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Large-scale screening for human parvovirus B19 DNA in clinical specimens by dot blot hybridization and polymerase chain reaction.

Large-scale screening for human parvovirus B19 (B19) DNA in serum samples was carried out by both dot blot hybridization and the polymerase chain reaction (PCR). Dot blot hybridization was undertaken with a digoxigenin-labeled DNA probe. Serum samples from four patients were pooled and tested by a dot blot hybridization assay. When a dot was positive, each of the four samples was tested separately to identify the positive sample. The PCR template was the DNA extracted from mixed serum samples from 10 patients. When B19 DNA was positive by PCR, each of the ten samples was tested separately. A total of 7,969 serum samples were tested by dot blot hybridization and 15 samples (11 patients) were positive for B19 DNA; 7,038 serum samples were tested by PCR and 71 samples (50 patients) were positive. Large-scale screening for B19 DNA by PCR suggested a broader spectrum of clinical manifestations associated with B19 infection.

Base Sequence↗

Antibody response to B19 parvovirus VP1 and VP2 linear epitopes in patients with haemophilic arthritis.

Parvovirus B19 infection occurs very frequently in patients with haemophilia on account of its transmission with plasma derivatives. In order to achieve a more defined serological pattern for the study of the role of B19 infection in haemophilic arthritis, 53 serum samples from 37 patients with haemophilic arthritis were investigated for the presence of IgG immune response against B19 VP2 and VP1 linear epitopes and VP2 conformational antigen compared to the serological reactivity against B19 NS1 and to the presence of B19 DNA in the synovial membranes. An IgG immune response against VP1 and VP2 linear epitopes was detected by immunoblot assay using recombinant proteins expressed in Escherichia coli. Specific IgG against VP2 and VP1 linear epitopes were present in 84.90 and 92.45% of haemophilic arthritis patients and in 28.0 and 64.0% of the controls (P<0.001) respectively. All 53 sera of the haemophiliacs (100%) and 66.0% of the controls (P<0.001) were IgG positive and IgM negative against VP2 structural epitopes. Specific IgG against VP2 linear epitopes, which are a serological marker of active or very recent B19 infection, proved to be significantly associated with the presence of anti-NS1 antibodies and with the presence of B19 DNA in synovial tissue in patients with haemophilic arthritis. In conclusion, in these patients the presence of B19 IgG anti-VP2 linear epitopes, in absence of IgM anti-VP2 structural antigens, can be a useful serological marker to diagnose active, recent or persistent B19 infection.

Adolescent↗

Evidence for persistence of parvovirus B19 DNA in livers of adults.

Recent studies have suggested a pathogenic role of human parvovirus B19 (B19) in the development of acute fulminant liver failure in children. The hypothesis was based on the detection of B19 DNA in 8 of 10 explanted livers of children requiring liver transplantation. In the present study, explanted livers from 43 adults selected at random undergoing orthotopic liver transplantation for various reasons were examined. Pre-transplant sera were available from 40 patients of whom 35 (88%) were anti-B19 IgG-seropositive. All but one serum were negative for anti-B19 IgM antibody. By polymerase chain reaction, B19 DNA was detected in the livers of 15/35 (43%) anti-B19 IgG-positive patients, in 2/3 livers of patients with unknown anti-B19 antibody status, and in the initial transplant of an anti-B19 IgG-positive patient who underwent liver retransplantation, and whose own liver was negative for B19 DNA. In a second study group, liver and bone marrow samples from 23 autopsied adults selected at random were tested. Serum specimens were available from 22 individuals, of whom 17 (77%) were anti-B19 IgG-seropositive. All sera were negative for anti-B19 IgM antibody. B19 DNA was detected in the livers of 4/17 (24%) anti-B19 IgG-positive individuals, three of whom had also B19 DNA in their bone marrow. This is the first report demonstrating that B19 DNA is frequently present in livers of anti-B19 seropositive adults suggesting persistence of B19 in the liver. Further studies are needed to address whether B19 is an innocent bystander in the liver or whether the presence of B19 in liver is of biological and clinical significance.

