Prenatal diagnosis of congenital parvovirus B19 infection: value of serological and PCR techniques in maternal and fetal serum

Parvovirus B19 Infection and Pregnancy: Review of the Current Knowledge

Parvovirus B19, a member of the Parvoviridae family, is a human pathogenic virus. It can be transmitted by respiratory secretions, hand-to-mouth contact, blood transfusion, or transplacental transmission. Most patients are asymptomatic or present with mild symptoms such as erythema infectiosum, especially in children. In rare cases, moderate-to-severe symptoms may occur, affecting blood cells and other systems, resulting in anemia, thrombocytopenia, and neutropenia. Non-immune pregnant women are at risk for fetal infection by parvovirus B19, with greater complications if transmission occurs in the first or second trimester. Infected fetuses may not show any abnormalities in most cases, but in more severe cases, there may be severe fetal anemia, hydrops, and even pregnancy loss. Maternal diagnosis of intrauterine parvovirus B19 infection includes IgG and IgM antibody testing. For fetal diagnosis, PCR is performed through amniocentesis. In addition to diagnosing the infection, it is important to monitor the peak of systolic velocity of the middle cerebral artery (PVS-MCA) Doppler to assess the presence of fetal anemia. There is no vaccine for parvovirus B19, and fetal management focuses on detecting moderate/severe anemia by fetal PVS-MCA Doppler, which, if diagnosed, should be treated with intrauterine transfusion by cordocentesis. Prevention focuses on reducing exposure in high-risk populations, particularly pregnant women.

Prevalence of parvovirus B19 antibodies in pregnant women in northern Benin

OBJECTIVES

Parvovirus B19 (B19V) infection in pregnancy is generally asymptomatic, but in about 3% it can cause complications, including miscarriage, severe foetal anaemia and foetal hydrops. The seroprevalence in pregnancy ranges from 20% to 82% in Africa, but there are no data for Benin. We therefore retrospectively assessed the seroprevalence of B19V in pregnant women attending the Saint Jean de Dieu Hospital in Tanguiéta, a rural district of Atacora, in northern Benin.

METHODS

We searched for anti-B19V immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in 227 sequential sera from as many women (mean age 26.3 years, range: 16-41) of whom 30 were in the first trimester, 66 in the second and 131 in the third. Samples that tested positive for IgM were analysed with an immunoblot test and the viral genome (DNA-B19V) was searched for using a polymerase chain reaction.

RESULTS

Of the 227 women, 153 (67.4%) were positive for IgG anti-B19V, 7 (3.1%) for IgM and 73 (32.2%) were non-immune. Six IgM-positive women were also IgG positive. The difference in IgG seroprevalence between trimesters or ages was not statistically significant. Of the seven IgM-positive samples, three were confirmed positive by immunoblot (of which two were DNA-B19V positive), three were indeterminate (DNA-B19V negative) and one was negative (DNA-B19V negative). Of the three women with confirmed positive IgM, two were in the third trimester and one in the second trimester of pregnancy.

CONCLUSIONS

The seroprevalence of anti-B19V IgG among pregnant women in Benin is high and in line with those reported in some African countries. IgM seroprevalence is also similar to that described in some African countries in non-epidemic periods. The low viral load observed depicts non-acute infections, but it is difficult to establish the precise time of the infection, especially for women tested in the second or third trimester of pregnancy, when the observed viremia could be a sign of an acute infection that occurred in the previous trimester. Consequently, clinical follow-up and further investigations to highlight possible foetal consequences are indicated.

Prevalence of anti-parvovirus B19 IgG and IgM and parvovirus B19 viremia in pregnant women in an urban area of Northern Italy

