High-sensitivity PCR detection of parvovirus B19 in plasma

Prevalence and disease association of human parvovirus B19 in Iran: a systematic review

Aim: The prevalence of human parvovirus B19 (B19V) and its association with other diseases in Iran are yet to be systematically assessed. This study aimed to evaluate the prevalence and disease association of B19V across Iran from 2000 to 2019. Methods: The literature search, based on different keywords in different databases, was performed. A total of 29 eligible studies were included and the essential information was collected from each article. Results: The results of this study show a relatively high prevalence of the B19V-associated diseases in all age groups of the Iranian population. Conclusion: The transmission of B19V and its complications should be prevented by developing preventative strategies.

Look-back study on recipients of Parvovirus B19 (B19V) DNA-positive blood components

BACKGROUND AND OBJECTIVES

To assess the relevance of Parvovirus B19 (B19V) DNA at low to intermediate concentrations in blood donors for the recipients of their blood components.

MATERIAL AND METHODS

We studied recipients of B19V DNA-positive blood components [red blood cell concentrates (RBCs), pooled platelet concentrates and fresh frozen plasma]. This included archived pretransfusion samples as well as follow-up samples investigated by ELISA or NAT and genome sequence analysis.

RESULTS

In 132 out of 424 recipients, we could detect no anti-B19V IgG before transfusion. In 67 out of 132 sero-negative recipients, a follow-up sample was available. Sixty-five of these received blood components from donors with <10(4) IU B19V DNA/ml plasma and had no evidence of transfusion-transmitted (TT)-B19V infection. Homology in genome sequences in donor and recipient provided evidence for a TT-B19V infection in two recipients. Both patients received RBC containing 3.4 × 10(6) and 1.8 × 10(4) IU B19V DNA/ml plasma, respectively. The anti-B19V IgG titres in the donors were 2 and 76 IU/ml plasma, respectively. The antibodies in the second donor were directed against capsid proteins and are thus considered as potential neutralizing antibodies.

CONCLUSIONS

TT-B19V infections through blood components with low (<10(4) IU/ml plasma) B19V DNA concentrations did not occur in our study. One of the TT-B19V infections occurred from RBC with intermediate B19V DNA concentration despite the presence of potential neutralizing antibodies in the donor, but its clinical significance was low.

Persistence of Parvovirus B19 (B19V) DNA and humoral immune response in B19V-infected blood donors

BACKGROUND AND OBJECTIVES

Parvovirus B19 (B19V) DNA seems to persist in the plasma of B19V-infected blood donors. The relevance of this for recipients of single-donor blood components is yet unclear.

MATERIAL AND METHODS

We studied serial archive and follow-up samples from 75 B19V-infected blood donors to obtain more data about the duration and degree of viraemia and the presence of IgG and IgM anti-B19V. IgG antibodies were further characterized by Western blot analysis in 29 donors.

RESULTS

In 411 B19V DNA-positive samples collected, we found high concentrations (>10(6) IU B19V DNA/ml plasma) in five. B19V DNA persisted for a mean of 21·5 months (range: 2·3-52·4; 95% confidence interval, 19·1-23·9 months) in all donors. Only 15 such samples had either no or low-titre IgG anti-B19V. IgG antibodies were predominantly directed against epitopes on the minor capsid protein VP1, thus probably of neutralizing type with high avidity. IgM anti-B19V was detectable in 9/13 samples with high DNA concentrations.

CONCLUSIONS

The vast majority of single-donor blood components with detectable B19V DNA are probably not infectious for their recipients because DNA is at only low levels and the donors also have potentially neutralizing antibodies with high avidity. Anti-B19V IgM testing does not identify every donation with high B19V DNA concentrations, but, in addition to B19V NAT testing, donors with persistent IgG anti-B19V might be considered 'B19V-safe' for single-donor blood components.