Adult↗

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.

B-Lymphocytes↗

Aberrant cellular immune responses in humans infected persistently with parvovirus B19.

A subset of parvovirus B19 (B19) infected patients retains the infection for years, as defined by detection of B19 DNA in bone marrow. Thus far, analysis of B19-specific humoral immune responses and viral genome variations has not revealed a mechanism for the absent viral clearance. In this study, ex-vivo cellular immune responses were assessed by enzyme linked immunospot assay mounted against the majority of the translated viral genome. Compared to seropositive healthy individuals, individuals with B19 persistence (2-8 years) showed larger number of responses to the structural proteins (P = 0.0022), whereas responses to the non-structural protein were of lower magnitude (P = 0.012). These observations provide the first findings of immunological discrepancies between individuals with B19 persistence and healthy individuals, findings that may reflect both failed immunity and antigenic exhaustion.

Adult↗

Correlates of placental infection with cytomegalovirus, parvovirus B19 or human herpes virus 7.

Vertical transmission of viruses is an important cause of morbidity in the fetus and neonate. Placental viral infection indicates risk of vertical transmission, but not always transmission to, or disease of the fetus. Specimens from mothers and babies from three groups-two prospective and one retrospective cohort-were tested for pathogens of teratogenic potential using multiplex PCR. Placental infection was present in 13% of the 105 samples collected. Assessment of the prospective cohorts showed cytomegalovirus (CMV) detected in 4% of placentae from unselected women, parvovirus B19 in 1% and Ureaplasma parvum in 1% of placentae. In a retrospective cohort of women at high risk of transmitting congenital infection due to seroconversion during pregnancy, miscarriage or stillbirth, CMV was detected in 64% and human herpes virus type 7 in 9% of placentae. Of 14 PCR-positive placentae, two were associated with the birth of a living symptomatic infant, two with stillbirth, one with miscarriage, and two with elective terminations of pregnancy. Directed laboratory assessment of women at high risk of transmitting congenital infection, on the basis of clinical or laboratory markers, is important for accurate diagnosis of adverse outcomes of pregnancy. However, routine screening for viruses in the placentae from women with a low-risk serological profile for transmitting congenital infection is unlikely to result in significant numbers of additional diagnoses and is confounded by inadequacy of current diagnostic methods. The major pathogen detected in all cases of placental infection associated with fetal death was human CMV.

Adolescent↗

Genetic drift of parvovirus B19 is found in AIDS patients with persistent B19 infection.

It is generally thought that parvovirus B19 is stable genetically. Consistently, genetic drift has not been found in patients with persistent B19 infection. In this report, longitudinal genetic changes in NS1 and VP1 gene of B19 isolates from three AIDS patients with persistent B19 infection were studied. One of the three patients was not treated with highly active anti-retroviral therapy (HAART). B19 viral DNA from these patients was amplified by polymerase chain reaction (PCR) and then sequenced directly. A single genetic change was found in the B19 isolate obtained from the patient not treated with HAART on Day 10 after intravenous immunoglobulin (IVIG) treatment. The nucleotide sequences of B19 isolated from this patient, then remained unchanged over a period of 11 months. Analysis of NS1 clones derived from his longitudinal viral isolates showed the existence of quasi-species but genetic drift was not found. One of the other two patients treated with HAART experienced treatment failure; he was later treated with mega-HAART. In contrast to the genetic stability of B19 isolates from the patient not treated with HAART, multiple genetic changes were discovered in the viral isolates from the two other patients after HAART and mega-HAART, respectively. Through analysis of B19 clones, the frequency of clones containing these mutations confirmed the genetic drift. Nucleotide substitutions seen in VP2 gene of isolates with genetic drift from both patients were all non-conserved, suggesting that they are positively selected.

AIDS-Related Opportunistic Infections↗

Fatal course of parvovirus B19-associated myocarditis in a female liver transplant recipient.

