Parvovirus B19 diagnosis in pregnant women--quantification of IgG antibody levels (IU/ml) with reference to the international parvovirus B19 standard serum

Current epidemiological aspects of human parvovirus B19 infection during pregnancy and childhood in the western part of Germany

This investigation was undertaken to provide detailed information on the epidemiology of human parvovirus B19 (B19) infection during pregnancy and childhood in the western part of Germany. Between 1997 and 2004, 40,517 sera from pregnant women aged 17-45 years and 6060 sera from children and young adults were tested for B19 IgG and IgM in our laboratory. In pregnant women, both the history of a 'specific' (OR 7.7, 95% CI 5.2-11.4) and a 'non-specific' rash (OR 3.3, 95% CI 1.5-7.1) was predictive for B19 IgM positivity. The B19 IgG prevalence was 69.2% (4097/5924) in a subgroup of asymptomatic pregnant women screened for B19 antibodies. In children, the age-specific IgG-positivity rate increased from 12.2% (66/541) at 2 years of age to 71.9% (396/551) in those older than 10 years. In conclusion, the prevalence of B19 IgG in pregnant women from the western part of Germany is higher then previously reported. Contact with children aged 3-10 years is a major risk factor for exposure to B19. Pregnant women with the history of a 'non-specific' rash should also be evaluated for acute B19 infection.

Parvovirus B19 infections in state of Rio de Janeiro, Brazil: 526 sera analyzed by IgM-enzyme-linked immunosorbent assay and polymerase chain reaction

In this study were analyzed 526 sera; the patients aged from two days to 65 years old presenting exanthema, which was the most frequent symptom observed, besides fever, adenomegaly, and arthralgia. These sera were negative by enzyme-linked immunosorbent assay (IgM-ELISA) for either rubella (495), toxoplasma (41), cytomegalovirus (12), measles (40), dengue (56), and they were submitted to nested polymerase chain reaction (PCR) for B19 DNA and commercial IgM-ELISA for B19. In 39 abortion cases, IgM or DNA were not detected, therefore they were not took into account for analysis. Specific DNA and IgM were detected respectively in 71 (14.5%) and IgM in 62 (12.7%) sera from 487 sera analyzed. IgM and DNA were simultaneously detected in 43 (8.8%), while agreement among the results by PCR and IgM-ELISA was observed in 440 (90.4%). The sera were collected from January 1999 to December 2000, most of them in 1999 (325), during winter and spring. The major number of clinical cases was observed in the age group from one to ten years old. IgM or DNA were detected in 23 from 51 municipal districts of the state of Rio de Janeiro, where the samples were collected.

Sustained CD8+ T-cell responses induced after acute parvovirus B19 infection in humans

Murine models have suggested that CD8+ T-cell responses peak early in acute viral infections and are not sustained, but no evidence for humans has been available. To address this, we longitudinally analyzed the CD8+ T-cell response to human parvovirus B19 in acutely infected individuals. We observed striking CD8+ T-cell responses, which were sustained or even increased over many months after the resolution of acute disease, indicating that CD8+ T cells may play a prominent role in the control of parvovirus B19 and other acute viral infections of humans, including potentially those generated by live vaccines.

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.

Ex vivo cytokine responses against parvovirus B19 antigens in previously infected pregnant women

Parvovirus B19 infection is a significant cause of fetal death. The aim of this study was to investigate the role of maternal immune status in modulating susceptibility to fetal B19 infection. Peripheral blood was obtained from pregnant women (n = 199) with no clinical evidence of recent B19 infection. Evaluation of ex vivo T cell responses from 149/199 individuals showed significantly higher interferon-gamma levels for seropositive individuals following VP1 (268 +/- 36 versus 103 +/- 19 pg/ml; P = 0.003) and VP2 (242 +/- 42 versus 91 +/- 16 pg/ml; P = 0.01) antigen stimulation. Significantly higher levels of interleukin-2 were also observed in seropositive individuals following both VP1 (P = 0.0003) and VP2 (P = 0.0005) stimulation. The observed Th1 cellular response is lower than that documented previously for non-pregnant individuals and strongly suggests that diminution of the maternal anti-viral immune response may increase susceptibility to fetal B19 infection.

