Aplastic anemia due to B19 parvovirus infection in cadaveric renal transplant recipients: an underestimated infectious disease in the immunocompromised host

Parvovirus B19 has been identified as the etiological agent of "fifth disease" in childhood. It is also a rarely reported cause of anemia in transplanted patients. During a period of 18 months we observed four cases (2 male and 2 female; 53 +/- 4.24 years) of severe aplastic anemia due to parvovirus B19 in kidney transplant patients. The overall incidence of the disease was 6.3% of all our transplanted patients. Symptoms of the disease occurred 22.5 +/- 9.75 days post-operatively. Serum creatinine was 1.5 +/- 0.35 mg/dl. Hb was 6.58 +/- 0.6 g/dl. All patients recovered with 15 days of high doses of commercial immunoglobulins. We conclude that B19 parvovirus infection is probably an underestimated disease in transplant patients. It is a first-period infection, probably donor-transmitted. High dose immunoglobulins are an effective but costly therapy.

Survival of larvae of Nippostrongylus brasiliensis (nematoda) in solutions of toxic substances

The aim of this study was to determine the action of zinc, copper, lead and cadmium compounds upon N. brasiliensis invasive nematode larvae. The tested larvae were kept in ZnCl2, CuCl2, Pb(NO3)2 and CdCl2 solutions. The concentrations of toxic substances applied for the study corresponded with level of environmental pollution. All toxins reduced life-space of larvae. In control group they survived about 69 days. In solutions of the Zn, contaminated with 10, 50, 100 and 200 ppm of toxic substance, they survived 42, 16, 14 days and 72 hours. In solution of Cu, contaminated with 5, 10, 50 and 200 ppm of toxin, life--space was reduced to 51, 21, 7 days and 54 hours, respectively. Lead reduced live--space of larvae to 26 days already at the low concentration of 10 ppm and in all higher concentrations (20, 50 and 200 ppm) their survival changed insignificantly (to 22 days). In solution of Cd, contaminated with 0.1 and 0.3 ppm larvae died after 39 and 17 days, respectively, while at higher concentrations of this toxin (3 and 10 ppm) larvae survived only 54 and 30 hours, respectively.

Human parvovirus B19 infection within a family and risk for pregnant women

During an outbreak of parvovirus B19 infection among four related families at least 70% of the household contacts, including a woman at the 33rd week of pregnancy, became infected. Twins were born at the 39th week of pregnancy, both with B19 infection. B19 DNA was detected in their sera by a nested PCR, anti-B19 IgM was detectable only by an immunofluorescence assay, and low levels of maternal anti-B19 IgG were demonstrable by an immunoenzymatic test in the serum of both children. All the haematological parameters were normal at birth and 6 months later, when B19 DNA and anti-B19 antibody were no longer detectable in serum samples. This observation emphasizes the high risk of B19 infection among household contacts and the possibility of a favourable outcome of the foetal infection, possibly related to infection late in the pregnancy.

Molecular modelling of (A4T4NN)n and (T4A4NN)n: sequence elements responsible for curvature

The molecular modelling program JUMNA has been used to investigate the origins of the strikingly different curvature of the two sequences, (A4T4NN)n and (T4A4NN)n. Gel electrophoresis and cyclisation studies have shown that only the former of these two sequences is significantly curved. By developing novel superhelical symmetry constraints we were able to study the energetic and structural aspects of polymeric DNA having a controlled curvature. The results obtained (which do not take into account specific hydration effects) correlate well with the experimental data and offer a molecular level explanation of curvature. Although curvature is found to be initiated by specific dinucleotide junctions, deformations spread to surrounding dinucleotide steps and, moreover, sequence effects beyond the dinucleotide level are observed.