The detection of parvoviruses

Parvovirus B19 is a single-stranded DNA virus which causes severe disease in immunocompromised patients and foetal loss in pregnant women. It is classified as an Erythrovirus and this genus also comprises two related viral genotypes (so-called LaLi/A6 (genotype 2) and V9 (genotype 3)) which appear to be immunologically indistinguishable from Parvovirus B19. Serological and nucleic acid test (NAT) systems to detect Parvovirus B19-mediated infection are commercially available; however, some NAT systems are genotype-specific. International standard preparations of Parvovirus B19 IgG and DNA have been produced for assay standardisation purposes, and to ensure consistency of assay manufacture and performance. Immunological assays, such as B-cell ELISpot, T-cell stimulation, and cytokine detection can also be used to confirm exposure to Parvovirus B19. Immunohistochemical techniques, employing commercially available monoclonal antibodies, are used to localise the virus in infected tissue and Parvovirus B19 viral antigen can also be detected in serum and plasma using antigen-specific ELISA. NAT systems have also been described to detect newly identified parvoviruses such as human bocavirus (HBoV), PARV4, and PARV5, although absolute confirmation of clinical diseases associated with these agents is required. This chapter describes the current status of detection systems for all the aforementioned parvoviruses, with particular emphasis on Erythrovirus detection by serological, NAT, and immunological approaches.

Development of a microtiter plate hybridization-based PCR-enzyme-linked immunosorbent assay for identification of clinically relevant human group A rotavirus G and P genotypes

A microtiter plate hybridization-based PCR-enzyme-linked immunosorbent assay (PCR-ELISA) has been used for the detection and identification of a variety of microorganisms. Here, we report the development of a PCR-ELISA for the identification of clinically relevant human rotavirus VP7 (G1 to G6, G8 to G10, and G12) and VP4 (P[4], P[6], P[8], P[9], and P[14]) genotypes. The G and P types of reference human and animal rotavirus strains for which specific probes were available were correctly identified by the PCR-ELISA. In addition, reference strains bearing G or P genotypes for which specific probes were unavailable, such as G11, G14, P[3], P[10], and P[11], did not display any cross-reactivity to the probes. The usefulness of the assay was further evaluated by analyzing a total of 396 rotavirus-positive stool samples collected in four countries: Brazil, Ghana, Japan, and the United States. The results of this study showed that the PCR-ELISA was sensitive and easy to perform without the use of any expensive and sophisticated equipment, the reagents used are easy to obtain commercially and advantageous over multiplex PCR since more than one type-specific probe is used and the selection of probes is more flexible.

Neutralization of human parvovirus B19 by plasma and intravenous immunoglobulins

BACKGROUND

Human parvovirus B19 (B19V) is a highly prevalent pathogen, and plasma pools for manufacturing of plasma-derived products have been shown to contain antibodies against B19V (B19V immunoglobulin G [IgG]).

STUDY DESIGN AND METHODS

The megakaryoblastic cell line UT7/Epo-S1 can be infected with B19V Genotype 1 and as demonstrated here by immunocytochemistry, Western blot, and reverse transcription-polymerase chain reaction (RT-PCR) of B19V-specific mRNA, also with the more recently discovered Genotype 2. Based on B19V RT-PCR analysis of infected UT7/Epo-S1 cells, an infectivity assay was established and implemented for a B19V neutralization assay. To investigate the role of B19V neutralization in relation to B19V IgG titers, more than 1,000 manufacturing plasma pools were tested by enzyme-linked immunosorbent assay.

RESULTS

Plasma pools were found to contain a mean B19V IgG titer of 33 +/- 9 IU per mL, with the lowest titer at 11 IU per mL. These 11 IU per mL B19V IgG neutralized 4.6 log B19V Genotype 1 and greater than 3.9 log Genotype 2 infectivity. Accordingly, a 10 percent intravenous immunoglobulin (IVIG) product prepared from such pools was found to contain an even higher B19V neutralization capacity.

CONCLUSION

A high capacity of B19V Genotypes 1 and 2 neutralization was demonstrated in plasma pools for fractionation, an inherent feature based on the constantly high titer of B19V IgG in these pools. The neutralizing activity of B19V IgG was shown to be maintained in the 10 percent IVIG product tested.

Human erythrovirus B19 and blood transfusion ? an update

Erythrovirus (parvovirus) B19 (B19) is a common human pathogen. It is a non-enveloped single-strand DNA virus packaging its genome in small tight capsids consisting of viral VP1 and VP2 proteins. It is now accepted that B19 is a relatively quickly evolving virus having diverged in several genetic variants recently identified. The main route of B19 transmission is respiratory, with a majority of infections occurring during childhood and manifesting as erythema infectiousum. B19 can also be transmitted vertically and via blood transfusion and organ transplantation. The majority of adult populations show immunological evidence of previous exposure to B19. Although the immune response is able to clear infection and provide life-long protection against B19, recent data suggest that in some, if not the majority, of individuals the acute phase of infection is followed by viral persistence in the blood or other tissues regardless of the host's immunocompetence. Transmission of B19 by blood and blood products and its resistance to common viral inactivation methods raises several blood safety questions, still unanswered. The diversity of B19 strains and the ability of the virus to persist in the presence of specific antibodies raise the issue of transmissibility by transfusion not so much to immunocompetent recipients but rather to the large proportion of recipients in whom there is some degree of immunodeficiency. The ability of the virus to reactivate in immunodeficient recipients may create difficulties in differentiating between transfusion transmission and reactivation.