Long term follow up of serostatus after maternofetal parvovirus B19 infection

BACKGROUND

Maternofetal parvovirus B19 infection may result in fetal hydrops or abortion. Chronic infection has been associated with long term complications (polyarthritis, persistent aplastic anaemia, hepatitis). In pregnancy maternal immunosuppression caused by a TH2 dominant response to viral antigens has been observed. There is little information on long term reactivity to intrauterine infection.

AIMS

To assess the serological status in children and their mothers after maternofetal parvovirus B19 infection and development of fetal hydrops.

METHODS

A total of 18 children and their mothers, and 54 age matched control infants were studied. Main outcome measures were parvovirus B19 DNA, specific IgM and IgG against the virus proteins VP1/VP2, and NS-1 in venous blood.

RESULTS

Parvovirus B19 DNA and antiparvovirus B19 (IgM) were undetectable in all sera. A significant larger proportion of maternal sera compared to study children's sera contained IgG against the non-structural protein NS-1. Mean levels of VP1/VP2 IgG antibodies were significantly lower in the children than in their mothers (48 (36) v 197 (95) IU/ml). There was no history of chronic arthritis in mothers and children. Five women had subsequent acute but transient arthritis postpartum, which was not correlated with antibodies against NS-1.

CONCLUSIONS

Serological evidence of persistent infection after maternofetal parvovirus B19 disease could not be detected. Increased maternal prevalence of anti NS-1 (IgG) and increased levels of antiparvovirus B19 (IgG) may reflect prolonged viraemia compared to fetal disease.

Detection of human parvovirus B19 infection: a study of 212 suspected cases in the state of Rio de Janeiro, Brazil

BACKGROUND

Parvovirus B19 infections are associated with different clinical manifestations that vary from symptom-less to severe. The main clinical manifestations are erythema infectiosum or fifth disease, transient aplastic crisis in individuals with hemoglobinopathies, chronic anemia in the immunocompromised, acute polyarthralgia syndrome in adults, hydrops fetalis, spontaneous abortion and stillbirth. Although the classical features of B19 and rubella infections are distinct, uncommon presentations can lead to misdiagnosis.

OBJECTIVE

The goal of this study was to assess the occurrence of parvovirus B19 (B19) infection in patients with clinical signs of toxoplasmosis or rubella, both of which were not confirmed by laboratorial techniques.

STUDY DESIGN

Serum samples from 214 patients were collected between January 1996 and December 1997 in the state of Rio de Janeiro, Brazil, B19 specific IgG and IgM were detected by using commercial enzyme-linked immunosorbent assays (ELISA), and viral nucleic acid was detected employing a nested polymerase chain reaction (PCR) protocol.

RESULTS

Combining the results obtained by IgM ELISA and PCR, 14.5% of the samples were positive in one or both tests, with a concordance of 92.5% between the two techniques.

CONCLUSIONS

Specimens collected in 16 out of 22 municipalities were positive in at least one out of the three tests employed, indicating that parvovirus B19 circulates in several regions of the state of Rio de Janeiro.

Parvoviruses and blood products

Erythrovirus B19 (B19), a small isocahedral, non-enveloped virus (18-26 nm), is a ubiquitous infection agent in industrialised countries. Depending on the infected host, B19 has a wide range of disease manifestations from asymptomatic (the majority) to severe, including persistent infection. The risk of B19 transmission by blood products is enhanced by a high virus titre in the infected donor, by pooling of a large number of donations, and by the virus's resistance to effective inactivation methods such as heat and solvent-detergent treatments. B19-DNA has been detected in single donations, in manufacture plasma pools and in plasma derivatives (clotting factors, albumin, antithrombin III and immunoglobulins) produced by different processes. B19 transmission is mostly found in patients treated with clotting factors, as shown by a higher seroprevalence in treated haemophiliacs, by the presence of B19 DNA, and by active seroconversion. Chronic B19 infection can successfully be treated with polyvalent intravenous immunoglobulins. The key role of neutralising anti-B19 antibodies and of the virus titre has been demonstrated by B19 transmission after infusion of several B19-positive plasma batches treated with solvent-detergent. Two strategies can be followed to reduce the B19 risk: (1) reducing the viral load in the manufacture plasma pool by discarding B19-DNA-positive donations; (2) developing new strong virus inactivation methods. The physico-resistant properties of B19 make it a good model for new emergent viruses capable of infecting blood products.

