Comparison of 17 isolates of the human parvovirus B 19 by restriction enzyme analysis. Brief report

Genotypes of erythrovirus B19, their geographical distribution & circulation in cases with various clinical manifestations

Erythrovirus B19 (B19V) is one of the erythroviruses known to be pathogenic in humans. B19V is classified into three distinct genotypes; 1, 2 and 3, differing from each other by 2-13 per cent. Genotype 1 consists of the prototype B19V isolates, genotype 2 comprises the A6, LaLi and their related isolates while genotype 3 includes the V9- and V9-related isolates. The classification of genotype 1 into two subtypes (1A and 1B) and genotype 3 into two subtypes (3a and 3b) with an estimated nucleotide difference of about 5 per cent has been done. Predominance of genotype 1 across all the continents is seen followed by genotypes 2 and 3. There are no disease-specific genotypes. All the three genotypes have been found in symptomatic as well as asymptomatic individuals and have been reported from several countries across the world. The prevalence of genotype 2 in older populations and its absence from current circulation in Northern Europe has also been reported. The present review focuses on geographic distribution and association of genotypes of B19V with different clinical manifestations.

Global co-existence of two evolutionary lineages of parvovirus B19 1a, different in genome-wide synonymous positions

Parvovirus B19 (B19V) can cause infection in humans. To date, three genotypes of B19V, with subtypes, are known, of which genotype 1a is the most prevalent genotype in the Western world. We sequenced the genome of B19V strains of 65 asymptomatic, recently infected Dutch blood donors, to investigate the spatio-temporal distribution of B19V strains, in the years 2003-2009. The sequences were compared to B19V sequences from Dutch patients with fifth disease, and to global B19V sequences as available from GenBank. All Dutch B19V strains belonged to genotype 1a. Phylogenetic analysis of the strains from Dutch blood donors showed that two groups of genotype 1a co-exist. A clear-cut division into the two groups was also found among the B19V strains from Dutch patients, and among the B19V sequences in GenBank. The two groups of genotype 1a co-exist around the world and do not appear to differ in their ability to cause disease. Strikingly, the two groups of B19V predominantly differ in synonymous mutations, distributed throughout the entire genome of B19V. We propose to call the two groups of B19V genotype 1a respectively subtype 1a1 and 1a2.

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.

Parvovirus B19: a new emerging pathogenic agent of inflammatory cardiomyopathy

The human parvovirus B19 (PVB19), an erythrovirus causing diverse clinical manifestations ranging from asymptomatic or mild to more severe outcomes such as hydrops fetalis, is the only currently known human pathogenic parvovirus. Recently, PVB19 has been identified as a causative agent of pediatric and adult inflammatory cardiac diseases. The first hints for a possible etiopathogenetic role of the PVB19 infection and the development of cardiac dysfunction were demonstrated by molecular biology methods such as in situ hybridization (ISH) and polymerase chain reaction (PCR). In this regard, PVB19-associated inflammatory cardiomyopathy is characterized by infection of endothelial cells of small intracardiac arterioles and venules, which may be associated with endothelial dysfunction, impairment of myocardial microcirculation, and penetration of inflammatory cells in the myocardium.

B19 virus genome diversity: epidemiological and clinical correlations

Genetic analysis of parvovirus B19 has been carried out mainly to establish a framework to track molecular epidemiology of the virus and to correlate sequence variability with different pathological and clinical manifestations of the virus. A good amount of information regarding B19 virus sequence variability is available, and presently there are about 400 sequence records deposited in the nucleotide database of NCBI. A few are almost complete genomic sequences, and these allow the construction of a global alignment framework. Many others are partial genomic sequences, limited to selected regions, and these allow comparison of a higher number of isolates from well-defined epidemiological settings and/or pathological conditions. Most studies showed that the genetic variability of B19 virus is low, that molecular epidemiology is possible only on a limited geographical and temporal setting, and that no clear correlations are present between genome sequence and distinctive pathological and clinical manifestations. More recently, several viral isolates have been identified that show remarkable sequence diversity with respect to reference sequences. The identification of variant isolates added to the knowledge of genetic diversity in this virus group and allowed the identification of three divergent genetic clusters, about 10% divergent from each other and still quite distinct from other parvoviruses, that can be thought of as different genotypes within the human erythrovirus group and that show clearly resolved phylogenetic relationship. These variant isolates pose interesting questions regarding the real extent of genetic variability in the human erythroviruses, the relevance of these viruses in terms of epidemiology and their possible implication in the pathogenesis of erythrovirus-related diseases.