Parvovirus B19 (B19V) infection in pregnancy is mostly asymptomatic, but can cause complications including abortion and fetal hydrops. Although its infection is ubiquitous, seroprevalence among pregnant women varies according to different geographical areas. Since seroprevalence data in Italy are limited, the prevalence of antibodies and DNA in pregnant women was evaluated retrospectively, correlating the clinical situation of mothers and newborns. One thousand eight hundred and ninety-three sequential sera were examined from pregnant women (60.8% in the first trimester, 16.6% in the second one, and 22.6% in the third one, respectively) for anti-B19V IgG and IgM (confirmed by immunoblot); 1402 (74.1%) were of Italian origin and 491 (25.9%) non-Italian women. Molecular tests were used to search for viral genome. One thousand three hundred and fifteen (69.5%) samples were IgG-positive, 21 (1.1%) IgM-positive, and 578 (30.5%) nonimmune. The difference in IgG seroprevalence between Italian (71.1%) and non-Italian women (64.8%) was statistically significant. Of the 21 IgM-positive women, 16 were confirmed positive also by immunoblot (prevalence: 0.8%), of which 11 were viraemic (prevalence: 0.6%; mean 1.3 × 10⁴  geq/ml). Mothers were asymptomatic, and the newborns had no clinical signs of congenital infection. IgG seroprevalence in Italy is high, with differences between Italian women and non-Italian women from geographic areas with lower endemic levels of B19V. The consistent migratory flows in place could lead to an increase in the number of susceptible women. The prevalence of viremia is low, and has not been associated with evident fetal damage at birth.

Determinants of orofacial clefting II: Effects of 5-Aza-2'-deoxycytidine on gene methylation during development of the first branchial arch

Defects in development of the secondary palate, which arise from the embryonic first branchial arch (1-BA), can cause cleft palate (CP). Administration of 5-Aza-2'-deoxycytidine (AzaD), a demethylating agent, to pregnant mice on gestational day 9.5 resulted in complete penetrance of CP in fetuses. Several genes critical for normal palatogenesis were found to be upregulated in 1-BA, 12h after AzaD exposure. MethylCap-Seq (MCS) analysis identified several differentially methylated regions (DMRs) in DNA extracted from AzaD-exposed 1-BAs. Hypomethylated DMRs did not correlate with the upregulation of genes in AzaD-exposed 1-BAs. However, most DMRs were associated with endogenous retroviral elements. Expression analyses suggested that interferon signaling was activated in AzaD-exposed 1-BAs. Our data, thus, suggest that a 12-h in utero AzaD exposure demethylates and activates endogenous retroviral elements in the 1-BA, thereby triggering an interferon-mediated response. This may result in the dysregulation of key signaling pathways during palatogenesis, causing CP.

Gestational and fetal outcomes in B19 maternal infection: a problem of diagnosis

Parvovirus B19 infection during pregnancy is a potential hazard to the fetus because of the virus' ability to infect fetal erythroid precursor cells and fetal tissues. Fetal complications range from transitory fetal anemia and nonimmune fetal hydrops to miscarriage and intrauterine fetal death. In the present study, 72 pregnancies complicated by parvovirus B19 infection were followed up: fetal and neonatal specimens were investigated by serological and/or virological assays to detect fetal/congenital infection, and fetuses and neonates were clinically evaluated to monitor pregnancy outcomes following maternal infection. Analysis of serological and virological maternal B19 markers of infection demonstrated that neither B19 IgM nor B19 DNA detected all maternal infections. IgM serology correctly diagnosed 94.1% of the B19 infections, while DNA testing correctly diagnosed 96.3%. The maximum sensitivity was achieved with the combined detection of both parameters. B19 vertical transmission was observed in 39% of the pregnancies, with an overall 10.2% rate of fetal deaths. The highest rates of congenital infections and B19-related fatal outcomes were observed when maternal infections occurred by the gestational week 20. B19 fetal hydrops occurred in 11.9% of the fetuses, and 28.6% resolved the hydrops with a normal neurodevelopment outcome at 1- to 5-year follow-up. In conclusion, maternal screening based on the concurrent analysis of B19 IgM and DNA should be encouraged to reliably diagnose maternal B19 infection and correctly manage pregnancies at risk.

Parvovirus B19 infection in human pregnancy

Human parvovirus B19 infection is widespread. Approximately 30-50% of pregnant women are nonimmune, and vertical transmission is common following maternal infection in pregnancy. Fetal infection may be associated with a normal outcome, but fetal death may also occur without ultrasound evidence of infectious sequelae. B19 infection should be considered in any case of nonimmune hydrops. Diagnosis is mainly through serology and polymerase chain reaction. Surveillance requires sequential ultrasound and Doppler screening for signs of fetal anaemia, heart failure and hydrops. Immunoglobulins, antiviral and vaccination are not yet available, but intrauterine transfusion in selected cases can be life saving.

