Maternal IgG avidity and IgM detected by blot as diagnostic tools to identify pregnant women at risk of transmitting cytomegalovirus

New advances in the diagnosis of congenital cytomegalovirus infection

Although the diagnosis of congenital CMV infection is still complex, important goals have been achieved in recent years, among which are: the availability of more reliable IgM tests for screening pregnant women whose pre-pregnancy serological status for CMV is unknown, tests to determine the avidity index of anti-CMV IgG, allowing the diagnosis of a primary CMV infection and innovative and traditional virological tests to detect the virus in amniotic fluid. When a woman is found to be IgM-positive, further diagnostic evaluation focused on determining whether this is due to a primary infection should be carried out. Maternal primary infections that were difficult to determine until a few years ago unless documented by seroconversions can now be readily diagnosed from the presence of low/moderate avidity anti-CMV antibody which persists for approximately 18-20 weeks after primary infection. In mothers at risk of transmitting the virus prenatal diagnosis can be performed between 21 and 22 weeks of gestation, and the amniotic fluid represents the pathological material of choice to determine intrauterine virus transmission. At birth or in the first 2/3 weeks of life, it is essential to use appropriate tests for diagnosis of CMV congenital infection.

Relevance of parvovirus B19, herpes simplex virus 2, and cytomegalovirus virologic markers in maternal serum for diagnosis of unexplained recurrent abortions

CONTEXT

The impact of viral infections during pregnancy on adverse pregnancy outcomes is not understood fully.

OBJECTIVE

To assess the frequency of parvovirus B19, herpes simplex 2, and cytomegalovirus infections in relation to late abortions, in sera from Egyptian pregnant women to establish basic knowledge for future pregnancy care. In addition, to study the diagnostic value of specific immunoglobulin M (IgM) against those viruses compared with their genomes detection by polymerase chain reaction in maternal serum as a noninvasive method of laboratory diagnosis.

DESIGN

Patients were recruited at the Women's Clinic, Mansoura University. One group of patients with recurrent spontaneous abortions (RSA) and a second group of pregnant women without a history of RSA were evaluated including demographic, medical, and clinical data. Virologic markers were evaluated for specific IgM and for viral DNA to cytomegalovirus, herpes simplex virus 2, and parvovirus B19.

RESULTS

There was a statistically significant difference between the RSA group and the pregnant women without RSA group in frequency of parvovirus IgM (84% and 16.7%, respectively) (P < .001) and herpes simplex IgM (40% for RSA) (P = .001). Parvovirus B19 viremia was positive in 48% RSA, herpes simplex virus 2 was positive in 32% RSA, and cytomegalovirus was positive in 12% RSA patients. For RSA patients with parvovirus viremia, the mean +/- SD of IgM value was 78.5 +/- 30.12 IU/mL, and for RSA patients with negative viremia it was 30.02 +/- 17.64 IU/mL with statistically significant difference between both levels (P < .001).

CONCLUSIONS

From this study, we conclude that viral infections with parvovirus B19 and herpes simplex 2 were frequently associated with recurrent abortions, and careful investigation for this condition must include evaluating these patients for the previously mentioned viruses. Serologic study by specific IgM for parvovirus and herpes simplex seem to be reliable as screening tests for high-risk pregnancy.

Impact of diagnostic and confirmatory tests and prenatal counseling on the rate of pregnancy termination among women with positive cytomegalovirus immunoglobulin M antibody titers

OBJECTIVE

The purpose of this study was to determine if diagnostic tests performed in a reference laboratory and the correct interpretation and communication of results by an expert physician to the patient can reduce the rate of unnecessary abortions among women with positive cytomegalovirus (CMV) immunoglobulin M antibody titers.

STUDY DESIGN

This was a retrospective study of 1857 consecutive pregnant women with positive screening for IgM anti-CMV, in the first or second trimester of pregnancy, referred to our unit for further diagnostic evaluation. Patients with available follow-up were divided into 2 groups according to the results of confirmatory serologic testing: women with a CMV serologic profile suggestive of primary infection and hence at high risk of vertical transmission (group 1) and women with a CMV serologic profile consistent with nonprimary infection or past infection (group 2). The number of expected pregnancy terminations and the prevented fraction of abortions was calculated.