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.

Genetic diversity within human erythroviruses: identification of three genotypes

B19 virus is a human virus belonging to the genus Erythrovirus: The genetic diversity among B19 virus isolates has been reported to be very low, with less than 2% nucleotide divergence in the whole genome sequence. We have previously reported the isolation of a human erythrovirus isolate, termed V9, whose sequence was markedly distinct (>11% nucleotide divergence) from that of B19 virus. To date, the V9 isolate remains the unique representative of a new variant in the genus Erythrovirus, and its taxonomic position is unclear. We report here the isolation of 11 V9-related viruses. A prospective study conducted in France between 1999 and 2001 indicates that V9-related viruses actually circulate at a significant frequency (11.4%) along with B19 viruses. Analysis of the nearly full-length genome sequence of one V9-related isolate (D91.1) indicates that the D91.1 sequence clusters together with but is notably distant from the V9 sequence (5.3% divergence) and is distantly related to B19 virus sequences (13.8 to 14.2% divergence). Additional phylogenetic analysis of partial sequences from the V9-related isolates combined with erythrovirus sequences available in GenBank indicates that the erythrovirus group is more diverse than thought previously and can be divided into three well-individualized genotypes, with B19 viruses corresponding to genotype 1 and V9-related viruses being distributed into genotypes 2 and 3.

Current molecular epidemiology and human parvovirus B19 infection

Viruses evolve gradually through replication. Therefore, isolates of a virus species can have different genome sequences, albeit slightly, if isolates are epidemiologically unrelated. The difference in virus genome involves difference in virus functions and clinical manifestations of virus infection. Molecular epidemiology of virus infection is a relatively new field directed at infection in humans but not other animals. Analyses are based on genomic differences between virus strains with advances in methodology related to DNA analyses, progress is being made. Classification of virus strains, tracing of transmission of a strain, analyses of outbreaks (including nosocomial infection), and analyses of pathogenesis of virus infection in humans (a natural host) are given attention in molecular epidemiological studies. Human parvovirus B19 is a common human pathogen associated with a wide variety of diseases, including erythema infectiosum, aplastic crisis, hydrops fetalis, and arthritis. B19 is not propagatable in conventional cell lines, hence, molecular cloning of B19 DNA directly from clinical materials has to be done. Events concerning B19 infection were analyzed based on the concept of molecular epidemiology and studies proved to be productive to better understand the pathogenesis of B19 infection.

Integrity and full coding sequence of B19 virus DNA persisting in human synovial tissue

Primary infection by human parvovirus B19 is often accompanied by arthropathy of varying duration, of which the most severe cases can be indistinguishable from rheumatoid arthritis (RA). While this might seem to imply a role in RA pathogenesis, recent studies have verified long-term persistence of B19 DNA in synovial tissue not only in patients with rheumatoid or juvenile arthritis, but also in immunocompetent, non-arthritic individuals with a history of prior B19 infection. However, the latter data are based on PCR amplification of short segments of DNA, with little sequence information. We determined the nucleotide sequence and examined the integrity of the protein-coding regions of B19 genomes persisting in synovial tissue and compared the results with data from synovial tissues of recently infected patients. In synovium of both previously and recently infected subjects, the viral coding regions were found to be present in an apparently continuous, intact DNA molecule. Comparison with sequences reported from blood or bone marrow showed that the synoviotropism or persistence of the B19 virus DNA was not due to exceptional mutations or particular genotype variants. The synovial retention of full-length viral genomes may represent a physiological process functioning in long-term storage of foreign macromolecules in this tissue.

