Selective killing of transformed rat cells by minute virus of mice does not require infectious virus production.

Fischer rat fibroblasts, naturally resistant to killing by the fibrotropic strain of minute virus of mice [(parvovirus MVM(p)], became sensitive to MVM when transformed by polyomavirus. This sensitization did not involve an increase in the percentage of cells which synthesized viral capsid antigens or in the percentage of cells which produced infectious virus. The addition of anti-MVM antiserum to the growth medium of MVM-infected cells had only a small effect on their survival rates, indicating that the majority of the killing effect of MVM occurs in a single cycle of infection. The data indicate that cell killing by MVM is independent of infectious virus production and thus support the notion that the preferential cytolytic effect is affected by viral cytotoxic gene products which accumulate to intolerable levels in transformed cells but not in normal ones. Finally, using cells transformed with polyomavirus and genomic and subgenomic clones of polyomavirus, we showed that the extent of sensitization to killing by MVM depended on the transforming agent used.     

Virus safety of a porcine-derived medical device: evaluation of a viral inactivation method

The goal of this study was to evaluate the efficacy of a virus-inactivating process for use during the preparation of porcine-derived extracellular matrix biomaterials for human clinical implantation. Porcine small intestine, the source material for the tissue-engineered, small intestinal submucosa (SIS) biomaterial, was evaluated. Relevant enveloped, non-enveloped, and model viruses representative of different virus families were included in the investigation: porcine parvovirus (PPV), porcine reovirus, murine leukemia retrovirus (LRV), and porcine pseudorabies (herpes) virus (PRV). Samples of small intestine were deliberately inoculated with approximately 1 x 10(7) plaque-forming units (PFU) of virus which were thereafter exposed to a 0.18% peracetic acid/4.8% aqueous ethanol mixture for time periods ranging from 5 minutes to 2 hours. Enveloped viruses were more easily inactivated than non-enveloped viruses, but material processed for 30 minutes or longer inactivated all of the viruses. D(10) values were calculated and used to extrapolate the extent of inactivation after 2 hours. Viral titers were reduced by more than 14.0 log(10) PPV, 21.0 log(10) reovirus, 40.0 log(10) PRV, and 27.0 log(10) LRV, meeting international standards for viral sterility. These results demonstrate that treatment of porcine small intestine with a peracetic acid/ethanol solution leads to a virus-free, non-crosslinked biomaterial safe for xenotransplantation into humans.     

Prevalence of naturally occurring viral infections, Mycoplasma pulmonis and Clostridium piliforme in laboratory rodents in Western Europe screened from 2000 to 2003

In this report prevalence rates of rodent viruses in laboratory animals are presented based on routine serological screening of mouse and rat colonies from European institutes. The prevalences found during the period 2000-2003 are compared with those reported for 1981-1984 and 1990-1993. It is shown that some infections were eliminated from laboratory animal colonies (e.g. K-virus and polyomavirus) by taking preventative measures whereas other infections such as mouse hepatitis virus and parvoviruses remained at a high rate. Further decreases in prevalence rates in the last 10 years were found for infections such as pneumonia virus of mice, reovirus type 3, Sendai virus, sialodacryoadenitis/rat coronavirus and Mycoplasma pulmonis. The introduction of new detection methods showed that mouse parvovirus and rat parvovirus, both members of the Parvoviridae family, remain a major threat to laboratory mice and rats. Guinea pig cytomegalovirus and para-influenza virus appeared to be the most prevalent agents among laboratory guinea pigs. The importance of a standardized, up-to-date screening programme is discussed.     

