Impact of chemiluminescent enzyme immunoassay screening for human parvovirus B19 antigen in Japanese blood donors.

BACKGROUND: To reduce the risk of human parvovirus B19 (B19V) transmission through contaminated blood for transfusion and plasma-derived products, the Japanese Red Cross (JRC) Blood Centers introduced B19V antigen screening by chemiluminescent enzyme immunoassay (CLEIA-B19V) in 2008. STUDY DESIGN AND METHODS: Donor samples that were positive by CLEIA-B19V screening were tested for B19V DNA. The sensitivity of CLEIA-B19V was tested using samples of all three genotypes and B19V DNA-positive donations. B19V DNA-positive donations and pooled plasma were quantitatively assayed for B19V DNA. B19V DNA-positive donations were phylogenetically analyzed by polymerase chain reaction direct sequencing. RESULTS: The sensitivity of CLEIA-B19V was inferred to be approximately 6.3 log IU/mL with the genotype samples and 6.4 log IU/mL with B19V DNA-positive donor samples. Of 417 CLEIA-B19V-positive samples from 1,035,560 donations in Hokkaido, Japan, 101 were positive for B19V DNA. The 198 strains of B19V DNA-positive donations in Hokkaido over the past 15 years clustered exclusively with Genotype 1. After introduction of CLEIA-B19V, the viral load for B19V DNA in all 772 pooled plasma for fractionation from donors in nationwide Japan did not exceed 4 log IU/mL. CONCLUSION: CLEIA-B19V can detect all three genotypes of B19V (viral load >6.3 log IU/mL) and limit the viral load (<4 log IU/mL) in pooled plasma, and thus such screening has further reduced the risk of transfusion-transmitted B19V infection. These results show that CLEIA-B19V screening at the JRC Blood Centers can be an alternative approach to comply with recommendations regarding B19V in the United States and Europe.

Persistent growth of a human plasma-derived hepatitis C virus genotype 1b isolate in cell culture.

HCV (hepatitis C virus) research, including therapeutics and vaccine development, has been hampered by the lack of suitable tissue culture models. Development of cell culture systems for the growth of the most drug-resistant HCV genotype (1b) as well as natural isolates has remained a challenge. Transfection of cultured cells with adenovirus-associated RNA(I) (VA RNA(I)), a known interferon (IFN) antagonist and inhibitor of dsRNA-mediated antiviral pathways, enhanced the growth of plasma-derived HCV genotype 1b. Furthermore, persistent viral growth was achieved after passaging through IFN-alpha/beta-deficient VeroE6 cells for 2 years. Persistently infected cells were maintained in culture for an additional 4 years, and the virus rescued from these cells induced strong cytopathic effect (CPE). Using a CPE-based assay, we measured inhibition of viral production by anti-HCV specific inhibitors, including 2'-C-Methyl-D-Adenosine, demonstrating its utility for the evaluation of HCV antivirals. This virus constitutes a novel tool for the study of one of the most relevant strains of HCV, genotype 1b, which will now be available for HCV life cycle research and useful for the development of new therapeutics.

Parvovirus B19 infection transmitted by transfusion of red blood cells confirmed by molecular analysis of linked donor and recipient samples.

BACKGROUND: Extremely high viremic levels of parvovirus B19 (B19V) can be found in acutely infected, but asymptomatic donors. However, reports of transmission by single-donor blood components are rare. In this prospective study, paired donor-recipient samples were used to investigate the transfusion risk. STUDY DESIGN AND METHODS: Posttransfusion plasma or blood samples from recipients were tested for B19V DNA by polymerase chain reaction, generally at 4 and 8 weeks, and for anti-B19V immunoglobulin (Ig)G by enzyme immunoassay, at 12 and 24 weeks. To rule out infection unrelated to transfusion, pretransfusion samples and linked donor's samples for each B19V DNA-positive recipient were assayed for B19V DNA and anti-B19V IgG and IgM. To confirm transmission, sequencing and phylogenetic analysis were performed. RESULTS: A total of 14 of 869 (1.6%) recipients were B19V DNA positive, but only 1 of 869 (0.12%; 95% confidence interval, 0.0029%-0.6409%) was negative for B19V DNA and anti-B19V IgG before transfusion and seroconverted posttransfusion. This newly infected patient received 5 × 10(10) IU B19V DNA in one red blood cell (RBC) unit from an acutely infected anti-B19V-negative donor in addition to RBCs from three other donors that cumulatively contained 1320 IU of anti-B19V IgG. DNA sequencing and phylogenetic analysis showed that sequences from the linked donor and recipient were identical (Genotype 1), thus establishing transfusion transmission. CONCLUSIONS: The 0.12% transmission rate documented here, although low, could nonetheless result in hundreds or thousands of infections annually in the United States based on calculated confidence limits. Although most would be asymptomatic, some could have severe clinical outcomes, especially in neonates and those with immunocompromised or hemolytic states.