Novel human erythrovirus associated with transient aplastic anemia

Erythrovirus (formerly parvovirus) B19 causes a wide range of diseases in humans, including anemia due to aplastic crisis. Diagnosis of B19 infection relies on serology and the detection of viral DNA by PCR. These techniques are usually thought to detect all erythrovirus field isolates, since the B19 genome is known to undergo few genetic variations. We have detected an erythrovirus (V9) markedly different from B19 in the serum and bone marrow of a child with transient aplastic anemia. The B19 PCR assay yielded a product that hybridized only very weakly to the B19-specific probe and whose sequence diverged more from those of 24 B19 viruses (11 to 14%) than the divergence found within the B19 group (</=6.65%). Restriction enzyme analysis of the V9 genome revealed that this genetic divergence extended beyond the amplified region. Interestingly, serological tests failed to demonstrate a response characteristic of acute B19 infection. V9 could be a new erythrovirus, and new diagnostic tests are needed for its detection.

A clinical and epidemiological study of human parvovirus B19 infection in fetal hydrops using PCR Southern blot hybridization and chemiluminescence detection

Ninety-eight samples from 80 cases of spontaneous abortions after fetal death or hydrops fetalis from 12,000 pregnant women were examined using PCR. DNA was extracted from amniotic fluid, fetal blood, ascitic fluid and fetal biopsies or placenta specimens using QIA amp kits (QIAGEN). A 270-bp length fragment located within the B19 gene NS1 was amplified using PCR followed by electrophoresis and southern-blot hybridization assay using a horseradish peroxidase-labelled probe and chemiluminescence detection. This assay was able to detect 1 to 10 DNA copies in a 10 microliters sample. Parvovirus B19 was identified in 11 cases (14% of fetal hydrops; 1 case for 1,100 pregnancies). Amniotic fluid was the most common and reliable sample to assess the diagnosis. Gestational age ranged from 17 to 28 weeks (mean 23 weeks). IgM antibodies were detected in 3 maternal sera, 2 patients of which reported an exposure to B19 infection during pregnancy. In 2 cases, intrauterine blood transfusions led to the cessation of symptoms and to birth of normal babies.

[Human parvovirus B19 infection. Update]

Pathogenicity of parvovirus B19 has been demonstrated. The spectrum of clinical manifestations varies according to the age and immune status of affected patients. Parvovirus B19 is the aetiologic agent of erythema infectiosum in children. In normal adults, it is responsible for acute, bilateral and symmetrical arthritis, although chronic arthritis can develop. Parvovirus B19 has a particular tropism for erythroid precursors: in patients with underlying hemolysis, it induces transient aplastic crisis; in immunosuppressed patients the virus can lead to chronic pure red cell aplasia. Hydrops fetalis is one of the most severe manifestation of the infection. Diagnosis of recent parvovirus B19 infection is based upon serology and PCR, especially in immunosuppressed patients in whom polyvalent intravenous immunoglobulins must be started. The link between parvovirus B19 and systemic vasculitis is questioned.

Extent of sequence variability in a genomic region coding for capsid proteins of B19 parvovirus

Genomic variability in human parvovirus B19 was analysed by direct partial sequencing of different isolates collected in Italy between 1989 and 1994. DNA was purified from viremic serum samples and the region of viral genome coding for structural proteins was amplified by polymerase chain reaction and partially sequenced (nt. 2400-3400). Data were compared to reference isolates Wi (U.K., 1973) and Au (U.S.A., 1982). The average relative distance between isolates was estimated at the low level of 0.61%, comparable with the distance to reference isolates. Out of 22 nucleotide substitutions found, 9 resulted in amino acid changes. From our results, this region of human parvovirus B19 genome appears to be stably conserved.