Evaluation of a Virucidal Quantitative Carrier Test for Surface Disinfectants

Surface disinfectants are part of broader preventive strategies preventing the transmission of bacteria, fungi and viruses in medical institutions. To evaluate their virucidal efficacy, these products must be tested with appropriate model viruses with different physico-chemical properties under conditions representing practical application in hospitals.The aim of this study was to evaluate a quantitative carrier assay. Furthermore, different putative model viruses like adenovirus type 5 (AdV-5) and different animal parvoviruses were evaluated with respect to their tenacity and practicability in laboratory handling. To evaluate the robustness of the method, some of the viruses were tested in parallel in different laboratories in a multi-center study. Different biocides, which are common active ingredients of surface disinfectants, were used in the test. After drying on stainless steel discs as the carrier, model viruses were exposed to different concentrations of three alcohols, peracetic acid (PAA) or glutaraldehyde (GDA), with a fixed exposure time of 5 minutes. Residual virus was determined after treatment by endpoint titration.All parvoviruses exhibited a similar stability with respect to GDA, while AdV-5 was more susceptible. For PAA, the porcine parvovirus was more sensitive than the other parvoviruses, and again, AdV-5 presented a higher susceptibility than the parvoviruses. All parvoviruses were resistant to alcohols, while AdV-5 was only stable when treated with 2-propanol. The analysis of the results of the multi-center study showed a high reproducibility of this test system.In conclusion, two viruses with different physico-chemical properties can be recommended as appropriate model viruses for the evaluation of the virucidal efficacy of surface disinfectants: AdV-5, which has a high clinical impact, and murine parvovirus (MVM) with the highest practicability among the parvoviruses tested.     

Disinfectant effect of Persteril in combination with detergents

In laboratory conditions, the microbicidal effect, pH and changes in the content of peracetic acid and hydrogen peroxide were tested in Persteril at concentrations of 5 ml/l and 0.5 ml/l as well as in mixtures of these Persteril solutions with the detergents Jar, Pur, Hit, Corona, Sapon, Rekord and Universal. The efficiency and stability of Persteril solution in combination with the detergents were similar to those of Persteril aqueous solution. The tested mixtures ensured satisfactory bactericidal effect after 19-day storage. The sporicidal effect could be guaranteed during 5 days only at a concentration of 5 ml/l and provided disinfection was carried out by submerging. The above mixtures of Persteril and detergents have been recommended for one-stage disinfection in all types of medical facilities requiring simultaneous disinfection and washing.     

Inhibition of T cell-mediated functions by MVM(i), a parvovirus closely related to minute virus of mice

A purified preparation of MVM(i), a murine parvovirus closely related to minute virus of mice (MVM), was found to inhibit various functions mediated by murine T cells in vitro. Addition of MVM(i) virus to secondary allogeneic mixed leukocyte cultures resulted in the inhibition of both lymphocyte proliferation (3H-thymidine incorporation) and the generation of cytolytic T lymphocyte activity but not interferon production. MVM(i) virus also inhibited the growth and cytolytic activity of several cloned, long-term Lyt-2+ cytolytic T cell lines. Furthermore, the antigen-induced proliferative responses of parasite- (Leishmania) specific Lyt-1+ T cells in vitro was abrogated by the addition of MVM(i) virus to the culture. Finally, the suppression of an in vitro antibody response to SRBC by MVM(i) virus was the result of the inhibition of T helper cells required for the B cell response. These suppressive effects were specific for MVM(i); parallel studies in which the prototype MVM parvovirus was used showed no significant inhibition in the various systems tested.     

Molecular characterization of a newly recognized mouse parvovirus.

Mouse parvovirus (MPV), formerly known as orphan parvovirus, is a newly recognized rodent parvovirus distinct from both serotypes of minute virus of mice (MVM). Restriction analysis of the MPV genome indicated that many restriction sites in the capsid region were different from those of MVM, but most sites in the nonstructural (NS) region of the genome were conserved. MPV resembled MVM in genome size, replication intermediates, and NS proteins. Replication intermediates in infected cells were the same for MPV and MVM, including packaging of the 5-kb minus (V) strand. Furthermore, the MPV NS proteins were the same size as and present at the same ratio as the MVM(i) proteins in infected cells. Cloning and sequencing of the MPV genome revealed a genome organization closely resembling that of MVM, with conservation of open reading frames, promoter sequences, and splice sites. The left terminal hairpin was identical to that of MVM(i), but the right terminus was not conserved. Also, the MPV genome was unique in that it contained 1.8 copies of the terminal repeat sequence rather than the 1 or 2 copies found in other parvoviruses. The predicted amino acid sequence of the NS proteins of MPV and MVM(i) were nearly identical. In contrast, the predicted amino acid sequence of the capsid proteins of MPV was different from sequences of other parvoviruses. These results confirm that MPV is a distinct murine parvovirus and account for the antigenic differences between MPV and MVM.     

Bactericidal properties of peracetic acid and hydrogen peroxide, alone and in combination, and chlorine and formaldehyde against bacterial water strains.

The bactericidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a rapid micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against water isolates and culture collection strains. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a relatively rapid destruction of 10(5) bacteria/mL. The time-dependent bactericidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal bactericidal concentration was established in terms of time for a given mixture of peracetic acid and hydrogen peroxide. Determination of bactericidal concentrations showed that synergy was maintained with increasing contact time. Concentrations for minimal times of treatment by chemicals that provided interesting activities in vitro were tested for disinfection of ultrafiltration membranes. The bactericidal activities of peroxygen compounds were confirmed and synergism was maintained in working conditions. Chlorine showed a loss of efficacy when used on membranes.     

Characterization of an immunosuppressive parvovirus related to the minute virus of mice.

We have characterized an immunosuppressive parvovirus related to the minute virus of mice (MVM). The parvovirus, MVM(i), grew efficiently on the murine lymphoma cell line EL-4 and not on the A-9 strain of L-cells which is a host for the prototype MVM. MVM(i) was immunosuppressive for allogeneic mixed leukocyte cultures, inhibiting the generation of cytolytic T lymphocytes. MVM had no effect on mixed leukocyte cultures. MVM and MVM(i) particles were similar in buoyant density, sedimentation rate, appearance in the electron microscope, and polypeptide composition. We present restriction enzyme maps of the DNAs of MVM and MVM(i) which show that they are closely related. Out of 109 restriction endonuclease cleavage sites (representing together about 10% of the nucleotide sequence), 86 sites were shared by MVM and MVM(i), whereas 22 sites were absent from one of the two viruses. MVM(i) DNA had an apparent deletion of about 60 nucleotides relative to MVM, located near the 5' terminus of viral DNA.     

Humoral immunity and protection of mice challenged with homotypic or heterotypic parvovirus.

BACKGROUND AND OBJECTIVES: Two serotypes of autonomously replicating parvoviruses infect laboratory mice. Genome regions coding for the nonstructural proteins of minute virus of mice [MVM] and mouse parvovirus [MPV] are almost identical, whereas capsid-coding sequences are divergent. We addressed these questions: Does humoral immunity confer protection from acute infection after challenge with homotypic or heterotypic parvovirus, and if it confers protection against acute MPV infection, does it also protect against persistent MPV infection? METHODS: Infant mice without maternal antibody or antibody to MVM or MPV and young adult mice given normal mouse serum or antibody to MVM or MPV were challenged with homotypic or heterotypic virus. In situ hybridization with target tissues was the indicator of infection. RESULTS: Humoral immunity failed to confer protection against acute heterotypic parvovirus infection. In passive transfer studies, MPV DNA was observed occasionally in lymph nodes, intestine, or the spleen of MPV-challenged mice given homotypic antibody and kept for 6 or 28 days. Variable proportions of mice given MPV antibody and homotypic challenge had viral DNA in lymphoid tissues 56 days after virus inoculation. CONCLUSION: A mouse or colony that has sustained infection with MVM or MPV is probably fully susceptible to infection with the heterotypic virus.     

The structure of porcine parvovirus: comparison with related viruses

The structure of baculovirus-expressed porcine parvovirus (PPV) capsids was solved using X-ray crystallography and was found to be similar to the related canine parvovirus (CPV) and minute virus of mice (MVM). The PPV capsid protein has 57 % and 49 % amino acid sequence identity with CPV and MVM, respectively, but the degree of conservation of surface-exposed residues is lower than average. Consequently, most of the structural differences are on the surface and are the probable cause of the known variability in antigenicity and host range. The NADL-2 and Kresse strains of PPV have distinct tissue tropisms and pathogenicity, which are mediated by one or more of the amino acid residues 381, 386, and 436. These residues are on or near the surface of the virus capsid, where they are likely to be associated with virus-cell interactions.     

Effect of Biocides on MS2 and K Coliphages

Several biocides commonly used in disinfection processes as antibacterial and antifungal agents were tested for activity against MS2 and K coliphages. MS2 was resistant to most biocides; only glutaraldehyde (0.5%) and peracetic acid (1%) achieved a 4-log₁₀ titer reduction in 20 min. In contrast, K phage was sensitive to most biocides, being resistant only to phenol (2%) and chlorhexidine (1%).     

Rederivation of rat colonies seropositive for Bacillus piliformis and the subsequent screening for antibodies.