Transplacental infection of Coxsackievirus B3 pathological findings in the fetus

Coxsackievirus intrauterine infection has been documented mostly on the basis of indirect evidence of transplacental transmission, with neonatal manifestations ranging from asymptomatic infection to meningoencephalitis, myocarditis, and generalized sepsis. This is the first report of prenatal findings and fetoplacental pathology in a third trimester fetus with coxsackie B3 transplacental infection confirmed by molecular techniques. Prenatal ultrasound detected severe reduction of fetal movements at the 27th week. Late onset fetal akinesia deformation sequence with mild arthrogryposis, necrotic meningoencephalitis with vascular calcifications, interstitial pneumonitis, mild myocardial hypertrophy, and chronic monocytic placental villitis were the cardinal findings at fetal autopsy following interruption of the pregnancy.

Clinical aspects of parvovirus B19 infection

Parvovirus B19 is a significant human pathogen that causes a wide spectrum of clinical complications ranging from mild, self-limiting erythema infectiosum in immunocompetent children to lethal cytopenias in immunocompromised patients and intrauterine foetal death in primary infected pregnant women. The infection may also be persistent and can mimic or trigger autoimmune inflammatory disorders. Another important clinical aspect to consider is the risk of infection through B19-contaminated blood products. Recent advances in diagnosis and pathogenesis, new insights in the cellular immune response and newly discovered genotypes of human parvoviruses form a platform for the development of modern therapeutic and prophylactic alternatives.

Serologic and molecular detection of human Parvovirus B19 infection

Following its identification by Yvonne Cossart in 1975, human Parvovirus B19 has been recognized as the causative agent of a wide range of diseases. In childhood, the most common disease is a typical exanthema called "fifth disease". In adults, viral infection may be responsible for fetal loss and for aplastic anaemia in immuno-compromised patients. Because persistent viral infection may induce an autoimmune response, Parvovirus B19 is emerging as an environmental factor linked to the pathogenesis of autoimmunity. As a result of its expanding disease spectrum, Parvovirus B19 is the subject of intense efforts to clarify the pathogenesis of virus-related disorders as well as improve diagnostic laboratory testing including standardization of serological and nucleic acid-based detection assays. Enzymatic immunoassays based on conformational antigens have proven to be the most important tools for accurate diagnosis in the majority of cases. In other selected clinical cases, the detection of Parvovirus B19 infection can be complemented by PCR and, more recently, by the real-time PCR.

A cluster of parvovirus B19 infections in renal transplant recipients: a prospective case series and review of the literature

Up to 9% of renal transplant recipients have severe multifactorial erythropoietin-resistant anemia. Human parvovirus B19 (PVB19) infection can cause severe anemia and is likely underreported. Sparse information on epidemiology and management in this population exists. To address these issues, after our first index case, we modified our clinical practice to prospectively screen patients with persistent hemoglobin (Hb) <10 mg/dL for PVB19 infection after excluding common causes of anemia including erythropoietin resistance. Potentially infected patients were further evaluated by serology, qualitative polymerase chain reaction (quPCR) and bone marrow biopsy (BMB) for cytomegalovirus, Epstein-Barr virus, PVB19 and other etiologies. Over 3 months, 212 kidney recipients visited outpatient clinics. Of 52 recipients with anemia, 8 had an Hb <10 mg/dL with erythropoietin resistance and were screened for PVB19 infection. Three cases had PVB19 infection by quPCR and often-inconclusive serology/BMB results. Cases had immunosuppression reduced and received IVIG (0.5 gm/kg x 4 doses) with recovery from anemia, viral clearance in two cases and one recurrence. PVB19-mediated anemia occurred in up to three out of eight (38%) screened kidney recipients with Hb <10 mg/dL resistant to erythrypoietin. We recommend prospective risk stratification for this population, high indices of suspicion using at least qualitative techniques for diagnosis and treatment goal for viral eradication.

Real-time PCR in clinical microbiology: applications for routine laboratory testing

Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.