Genetic diversity in the non-structural gene of parvovirus B19 detected by single-stranded conformational polymorphism assay (SSCP) and partial nucleotide sequencing

A homologous region in the parvovirus B19 non-structural gene (B19 nt 1399-1682) was examined in 50 samples from patients with a wide variety of B19-related disease from various countries by PCR amplification, single-stranded conformational polymorphism (SSCP) assay and nucleotide sequencing. Five SSCP types were confirmed by nucleotide sequence analysis. Of a total of 6 mutations, all were silent. Types 3 and 4 accounted for 92% of strains. There was no correlation between genome type and either clinical illness or patient age. However, there was a correlation between SSCP type and country of origin. Type 3 strains predominated in Japan (18/26) and the UK (6/8), whereas type 4 predominated in the USA (9/12). Notably, type 3 strains also predominated among females (14/18), whereas there were approximately equal numbers of strain types 3 (7/17) and 4 (8/17) among males; an observation which remains unexplained. Within the Japanese group, although type 3 strains predominated overall, strains isolated from 1981 to 1987 consisted of types 1 (2/15), 2 (1/15), 3 (8/15), and 4 (4/15), whereas strains isolated from 1990 to 1994 consisted almost entirely of type 3 (10/11).

Biochemical and genomic characterization of muscovy duck parvovirus

A duck parvovirus (DPV) isolated from muscovy ducks during the epizootic in France in 1989 was purified from inoculated allanto-amniotic fluids by CsCl density gradient centrifugation and characterized. Full and empty non-enveloped icosahedral viral particles were observed banding at densities of 1.39 to 1.42 and 1.38 respectively, with a diameter of 22 to 23 nm. Viral proteins were analyzed by SDS-PAGE and the estimated molecular weights of the 3 major proteins were 91, 78 and 58 kDa. The nucleic acid was shown to be a single-stranded DNA of about 5,300 bases with terminal palindromic hairpins. These results confirm the previous classification of the virus in the family Parvoviridae established by Jestin et al. [14] on morphological and serological bases. The DPV DNA was reannealed indicating that complementary DNA strands were encapsidated. A partial restriction endonuclease map was also established. This work constitutes the first biochemical and genomic description of a muscovy duck parvovirus.

Rapid and sensitive method for the detection of B19 virus DNA using the polymerase chain reaction with nested primers

The sensitivity of detection of B19 virus DNA in clinical specimens was evaluated by comparing the results of single PCR and nested PCR assays, with or without subsequent Southern blot hybridization to a radiolabelled B19 DNA probe. The inhibitory activity of human serum components on polymerase reaction was also determined. The sensitivity of B19 virus DNA detection decreased by a factor of 10(7) in the presence of 10% serum in the single PCR reaction mixture, and of 10(3) for nested PCR. When nested PCR products were analysed by Southern blot hybridization to a B19 radioactive DNA probe, the sensitivity of the assay increased to such a level of B19 DNA detection that the reaction was no longer influenced by the presence of serum inhibitors in the original sample. Less than ten B19 genome copies could thus be detected in a 10-microliters sample. A panel of 38 clinical samples, originating from patients with possibility of B19 virus infection, were assayed by this method. Only one sample was found to be positive after single PCR, whereas seven samples (including the former) gave a positive signal after nested PCR. The specificity of the nested PCR products was controlled by hybridization to the B19 DNA probe and DNA sequencing. No discrepancy in the results was observed between nested PCR alone and nested PCR followed by Southern blot analysis.

Analysis of genetic variability of populations of herpes simplex viruses

An analysis of genetic variability of herpes simplex virus type 1 and type 2 populations of the Madrid (Spain) area has been carried out by digestion of viral DNA with restriction endonucleases. The index of nucleotide diversity indicated that herpes simplex virus type 1 has a slightly, although statistically significant, higher degree of heterogeneity than type 2. A phylogenetic tree for each type of virus has been constructed. The evolutionary pattern followed by both types of viruses ('star-like' topology) suggest that all the isolates analyzed evolved from a unique origin for each type of virus.