West Nile virus infection in plasma of blood and plasma donors, United States.

This study investigated the association of ongoing West Nile virus (WNV) infections with neutralizing antibody titers in US plasma-derived intravenous immune globulin released during 2003-2008. Titers correlated closely with the prevalence of past WNV infection in blood donors, with 2008 lots indicating a prevalence of 1%.

A linked donor-recipient study to evaluate parvovirus B19 transmission by blood component transfusion.

Parvovirus B19V infection can be a serious infection for hematology patients with underlying hemolysis or compromised erythropoiesis syndromes. Although case reports of B19V transmission by blood component transfusion (as contrasted to manufactured plasma derivatives) are rare, no studies have systematically determined a rate of transmission to recipients transfused with B19V DNA-positive components. We used a linked donor and recipient repository and a sensitive, quantitative B19V DNA polymerase chain reaction (PCR) assay to assess such transmission in B19V-susceptible (ie, anti-B19V immunoglobulin G [IgG] negative) recipients. We assessed 112 B19V DNA-positive components from 105 donors (of 12 529 tested donations) transfused into a population of surgical patients with a pretransfusion B19V IgG seroprevalence of 78%. We found no transmission to 24 susceptible recipients from transfusion of components with B19V DNA at concentrations less than 10(6) IU/mL (upper 95% confidence interval, 11.7%). We found an anamnestic IgG response in one pretransfusion seropositive recipient transfused with a component containing greater than 10(10) IU/mL B19V DNA. These findings show either that transmission from components with less than 10(6) IU/mL does not occur, or, if it does, it is an uncommon event. These data do not support the need to routinely screen blood donations with a sensitive B19V DNA nucleic acid assay.

A simple and rapid Hepatitis A Virus (HAV) titration assay based on antibiotic resistance of infected cells: evaluation of the HAV neutralization potency of human immune globulin preparations.

BACKGROUND: Hepatitis A virus (HAV), the causative agent of acute hepatitis in humans, is an atypical Picornaviridae that grows poorly in cell culture. HAV titrations are laborious and time-consuming because the virus in general does not cause cytopathic effect and is detected by immunochemical or molecular probes. Simple HAV titration assays could be developed using currently available viral construct containing selectable markers. RESULTS: We developed an antibiotic resistance titration assay (ARTA) based on the infection of human hepatoma cells with a wild type HAV construct containing a blasticidin (Bsd) resistance gene. Human hepatoma cells infected with the HAV-Bsd construct survived selection with 2 microg/ml of blasticidin whereas uninfected cells died within a few days. At 8 days postinfection, the color of the pH indicator phenol red in cell culture media correlated with the presence of HAV-Bsd-infected blasticidin-resistant cells: an orange-to-yellow color indicated the presence of growing cells whereas a pink-to-purple color indicated that the cells were dead. HAV-Bsd titers were determined by an endpoint dilution assay based on the color of the cell culture medium scoring orange-to-yellow wells as positive and pink-to-purple wells as negative for HAV. As a proof-of-concept, we used the ARTA to evaluate the HAV neutralization potency of two commercially available human immune globulin (IG) preparations and a WHO International Standard for anti-HAV. The three IG preparations contained comparable levels of anti-HAV antibodies that neutralized approximately 1.5 log of HAV-Bsd. Similar neutralization results were obtained in the absence of blasticidin by an endpoint dilution ELISA at 2 weeks postinfection. CONCLUSION: The ARTA is a simple and rapid method to determine HAV titers without using HAV-specific probes. We determined the HAV neutralization potency of human IG preparations in 8 days by ARTA compared to the 14 days required by the endpoint dilution ELISA. The ARTA reduced the labour, time, and cost of HAV titrations making it suitable for high throughput screening of sera and antivirals, determination of anti-HAV antibodies in human immune globulin preparations, and research applications that involve the routine evaluation of HAV titers.