RESULTS

Of 445 group 1 patients, 53 (11.9%) elected to terminate the pregnancy after being informed of the results of diagnostic tests; in contrast, only 5 (0.4%) women in group 2 underwent terminations (P < .001). At autopsy, 38 fetuses in group 1 proved infected. No information on fetal infection is available for pregnancies terminated in the first trimester (15 in group 1; 5 in group 2). We estimated that > or = 196 (11.9%) of all patients in groups 1 and 2 (n = 1650 patients) would have elected abortion on the basis of the positive result of screening for fetal CMV infection. After the results of confirmatory tests, only 58 women (53 in group 1 and 5 in group 2) elected to terminate the pregnancy. Thus, the number of abortions is presumed to have been decreased by 73% (P < .001).

CONCLUSION

The correct interpretation and communication of confirmatory test results by expert physicians to pregnant women with positive screening for IgM anti-CMV may significantly reduce the rate of unnecessary abortions.

Avidity Maturation following Immunization with Two Human Cytomegalovirus (CMV) Vaccines: A Live Attenuated Vaccine (Towne) and a Recombinant Glycoprotein Vaccine (gB/MF59)

Two human cytomegalovirus (CMV) vaccines have been previously evaluated for their immunogenicity: a recombinant gB/MF59 vaccine and an attenuated strain of CMV (Towne). In healthy adults, we measured the antibody avidity maturation indices that occurred after vaccination with each. For Towne, administered as a single dose, the rise in IgG antibody avidity to CMV glycoprotein gB occurred slowly and continued for 24 months post-immunization. For gB/MF59, administered as two priming doses and a booster dose given at 6 months, the booster rapidly induced IgG antibodies to gB whose avidity was maximal at 7 months after the initial priming dose. Both vaccines induced antibody levels and avidity maturation indices that equaled those induced by wild-type virus suggesting that both vaccines may be effective in controlling CMV infections.

Validation of an in-house assay for cytomegalovirus immunoglobulin G (CMV IgG) avidity and relationship of avidity to CMV IgM levels

Measurement of cytomegalovirus (CMV)-specific immunoglobulin G (IgG) avidity has proven to be a powerful tool for distinguishing primary from nonprimary CMV infection. An in-house enzyme-linked immunosorbent assay (ELISA) for measuring CMV IgG avidity was validated using 84 sera from pregnant women who had recently seroconverted following primary CMV infection and 74 sera from individuals with past CMV infection (IgG-positive and IgM-negative profile). Of the 84 sera from pregnant women, 73 sera were collected within 120 days of the last IgG-negative sample, and 72 of these 73 sera (99%) exhibited an avidity index (AI) of <50%. In contrast, 71 of 74 (96%) sera from individuals with past CMV infection exhibited CMV AI values of > 60%. Thus, low avidity in the in-house ELISA was defined as an AI of < or = 50%, whereas high avidity was defined as an AI of > or = 60%. In additional studies, the relationship between CMV IgG avidity and CMV IgM levels was examined using 64 CMV IgG-positive sera (time since seroconversion unknown) exhibiting equivocal or positive results in a CMV IgM capture ELISA (Diamedix). Of these 64 sera, 29 exhibited IgM index values of > or = 3.0, and 27 of these 29 (93%) exhibited low IgG avidity. A similar trend was observed when a subset of these 64 sera (n = 48) was tested in another CMV IgM capture ELISA (Trinity); of 18 sera with IgM index values of > or = 3.0, 17 (94%) exhibited low IgG avidity. These findings demonstrate the validity of an in-house ELISA for CMV IgG avidity and further show that strong reactivity of CMV IgG-positive sera in either of two CMV IgM capture assays is a reliable indicator of low CMV IgG avidity, and thus, recent CMV infection.

Seropositivity of cytomegalovirus, parvovirus and rubella in pregnant women and recurrent aborters in Leningrad County, Russia

BACKGROUND

The objectives of this paper were to assess the prevalence of different viral infections in relation to late abortions, stillbirths, and congenital malformations in sera from Russian pregnant women and recurrent aborters in order to establish basic knowledge for future pregnancy care.

