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

Prevalence and Quantity of Parvovirus B19 DNA Among Blood Donors from a Regional Blood Center in Turkey

OBJECTIVE

Parvovirus B19 causes a range of diseases and morbidity in humans and is transmissible by transfusion of blood, blood components and plasma derivatives. The objective of the study was to investigate the prevalence and quantity of B19 DNA among blood donors.

METHOD

Totally 1053 samples were collected from March to July 2016 at a blood bank for detection of Parvovirus B19 DNA and serological status of blood donors. Testing of the presence of viral DNA was performed by a quantitative real-time PCR with a 101 copies/ml detection limit. All DNA positive and randomly selected 267 samples were tested for the presence of anti-B19 IgM and IgG by ELISA.

RESULTS

Age distribution of donors was between 18-64; mean age was 27 and median was 23. Among the 1053 samples, 5 (0.47%) had PB19 DNA. All PB19 DNA positive donations had both B19 IgM and IgG antibodies. The DNA level for positive donations were between 0.9 × 102 to 3.1 × 104 copies/ml. IgG and IgM were present in 59.9% (160/267) and 0,74% (2/267) respectively among the healthy donors without PB19 DNA.

CONCLUSION

Detected DNA concentration was less than 105 copies/ml. The presence of IgM in low level PB19 DNA positive donors may indicate that there might be a risk in transmission of PB19 to particularly immunosuppressed recipients. The clinical follow-up of blood donation with low level of PB19DNA should be considered to answer the questions about blood safety.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Competitive PCR-ELISA protocols for the quantitative and the standardized detection of viral genomes

Competitive PCR-ELISA combines competitive PCR with an ELISA to allow quantitative detection of PCR products. It is based on the inclusion of an internal standard competitor molecule that is designed to differ from the target by a short sequence of nucleotides. Once such a competitor molecule has been designed and constructed, target and competitor sequences are concurrently PCR-amplified, before hybridization to two different specific probes and determination of their respective OD values by ELISA. The target can be quantified in relation to a titration curve of different dilutions of the competitor. The competitor can alternatively be used at a unique optimal concentration to allow for standardized detection of the target sequence. PCR-ELISA can be performed in 1 d in laboratories without access to a real-time PCR thermocycler. This technique is applied in diagnostics to monitor the course of infections and drug efficacy. Competitive PCR-ELISA protocols for the quantitative and for the standardized detection of parvovirus B19 are detailed here as an example of the technique.

Dose-by-dose virological and hematological responses to intravenous immunoglobulin in an immunocompromised patient with persistent parvovirus B19 infection

A 42-year-old male with stage IV mantle cell lymphoma received chemotherapy and autologous peripheral blood stem cell transplantation. He developed pancytopaenia, and bone marrow examination indicated a parvovirus B19 (PVB 19)-induced red cell aplasia, confirmed by virological tests. Multiple doses of intravenous immunoglobulin (IVIG) were given over the following months, with blood samples being taken after each dose for quantitative PVB 19 DNA and hematological testing to assess the response. Each dose of IVIG produced a 1-3 log(10) drop in PVB 19 DNA levels. Eventually, after the fifth dose of IVIG, the PVB 19 DNA was reduced to <10 copies/ml serum, with a gradual improvement in his hematological parameters. This report demonstrates how close monitoring of the virological and hematological response to IVIG therapy for persistent PVB 19 infection in an immunocompromised patient can optimize the usage of this relatively expensive, and sometimes scarce intervention.

Different behavior of erythrovirus B19 and torquetenovirus in response to a single step of albumin purification

BACKGROUND

The safety of human serum albumin (HSA) is of special interest with respect to virus transmission because of the wide use of this blood product as a therapeutic agent and also, added to other products, as an excipient or a stabilizer. Conflicting data are reported concerning HSA contamination by small, naked viruses such as the erythrovirus B19 (B19V) and the anellovirus torquetenovirus (TTV). This study has been performed to assess the effect of the HSA purification procedures on the viral contamination.

STUDY DESIGN AND METHODS

Known concentrations of B19V and TTV virus were spiked in raw Fraction V, the starting material from fractionated human plasma for HSA purification, which was subsequently submitted to the depth filtration procedure. After spiking, B19V and TTV genome copies were determined by real-time quantitative polymerase chain reaction assays in the mixture at the end of Fraction V dissolution, to determine the virus concentration achieved, in the HSA solution after the filtration step, in the filtered postwashing fluid, and in the supernatant of resuspended Celite.

RESULTS

B19V was completely adsorbed by the Celite used as a filter aid in the depth filtration process and was thus undetectable in the resulting HSA-containing fraction. In contrast, in 2 out of 3 experiments, TTV was detected in all samples.

CONCLUSION

The different behavior of the two viruses might be a reflection of their different surface charge.

Exposure of hematologic patients to parvovirus B19 as a contaminant of blood cell preparations and blood products

BACKGROUND

Patients with hematologic malignancies often require blood products, and parvovirus B19 is known to be transmitted by this route. Primary infection with parvovirus B19 shows a wide variety of disease manifestation. In immunocompromised patients, symptoms are severe and viral clearance is delayed or missing.

STUDY DESIGN AND METHODS

A total of 2123 blood products given to all patients of a hematologic ward over a period of 6 months were retrospectively examined for the presence of parvovirus B19 DNA by an in-house real-time polymerase chain reaction (PCR; TaqMan). Patients who had received B19 DNA-positive blood products were further investigated serologically and by PCR for the presence of parvovirus B19 antibodies and DNA.

RESULTS

Twenty-one (1%) of 2123 blood products tested positive for the presence of B19 DNA (2% of pooled products, 0.7% of single-donor products, and 17.6% of allogeneic peripheral blood progenitor cells), the median viral load was 700 genome equivalents per mL. During the study period, 114 patients were treated on the ward, and 14 (12%) of them received B19 DNA-positive blood components. None of them developed symptoms of an acute B19 infection, although one had a short low-level viremia.

CONCLUSIONS

Although B19 DNA was detected in 1 percent of blood products given to hematologic patients, the exposure of 12 percent of patients did not result in symptomatic infections.

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.

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.