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(1/273) Susceptibility of TT virus to interferon therapy.

TT virus (TTV) is a newly identified single-stranded DNA virus. We retrospectively analysed serum samples from sixteen patients, infected with both hepatitis C virus (HCV) and TTV, and who had been treated with interferon. An elevated serum alanine aminotransferase level after interferon was associated with persistence of HCV (abnormal in five of seven patients with persistence of HCV compared with normal in all nine patients who showed eradication of HCV) irrespective of persistence of TTV. Comparison of partial viral DNA nucleotide sequences and phylogenetic analysis showed that viral strains that had a high identity to the prototype virus were more resistant to interferon than those showing low nucleotide sequence identity. Although we observed no liver cell injury caused by persistent TTV infection, the mechanism(s) of TTV resistance to interferon should be further investigated for a better understanding of viral diseases and establishment of therapy.  (+info)

(2/273) Further observations on the epidemiology and spread of epizootic haematopoietic necrosis virus (EHNV) in farmed rainbow trout Oncorhynchus mykiss in southeastern Australia and a recommended sampling strategy for surveillance.

Epizootic haematopoietic necrosis virus (EHNV) is an iridovirus confined to Australia and is known only from rainbow trout Oncorhynchus mykiss and redfin perch Perca fluviatilis. Outbreaks of disease caused by EHNV in trout populations have invariably been of low severity, affecting only 0+ post-hatchery phase fingerlings < 125 mm in length. To date the virus has been demonstrated in very few live in-contact fish, and anti-EHNV antibodies have not been found in survivors of outbreaks, suggesting low infectivity but high case fatality rates in trout. During an on-going study on an endemically infected farm (Farm A) in the Murrumbidgee River catchment of southeastern New South Wales, EHNV infection was demonstrated in 4 to 6 wk old trout fingerlings in the hatchery as well as in 1+ to 2+ grower fish. During a separate investigation of mortalities in 1+ to 2+ trout on Farm B in the Shoalhaven River catchment in southeastern New South Wales, EHNV infection was demonstrated in both fingerlings and adult fish in association with nocardiosis. A 0.7% prevalence of antibodies against EHNV was detected by ELISA in the serum of grower fish at this time, providing the first evidence that EHNV might not kill all infected trout. EHNV infection on Farm B occurred after transfer of fingerlings from Farm C in the Murrumbidgee river catchment. When investigated, there were no obvious signs of diseases on Farm C. 'Routine' mortalities were collected over 10 d on Farm C and EHNV was detected in 2.1% of 190 fish. Tracing investigations of sources of supply of fingerlings to Farm B also led to investigation of Farm D in Victoria, where the prevalence of anti-EHNV antibodies in 3+ to 4+ fish was 1.3%. The results of this study indicate that EHNV may be found in trout in all age classes, need not be associated with clinically detectable disease in the population, can be transferred with shipments of live fish, can be detected in a small proportion of 'routine' mortalities and may be associated with specific antibodies in a small proportion of older fish. Sampling to detect EHNV for certification purposes should be based on examination of 'routine' mortalities rather than random samples of live fish. Antigen-capture ELISA can be used as a cost effective screening test to detect EHNV on a farm provided that sampling rates conform with statistical principles.  (+info)

(3/273) Early acquisition of TT virus (TTV) in an area endemic for TTV infection.

TT virus (TTV) is widely distributed, with high frequencies of viremia in South America, Central Africa, and Papua New Guinea. The incidence and timing of infection in children born in a rural area of the Democratic Republic of Congo was investigated. TTV viremia was detected in 61 (58%) of 105 women attending an antenatal clinic and in 36 (54%) of 68 infants. Most infants acquired the infection at >/=3 months postpartum. Surprisingly, TTV infection was detected in a large proportion of children with TTV-negative mothers (13 [43%] of 30). Nucleotide sequences of TTV-infected children were frequently epidemiologically unlinked to variants detected in the mother. These three aspects contrast with the maternal transmission of hepatitis G virus/GB virus C in this cohort and suggest an environmental source of TTV infection comparable to hepatitis A virus and other enterically transmitted infections.  (+info)

(4/273) Prevalence of TT virus infection in US blood donors and populations at risk for acquiring parenterally transmitted viruses.

Two overlapping sets of TT virus (TTV)-specific polymerase chain reaction primers were used to test for presence of TTV, which was found in approximately 10% of US volunteer blood donors, 13% of commercial blood donors, and 17% of intravenous drug abusers. The rate of TTV infection among US non-A, non-B, non-C, non-D, non-E hepatitis patients was only 2%. Among commercial blood donors and intravenous drug abusers, only 1%-3% of the TTV-positive individuals were coinfected with GB virus C (GBV-C), a parenterally transmitted virus. This suggests that GBV-C and TTV may have different routes of transmission. Comparison of the sensitivities of 2 TTV polymerase chain reaction (PCR) primer sets showed that the majority of samples were detected with only 1 of the 2 sets. Therefore, previous studies in which only a single PCR primer pair was used may have significantly underestimated the true prevalence of TTV.  (+info)

(5/273) Excretion into bile of a novel unenveloped DNA virus (TT virus) associated with acute and chronic non-A-G hepatitis.

