection to the fetus (95% confidence interval of transmission rate: 0-3.5%).

CONCLUSION

Although HCMV non-primary infection is frequent during pregnancy, the rate of congenital infection as a consequence of non-primary infection is likely to be ≤3.5%.