Parvovirus B19 viral loads in relation to VP1 and VP2 antibody responses in diagnostic blood samples

BACKGROUND

Human parvovirus B19 infection is characterised by high peak viral load levels followed by episodes of prolonged viremia. The risk of transmission of parvovirus B19 by blood or blood products has been increasingly recognised and parameters that can predict the risk of transmission are subject of interest.

OBJECTIVES

This study aimed to study correlations between B19 viral DNA loads and antibody responses to the viral antigens VP1 and VP2 in clinical serum samples.

STUDY DESIGN

A panel of 1610 serum samples from patients clinically suspected from acute B19 infection were analysed. Antibodies were measured by the parvovirus anti-VP1 immuno-fluorescence assay (IFA) and the anti-VP2 enzyme immunoassay (EIA) from Biotrin. B19 viral loads were measured by a real-time PCR using the external WHO standard for DNA quantification.

RESULTS

Positive IgM responses were found in 154 (9.6%) of the 1610 sera tested. Based on the PCR results in a subset of 312 sera, the anti-VP2 EIA IgM showed a better combination of sensitivity/specificity (91%/94%) compared to the anti-VP1 IFA (66%/97%). B19 DNA levels in the sera strongly correlated with the levels of IgM antibodies, all sera with high viral loads (>10(6)IU/ml) having VP2 EIA IgM ratios above 3.0.

CONCLUSIONS

The B19 VP2 IgM ELISA is superior to the B19 VP1 IgM IFA if verified by PCR. Anti-VP2 IgM antibodies in sera are indicative for the presence B19 DNA and can be used to predict high levels of B19 DNA in diagnostic sera.

Establishment of functional B cell memory against parvovirus B19 capsid proteins may be associated with resolution of persistent infection

Parvovirus B19 (B19) infection can occur during acute lymphoblastic leukemia and persistent viral infection can occur despite intravenous immunoglobulin administration. Here, evidence is presented that resolution of persistent B19 infection in an acute lymphoblastic leukemia patient may be associated with the simultaneous strengthening of antigen-specific B cell memory against the B19 capsid protein VP2 and diminution in the memory response against the B19 non-structural protein 1 (NS1). Determination of antigen-specific B cell memory status may enhance the serological and molecular analyses of persistent B19 infection.

Efficient delivery of small interfering RNA for inhibition of IL-12p40 expression in vivo

Background

RNA interference is an evolutionary conserved immune response mechanism that can be used as a tool to provide novel insights into gene function and structure. The ability to efficiently deliver small interfering RNA to modulate gene expression in vivo may provide new therapeutic approaches to currently intractable diseases.

Methods

In vitro, siRNA targeting IL-12p40 was delivered to the murine macrophage cell line (J774A.1) encapsulated in a liposome with an IL-12 inducing agent (LPS/IFN-γ) over a number of time points. Controls included a variety of non-target specific siRNA reagents. Supernatants were analyzed for cytokine production while the cells were removed for mRNA profiling.

In vivo, siRNA-targeting IL-12p40 was delivered to the murine peritoneal cavity in a therapeutic fashion, after endotoxin (LPS) challenge. Cells from the peritoneal cavity were removed by lavage and analyzed by flow cytometry. Levels of IL-12 present in lavage and in serum were also examined by ELISA.

Results

In this report, we show that IL-12p40 siRNA can specifically silence macrophage expression of IL-12p40 mRNA and IL-12p70 protein in vitro. We extend this finding to demonstrate that delivery of liposome encapsulated siRNA targeting IL-12p40 to the murine peritoneal cavity can modulate an inflammatory stimulus in vivo. Furthermore, specific siRNA can be used therapeutically after endotoxin challenge to reduce both the local and systemic inflammatory response. Thus, the delivery of siRNA can be used to elicit specific non-permanent inhibition of endogenous protein expression.

Conclusion

In vitro silencing of IL-12p40 using siRNA at selected doses leads to specific knockdown of IL-12p70 protein production without inducing type I interferons. Furthermore, siRNA targeting murine IL-12p40 can be used therapeutically to counter an inflammatory response in vivo.

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.

Quantitative real-time detection of parvovirus B19 DNA in plasma

BACKGROUND

As of 2004, the European Pharmacopoeia demands that plasma pools for production of anti-D immunoglobulin should not contain more than 104 IU per mL of parvovirus B19 (B19V) DNA. Hence, before pooling, highly viremic donations have to be identified, and after pooling the level of B19V DNA must be determined. The performance of a new real-time B19V DNA PCR test (Roche, Mannheim, Germany) was studied, using a DNA extractor (NucliSens, bioMerieux, Boxtel, the Netherlands) for isolation of nucleic acid, and using a DNA quantification test (LightCycler apparatus, Roche, Mannheim, Germany) for amplification and detection.