Parvovirus B19 infection

Human parvovirus B19 (B19) is common in society. Among adults, more than 50% have contracted the infection and immunity is believed to last lifelong. Infection occurs in a few percent of pregnancies, and albeit rare it can then cause fetal anemia, non-immune fetal hydrops and fetal death. Among cases with fetal demise, B19 is found in significant numbers, especially in the second and third trimesters of pregnancy. There is no specific treatment or prophylaxis available against B19 infection, but counseling of non-immune mothers and active monitoring of confirmed maternal infections with intervention to correct fetal anemia is likely to decrease mortality. Passive immunization also has potential to resolve fetal complications, but needs further study.

Diagnosis of fetal parvovirus B19 infection: value of virological assays in fetal specimens

OBJECTIVE

The purpose of our work was to examine the most reliable laboratory diagnosis of fetal parvovirus B19 infection in hydropic fetuses by evaluating the most appropriate clinical sample and laboratory test.

DESIGN

B19 DNA detection in fetal samples and serological signs of B19 infection in the respective mothers. Samples collected between January 2000 and July 2008.

SETTING

Microbiology, University of Bologna, Bologna, Italy.

SAMPLES

One hundred thirty-five fetal samples (58 fetal cord blood and 77 amniotic fluid samples) and 109 serum samples collected from 109 pregnant women.

METHODS

Validated and certified in situ hybridisation assay (ISH) and polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) were performed on fetal samples to detect B19 DNA. B19-specific antibodies were investigated in maternal serum samples by a commercial enzyme immunoassay.

MAIN OUTCOME MEASURES

Parvovirus B19 DNA detection in fetal specimens was analysed in relation to maternal serological signs of infection.

RESULTS

Parvovirus B19 DNA was detected in 22.41% of fetal cord blood and 36.36% of amniotic fluid samples. A statistically significant difference was found between DNA detection by ISH (23.70%) and PCR-ELISA (14.81%) (P= 0.004). Only 11.76% of fetuses with virological diagnosis of B19 infection were from women with serological signs of acute/recent B19 infection.

CONCLUSIONS

Diagnosis of fetal parvovirus B19 infection cannot always rely on maternal serological investigations but rather on the virological analysis of fetal samples. Both fetal cord blood and amniotic fluid samples are suitable for diagnosis, but the detection of B19 DNA in the cells of amniotic fluid samples by ISH proved to be the most reliable diagnostic system.

Fetal anaemia as a cause of fetal injury: diagnosis and management

PURPOSE OF REVIEW

This review provides up-to-date information on the diagnosis and management of fetal anaemia.

RECENT FINDINGS

Exciting advances in the field of red blood cell isoimmunization are phasing out the need for invasive procedures. Rhesus blood group genotyping using fetal DNA in maternal plasma has been introduced into clinical practice with remarkable success. The role of middle cerebral artery peak systolic velocity in screening for fetal anaemia has been confirmed in various causes of fetal anaemia. A recent review of a successful Iran national screening programme for thalassaemia provided a timely and valuable educational opportunity. The value of intrauterine transfusion as a treatment for fetal anaemia was demonstrated by both high success rate and low procedure-related pregnancy loss rate.

SUMMARY

Fetal anaemia is one of the severe fetal conditions that affect the worldwide population. Rhesus isoimmunization remains an important health issue despite the recommendation for anti-D immunoglobulin prophylaxis and injection after sensitizing events. Noninvasive ultrasound diagnostic methods have replaced traditional invasive procedures in the assessment of fetus at risk of anaemia due to various causes, including red blood cell isoimmunization, parvovirus B19 infection and thalassaemia. The increased availability of intrauterine transfusion will help to improve the prognosis of these anaemic fetuses.

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.

Parvovirus B19 infection in pregnancy: maternal and fetal viral load measurements related to clinical parameters

OBJECTIVE

To correlate quantitative maternal and fetal parvovirus B19 (B19V) viral loads and antibody levels at intrauterine transfusion (IUT) as a predictor of fetal morbidity.

METHODS

Prospectively collected clinical data and quantitative B19V viral load and specific IgM and IgG values in fetal and maternal blood samples taken during IUT.

