Epidemiological studies of congenital cytomegalovirus infection

Changing patterns of cytomegalovirus seroprevalence among pregnant women in Norway between 1995 and 2009 examined in the Norwegian Mother and Child Cohort Study and two cohorts from Sor-Trondelag County: a cross-sectional study

OBJECTIVES

To examine cytomegalovirus (CMV) seroprevalence and associated risk factors for CMV seropositivity in pregnant Norwegian women.

DESIGN

Cross-sectional study.

SETTING

The Norwegian Mother and Child Cohort Study (MoBa) in addition to two random samples of pregnant women from Sør-Trøndelag County in Norway.

PARTICIPANTS

Study group 1 were 1000 pregnant women, randomly selected among 46 127 pregnancies in the MoBa (1999-2006) at 17/18 week of gestation. Non-ethnic Norwegian women were excluded. Study groups 2 (n=1013 from 1995) and 3 (n=979 from 2009) were pregnant women at 12 weeks of gestation from Sør-Trøndelag County.

OUTCOME MEASURES

CMV seropositivity in blood samples from pregnant Norwegian women.

RESULTS

CMV-IgG antibodies were detected in 59.9% and CMV-IgM antibodies in 1.3% of pregnant Norwegian women in study group 1. Women from North Norway demonstrated a higher CMV-IgG seroprevalence (72.1%) than women from South Norway (58.5%) (OR 1.83, 95% CI 1.17 to 2.88). The CMV-IgG seroprevalence was higher among women with low education (70.5%) compared to women with higher education (OR 2.20, 95% CI 1.24 to 3.90). Between 1995 and 2009 the CMV-IgG seroprevalence increased from 63.1% to 71.4% in pregnant women from Sør-Trøndelag County (study groups 2 and 3; p<0.001). The highest CMV-IgG seroprevalence (79.0%) was observed among the youngest pregnant women (<25 years) from Sør-Trøndelag County in 2009 (study group 3).

CONCLUSIONS

The CMV-IgG seroprevalence of pregnant Norwegian women varies with geographic location and educational level. Additionally, the CMV-IgG seroprevalence appears to have increased over the last years, particularly among young pregnant women.

Extrahepatic bile duct atresia and viral involvement

Several etiological factors have been suggested in the pathogenesis of extrahepatic biliary atresia (EHBA); congenital, metabolic, infectious, and multifactorial. Herein we present a study of 10 children with EHBA, the aim being to explore viral infection as a possible cause of their condition. During a period of 2 yr, all infants with EHBA were included in a study and examined on viral disease on admittance for Kasai operation. In eight of the 10 children and in one parental couple the laboratory results suggested recent or persistent viral infection. Four infections were caused by cytomegalovirus (CMV) and another five by Epstein-Barr virus (EBV). CMV-DNA was detected in two liver biopsies, EBV-DNA in one liver biopsy. In a control group of 10 patients matched by age and tested by PCR in serum and viral antibodies, no sign of viral infections were detected. CMV or EBV infection were present in an unexpectedly high proportion of infants with EHBA, justifying exhaustive examination on viral disease in these children.

Use of serial maternal urine cytomegalovirus PCR to detect primary CMV infection in seronegative pregnant women

The aim of the study was to determine if serial maternal urine polymerase chain reaction (PCR) tests can detect primary CMV infection during pregnancy. This was a prospective study conducted from 1 January 1999 to 31 December 1999 in an antenatal clinic setting of a teaching hospital. The study group included women who were CMV IgG negative and aged <30 years or had a pre-school child. They were invited to self-collect urine samples monthly and send them to the laboratory by post. Cord bloods were tested for CMV IgG to detect seroconversion. An anxiety questionnaire was sent to all study participants. At first attendance, 1549 (42%) women were CMV IgG negative. Of the 696 eligible women, 609 (88%) participated in the urine PCR study. PCR was performed on 2263 urine samples (median of 4/pregnancy). Primary CMV infection was identified in one woman by urine PCR at 36 weeks (baby CMV negative). Cord blood samples were available from 152/609 infants (25%). Seroconversion was noted in only one woman. Replies to the questionnaire were received from 264/609 women (43%): 214 (81%) had little or no anxiety, and 220 (83%) felt reassured by their study participation. Serial urine PCR is a feasible method of detecting primary maternal CMV infection during pregnancy which has potential for evaluation in further studies.