STUDY DESIGN AND METHODS

Dilutions of the international B19V DNA standard and reference preparations were tested to determine the precision, linear range, and accuracy of the assay and to calculate the factor for conversion of B19V DNA copies to IUs. The internal control signals, invalid test results, and the effect of cryo-poor plasma were studied as a measure for robustness. Routine performance was assessed by testing 164 manufacturing pools (not screened for B19V) and 1048 test pools of 480 donations each.

RESULTS

The copies-to-IU conversion factor was calculated to be 3.34 (95% CI, 3.07-3.63). The assay appears linear between 10(3) and 10(7) IU per mL. Between 10(3) and 10(5) IU per mL, the test can discriminate samples differing a factor two in B19V DNA content. Overall, 0.78 percent of the test results were invalid. Of 127 B19V DNA negative control plasma samples, 7 were contaminated with low levels of B19V DNA. Of 164 nonscreened manufacturing plasma pools, 92 contained B19V DNA (56%); 13 contained more than 10(4) IU per mL. Of 503,040 donations, 29 contained more than 5 x 10(6) IU per mL B19V DNA (1:17,346).

CONCLUSION

The B19V DNA quantification test (LightCycler, Roche ) is suitable for quantitative, routine, in-process measurement of B19V DNA levels in plasma pools, using the DNA extractor (NucliSens, bioMerieux) for nucleic acid isolation.

Molecular testing for detection of in vitro infectivity of plasma pools contaminated with B19 virus

B19 virus can be transmitted by contaminated blood or blood products. Recent observations, in healthy volunteers, suggest that active B19 infection can follow the administration of plasma pools with a concentration > or =10(7) genome equivalents/ml (geq/ml) of B19 DNA. However, patients receiving batches with levels of virus DNA lower than 10(4) geq/ml do not show any evidence of transmission of the virus. The aim of the study was to show, by in vitro assays, a threshold of viral load in B19 contaminated plasma pools over which the infection can be transmitted. Twenty plasma pools, each containing 960 single donations, were tested to correlate the viral load and the level of antibodies anti-B19 with the in vitro infectivity and expression of B19 virus. All the plasma pools, titrated for B19 viral load by competitive PCR, were inoculated into KU812Ep6 erythroid human cell line. Five of the nine contaminated plasma pools, with a B19 DNA concentration > or =3.60 x 10(6) geq/ml, were able to infect KU812Ep6 cells. In vitro infectivity was shown in KU812Ep6 cells at 24 h post-infection by in situ hybridisation and amplification assays for viral DNA and RNAs. Plasma pools with a viral load in the range of 6.00 x 10(3)-8.96 x 10(4) geq/ml did not show infectivity when inoculated into KU812Ep6 cells. Medium-high titres of IgG antibodies anti-B19 were detectable in all the plasma pools and the neutralising activity associated with specific IgG anti-B19 may explain the lack of infectivity of plasma pools contaminated with a low viral load. In conclusion, in situ hybridisation and amplification assays for viral DNA and RNAs in KU812Ep6 cells inoculated with plasma pools can be valid assays to test for the presence of infectious virus in the production of B19-safe material.

Analysis of B19 virus contamination in plasma pools for manufacturing, by using a competitive polymerase chain reaction assay

BACKGROUND AND OBJECTIVES

The presence of B19 virus in blood poses a risk of transmission of the virus via blood or blood products. Screening processes for manufacturing should be aimed at achieving production plasma pools with B19 virus contamination levels below 104 genome equivalents/ml (geq/ml) in order to prevent transmission of infection through plasma derivatives.

MATERIALS AND METHODS

The suitability of a competitor plasmid as an internal analytical standard for the detection of B19 virus in plasma pools was assessed by using a competitive polymerase chain reaction (PCR) assay. Seventy-five plasma pools, each consisting of 960 single donations, were analysed for B19 virus contamination following a lysis treatment.

RESULTS

The amount of competitor plasmid in the competitive PCR assay established, with good accuracy, a threshold value for discrimination of the viral load in plasma pools. Analysis of samples from plasma pools showed that 12% of pools were contaminated with B19 virus at levels above the set threshold value.

CONCLUSIONS

The competitive PCR assay developed proved to be effective for discrimination of the B19 virus contamination level in screening of plasma pools for manufacturing.