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.

Impaired gamma interferon responses against parvovirus B19 by recently infected children

Parvovirus B19 is the causative agent of "fifth disease" of childhood. It has been implicated in a variety of conditions, including unsuccessful pregnancy and rheumatoid arthritis, and is a potential contaminant of blood products. There has been little study of immunity to parvovirus B19, and the exact nature of the protective humoral and cell-mediated immune response is unclear. Immune responses to purified virus capsid proteins, VP1 and VP2, were examined from a cohort of recently infected children and compared with responses from long-term convalescent volunteers. The results demonstrate that antibody reactivity is primarily maintained against conformational epitopes in VP1 and VP2. The unique region of VP1 appears to be a major target for cell-mediated immune responses, particularly in recently infected individuals. We confirm that antibody reactivity against linear epitopes of VP2 is lost shortly after infection but find no evidence of the proposed phenotypic switch in either the subclass of parvovirus B19-specific antibody or the pattern of cytokine production by antigen-specific T cells. The dominant subclass of specific antibody detected from both children and adults was immunoglobulin G1. No evidence was found for interleukin 4 (IL-4) or IL-5 production by isolated lymphocytes from children or adults. In contrast, lymphocytes from convalescent adults produced a typical type 1 response associated with high levels of IL-2 and gamma interferon (IFN-gamma). However, we observed a significant (P<0.001) deficit in the production of IFN-gamma in response to VP1 or VP2 from lymphocytes isolated from children. Taken together, these results imply that future parvovirus B19 vaccines designed for children will require the use of conformationally preserved capsid proteins incorporating Th1 driving adjuvants. Furthermore, these data suggest novel mechanisms whereby parvovirus B19 infection may contribute to rheumatoid arthritis and unsuccessful pregnancy.

Development of antibodies to the nonstructural protein NS1 of parvovirus B19 during acute symptomatic and subclinical infection in pregnancy: implications for pathogenesis doubtful

At present little is known about the mechanisms influencing the course and severity of parvovirus B19 infection. Antibodies to the parvovirus nonstructural protein NS1 were reported in patients with parvovirus-associated arthritis and those with persisting infection but not in those without complications, suggesting a potential involvement of NS1 or anti-NS1 antibodies in pathogenesis. The immune response to NS1 was examined retrospectively in 33 pregnant women with acute parvovirus B19 infection, 14 of whom experienced symptomatic infection and 19 in whom the infection was subclinical. Antibodies to NS1 were found in 15 (45%) of the women, seven with symptomatic and eight with subclinical infection. No association was found between the development of anti-NS1 antibodies and the occurrence of fetal complications. Of the seven cases in which fetal complications were observed, anti-NS1 antibodies were detected in only three. The finding that an immune response to NS1 can also be demonstrated in patients with asymptomatic infection suggests that anti-NS1 antibodies do not appear to represent a marker for an altered or severe course of infection in pregnant women or to contribute significantly to pathogenesis. Since anti-NS1 antibodies first become detectable at least six weeks postinfection, their presence can be used to exclude acute infection in patients with unclear serology or be used to aid differential diagnosis of rashlike illnesses.

Acute parvovirus B19 infection in pregnant women--an analysis of serial samples by serological and semi-quantitative PCR techniques

The serological and virological course of parvovirus B19 infection was followed in 14 women who suffered symptomatic or subclinical acute infection during pregnancy. Serial serum samples from the patients were tested for IgG and IgM antibodies and the levels of parvovirus B19 DNA were monitored using a semi-quantitative PCR assay. In addition, the outcome of the pregnancies was documented by clinical information and by testing cord blood for parvovirus B19 specific antibodies as well as for parvovirus B19 DNA by PCR. Levels of IgG antibodies rose steadily within 2 months of infection and in some cases began to decline at the end of pregnancy. IgM antibodies were usually detected for at least 2 months and persisted for as long as 9 months in one case. Viral DNA was detectable for at least 8 weeks following infection and semi-quantitative analysis revealed a gradual reduction in virus load during the viraemic phase of infection. There were no apparent differences in the course of antibody development and duration of viraemia in symptomatic versus subclinical infections.