Hepatitis C virus epitope-specific neutralizing antibodies in Igs prepared from human plasma.

Neutralizing antibodies directed against hepatitis C virus (HCV) are present in Igs made from anti-HCV-positive plasma. However, these HCV-specific Igs are largely ineffective in vivo. The mechanism for the poor effectiveness is currently unknown. We hypothesize that the presence of nonneutralizing antibodies in HCV-specific Igs interferes with the function of neutralizing antibodies, resulting in the reduction or blockage of their effect. In the present study, we identified at least two epitopes at amino acid residues 412-419 (epitope I) and 434-446 (epitope II), located downstream of the hypervariable region I within the HCV E2 protein. We demonstrated that epitope I, but not epitope II, was implicated in HCV neutralization and that binding of a nonneutralizing antibody to epitope II completely disrupted virus neutralization mediated by antibody binding at epitope I. The dynamic interaction between nonneutralizing and neutralizing antibodies may thus play a key role in determining the outcomes of HCV infection. Further exploration of this interplay should lead to a better understanding of the mechanisms of neutralization and immune escape and may indicate pathways for the manufacture of an effective HCV-specific Ig product for immune prophylaxis of HCV infection.

Parvovirus B19 DNA in Factor VIII concentrates: effects of manufacturing procedures and B19 screening by nucleic acid testing.

BACKGROUND: Parvovirus B19 (B19) is a common contaminant, especially in coagulation factors. Because of B19 transmission by pooled plasma, solvent/detergent treated in 1999, some fractionators initiated minipool nucleic acid testing (NAT) to limit the B19 load in manufacturing pools. In this study, the extent of B19 DNA contamination in commercial Factor VIII concentrates, that is, antihemophilic factor (human) (AHF), manufactured before and after B19 NAT screening was implemented, was determined. STUDY DESIGN AND METHODS: A total of 284 lots representing six AHF products made during 1993 to 1998 and 2001 to 2004 were assayed for B19 DNA by an in-house NAT procedure. Anti-B19 immunoglobulin G (IgG) was also measured. RESULTS: Most lots made during 1993 to 1998 had detectable B19 DNA. The prevalence ranged from 56 to 100 percent and appeared to differ between manufacturers. The highest level of B19 DNA found was 10(6) genome equivalents (geq or international units [IU]) per mL. Forty percent of the lots tested contained 10(3) geq (IU) per mL. In comparison, both prevalence and levels in source plasma-derived AHF products made in 2001 to 2004 were lower. Both, however, remained unchanged in the recovered plasma-derived product because B19 NAT screening had not been implemented. Only an intermediate-purity AHF product was positive for the presence of anti-B19 IgG. CONCLUSION: The prevalence and levels of B19 DNA in AHF prepared from B19 NAT unscreened plasma were high but varied among products with different manufacturing procedures. B19 NAT screening of plasma effectively lowered the B19 DNA level in the final products and in the majority of cases rendered it undetectable and hence potentially reduced the risk of B19 transmission.

Quantification of hepatitis B virus genomes and infectivity in human serum samples.