Gastric acid secretion after blockade of angiotensin AT1 receptors in the Na(+)-depleted rat

This study tested the hypothesis that angiotensin II acting through the angiotensin AT1 receptor plays an important role in the control of gastric acid secretion. Basal gastric acid secretion and gastric blood flow were lower in Na(+)-depleted animals, in which the renin-angiotensin system was activated, than in animals maintained on a normal Na+ diet. Intravenous infusion of pentagastrin at 0.6 microgram/kg/min increased gastric acid secretion to a greater extent in normal Na+ than in Na(+)-depleted animals. In addition to stimulating gastric acid secretion, pentagastrin increased gastric blood flow by proportionally the same amount in both normal and low Na+ animals. However, because basal gastric blood flow was considerably reduced in Na(+)-depleted animals, the increase produced by pentagastrin extended only to the levels observed in non-pentagastrin-treated normal Na+ animals. Lower gastric blood flow in response to pentagastrin may explain the smaller increase in gastric acid secretion observed in Na(+)-depleted animals. In Na(+)-depleted animals, the selective angiotensin AT1 receptor antagonist losartan did not affect basal gastric acid secretion or gastric blood flow, suggesting the involvement of mechanisms other than angiotensin II. Following blockade of angiotensin AT1 receptors, pentagastrin significantly increased gastric blood flow in Na(+)-depleted animals to levels observed with infusion of the pentapeptide in normal Na+ animals. The results suggested that the decrease in pentagastrin-stimulated acid secretion in Na(+)-depleted animals is mediated by angiotensin II acting through the angiotensin AT1 receptor, most probably through vascular mechanisms.

Monitoring of polyomavirus BK viruria in bone marrow transplantation patients by DNA hybridization assay and by polymerase chain reaction: an approach to assess the relationship between BK viruria and hemorrhagic cystitis

An association between long-lasting hemorrhagic cystitis (HC) in bone marrow transplantation (BMT) patients and viral infections, mostly with reactivation of the human polyomavirus BK (BKV), is suggested by several previous reports. We have carried out a prospective study in 55 (30 allogeneic, 24 autologous, 1 syngeneic) BMT recipients with the aim of evaluating the role of BKV in this frequent complication after BMT. To overcome the well known difficulties in BK virus isolation in cell cultures, a DNA hybridization assay and the polymerase chain reaction (PCR) were used for the detection and monitoring of viral urinary shedding, respectively. The presence of human polyomavirus JC and adenovirus DNA was also sought in urine specimens. BK viruria was demonstrated in 52.7% of patients (in 53.3% allogeneic and in 54.1% autologous BMT), whereas JCV and adenovirus were seldom present. Seven cases of HC (20% in allogeneic and 4% in autologous BMT) occurred and in all cases the clinical event was associated with BKV urinary shedding. This study suggests that BKV infection alone does not invariably lead to HC in BMT patients; for HC to occur the presence of other, at present unidentified, factors seems to be necessary.

Cytopenia caused by parvovirus in an adult ALL patient

A young woman in maintenance therapy for acute lymphoblastic leukemia in second complete remission developed fever and a skin rash associated with severe anemia, neutropenia and erythroblastopenia. A complete recovery was obtained in 4 weeks' time after red cell transfusion, i.v. immunoglobulin and withdrawal of the maintenance chemotherapy. Parvovirus B19 infection was demonstrated by detection of B19 DNA in the patient's serum using a dot-blot hybridization assay and a nested polymerase chain reaction. Serological tests were positive for anti-B19 IgG but not for IgM. Erythroblastopenia due to parvovirus infection has already been reported in ALL patients. B19 infection should be suspected in leukemic patients if unexplained cytopenia (mainly anemia) follows an acute febrile illness. Very sensitive methods are often needed to confirm the diagnosis, since routine serological tests may be unreliable in immunocompromised patients.

Human parvovirus B19 infection in bone marrow transplantation patients

We report the results of a survey of parvovirus B19 infection carried out with the aim to evaluate the frequency and the role of this infection in bone marrow transplant (BMT) recipients, as it is known that B19 virus can persist in clinical circumstances of immunodeficiency. Fifty-one patients subjected to BMT in the Bone Marrow Transplantation Center of Florence were enrolled in this study. Immunological and virological indications of B19 infection were tested weekly during the stay in hospital. A high rate of seroconversion or B19 antibody rise was observed, but, in absence of B19 IgM or B19 DNA presence, this result seems to be attributable to a passive immunization, rather than to a recent viral infection. In these 51 patients, as well as in 59 others not included in this study, clinical manifestations imputable to B19 infection have never been observed. It is possible that the isolation measures and the intravenous immunoglobulins (IVIG) administration may contribute in preventing B19 infection in the BMT recipients at least until the hospital discharge.