Latent infection of rats in a breeding colony with Bacillus piliformis detectable by antibodies to the agent in an immunofluorescence assay was eliminated by a combination of traditional rederivation techniques, using animal units not previously used for rat breeding, and the use of specific disinfection procedures. The success rate was apparently correlated with the use of peracetic acid instead of aldehyde products to decontaminate the animal unit.     

Coping with parvovirus infections in mice: health surveillance and control

Parvoviruses of mice, minute virus of mice (MVM) and mouse parvovirus (MPV), are challenging pathogens to eradicate from laboratory animal facilities. Due to the impediment on rodent-based research, recent studies have focused on the assessment of re-derivation techniques and parvoviral potential to induce persistent infections. Summarizing recent data, this review gives an overview on studies associated with parvoviral impact on research, diagnostic methods, parvoviral persistence and re-derivation techniques, demonstrating the complex nature of parvovirus infection in mice and unfolding the challenge of controlling parvovirus infections in laboratory animal facilities.     

Detection of rodent parvoviruses by use of fluorogenic nuclease polymerase chain reaction assays

Polymerase chain reaction (PCR) assays have proven useful for detection of rodent parvoviruses in animals and contaminated biological materials. Fluorogenic nuclease PCR assays combine PCR with an internal fluorogenic hybridization probe, eliminating post-PCR processing and potentially enhancing specificity. Consequently, three fluorogenic nuclease PCR assays were developed, one that detects all rodent parvoviruses, one that specifically detects minute virus of mice (MVM), and one that specifically detects mouse parvovirus 1 (MPV) and hamster parvovirus (HaPV). When rodent parvoviruses and other rodent DNA viruses were evaluated, the rodent parvovirus assay detected only rodent parvovirus isolates, whereas the MVM and MPV/HaPV assays detected only the MVM or MPV/ HaPV isolates, respectively. Each assay detected the equivalent of 10 or fewer copies of target template, and all fluorogenic nuclease PCR assays exceeded the sensitivities associated with previously reported PCR assays and mouse antibody production testing. In addition, each fluorogenic nuclease PCR assay detected the targeted parvovirus DNA in tissues obtained from mice experimentally infected with MVM or MPV. Results of these studies indicate that fluorogenic nuclease PCR assays provide a potentially high-throughput, PCR-based method to detect rodent parvoviruses in infected mice and contaminated biological materials.     

Nonhomologous recombination in the parvovirus chromosome: role for a CTATTTCT motif.

The mechanism of nonhomologous recombination in murine cells infected with the parvovirus minute virus of mice (MVM) has been investigated by analysis of DNA sequences at recombination junctions in naturally occurring deletion variants of the virus. We report here that nonhomologous recombination in the MVM chromosome is characterized by short homologies, by insertion at recombination junctions of foreign DNA sequences that are enriched for preferred eucaryotic topoisomerase I cleavage sites, and by an association with a common DNA sequence motif of the type 5'-CTATTTCT-3'. Additional analyses of broken MVM chromosomes provided evidence for specific enzymatic cleavage within 5'-CTTATC-3' and 5'-CTATTC-3' sequences. The results indicate that the 5'-CTATTTCT-3' motif is an important genetic element for nonhomologous recombination in the parvovirus chromosome.     

Comparison of promoter activity in Aleutian mink disease parvovirus, minute virus of mice, and canine parvovirus: possible role of weak promoters in the pathogenesis of Aleutian mink disease parvovirus infection.