BACKGROUND: Hepatitis B virus (HBV) infections are still a major health issue, with approximately 350 million people chronically infected with HBV worldwide. Information about the minimum copy number of HBV genomes required for infection would be useful as a reference for drug and vaccine development; for monitoring HBV patients during treatment; for screening of blood, organ, and tissue donors; and for regulating nucleic acid amplification assays for HBV. STUDY DESIGN AND METHODS: Serum samples from chronic carriers (hepatitis B surface antigen-positive and antibody to HBV core antigen-positive) of the three most common subtypes of HBV were studied; their infectivity titers had been evaluated previously in chimpanzees. The genotypes of the HBV samples were determined by DNA sequences and type-specific amino acids of the S gene of HBV. Copy numbers of HBV DNA were quantified by real-time TaqMan polymerase chain reaction (PCR) and by nested PCR applied to limiting dilutions. The copy number determined for each inoculum was compared with previously defined chimpanzee infectivity titers. RESULTS: The genotypes of the HBV adw, ayw, and adr inocula were A, D, and C, respectively. The concentration of HBV DNA was determined to be 5.4 x 10(9), 2.5 x 10(9), and 3.1 x 10(8) genome equivalents (geq) per mL for serum samples containing the adw, ayw, and adr, respectively. The chimpanzee infectivity titers per milliliter of these initial HBV-containing serum samples were previously determined to be 10(7.5) for adw, 10(7.5) for ayw (MS-2 strain), and 10(8) for adr. CONCLUSION: The minimal copy number of HBV DNA in chronic carriers of HBV that can infect the chimpanzee model was estimated to be from 3 to 169 geq based upon the three well-characterized inocula.

Measles-virus-neutralizing antibodies in intravenous immunoglobulins.

Measles infection induces lifelong immunity; however, wild-type infection stimulates higher levels of measles-virus-neutralizing antibodies (mnAbs) than does vaccination. Because the proportion of the donor population with vaccine-induced measles immunity is increasing, this study was conducted to determine whether this shift in demographic characteristics affects mnAb levels in contemporary lots of Immune Globulin Intravenous (Human) (IGIV). When 166 lots of 7 IGIV products manufactured between 1998 and 2003 were assayed by plaque-reduction neutralization test, there was a progressive decrease in geometric mean titers in lots manufactured between 1999 and 2002. IGIV products manufactured from recovered plasma had significantly higher titers than did those manufactured from Source Plasma, which could reflect a change in donor demographic characteristics, because Source Plasma donors tend to be much younger. A reduction in mnAbs also correlated with the loss of either IgG1 and IgG3, possibly because of certain manufacturing procedures, or bivalent antibodies (i.e., intact IgG and F(ab')2), because of fragmentation.

Neutralization epitope responsible for the hepatitis B virus subtype-specific protection in chimpanzees.

Neutralizing monoclonal antibody (BX-182) directed against the d determinant of hepatitis B virus (HBV) surface antigen protected chimpanzees from infection by HBV subtype adw but not by subtype ayw, as demonstrated by intravenously inoculating a mixture of the antibody with the respective subtype of the virus. To elucidate the mechanism underlying the subtype-specific protection, a combinatorial approach of screening random peptide phage libraries, bioinformatics, and structure analysis was used in this study to identify the neutralization epitope responsible for the observed protection. The epitope was mapped at the N terminus of the pre-S1 region of the hepatitis B surface antigen between residues 17 and 21, of which the residues Val-18/Pro-19 were critical for antibody binding. Alignment of amino acid sequences derived from diverse genetic variants of HBV revealed that the epitope was present in ad subtypes and in their corresponding genotypes A, B, C, F, and H. By contrast, this epitope was not found in a majority of ay subtypes or in genotypes D, E, and G, where the antigenic residues Val-18/Pro-19 within the epitope were replaced by Thr/Ser, Thr/Thr, or Ala/Ser, respectively, resulting in a drastic conformational change of the epitope. These data indicate that, by binding discriminately to the subtype "d" epitope in the pre-S1 region, neutralizing antibody BX-182 protects chimpanzees from HBV infection in a subtype-specific manner, suggesting a potential escape mechanism for HBV genetic variants.

International collaborative study to assess candidate reference preparations to control the level of anti-D in IVIG for use in Europe and the United States.