An analysis of the conformational paths of citrate synthase

Previous simulation studies have provided reaction pathways leading from the closed to the open form of citrate synthase. We now undertake a detailed analysis of these pathways using a variety of different tools including backbone dihedral angles, P-Curves helicoidal parameters, inter-helix geometrical parameters, and accessibility calculations. The results point to a relatively small number of residues, mostly in loop regions, which are responsible for the majority of the conformational changes observed. An important role is attributed to transient changes in the backbone which facilitate movement along the reaction coordinate. Comparisons between the two pathways show that they share many common features despite the different algorithms used to generate them.

The haemagglutinins of influenza A (H1N1) viruses in the 'O' or 'D' phases exhibit biological and antigenic differences

Influenza A (H1N1) viruses when initially isolated in mammalian cell cultures (MDCK cells) had different agglutination reactions with chicken and guinea-pig erythrocytes compared to the same viruses after passage. On first isolation the virus HA resembled the 'O' phase viruses described originally by Burnet and Bull and agglutinated mammalian but not avian erythrocytes. After passage, the virus HA resembled a classical 'D' phase virus and agglutinated both avian and mammalian erythrocytes. Monoclonal and polyclonal antisera detected antigenic differences between the HAs of the viruses in the 'O' and 'D' phases. The 'O' phase virus HA reacted preferentially with antibodies in post infection human antisera. Viruses in the 'O' phase replicated poorly in the allantoic cavity of embryonated hens' eggs whilst 'D' phase virus replicated in both MDCK cells and in embryonated hens' eggs. At least three distinguishable subpopulations of influenza A (H1N1) viruses may co-exist in clinical throat swab material, including viruses possessing HAs in the 'O' and 'D' phases and other 'D' phase viruses cultivable in embryonated hens' eggs but antigenically distinguishable from the corresponding 'D' phase virus in MDCK cells.

Nested polymerase chain reaction assay for the detection of B19 parvovirus DNA in human immunodeficiency virus patients

Persistent B19 parvovirus infection has been recognized in immunocompromised patients, often occurring with a low-titer viremia. In this study, nested polymerase chain reaction (PCR) for the detection of B19 parvovirus DNA was carried out on the sera of 49 human immunodeficiency virus (HIV)-1-seropositive patients, negative for the detection of B19 DNA at dot blot hybridization assay and with different values of serum anti-B19 IgM (27 patients proved positive and 22 negative). Of the 49 HIV-seropositive samples tested by nested PCR, seven were positive for the detection of B19 DNA. All seven belonged to the group of subjects seropositive for specific anti-B19 IgM. The study shows that, in the presence of specific B19 IgM, circulating virus may still be present but can be detected only by PCR. In that B19 infection can occur with low-titer viremia in immunocompromised patients, PCR may be the only method for virus detection.

Looking into the grooves of DNA

The present study is aimed at understanding the effects of DNA sequence, local conformation, and curvature on groove geometry. Energy-optimized structures are obtained by Jumna methodology; groove geometry is analyzed by a recently developed technique that allows an accurate and continuous measurement of width and depth. The mechanics of groove deformations is also studied and analyzed in terms of helicoidal parameters.

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.

A comprehensive classification of nucleic acid structural families based on strand direction and base pairing

We propose a classification of DNA structures formed from 1 to 4 strands, based only on relative strand directions, base to strand orientation and base pairing geometries. This classification and its associated notation enable all nucleic acids to be grouped into structural families and bring to light possible structures which have not yet been observed experimentally. It also helps in understanding transitions between families and can assist in the design of multistrand structures.