RESULTS

Maternal IgM and IgG levels exceeded fetal antibody levels. Fetal viral load measurements correlated positively with maternal viral loads and exceeded maternal viral load 10(5)-fold (p < 0.0001). Maternal B19V IgM and fetal B19V viral load showed a positive correlation (r = 0.840, p = 0.007). No relation was found between fetal viral load and severity of fetal anemia derived from Doppler flow measurements in the middle cerebral artery.

CONCLUSIONS

Maternal and fetal B19V viral load values are highly interrelated, suggesting continuous maternal and fetal viral replication or a fetal source of maternal viremia. Maternal B19V IgM values may predict the severity of fetal infection, but the severity of B19V induced fetal anemia cannot be predicted using fetal or maternal viral loads. Fetal ultrasound remains the gold standard for identifying fetal anemia in B19V infection.

Parvovirus B19 infection in pregnancy studied by maternal viral load and immune responses

OBJECTIVES

Facilitate risk assessment of vital complications in fetuses of pregnancies affected by acute parvovirus B19 (B19V) infection.

DESIGN

Study of the natural course of maternal B19V infection in four cases, from early pregnancy on.

SETTING

University Medical Center in the Netherlands.

POPULATION

Pregnant mothers attending obstetric services.

METHODS

Serial measurements of the maternal and fetal or neonatal viral load and antibody responses.

MAIN OUTCOME MEASURES

Maternal and fetal/neonatal serum B19V viral DNA load and specific IgM and IgG antibodies in maternal serum.

RESULTS

Peak viral load levels occurred within 1 week after maternal infection and peak IgM levels were observed 1 week after the peak viral load levels. Approximation of IgG and IgM ratios usually took place 4 weeks after infection. Vertical transmission occurred 1-3 weeks after maternal infection, suggesting that fetal infection occurs during the maternal peak viral load.

CONCLUSIONS

Maternal B19V DNA load levels and IgM responses are useful to estimate the risk of parvovirus B19-associated fetal complications. The maternal peak viral load directly precedes the onset of fetal infection and may be used to indicate the stage of intrauterine B19V infection.

Detection of human parvovirus B19 nonstrutural protein DNA by nested-polymerase chain reaction in gravida serum and pregnant tissues

A new nested-polymerase chain reaction (nested-PCR) assay was developed to detect human parvovirus B19 DNA corresponding to the nonstructural protein in clinical specimens in a routine diagnostic laboratory. The sensitivity of this highly specific assay was up to 0.005 fg of B19 DNA. Parvovirus B19 was identified in sera of 20 pregnant women with abnormal pregnant outcome. Among these 20 cases, intrauterine parvovirus infection did exist in 7 pregnant women because parvovirus B19 DNA was detected in the pregnant tissues of them such as placenta tissues, chorionic villi, amniotic fluid, fetal spleen, liver and abdominal fluids.

Incidence of parvovirus B19 infection among an unselected population of pregnant women in the Netherlands: A prospective study

OBJECTIVE

To evaluate seroprevalence of anti-parvovirus B19 IgG immunoglobulins and the rate of seroconversion in seronegative pregnant women.

DESIGN

Prospective assessment of anti-parvovirus B19 IgG immunoglobulins in an unselected population of pregnant women booked for antenatal care from 1998 to 2000.

SETTING

Maternity departments of an academic hospital and four affiliated teaching hospitals in the Netherlands.

SUBJECTS

Two thousand five hundred and sixty seven pregnant women.

MAIN OUTCOME MEASURES

Seroprevalence of anti-parvovirus B19 IgG immunoglobulin in the first trimester of pregnancy and subsequent seroconversion in those women who were tested negative for parvovirus B19 antibodies in the first trimester of pregnancy.

RESULTS

The estimated seroprevalence of anti-parvovirus B19 IgG immunoglobulins among the study population is 70% (95% CI: 68-71) in the first trimester of pregnancy. Seven hundred and seventy nine women tested negative for parvovirus B19 antibodies in the first trimester of pregnancy. Paired testing in these women confirmed 18 seroconversions. Based on these findings the estimated incidence of maternal parvovirus B19 infection in this population among seronegative Dutch women is 2.4% (95% CI: 1.4-3.7).