Acute myocarditis may result in severe hemodynamic compromise with fatal outcome. Furthermore, recent studies suggest myocarditis as a major cause of sudden unexpected death. A variety of cardiotropic viral, rickettsial, and bacterial infectious agents have been identified to date. Parvovirus B19 (PVB19) is usually benign in childhood, but it may also cause death due to myocarditis. We present here the case of an adult female who presented with fatigue, dyspnea on exertion, and orthostatic dizziness 8 months after successful liver transplantation. Cardiologic work-up, including left ventricular endomyocardial biopsy, revealed acute myocarditis secondary to PVB19. Since no specific therapy for this virus is available, the patient was treated symptomatically with an angiotensin-converting enzyme inhibitor plus beta-blocker and diuretics. After a period of stabilization, new-onset rapid atrial fibrillation caused acute low-output syndrome within 14 days after hospital admission. The patient eventually died because of refractory cardiogenic shock. In conclusion, to our knowledge this is the first report of PVB19-induced myocarditis confirmed by detection of viral genome in myocardium in a liver transplant recipient.

Acute Disease↗

B19 parvovirus infection in children with malignant solid tumors receiving chemotherapy.

Two children with rhabdomyosarcoma developed severe anemia following chemotherapy; anemia was more severe compared to that observed following earlier chemotherapy cycles. While one patient had a brisk reticulocytosis, the other had no demonstrable reticulocytes. Both patients had evidence of acute B19 parovirus infection and subsequently developed appropriate antibody response. A diagnosis of B19 parvovirus infection should be considered in any patient who develops persistent or severe anemia while on chemotherapy.

Acute Disease↗

Human parvovirus B19 DNA is not detected in Guthrie cards from children who have developed acute lymphoblastic leukemia.

BACKGROUND: There has been much speculation about the cause of childhood acute lymphoblastic leukemia (ALL). It has been suggested, on the basis of findings in epidemiological studies, that ALL may be initiated by an in utero infection of the fetus. The human parvovirus B19 (B19) is etiologically related to human diseases, including erythema infectiosum and aplastic crisis, but it has not yet been considered to be involved in the development of ALL. Therefore, the aim of this study was to investigate, whether prenatal B19 infection could still be indirectly correlated with the development of childhood ALL. PROCEDURES: Fifty-four Guthrie cards, collected at 3-5 days of age, from Swedish children who subsequently developed ALL, as well as from 50 healthy controls, were investigated by nested PCR for the presence of B19 DNA. RESULTS: B19 DNA was not detected in any of the Guthrie cards from ALL patients or from healthy controls, although all tested samples had amplifiable cellular DNA as confirmed by an HLA DQ specific PCR. CONCLUSION: B19 DNA was not found in any of the Guthrie cards from children who later developed ALL or in the healthy controls. These findings suggest that it is less likely that childhood ALL is associated with an in utero in fection with B19.

Adolescent↗

Life threatening parvovirus B19 and herpes simplex virus associated acute myocardial dysfunction in a child with homozygous sickle cell disease.

Human parvovirus (HPV) B19, a common infection, frequently causes transient red cell aplasia in children with hemolytic anemia, such as sickle cell disease (SCD). It was considered to be a self-limited condition, easily treated with blood transfusion. However, acute splenic sequestration, acute chest syndrome, nephrotic syndrome, and stroke have been reported in SCD patients following HPV B19 infection. We report a 3-year-old child with SCD who developed fulminant myocarditis following HPV B19-related aplastic crisis. The diagnosis of myocarditis should be considered in a patient with hemolytic anemia with an infection with HPV B19 who develops signs of cardiopulmonary failure despite correction of anemia.

Anemia, Sickle Cell↗

Screening maternal serum alpha-fetoprotein levels and human parvovirus antibodies.

The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 cases samples--from women with MSAFP levels greater than 3.0 multiples of the median (MOM) and pregnancies that ended in fetal loss--and 44 matched control samples--from women with MSAFP levels greater than 0.4 and less than 2.2 MOM and live births at term--were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio = 0.77, 95 per cent confidence interval 0.28-2.11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing.

