Sequence diversity of TT virus in geographically dispersed human populations.
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TT virus (TTV) is a newly discovered DNA virus originally classified as a member of the Parvoviridae. TTV is transmitted by blood transfusion where it has been reported to be associated with mild post-transfusion hepatitis. TTV can cause persistent infection, and is widely distributed geographically; we recently reported extremely high prevalences of viraemia in individuals living in tropical countries (e.g. 74% in Papua New Guinea, 83% in Gambia; Prescott & Simmonds, New England Journal of Medicine 339, 776, 1998). In the current study we have compared nucleotide sequences from the N22 region of TTV (222 bases) detected in eight widely dispersed human populations. Some variants of TTV, previously classified as genotypes 1a, 1b and 2, were widely distributed throughout the world, while others, such as a novel subtype of type 1 in Papua New Guinea, were confined to a single geographical area. Five of the 122 sequences obtained in this study (from Gambia, Nigeria, Papua New Guinea, Brazil and Ecuador) could not be classified as types 1, 2 or 3, with the variant from Brazil displaying only 46-50% nucleotide (32-35% amino acid) sequence similarity to other variants. This study provides an indication of the extreme sequence diversity of TTV, a characteristic which is untypical of parvoviruses. (+info)
A mosquito densovirus infecting Aedes aegypti and Aedes albopictus from Thailand.
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A previously undescribed mosquito densovirus was detected in colonies of Aedes aegypti and Ae. albopictus from Thailand, using a polymerase chain reaction (PCR)-based assay. Phylogenetic analysis of this virus showed it to be most closely related to ADNV isolated from Russian Ae. aegypti. Both Aedes species were susceptible to oral infection with the Thai-strain virus. Larval mortality for Ae. albopictus was higher (82%) than for Ae. aegypti (51%). Aedes aegypti were able to transmit the virus vertically to a high (58%) proportion of G1 progeny, and the virus was maintained persistently for up to six generations. A PCR survey of adult Ae. aegypti and Ae. albopictus in Thailand indicated that only Ae. aegypti are infected in the field, with an overall prevalence of 44%. Densovirus infection in adult Ae. aegypti showed distinct seasonal variation. The Thai strain densovirus may play a role in structuring Ae. albopictus and Ae. aegypti populations in nature. (+info)
Immunofluorescent studies of the local immune response in the mammary glands of rats.
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Two irritants, phosphate-buffered saline and alcohol, and antigens including killed Brucella abortus, live B. abortus, Staphylococcus aureus, and rat parvovirus were separately infused into rat mammary glands during pregnancy, and by using immunofluorescent techniques, the numbers of immunoglobulin-containing cells in glands during lactation and involution were determined. The study provided basic information on the local immune response of the mammary gland to antigens of various types. In all experiments, the number of immunoglobulin M (IgM) cells present was small and no trends were apparent. IgA cells were always more prevalent than IgG cells. Fewer IgA cells were in the glands of rats infused with phosphate-buffered saline and alcohol than in normal rats. IgA cell prevalence was greatest in response to infusion of live B. abortus. Responses to live S. aureus and parvovirus were less pronounced, and infusion of killed B. abortus did not induce an elevation in IgA cell prevalence. IgG cell prevalence was greatest in response to infusion of live B. abortus or S. aureus and was decreasingly less pronounced in response to killed B. abortus and rat parvovirus. With the exception of parvovirus infusion, in regard to IgA cells, all glands locally infused with antigen had elevated IgA and IgG cell numbers when compared with noninfused glands in the same animal. (+info)
Concatemers of alternating plus and minus strands are intermediates in adenovirus-associated virus DNA synthesis.
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Replicating DNA molecules of adenovirus-associated virus (AAV) were selectively extracted from KB cells coinfected at 39.5 detrees with a DNA minus, temperature-sensitive mutant of adenovirus 5 (ts125) as helper. Under these conditions AAV DNA replication proceeds normally, but there is little, if any, adenovirus DNA synthesis. An analysis of the replicating molecules in sucrose density gradients reveals that there are AAV DNA intermediates which consist of covalently linked plus and minus DNA strands. Under denaturing conditions, these concatemers are linear single strands whose lengths can reach at least four times the size of the AAV genome. The most abundant concatemeric species is a dimer which presumably exists in vivo as a unit length hairpin. Unit length linear duplexes appear to be immediate precursors of plus and minus progeny strands. These findings are compatible with a self-priming mechanism for the synthesis of AAV DNA. (+info)
Uptake of minute virus of mice into cultured rodent cells.