CONCLUSION

Maternal infection with parvovirus B19 is relatively common. However, it is argued that in the Netherlands routine assessment of parvovirus antibodies in pregnant women is not warranted as there is a low risk of adverse fetal outcome and measures to prevent the parvovirus B19 infection and its consequences are very limited.

Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and beta-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

Prenatal testing for infectious disease

Prenatal testing for infectious diseases is performed frequently and for a variety of indications. The purpose of this article is to review the maternal and fetal infections that pose diagnostic concerns. Recent advances in diagnostic testing (such as avidity testing) is included. Testing issues focus on the diagnosis of maternal and fetal infection.

Testing for hematologic disorders and complications

This review summarizes state-of-the-art and emerging techniques in the antenatal diagnosis of fetal anemia and hemoglobinopathies. Fetal anemia may result from hemolytic disease, hemorrhage, suppression of erythropoiesis, infection (eg, parvovirus B19), or trauma. The clinical laboratory plays an essential role in the evaluation of these disorders by way of the use of various hematologic, biochemical, serologic, cytometric, and molecular genetics methods. Hemoglobinopathies are the most common class of single gene disorders worldwide. The authors have used the example of homozygous alpha-thalassemia major (Hb Barts disease) as a paradigmatic case for antenatal hemoglobinopathy screening. Perhaps the most familiar indication for hematologic screening in pregnancy is HDFN, most commonly in pregnancies previously sensitized to the RhD antigen. All pregnant women, regardless of their past medical or obstetric history or previous antibody screens, should have ABO/Rh blood typing and a red cell antibody screen performed at the first prenatal visit. Long-established methods for assaying FMH (KB method), microcytosis (hemogram with red cell indices), and blood group incompatibility (direct antigen test, serologies) remain critical for rapid, sensitive diagnosis. Analysis of fetal free DNA in maternal plasma holds the promise for rapid, ultrasensitive, and noninvasive detection of many fetal hematologic disorders.

Parvovirus B19 infection in pregnancy: quantitative viral DNA analysis using a kinetic fluorescence detection system (TaqMan PCR)

Human parvovirus B19 infections are common in the general population, and infection during pregnancy may cause hydrops fetalis and fetal death. To initiate adequate treatment, accurate laboratory diagnosis is essential. The most sensitive tests are nested PCR systems, but these assays provide semiquantitative results at best. A parvovirus B19 DNA assay was developed based on the real time TaqMan PCR. This method was calibrated on the basis of serial plasmid dilutions and tested with an international parvovirus B19 standard. The assay was capable of quantifying parvovirus B19 DNA from one to about 5 x 10(7) genome equivalents per reaction (corresponding to 100 to 5 x 10(9) genome equivalents per ml serum). Samples from 51 pregnant women with suspected acute parvovirus B19 infection were tested, and positive PCR results were obtained in at least one of the materials investigated in 41 cases. The median viral DNA load in maternal blood samples was 1.3 x 10(4) copies/ml (range 7.2 x 10(2)-2.6 x 10(7)). Maternal virus DNA concentration was not associated with the presence of maternal symptoms and/or fetal complications. As the stage of infection was not known in the majority of cases, our data do not exclude an association between peak levels of parvovirus B19 DNA and the development of complications. Maternal sera and corresponding fetal material were available for concurrent testing from 15 DNA-positive cases: in most fetal samples, viral DNA concentrations were several orders of magnitude higher (up to 2.1 x 10(12) copies/ml) compared to the corresponding maternal blood samples.