Adult↗

Neurological manifestations of human parvovirus B19 infection.

Since its discovery, human parvovirus B19 has been linked with a broad spectrum of clinical syndromes. An aetiological role for the virus has been confirmed in erythema infectiosum, transient aplastic crisis, persistent infection manifesting as pure red cell aplasia in immunocompromised persons, non-immune hydrops fetalis and arthritis. Less commonly recognised, but receiving increasing attention recently, are the neurological manifestations, a variety of which have been described in patients with either clinically diagnosed or laboratory confirmed B19 infection. The purpose of this review is to summarise present knowledge of B19, its known and potential pathogenic mechanisms and its association with human diseases, particularly those with neurological manifestations. The outcome of the review supports an aetiological role of the virus in neurological disease. However, the pathogenesis remains unknown and elucidating this is a priority.

Erythema Infectiosum↗

Parvovirus B19 and the pathogenesis of anaemia.

Human parvovirus B19 (B19) infection causes human bone marrow failure, by affecting erythroid-lineage cells which are well-known target cells for B19. The anaemia induced by B19 infection is of minor clinical significance in healthy children and adults, however, it becomes critical in those afflicted with haemolytic diseases. This condition is called transient aplastic crisis, and the pathogenesis is explained by the short life-span of red blood cells. Similarly, fetuses are thought to be severely affected by B19-intrauterine infection in the first and second trimester, as the half-life of red blood cells is apparently shorter than RBC at the bone marrow haematopoietic stage. On the other hand, B19 is also the causative agent of persistent anaemia in immunocompromised patients, transplant recipients and infants. The deficiencies of appropriate immune responses to B19 impair viral elimination in vivo, which results in enlargement of B19-infected erythroid-lineage cells. The B19-associated damage of erythroid lineage cells is due to cytotoxicity mediated by viral proteins. B19-infected erythroid-lineage cells show apoptotic features, which are thought to be induced by the non-structural protein, NS1, of B19. In addition, B19 infection induces cell cycle arrests at the G(1) and G(2) phases. The G(1) arrest is induced by NS1 expression prior to apoptosis induction in B19-infected cells, while the G(2) arrest is induced not only by infectious B19 but also by UV-inactivated B19, which lacks the ability to express NS1. In this review, we address the clinical manifestations and molecular mechanisms for B19-induced anaemia in humans and a mouse model, and of B19-induced cell cycle arrests in erythroid cells.

Adult↗

Chemiluminescent immunoperoxidase assay for the dot blot hybridization detection of Parvovirus B19 DNA using a low light imaging device.

A new synthesized stable trifluoro-substituted acridan (2',3',6'-trifluorophenyl 10-methylacridan-9-carboxylate known as Lumigen PS-3) has been applied as chemiluminescent substrate of the horseradish peroxidase (HRP) enzyme (neutral isoenzyme C) in a dot blot hybridization assay for the detection of B19 Parvovirus DNA. The dot blot hybridization assay uses digoxigenin-labeled DNA probes which are immunoenzymatically revealed by anti-digoxigenin Fab fragments conjugated with HRP. The results obtained using PS-3 reagent or the luminol-based enhanced chemiluminescence detection system (ECL Amersham and Renaissance DuPont NEN kits) were compared. A high-performance, low-intensity-light imaging luminograph apparatus to collect light emission was used. The detection systems using the different chemiluminescent substrates gave sensitive and reproducible results for calibration graphs, with high precision (relative standard deviation 5-18%). With the chemiluminescent assay it was possible to detect 0.5, 1, or 2 pg of target homologous DNA, using PS-3, ECL, or Renaissance (RE) reagents, respectively, while colorimetry had a detection limit of 5 pg. When clinical samples were analyzed the positive reference sera and the PCR-positive products gave light emissions with values higher than background at 2 sigma level, while the negative samples gave a signal comparable to the background noise for all chemiluminescent reagents. The PS-3 reagent detected one more dilution (1/256) than ECL and RE (1/128) of positive reference sera.