Aleutian mink disease parvovirus (ADV) infection causes both acute and chronic disease in mink, and we have previously shown that it is the level of viral gene expression that determines the disease pattern. To study the gene regulation of ADV, we have cloned the P3 ADV and P36 ADV promoters in front of a reporter gene, the chloramphenicol acetyltransferase (CAT) gene, and analyzed these constructs by transient transfection in a feline kidney cell line and mouse NIH 3T3 cells. The genes for ADV structural proteins (VP1 and VP2) and the nonstructural proteins (NS-1, NS-2, and NS-3) were cloned into a eukaryotic expression vector, and their functions in regulation of the P3 ADV and P36 ADV promoters were examined in cotransfection experiments. The ADV NS-1 protein was able to transactivate the P36 ADV promoter and, to a lesser degree, the P3 ADV promoter. Constitutive activities of the P3 ADV and P36 ADV promoters were weaker than those of the corresponding promoters from the prototypic parvovirus minute virus of mice (MVM) and canine parvovirus (CPV). Also, the level of transactivation of the P36 ADV promoter was much lower than those of the corresponding P38 MVM and P38 CPV promoters transactivated with MVM NS-1. Moreover, the ADV NS-1 gene product could transactivate the P38 MVM promoter to higher levels than it could transactivate the P36 ADV promoter, while the P36 ADV promoter could be transactivated by MVM NS-1 and ADV NS-1 to similar levels. Taken together, these data indicated that cis-acting sequences in the P36 ADV promoter play a major role in determining the low level of transactivation observed. The P3 ADV and P4 MVM promoters could be transactivated to some degree by their respective NS-1 gene products. However, in contrast to the situation for the late promoters, switching NS-1 proteins between the two viruses was not possible. This finding may indicate a different mechanism of transactivation of the early promoters (P3 ADV and P4 MVM) compared with the late (P36 ADV and P38 MVM) promoters. In summary, the constitutive levels of expression from the ADV promoters are weaker than the levels from the corresponding promoters of MVM and CPV. Moreover, the level of NS-1-mediated transactivation of the late ADV promoter is impaired compared with the level of transactivation of the late promoters of MVM and CPV.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nuclear envelope disruption involving host caspases plays a role in the parvovirus replication cycle

Parvoviruses are small, nonenveloped, single-stranded DNA viruses which replicate in the nucleus of the host cell. We have previously found that early during infection the parvovirus minute virus of mice (MVM) causes small, transient disruptions of the nuclear envelope (NE). We have now investigated the mechanism used by MVM to disrupt the NE. Here we show that the viral phospholipase A2, the only known enzymatic domain on the parvovirus capsid, is not involved in causing NE disruption. Instead, the virus utilizes host cell caspases, which are proteases involved in causing NE breakdown during apoptosis, to facilitate these nuclear membrane disruptions. Studies with pharmacological inhibitors indicate that caspase-3 in particular is involved. A caspase-3 inhibitor prevents nuclear lamin cleavage and NE disruption in MVM-infected mouse fibroblast cells and reduces nuclear entry of MVM capsids and viral gene expression. Caspase-3 is, however, not activated above basal levels in MVM-infected cells, and other aspects of apoptosis are not triggered during early MVM infection. Instead, basally active caspase-3 is relocalized to the nuclei of infected cells. We propose that NE disruption involving caspases plays a role in (i) parvovirus entry into the nucleus and (ii) alteration of the compartmentalization of host proteins in a way that is favorable for the virus.     

New methods of disinfecting the hands]

An equimolar mixture--9.6 g of 85% formic acid and 19 g of 30% hydrogen peroxide which after 60-minute contact at room temperature contained over 3% and after 120-minute contact--over 5% performic acid was used. Before use the mentioned mixture was diluted with water (to the volume of 1 litre). Exposure period--3 minutes. Comparative tests demonstrated that a mixture with performic acid in hand disinfection provided somewhat better results than 0.2% peracetic acid, and that both peracids produced a much stronger disinfecting action on the skin microbial flora than 80% methyl alcohol.     

Clearance of minute virus of mice by flocculation and microfiltration

Clearance of minute virus of mice (MVM) from CHO cell suspensions by flocculation and microfiltration has been investigated. MVM is a parvovirus that is recommended by the U.S. Food and Drug Administration for validating clearance of parvoviruses. The feed streams were flocculated using a cationic polyelectrolyte. Virus clearance in excess of 10,000-fold was obtained in the bulk permeate for flocculated feeds streams. However, the level of clearance was only about 10- to 100-fold for unflocculated feed streams. The results suggest that virus clearance involves interactions between the MVM particles, the cationic polyelectrolyte, and the CHO cells present. Validating virus clearance is a major concern in the biotechnology industry. New unit operations are frequently added to the purification train simply to validate virus clearance. However, many of these unit operations are less effective at validating clearance of nonenveloped viruses. Validating clearance of parvoviruses is often particularly problematic as they are nonenveloped and the virus particles are small (18 to 24 nm), making physical removal difficult. The results obtained herein indicate that addition of the cationic polyelectrolyte not only results in significant clearance of MVM but also leads to an increase in permeate flux.