METHODS

Patients were recruited at the Women's Clinic, Leningrad Regional Hospital during the period March-June 1995. One group of normally pregnant women (Group 1; n=182) and one group of recurrent aborters (Group 2; n=127) were evaluated, including demographic, medical, clinical, and serological data.

RESULTS AND CONCLUSIONS

The mean age of the two groups was 27.1 and 28.2 years, respectively. The mean number of deliveries was low (0.4 and 0.5, respectively). Thirty-one point six percent of Group 1 and 41.9% of Group 2 were daily smokers. The group of normally pregnant women had a significantly increased frequency of induced abortions compared to the recurrent aborters, while the recurrent aborters reported more genital infections. There was little difference in total antibodies to cytomegalovirus (CMV) (78.0% and 81.1%, respectively) or B19 IgG (75.3% and 66.9%, respectively) between the groups, while the normal pregnant women had a significantly higher prevalence of rubella antibodies (77.5% and 59.8%, respectively). Our results indicate that less women remain susceptible to primary CMV infection in pregnancy in Russia compared to western Europe and North America. The prevalence of B19 IgG was slightly lower than data from Sweden. Natural immunization against rubella virus was lower than in other, unvaccinated female populations. Vaccination strategies for rubella are now initiated in the Russian Federation. Results from this study are utilized in a federally supported, comprehensive pregnancy care project of North-West Russia.

Cross-reactivity of Epstein-Barr virus-specific immunoglobulin M antibodies with cytomegalovirus antigens containing glycine homopolymers

Timely and reliable detection of acute primary human cytomegalovirus (HCMV) infection is important in prenatal screening programs and for differential diagnosis of infectious mononucleosis-like disease. Enzyme-linked immunosorbent assays (ELISAs) based on HCMV proteins enable the sensitive detection of immunoglobulin M (IgM) antibodies during primary infection. However, concerns have been raised about possible cross-reactivities of the HCMV antigens used for the design of such ELISAs with IgM antibodies induced by Epstein-Barr Virus (EBV). In this study we investigated whether IgM antibodies generated during acute EBV infection reacted with recombinant HCMV antigens. Serum samples from patients with primary EBV infection frequently scored positive when tested in different HCMV IgM ELISAs, irrespective of whether conventional or recombinant antigens were used for the design of the HCMV IgM assays. Such cross-reactive IgM antibodies were found to be directed against short glycine-rich motifs contained within the nonstructural HCMV proteins pUL44 and pUL57. Further analyses revealed that these glycine-rich motifs were major antigenic domains for IgM antibodies induced during HCMV infection. Their deletion from recombinant proteins abrogated reactivity with IgM synthesized during HCMV infection. EBV-induced IgM antibodies that reacted with HCMV antigens showed similar kinetics of reactivity in HCMV- or EBV-specific assays in the course of primary EBV infection, indicating that the two populations of antibodies were highly overlapping. The results demonstrate that primary EBV infection leads to the induction of IgM antibodies that specifically bind to widely used diagnostic antigens of HCMV. This has to be considered in the interpretation of HCMV-specific IgM assays.

Recent advances in the diagnosis of cytomegalovirus infection

Herpesviruses are highly disseminated in nature, and nearly 100 Herpesviruses have been at least partially characterized. Seven Herpesviruses have been isolated so far from humans and one has recently been detected by sequence analysis. Consequently, the diagnosis of human Herpesvirus infection is based on eight different viruses. The diagnosis of a Herpesvirus infection can be achieved through the direct demonstration of the presence of the virus or its components (mainly nucleic acids and antigens) in pathological materials or indirectly through serology. In recent years much progress has been made in both directions and thanks to the detailed study of the viral genomes and their antigenic gene products and by the determination of the immune reactivity against individual antigenic polypeptides in different clinical settings. Progress in the direct detection of the viruses in pathological materials mainly regards the production of specific probes and their use with or without DNA amplification for the detection of viral genomes. Serological advances are mainly linked to the production, characterization and use of specific viral antigens by DNA recombinant procedures and by the production and use of synthetic peptides acting as good antigenic epitopes.