Recently, an unenveloped, single-stranded DNA virus named TT virus (TTV) has been reported in association with hepatitis of non-A-G etiology. Five patients with TTV viremia, who received bile drainage or cholecystectomy, were tested for TTV DNA in bile by polymerase chain reaction with heminested primers. TTV DNA was detected in bile from all patients; titers were 10-100 times higher than in serum in 4 and at a comparable level in the remaining 1 patient. TTV DNA was detected in feces, also, in 1 of the 2 patients tested. The buoyant density of TTV in bile from 1 tested patient (1.33-1.35 g/cm3) was the same as that in feces (1.32-1.35 g/cm3). TTV may be secreted via bile into feces in a transmissible form and would spread by a fecal-oral route for deep and wide penetration into the general population.  (+info)

(6/273) High prevalence of TT virus infection in healthy children and adults and in patients with liver disease in Taiwan.

A newly identified DNA virus, named TT virus (TTV), was found to be related to transfusion-associated hepatitis. We conducted the following experiments to evaluate its pathogenic role in liver disease and potential modes of transmission. We used PCR to detect TTV DNA in serum. The rates of TTV viremia in 13 patients with idiopathic acute hepatitis, 14 patients with idiopathic fulminant hepatitis, 22 patients with chronic hepatitis, and 19 patients with cirrhosis of the liver were 46, 64, 55, and 63%, respectively, and were not significantly different from those in 50 healthy control subjects (53%). PCR products derived from seven patients with liver disease and three healthy controls were cloned and then subjected to phylogenetic analyses, which failed to link a virulent strain of TTV to severe liver disease. TTV infection was further assessed in an additional 148 subjects with normal liver biochemical tests, including 30 newborns (sera collected from the umbilical cord), 23 infants, 16 preschool children, 21 individuals of an age prior to that of sexual experience (aged 6 to 15 years), 15 young adults (aged under 30 years), and 43 individuals older than 30 years. The rates of TTV viremia were 0, 17, 25, 33, 47, and 54%, respectively. These findings suggest that TTV is transmitted mainly via nonparenteral daily contact and frequently occurs very early in life and that TTV infection does not have a significant effect on liver disease.  (+info)

(7/273) TT virus infection in patients with hepatitis C: frequency, persistence, and sequence heterogeneity.

TT virus (TTV) was recently identified in the serum of a patient with hepatitis. The role of TTV in liver disease has not been established. Three polymerase chain reaction (PCR) protocols were used to detect TTV DNA in sera of persons infected with hepatitis C virus (HCV) and in blood donors. Sera from 11.5% of HCV-infected patients and 7.7% of blood donors were positive by protocols 1 or 2. In contrast, 48.7% and 57.7% of sera, respectively, were positive when tested by protocol 3. There was no difference in the severity of hepatitis in persons coinfected with TTV and HCV when compared with those infected with HCV alone, regardless of which TTV PCR protocol was used. TTV DNA persisted in serum samples taken up to 6 years apart in individual patients. Sequence analysis indicated that most viral sequences were distinct between patients, and there was evidence of genetic heterogeneity and viral evolution within individuals.  (+info)

(8/273) Marked genomic heterogeneity and frequent mixed infection of TT virus demonstrated by PCR with primers from coding and noncoding regions.

A nonenveloped, single-stranded, and circular DNA virus designated TT virus (TTV) has been reported in association with hepatitis of unknown etiology. TTV has a wide sequence divergence (approximately 52%), by which it is classified into at least 16 genotypes separated by an evolutionary distance of >0.30. Therefore, the detection of TTV DNA by polymerase chain reaction would be influenced by primers deduced from conserved or divergent regions of the genome. Of the 30 sera from healthy individuals, up to 17% tested positive with primers deduced from coding region, much less frequently than up to 93% testing positive with primers from noncoding region. These differences were not attributable to the sensitivity of detection, because a cloned TTV DNA of genotype 1a was detected sensitively (up to 1 copy per test) with primers deduced from either the coding or the noncoding region of the same genotype. Sera testing positive only with noncoding region primers, or those showing higher titers with noncoding than coding region primers, contained TTV DNA strains with sequence divergence of 47-53% from the TA278 isolate of genotype 1a within the N22 region spanning 222-231 nucleotides. Some of the sera contained two or three TTV DNA strains of distinct genotypes. These results indicate TTV strains with extremely high sequence divergence prevailing in healthy individuals and frequent mixed infection with TTV strains of distinct genotypes.  (+info)