Partial nucleotide sequencing and characterization of human parvovirus B19 genome DNAs from damaged human fetuses and from patients with leukemia

While human parvovirus B19 is associated with fetal damage and chronic suppression of bone marrow in patients with leukemia, much less is known of the genomic characteristics of B19 isolated from damaged human fetuses and leukemia patients. B19 genome DNAs from human fetal organs and fluids and sera from leukemia patients were amplified by the polymerase chain reaction. The nucleotide sequences of amplified products in the region between nucleotide (nt) 3141 and nt3411 were determined following molecular cloning in M13 phage. The genome types of B19 from the fetuses and leukemia patients were similar to the types from patients with aplastic crisis and an asymptomatic individual. Wide diversity of the nucleotide sequence, i.e., six or more (6-11) substitutions, were evident in ten M13 phage clones of each DNA source from fetal materials, while substitutions in sera from patients with leukemia and aplastic crisis and of an asymptomatic individual numbered four or fewer (0-4). This wide diversity of B19 viruses in the fetus, revealed after many rounds of DNA replication, probably depends on a persistent state of infection.

Characterization of a nested polymerase chain reaction assay for detection of parvovirus B19

The characterization and application of a nested polymerase chain reaction (PCR) assay for the detection of human parvovirus B19 DNA is described. The assay was evaluated with 149 diagnostic serum samples (collected up to 150 days after the onset of symptoms) previously tested by dot blot hybridization for B19 DNA and by class-specific capture radioimmunoassays for the detection of B19 immunoglobulin M (IgM) and IgG. B19 DNA was detectable by the PCR in 70% of the sera. There was a statistically significant association between the detection of B19 DNA by PCR and high B19 IgM values (P < 0.005), low B19 IgG values (P < 0.05), and a short interval between onset of symptoms and serum collection (P < 0.005). Serial serum samples, throat swabs, and peripheral blood mononuclear cells collected from 10 individuals during an outbreak of parvovirus B19 were also tested by the nested PCR. B19 DNA was detectable in the throat swabs at the time of the clinical illness and in the peripheral blood mononuclear cell fraction up to the end point of the study 6 months after infection. The location of the B19 DNA could not be determined in cytocentrifuge preparations of peripheral blood mononuclear cells with nonisotopic in situ hybridization and immunolabelling.

Efficient parvovirus B19 DNA purification and molecular cloning

A simple and efficient method of purification and molecular cloning of Parvovirus B19 DNA directly from small quantities of viremic sera was developed. Purified virions were lysed in annealing conditions, then viral DNA purification in double strand (ds) DNA form was achieved using an affinity DNA binding matrix. Affinity purification yielded a consistently high recovery of viral DNA. Using affinity purified ds viral DNA, we efficiently and stably cloned the complete coding internal unique sequence of B19 DNA. In our cloning strategy AatII and BamHI restriction endonuclease sites were exploited. This permitted cleavage of the 5.0 kbp AatII fragment in two AatII-BamHI fragments which could be efficiently cloned in a directional way in pUC18 plasmid vector. The availability of the two cloned AatII-BamHI fragments thus allowed the construction of a full length clone in a single ligation reaction.

Localization of an immunodominant domain on baculovirus-produced parvovirus B19 capsids: correlation to a major surface region on the native virus particle

An immunodominant region on baculovirus-produced parvovirus B19 VP2 capsids was localized between amino acids 259 and 426 by mapping the binding sites of a panel of monoclonal antibodies which recognize determinants on the particles. The binding sites of three monoclonal antibodies were fine-mapped within this antigenic domain. Six VP2-specific monoclonal antibodies recognized determinants common to both the empty capsids and native parvovirus. The defined antigenic region is most probably exposed on the native B19 virion and corresponds to part of the threefold spike on the surface of canine parvovirus particles.