Regulatory requirements to control the level of anti-D in intravenous immunoglobulin (IVIG) products with European and United States (US) licences are to be introduced. A reference preparation of IVIG containing anti-D at 0.0475 IU/ml and having a nominal titre of 8 using the proposed direct haemagglutination reference method was deemed suitable to define the anti-D limit. This preparation, code 02/228, and a negative control IVIG preparation, code 02/226, were established by the World Health Organization as International Reference Reagents (IRRs). As stocks of the IRRs are limited, new larger fill stocks of positive and negative reference preparations, codes 04/132 and 04/140, respectively, were produced. The results from an international collaborative study involving 16 laboratories showed that preparations 04/132 and 04/140 are indistinguishable from the corresponding IRRs 02/228 and 02/226, respectively, using the proposed direct haemagglutination reference method. Stocks of 04/132 and 04/140 have been shared with the European Directorate for the Quality of Medicines (re-coded as 23613 and 23614, respectively) and with the Center for Biologics Evaluation and Research of the United States Food and Drug Administration (re-coded as CBER Lots 1B and 1N-b, respectively) for use as European and US Biological Reference Preparations, respectively.

Parvovirus B19 transmission by a high-purity factor VIII concentrate.

BACKGROUND: Parvovirus B19 (B19) is known to cause a variety of human diseases in susceptible individuals by close contact via the respiratory route or by transfusion of contaminated blood or blood products. In this study, whether a case of B19 transmission was causally related to the infusion of implicated lots of a solvent/detergent (S/D)-treated, immunoaffinity-purified factor VIII concentrate (antihemophilic factor [human][AHF]) was investigated. STUDY DESIGN AND METHODS: Anti-B19 (both immunoglobulin M [IgM] and immunoglobulin G [IgG]) and B19 DNA (by a nucleic acid testing [NAT] procedure) were assayed in two implicated product lots, a plasma pool, and a recipient's serum sample. Analysis of the partial B19 sequences obtained from sequencing clones or direct sequencing of the samples was performed. RESULTS: Only one of the two implicated lots was B19 DNA-positive. It contained 1.3 x 10(3) genome equivalents (geq or international units [IU]) per mL. The negative lot was derived from plasma screened for B19 DNA by NAT in a minipool format to exclude high-titer donations, whereas the positive lot was mostly from unscreened plasma. This high-purity AHF product had no detectable anti-B19 IgG. A 4-week postinfusion serum sample from a recipient, who received both lots and became ill, was positive for the presence of B19 antibodies (both IgM and IgG) as well as B19 DNA. The B19 sequences from the positive lot, its plasma pool, and the recipient's serum sample were closely related. CONCLUSION: These findings and the recipient's clinical history support a causal relationship between the implicated AHF product and B19 infection in this recipient. The seronegative patient became infected after receiving 2x10(4) IU (or geq) of B19 DNA, which was present in this S/D-treated, high-purity AHF product.

Neutralizing antibodies to hepatitis C virus (HCV) in immune globulins derived from anti-HCV-positive plasma.

The role of humoral immunity in hepatitis C virus (HCV) infections is uncertain. Nevertheless, there is increasing evidence for neutralizing antibodies to HCV in the serum or plasma of chronically infected individuals. Immune globulins prepared by ethanol fractionation of plasma had long been considered safe until a commercial immune globulin product, Gammagard, prepared from plasma from which units containing anti-HCV had been excluded, transmitted HCV to recipients. Studies suggested that the exclusion might have removed neutralizing antibodies from the plasma and hence compromised the safety of the resulting immune globulins. In the present study, by using chimpanzees and a recently validated in vitro system based on neutralization of infectious HCV pseudoparticles, we found broadly reactive neutralizing and protective antibodies in experimental immune globulin preparations made from anti-HCV-positive donations. Neutralizing antibodies were also found in Gammagard lots made from unscreened plasma that did not transmit hepatitis C but not in Gammagard lots, which were prepared from anti-HCV-screened plasma, that did transmit hepatitis C. The results provide an explanation for the mechanism by which the safety of this product was compromised. Immune globulins made from anti-HCV-positive plasma and containing broadly reactive neutralizing antibodies may provide a method of preventing HCV infection.