DNA, Viral↗

Canine parvovirus capsid structure, analyzed at 2.9 A resolution.

The DNA-containing capsid of canine parvovirus (CPV) is analyzed following atomic refinement at 2.9 A resolution. The capsid contains 60 copies of the capsid protein related by icosahedral symmetry. The atomic model has been extended from the first residue (Gly37) of the unrefined 3.25 A structure towards the N terminus. The electron density shows that approximately 87% of the capsid proteins have N termini on the inside of the capsid, but for approximately 13%, the polypeptide starts on the outside and runs through one of the pores surrounding each 5-fold axis, explaining apparently conflicting antigenic data. Analysis of potential hydrogen bonds reveals approximately 50% more secondary structure than previously apparent. Most of the additional secondary structure are in the 71 and 221 residue-long loop insertions between beta-strands E and F and G and H, forming subunit-bridging sheets that likely add specificity to assembly interactions. Structural analysis of the extensive subunit interactions around the 3-fold axes shows that assembly is a multistep process with loops intertwining following initial contact. Estimated free energies of association suggest that the formation of 3 and 5-fold contacts likely takes precedence over 2-fold interactions. Energies for initial association into trimers or pentamers would be similar, but the intertwining of loops about the 3-fold axis adds an additional large activation barrier to dissociation. Analysis of the surfaces of the assembled capsid shows a surprising lack of basic amino acids that might have been expected to interact with the negatively charged phosphoribose backbone of the DNA. Instead, uncharged polar and van der Waal's interactions predominate in the packaging of single-stranded DNA into the capsid.

Amino Acid Sequence↗

Host range and variability of calcium binding by surface loops in the capsids of canine and feline parvoviruses.

Canine parvovirus (CPV) emerged in 1978 as a host range variant of feline panleukopenia virus (FPV). This change of host was mediated by the mutation of five residues on the surface of the capsid. CPV and FPV enter cells by endocytosis and can be taken up by many non-permissive cell lines, showing that their host range and tissue specificity are largely determined by events occurring after cell entry. We have determined the structures of a variety of strains of CPV and FPV at various pH values and in the presence or absence of Ca(2+). The largest structural difference was found to occur in a flexible surface loop, consisting of residues 359 to 375 of the capsid protein. This loop binds a divalent calcium ion in FPV and is adjacent to a double Ca(2+)-binding site, both in CPV and FPV. Residues within the loop and those associated with the double Ca(2+)-binding site were found to be essential for virus infectivity. The residues involved in the double Ca(2+)-binding site are conserved only in FPV and CPV. Our results show that the loop conformation and the associated Ca(2+)-binding are influenced by the Ca(2+) concentration, as well as pH. These changes are correlated with the ability of the virus to hemagglutinate erythrocytes. The co-localization of hemagglutinating activity and host range determinants on the virus surface implies that these properties may be functionally linked. We speculate that the flexible loop and surrounding regions are involved in binding an as yet unidentified host molecule and that this interaction influences host range.

Amino Acid Substitution↗

Polymerase chain reaction for synthesis of digoxigenin-labelled DNA probe: application to parvovirus B19 and to polyomavirus BK.

A one-step polymerase chain reaction (PCR) was used to synthesize a digoxigenin-labelled probe, 176 bp long, for the detection of human polyomavirus BK (BKV). A 104 bp-long digoxigenin-labelled probe was generated by 'nested' PCR for the detection of human parvovirus B19 (virus B19). In both cases the whole viral genome was used as template. Different amounts of template as well as different percentages of dTTP substituted by digoxigenin-dUTP (dig-dUTP) in the reaction mixture were employed in order to determine the optimum conditions for the labelled probe synthesis. The sensitivity and the specificity of these PCR-produced probes, together with the simplicity and the reduced time scale of the procedure, suggest the potential of this technique as an additional method for preparing non-radioactive molecular probes for routine diagnosis of viral infections.

BK Virus↗