Retrospective diagnostics of congenital cytomegalovirus infection performed by polymerase chain reaction in blood stored on filter paper

Capillary blood samples from 63 infants collected 3-7 days after birth, and thereafter stored on filter papers for 12-18 y, were tested for the presence of CMV DNA by the polymerase chain reaction (PCR) method. Of 16 infants with proven congenital CMV infection (positive virus isolation test in urine sampled within 1 week of age), 13 (81%) had a positive CMV PCR test and 3 (19%) a negative PCR test. All blood samples from 16 control infants without congenital CMV infection (negative virus isolation test in urine sampled within 1 week of age) were CMV PCR-negative. When 31 samples on filter papers stored above or below the samples of the infected infants were tested, 6 (19%) had a weak reactivity. This suggests that CMV DNA can be transferred from one filter paper to another during storage. We conclude that PCR performed on dried blood stored on filter paper is a useful method in the retrospective diagnostics of congenital CMV infection. Consideration must be given, however, to the possibility of transfer of CMV DNA from blood samples stored nearby.

Prevalence of antibodies to herpes simplex virus types 1 and 2, Epstein-Barr virus and cytomegalovirus in teenage girls

Seropositivity to herpes virus type 1 (HSV-1), herpes virus type 2 (HSV-2), cytomegalovirus (CMV) and Epstein-Barr virus (EBV) was estimated in a group of 98 16-year-old Swedish girls. Antibodies to HSV-1 were seen in 41% of the girls and to HSV-2 in 1%, and antibodies to CMV in 45 and to EBV in 82%. In girls with coitus experience, there was significantly higher prevalence of HSV-1 and EBV antibodies, compared with girls with no sexual contact. The age of coitarche or number of coitus partners did not affect the rate of seropositivity. During 2 years of follow-up, 13 girls seroconverted. All but one EBV-seroconverting girl, were sexually active, and no girl converted for more than one type of virus. We concluded that transmission of herpes viruses is common in adolescence, and sexuality, even with regard to its close association with kissing, is one important determinant.

Fine specificity of the human immune response to the major neutralization epitopes expressed on cytomegalovirus gp58/116 (gB), as determined with human monoclonal antibodies

The humoral immune response to human cytomegalovirus (CMV) membrane glycoprotein gp58/116 (gB) has been studied by establishing cell lines producing specific human monoclonal antibodies. These cell lines were generated from peripheral blood lymphocytes obtained from a healthy carrier. Hybridomas producing gp58/116-specific antibodies were detected by reactivity to procaryotically expressed proteins containing the major neutralizing epitopes of this glycoprotein complex. One antibody, ITC88, which recognized an epitope located between amino acid residues 67 and 86 of gp116, potently neutralized the virus at 1 to 2 micrograms of immunoglobulin G per ml. Only four of the six human antibodies detecting the major neutralizing domain of gp58 neutralized the virus, and none of them required complement for activity. All antibodies that bound mature, processed gp58 recognized a conformational epitope involving sequences between residues 549 and 635. However, small differences existed between the antibodies in the actual minimal requirement for C- and N-terminal parts of this epitope. By peptide mapping with several of the antibodies, the epitope was shown to consist mainly of residues between amino acids 570 to 579 and 606 to 619. Despite the conformational nature of the epitope, the antibodies recognized both reduced and denatured native antigen. Presence of carbohydrates was not required for antigen binding of these gp58-specific human antibodies, but in at least one case, it greatly enhanced antigen recognition, indicating an importance of carbohydrate structures in some epitopes within the major neutralizing specificity of gp58.

Restriction enzyme analysis of human cytomegalovirus using DNA extracted from infected cells

Cytomegalovirus (CMV) isolates were investigated by restriction enzyme analysis. A method for extraction of cellular CMV DNA is described which uses CMV DNA released into the Hirt supernatant after precipitation of cellular DNA. CMV DNA is further purified by ultracentrifugation in neutral sucrose gradient. Fifteen strains from unrelated patients all had unique cleavage patterns with three restriction enzymes, although many of the fragments comigrated. Strains from related patients mostly showed identical patterns. The CMV genome seems to be stable since the pattern did not change in five isolates obtained from the same patient during a 5-year period.