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The uptake of minute virus of mice into cells in tissue culture was examined biochemically and by electron microscopy. Cell-virus complexes were formed at 4 degrees C, and uptake of virus was followed after the cells were shifted to 37 degrees C. The infectious particles appeared to enter cells at 37 degrees C by a two-step process. The first and rapid phase was measured by the resistance of cell-bound virus to elution by EDTA. The bulk of the bound virus particles became refractory to elution with EDTA within 30 min of incubation at 37 degrees C. The infectious particles became resistant to EDTA elution at the same rate. The second, slower phase of the uptake process was measured by the resistance of infectious particles to neutralization by antiserum. This process was complete within 2 h of incubation at 37 degrees C. During this 2-h period, labeled viral DNA became progressively associated with the nuclear fraction of disrupted cells. The uptake of infectious virus could occur during the G1 phase of the cell cycle and was not an S phase-specific event. The uptake process was not the cause of the S phase dependence of minute virus of mice replication. In electron micrographs, virus absorbed to any area of the cell surface appeared to be taken into the cell by pinocytosis. (+info)
Experimental in utero infection of fetal pigs with a porcine parvovirus.
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In utero infection of fetuses of six specific-pathogen-free large white sows at 35, 48, 55, 72, 99, and 105 days was studied. The fetuses were infected by direct inoculation of porcine parvovirus into the amniotic sac. The inoculation consisted of 0.25 ml of tissue culture fluid containing 10(5.5) mean tissue culture infective doses per ml of porcine parvovirus strain G10/1. Fetuses of one uterus horn were infected, whereas fetuses in the opposite horn were given 0.25 ml of noninfected cell culture material. No clinical signs of infection were observed; however, all sows developed antibodies 7 to 9 days postinfection. A total of 24 virus-inoculated fetuses and 20 control fetuses were studied. Fetuses infected at 35, 48, and 55 days of gestation died between about 5 and 22 days after infection. Virus was isolated from their organs and fetal blood. Virus spread to control fetuses but did not cause death and mummification or stimulate antibody production. Fetuses from sows infected at 72, 99, and 105 days of gestation survived. They developed high antibody titer in utero. Control piglets remained antibody free. (+info)
Immunosuppressive activity of a subline of the mouse EL-4 lymphoma. Evidence for minute virus of mice causing the inhibition.
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Filtered culture fluids from the early in vitro passages of a subline of the C57BL/6 mouse EL-4 lymphoma, EL-4(G-), were strongly inhibitory for BABL/c vs. C57BL/6 mixed lymphocyte cultures (MLC). The inhibitory activity could be preserved by storage at -75 degrees C or 4 degrees C, thus allowing its further characterization. The inhibitory factor was particulate (nondialyzable, sedimentable at 100,000 g for 1 h), very small (recovered after 0.10 mum filtration), sensitive to UV irradiation, but heat stable (56 degrees C, 1 h) and resistant to chloroform. It was infectious, since later, noninhibitory passages of EL-4(G-) tissue culture cells became strongly inhibitory upon inoculation with the culture fluid. This data was consistent with the inhibitory factor being an infectious virus. Virus analysis by mouse antibody production tests revealed that viruses were indeed present in EL-4(G-) ascites cells and in the culture fluid, and not in a late passage of EL-4(G-) tissue culture cells which were not inhibitory. Neutralization of the inhibitory factor was achieved by pretreatment with ascitic fluid or with the sera raised against those (EL-4(G-)-derived materials which contained viruses. Mouse reference immune sera against minute virus of mice (MVM) completely neutralized the inhibitory factor in the culture fluid or in EL-4(G-) ascites cells. Two prototype MVM strains, and one Kilham rat virus preparation, did not inhibit the mouse MLC. Thus, the possibility exists that a variant of MVM, or an unidentified virus, has been grown and selected for in EL-4(G-) cells and recognized, due to its immunosuppressive characteristics. In any event, immunosuppression by EL-4(G-) cells was not mediated by the tumor cells, their metabolic products, or associated endogenous type C viruses, but by an exogenous virus, most likely a variant MVM with immunosuppressive characteristics. This adds weight to a parallel observation from our laboratory on the immunosuppressive effects of Kilham rat virus in rat lymphocyte cultures. (+info)
The replication of rodent parvovirus X14.
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The replication of rodent parvovirus X14 DNA has been studied in rat embryo tissue culture cells. Virus DNA was isolated from I M-NaCl-SDS-pronase supernatant fluids from 24 h after infection. The majority of this DNA was 1-7 mum in length and double-stranded, indicating that it was an intermediate in the replication cycle of this single-stranded DNA virus. Single-stranded DNA of equivalent length was isolated directly from X14 virions. The buoyant density of this DNA was 1-728 g/ml whereas the double-stranded form banded at 1-714 g/ml in caesium chloride gradients. Difficulties in detecting significant amounts of single-stranded viral DNA directly from infected cells would appear to indicate that progeny single-stranded DNA is rapidly encapsidated after synthesis. (+info)