High-sensitivity PCR detection of parvovirus B19 in plasma

Parvovirus B19 (B19) is a human pathogen transmitted to susceptible individuals via respiratory secretions and contaminated blood or blood products. B19 levels in pooled plasma of less than 10(4) genome equivalents/ml may not be infectious, while those greater than 10(7)/ml are capable of transmitting infection. A World Health Organization (WHO) B19 DNA international standard has been recently introduced. The purpose of the present work was to develop a PCR-enzyme-linked immunosorbent assay (PCR-ELISA) calibrated against the WHO B19 DNA international standard which could easily and reliably detect B19 DNA levels in plasma above 10(4) IU/ml (6.5 x 10(3) genome equivalents/ml). A B19 PCR-ELISA system was developed which uses a dinitrophenylated oligonucleotide probe to detect immobilized biotinylated amplicons following single-round PCR amplification. The level of B19 DNA (in international units per milliliter) in individual and pooled plasma specimens was evaluated. Proteinase K treatment of plasma was found to be sufficient to quantitatively release B19 DNA. The B19 PCR-ELISA had a sensitivity of detection of 1.6 x 10(3) IU/ml B19 DNA and a dynamic range extending from 8 to 1,000 IU of B19 DNA (equivalent to 1.6 x 10(3) to 2 x 10(5) IU of B19 DNA/ml). Furthermore, the antibody profile of pooled plasma products was determined in terms of B19 immunoglobulin G (IgG) (in international units per milliliter). The B19 IgG level was found to be 64.7 +/- 17.5 IU/ml (mean +/- standard deviation). The B19 PCR-ELISA, which is calibrated against the B19 DNA international standard, may have an application for the rapid screening of plasma minipools for B19 DNA, thereby leading to an improvement in blood product safety.

[Viral infections and pregnancy: contribution of amniotic fluid and blood samples]

The main viral infections prenatally detected in fetuses are: cytomegalovirus, parvovirus B19, rubella virus and varicellazoster virus infections. Prenatal diagnosis is based on the direct detection of the virus by culture (CMV), of its antigens or of its genome, essentially by PCR. This direct detection can be done either on fetal blood or on amniotic fluid. Prenatal diagnosis can also be performed by detection of specific IgM in fetal blood (rubella). Non specific markers of viral infection can also help in diagnosis. At the present time, prenatal diagnosis is essentially based on the detection of the viral genome in amniotic fluid. In order to better appreciate the severity of fetal infections, some groups have tried to identify prognostic markers of these infections. The viral load as well as the level of specific IgM could play a role in certain infections (CMV).

New LightCycler PCR for rapid and sensitive quantification of parvovirus B19 DNA guides therapeutic decision-making in relapsing infections

Detection of parvovirus B19 DNA offers diagnostic advantages over serology, particularly in persistent infections of immunocompromised patients. A rapid, novel method of B19 DNA detection and quantification is introduced. This method, a quantitative PCR assay, is based on real-time glass capillary thermocycling (LightCycler [LC]) and fluorescence resonance energy transfer (FRET). The PCR assay allowed quantification over a dynamic range of over 7 logs and could quantify as little as 250 B19 genome equivalents (geq) per ml as calculated for plasmid DNA (i.e., theoretically >or=5 geq per assay). Interrater agreement analysis demonstrated equivalence of LC-FRET PCR and conventional nested PCR in the diagnosis of an active B19 infection (kappa coefficient = 0.83). The benefit of the new method was demonstrated in an immunocompromised child with a relapsing infection, who required an attenuation of the immunosuppressive therapy in addition to repeated doses of immunoglobulin to eliminate the virus.

Detection of parvovirus B19 IgM by antibody capture enzyme immunoassay: receiver operating characteristic analysis

Parvovirus B19 infection can cause severe effects in high-risk groups including pregnant women and immunocompromised individuals. Although serological detection of B19 infection is commonplace, minimal information is available on the absolute performance characteristics of various tests for the detection of B19 IgM. The performance of the first parvovirus B19 IgM enzyme immunoassay to be cleared by the US Food and Drug Administration (FDA) is described. The immunoassay cut-off has been established using receiver operating characteristic (ROC) analysis giving a sensitivity and specificity of detection of 89.1 and 99.4%, respectively. No cross-reactivity is observed with rubella or other viral disease IgM which cause similar symptomologies to parvovirus B19. Multi-site reproducibility studies have shown high immunoassay reproducibility with detection rates (observed/expected result) of 100% for nonreactive specimens (N=324) and strongly reactive (N=403), respectively. Immunoassay reproducibility ranged from 11.76 to 17. 46% coefficient of variation for all reactive specimens tested (N=12) whereby each specimen was assayed a total of 81 times. Parvovirus B19 IgM seroprevalence of 1% was observed in a US blood donor population (N=399). In the absence of international performance criteria, this study will be of major benefit to the clinical virologist in assessing immunoassay reliability for the detection of recent infection with parvovirus B19.