Rapid antigenic-type replacement and DNA sequence evolution of canine parvovirus

Analysis of canine parvovirus (CPV) isolates with a panel of monoclonal antibodies showed that after 1986, most viruses isolated from dogs in many parts of the United States differed antigenically from the viruses isolated prior to that date. The new antigenic type (designated CPV type 2b) has largely replaced the previous antigenic type (CPV type 2a) among virus isolates from the United States. This represents the second occurrence of a new antigenic type of this DNA virus since its emergence in 1978, as the original CPV type (CPV type 2) had previously been replaced between 1979 and 1981 by the CPV type 2a strain. DNA sequence comparisons showed that CPV types 2b and 2a differed by as few as two nonsynonymous (amino acid-changing) nucleotide substitutions in the VP-1 and VP-2 capsid protein genes. One mutation, resulting in an Asn-Asp difference at residue 426 in the VP-2 sequence, was shown by comparison with a neutralization-escape mutant selected with a non-CPV type 2b-reactive monoclonal antibody to determine the antigenic change. The mutation selected by that monoclonal antibody, a His-Tyr difference in VP-2 amino acid 222, was immediately adjacent to residue 426 in the three-dimensional structure of the CPV capsid. The CPV type 2b isolates are phylogenetically closely related to the CPV type 2a isolates and are probably derived from a common ancestor. Phylogenetic analysis showed a progressive evolution away from the original CPV type. This pattern of viral evolution appears most similar to that seen in some influenza A viruses.

Use of M13 single-stranded DNA digoxigenin labelled probe for detection of human parvovirus B19 viraemia

A dot-blot hybridization assay for serum B19 DNA is described using a non-radioactive (digoxigenin) M13 single-stranded DNA probe. The assay is sensitive (0.3 pg of B19 DNA) and has several advantages over similar assays which use radioactive or non-radioactive labelled plasmid probe for the routine detection of B19 DNA in sera.

The use of labeled fusion protein for detection of B19 parvovirus IgM antibodies by an immunocapture test

A new anti-B19 IgM ELISA was developed taking advantage of antibody-capture with biotinylated fusion protein as antigen. Specificity was examined using serum IgM antibody positive for rubella, hepatitis B core antigen, cytomegalovirus and Epstein-Barr virus as well as with sera positive for rheumatoid factors or antinuclear antibodies. The specificity was found to be 96%. Of one hundred serum samples compared using the new ELISA or the standard MACRIA tests for the presence of B19 IgM, 88 gave the same results. Fifty-three were negative and 35 were positive. Six sera were ELISA-negative MACRIA-positive, and six MACRIA-negative ELISA-positive. Thus, the ELISA gave 90% agreement with MACRIA. In a clinical study with 725 sera from suspected B19 infections, 161 (22%) were found positive by ELISA. The positive sera were from patients suffering from arthritis (35%), rash (35%), acute or chronic erythroblastopenia (21%), pancytopenia (5%), vascular purpura (2%) and lymphadenopathy (2%). A series of serum specimens obtained from two-B19 infected individuals were also studied. The IgM antibody became undetectable after four months.

Identification of the region including the epitope for a monoclonal antibody which can neutralize human parvovirus B19

In this study, we identified a region in the human parvovirus structural protein which involves the neutralization of the virus by a monoclonal antibody and site-specific synthetic peptides. A newly established monoclonal antibody reacted with both viral capsid proteins VP1 and VP2. The epitope was found in six strains of independently isolated human parvovirus B19. The monoclonal antibody could protect colony-forming unit erythroid in human bone marrow cell culture from injury by the virus. The monoclonal antibody reacted with only 1 of 12 peptides that were synthesized according to a predicted amino acid sequence based on nucleotide sequences of the coding region for the structural protein of B19 virus. The sequence recognized by the antibody was a site corresponding to amino acids 328 to 344 from the amino-terminal portion of VP2. This evidence suggests that the epitope of the viral capsid protein is located on the surface of the virus and may be recognized by virus-neutralizing antibodies.