Human parvovirus B19 in clotting factor concentrates: B19 DNA detection by the nested polymerase chain reaction

The presence of B19 parvovirus in plasma from blood donors is seldom demonstrable, but clotting factor concentrates, prepared from large plasma pools, may be able to transmit B19 virus infection, and the effectiveness of different chemical and physical treatment to inactivate this virus is not yet known. In this study we report on the detection of B19 DNA in 25 clotting factor concentrates, prepared by a variety of procedures of purification and inactivation; dot blot hybridization and Southern blot hybridization assays, as well as a 'nested' polymerase chain reaction (PCR) have been employed. Nine out of 25 products were B19 DNA positive by PCR, whereas only two gave positive results by hybridization techniques. B19 DNA positive concentrates have been found in 'untreated' products but also in some solvent/detergent or steam-treated products and even in monoclonal purified concentrates. PCR may be useful for the screening of blood products to be used in immunocompromised haemophiliacs, particularly in HIV positive subjects, at risk of severe chronic anaemia following B19 infection.

Static and dynamic conformational properties of AT sequences in B-DNA

A theoretical study of the optimal conformations of nucleic acid oligomers containing tracts of AT base pairs is presented. The oligomers are studied in isolation and complexed with netropsin, a minor groove binding ligand. The flexibility of the oligomers and of their complexes is calculated by adiabatic mapping with respect to the total winding angle. The results of this study show that in uncomplexed oligomers the dinucleotide junctions AA, AT and TA have very different structural parameters and different responses to winding stress. The TA junction is clearly the most flexible and is the principal site for accommodating the imposed overwinding. Complexation by netropsin leads to two important effects: firstly, the three junctions adopt more uniform structures, the largest changes again being observed for TA, secondly, the differences in flexibility as a function of sequence are strongly attenuated.

Theoretical study of ethidium intercalation in triple-stranded DNA and at triplex-duplex junctions

The contribution of different factors in the interaction of ethidium intercalated into various sequences of a triple helix, or in the region of the junction between the double- and triple-stranded DNA has been studied by energy minimization. It is found that in the total energy of the ethidium- triple helix complexes, a particular electrostatic contribution emerges due to the presence of protonated cytosines in the triple helix. This parameters is determinant in the sequence-specificity of ethidium binding to the triple helix. The preferred intercalation sites of ethidium in the triple helix are proposed. The interaction of ethidium at the triplex-duplex junction, and its effects are also discussed. This study is aimed at searching for new drugs specific for the triple helix, or for the triplex-duplex junctions.

Detection of B19 parvovirus infections by a dot-blot hybridization assay using a digoxigenin-labelled probe

A non-radioactive dot-blot hybridization assay for the detection of B19 parvovirus infections was developed using a digoxigenin-labelled probe both on nylon and nitrocellulose filters. A 700 bp BamHI HindIII fragment of B19 DNA was used to construct the probe. Probe labelling was carried out by incorporating deoxyuridine triphosphate labelled with digoxigenin. The dot-blot hybridization assay was visualized by an immunoenzymatic reaction using antidigoxigenin Fab fragments labelled with alkaline phosphatase. The specificity and sensitivity of digoxigenin-labelled B19 DNA probe was compared with the results obtained with 32P-labelled B19 DNA probe. Out of the 504 serum samples tested, 3 samples were positive in all the hybridization assays performed and 494 were negative, 7 serum samples gave a weak positive reaction when Dig-B19 probe was used on nitrocellulose filters. The 77 pharyngeal swabs tested were negative in all the hybridization assays performed. Our hybridization assay showed a high sensitivity and reproducibility and it appears to be a rapid, practical and reliable test for routine screening of B19 parvovirus DNA in large numbers of clinical specimens.

Modelling basic features of specificity in DNA-aureolic acid-derived antibiotic interactions

The nonintercalative groove binding of a simplified model of olivomycin, to sequences d(CGCGCGC)2, d(TATATAT)2, and d(CICICIC)2 is investigated. A significant preference is displayed for the minor groove of the d(CG) sequence. This is due predominantly to the formation of H-bonds between the hydroxyl groups on the aglycone of the drug and the 2-amino group of the central guanine of the oligonucleotide.