Recent Developments of Parvoviruses

-ACUTE RESPIRATORY DISTRESS SYNDROME IN A CHILD WITH HUMAN PARVOVIRUS B19 INFECTION

Ferraz, Cláudia MD; Cunha, Francisco MD; Mota, Teresa C. MD; Carvalho, José M. MD; Simões, Joana S. MD; Aparicio, José M. PhD

A 6-year-old girl developed shock and multiple organ dysfunction including acute respiratory distress syndrome in association with parvovirus B19 infection. The diagnosis was based on positive antibodies and the detection of parvovirus 19 DNA in serum, bronchial secretions and skin biopsy. It seems likely, but it was not proved, that the parvovirus infection caused acute respiratory distress syndrome.

Human parvovirus B19 (PB19) usually causes erythema infectiosum, a common childhood benign condition with a typical slapped-face rash. Infection can be asymptomatic or uncommonly give rise to a variety of clinical manifestations: chronic anemia; arthritis; transient aplastic crisis; thrombocytopenia; neutropenia; myocarditis; hepatitis; meningitis; encephalitis; atypical rash; hydrops fetalis; and congenital anemia. PB19 can cause a mild respiratory tract illness with no rash, but there are also reports of acute obstructive respiratory disease and severe pneumonia.

 

- ACUTE RENAL FAILURE IN A PEDIATRIC KIDNEY ALLOGRAFT RECIPIENT TREATED WITH INTRAVENOUS IMMUNOGLOBULIN FOR PARVOVIRUS B19 INDUCED PURE RED CELL APLASIA

Mihail M. Subtirelu, Joseph T. Flynn, Richard S. Schechner, James M. Pullman, Dianne Feuerstein and Marcela Del Rio

Infection with parvovirus B19 (PV-B19) after solid organ transplantation may cause pure red cell aplasia (PRCA). Intravenous immunoglobulin (IVIg) may be of benefit in clearing the infection. Acute renal failure is a known adverse effect of IVIg administration. A 14-yr-old male received a cadaveric renal transplant. Three weeks after surgery he developed symptomatic anemia (hemoglobin 4.5 g/dL, reticulocyte count 0.2%). Anti-PV-B19 IgM and IgG titers, which had been negative pretransplant, were positive. He received two IVIg infusions as treatment for the PV-B19 infection. Four days after the IVIg infusions he developed non-oliguric acute renal failure (ARF) with a rise in serum creatinine from 1 to 1.8 mg/dL. Allograft biopsy showed changes consistent with an osmotic load. Anemia and the renal failure resolved after transfusions and IVIg. PV-B19 infection in immunosuppressed transplant recipients is associated with significant morbidity and may respond to IVIg therapy. High sucrose IVIg preparations may be associated with renal failure in renal allograft recipients. Adding PV-B19 testing of the donor and recipient to the standard pretransplant evaluation may be beneficial in diagnosing and managing a potential infection. If IVIg is to be used it may be safer to use a sucrose-free IVIg preparation.

 

- CHARACTERIZATION OF PARVOVIRUS B19 GENOTYPE 2 IN KU812Ep6 CELLS.

Blumel J, Eis-Hubinger AM, Stuhler A, Bonsch C, Gessner M, Lower J.

An infectious parvovirus B19 (B19V) genotype 2 variant was identified as a high-titer contaminant in a human plasma donation. Genome analysis revealed a 138-bp insertion within the p6 promoter. The inserted sequence was represented by an additional 30 bp from the end of the inverted terminal repeat adjacent to a 108-bp element found also, in inverted orientation, at the extreme right end of the unique sequence of the genome. However, despite the profound variations in the promoter region, the pattern of gene expression and DNA replication did not differ between genotype 1 and genotype 2 in permissive erythroid KU812Ep6 cells. Capsid proteins of both genotypes differ in their amino acid sequences. However, equivalent kinetics of virus inactivation at 56 degrees C or pH 4 indicated a comparable physicochemical stability of virus capsids. Sera from six individuals infected by B19V genotype 1 were investigated on cross-neutralization of B19V genotype 2 in vitro. Similar neutralization of both B19V genotypes was observed in sera from three individuals, while the sera from three other individuals showed weaker cross-neutralization for genotype 2. In conclusion, the in vitro replication characteristics and physical stability of B19V capsids are very similar between human parvovirus B19 genotypes 1 and 2, and cross-neutralization indicates a close antigenic relation of genotypes 1 and 2.

 

- PARVOVIRUS UNCOATING IN VITRO REVEALS A MECHANISM OF DNA RELEASE WITHOUT CAPSID DISASSEMBLY AND STRIKING DIFFERENCES IN ENCAPSIDATED DNA STABILITY.

Ros C, Baltzer C, Mani B, Kempf C.

The uncoating mechanism of parvoviruses is unknown. Their capsid robustness and increasing experimental data would suggest an uncoating mechanism without capsid disassembly. We have developed an in vitro system to detect and quantify viral DNA externalization and applied the assay on two parvoviruses with important differences in capsid structure, human B19 and minute virus of mice (MVM). Upon briefly treating the capsids to increasing temperatures, the viral genome became accessible in its full-length in a growing proportion of virions. Capsid disassembly started at temperatures above 60 degrees C for B19 and 70 degrees C for MVM. For both viruses, the externalization followed an all-or-nothing mechanism, without transitions exposing only a particular genomic region. However, the heat-induced DNA accessibility was remarkably more pronounced in B19 than in MVM. This difference was also evident under conditions mimicking endosomal acidification (pH 6.5 to 5), which triggered the externalization of B19-DNA but not of MVM-DNA. The externalized ssDNA was a suitable template for the full second-strand synthesis. Immunoprecipitation with antibodies against conformational epitopes and quantitative PCR revealed that the DNA externalized by heat was mostly dissociated from its capsid, however, the low pH-induced DNA externalization of B19 was predominantly capsid-associated. These results provide new insights into parvovirus uncoating suggesting a mechanism by which the full-length viral genome is released without capsid disassembly. The remarkable instability of the encapsidated B19 DNA, which is easily released from its capsid, would also explain the faster heat inactivation of B19 when compared to other parvoviruses.

 

- PARVOVIRUS NONSTRUCTURAL PROTEINS INDUCE AN EPIGENETIC MODIFICATION THROUGH HISTONE ACETYLATION IN HOST GENES AND REVERT TUMOR MALIGNANCY TO BENIGNANCY.

Hiroyoshi Iseki, Rie Shimizukawa, Fumihiro Sugiyama, Satoshi Kunita, Atsushi Iwama, Masafumi Onodera, Hiromitsu Nakauchi, and Ken-ichi Yagami

Several malignant tumor cells become apoptotic and revert to the benign phenotype upon parvovirus infection. Recently, we demonstrated that the rat parvovirus RPV/UT also induces apoptosis in the rat thymic lymphoma cell line C58(NT)D. However, a minority of cells that escaped apoptosis showed properties different from the parental cells, such as resistance to apoptosis, enhanced cell adherence, and suppressed tumorigenicity. The present study was performed to determine the molecular mechanism of parvovirus-induced phenotypic modification, including oncosuppression. We demonstrated that the nonstructural (NS) proteins of RPV/UT induced apoptosis in C58(NT)D cells and suppressed tumor growth in vivo. Interestingly, NS proteins induced the expression of ciliary neurotrophic factor receptor alpha, which is up-regulated in revertant cell clones, and enhanced histone acetylation of its gene. These results indicate that parvoviral NS regulate host gene expression through histone acetylation, suggesting a possible mechanism of oncosuppression.