In situ hybridization for the detection of human parvovirus B19 nucleic acid sequences in paraffin-embedded specimens

Parvovirus infection of pregnant women leading to a transplacentar infection of the fetus may result in hydrops fetalis, and ultimately in intrauterine death of the fetus. In situ hybridization with a biotinylated as well as with a 35S-labeled probe for human parvovirus B19 was performed on formalin-fixed paraffin-embedded (FFPE) tissue from a fetus suffering from non-immunologic hydrops fetalis. Histology was suggestive of viral infection probably with human parvovirus. Parvovirus DNA could be detected and precisely localized mainly in the nuclei of erythroid precursors cells within fetal blood vessels of all organs examined. There was no detection of B19 nucleic acid in parenchymal cells of the placenta or the fetal organs, nor within maternal blood cells. These findings are in agreement with the well-known properties of animal parvoviruses to replicate exclusively in proliferating cells. Taking into consideration the problems in diagnosing human parvovirus infection by light microscopy, we conclude that in situ hybridization with an appropriate non-radioactive probe is a valuable, rapid and safe complementary detection method for the diagnosis and study of human parvovirus infections. The 35S-labeled probe is more sensitive than the biotinylated probe, but has the disadvantages of lower resolution of the signal, longer duration of the assay, the hazard of radioactivity and the shorter shelf-life of the probe.

Expression of an antigenic polypeptide of the human parvovirus B19

The DNA fragment of the human parvovirus B19, with 715 nucleotides between nucleotide positions 3141-3856 was expressed in Escherichia coli as a beta-galactosidase fusion protein. The plasmid vector pSS20d used for this purpose permits cleavage of the viral gene product from the beta-galactosidase moiety by collagenase. After purification by p-aminophenyl-beta-D-thiogalactoside-sepharose and superose, a soluble protein with a molecular mass of 28 kDa was isolated. It represents a common part of the viral capsid proteins VP1 and VP2. This bacterially derived parvoviral gene product can be used for detection of anti-B19 antibodies in human sera.

Similarities in nucleotide sequence between serum and faecal human parvovirus DNA

Two DNA clones were obtained from faecal specimens containing a parvovirus-like small round virus from a 1977 outbreak of gastroenteritis, and their nucleotide sequences were determined and found to be essentially identical with parts of the published sequence of serum parvovirus B19 and with a B19 isolate (JB) partially sequenced in this study. The clones corresponded mainly to genome regions coding for non-structural proteins, but also include a sequence of some 160 bp coding for structural proteins. Southern blotting experiments with a full-length B19 probe revealed a virion-sized 5 x 5 kbp DNA band in specimens from gastroenteritis cases in both 1977 and 1986. Thus the nucleotide sequence and hybridization results suggest that the virus seen in these studies is very similar to B19. Further work is necessary to clarify the antigenic relationship of these viruses.

Cloning of the human parvovirus B19 genome and structural analysis of its palindromic termini

We describe the molecular cloning of the entire 5.6-kb single-stranded DNA genome of the human parvovirus B19 in bacterial plasmids. Stable amplification of the recombinant plasmid DNA was achieved in Escherichia coli JC8111 but not in HB101 cells. Sequence analysis of the cloned DNA shows that the terminal 383 nucleotides at each end of the genome are identical inverted repeats. The distal 365 nucleotides of the repeat represent an imperfect palindrome which presumably folds over to form a hairpin structure. The sequence of the hairpin occurs in two distinct configurations which are related in that one is the inverted complement of the other. Such alternative configurations of the terminal hairpins have been found for all parvoviruses analyzed so far and are referred to as flip and flop.