Abstract
The SEN virus has been tentatively linked to transfusion-associated non-A to E hepatitis. The aim of the present study was to 1) determine the prevalence of SEN virus among Egyptian patients with hepatitis C virus (HCV)-related chronic liver disease and patients undergoing hemodialysis and 2) demonstrate the clinical effect of SEN virus infection on coexistent hepatitis C in terms of severity and probability of developing hepatocellular carcinoma. Polymerase chain reaction was used to detect SEN virus-D and SEN virus-H DNA in serum samples of 74 patients with HCV-related chronic liver disease, 45 uremic patients undergoing maintenance hemodialysis, and 28 healthy controls. SEN virus-D/H DNA was detected in 13.5% of patients with chronic liver disease, 11.1% of patients undergoing hemodialysis, and 7.1% of healthy controls, with no significant differences between patients and the control group. Clinical and biochemical measures did not significantly differ between SEN virus-infected and noninfected patients in the chronic liver disease group or the hemodialysis group. The rate of SEN virus infection was significantly higher in patients with chronic liver disease and hepatocellular carcinoma (33.3%) than in those with chronic liver disease only (8.5%) (P < .05). In conclusion, SEN virus does not seem to be a common infection in Egyptian patients. It has no apparent influence on the severity of coexistent HCV-related chronic liver disease but could be a risk factor for hepatocellular carcinoma in such patients. Further studies are needed to define the etiopathogenic role of SEN virus infection in the development of hepatocellular carcinoma.
Introduction
SEN virus is a putative non-A to E hepatitis virus.[1] It was first isolated from the serum of an intravenous drug user infected with HIV.[2] By phylogenetic analysis, 9 different strains (A through I) have been identified and provisionally classified as members of the Circoviridae family, a group of single-stranded DNA viruses that includes the TT virus (TTV), TUS01, SANBAN, and YONBAN.[3–5] SEN virus is transmitted by blood, as seen by comparing the sequence homology between donors and recipients. Moreover, transfused patients are at higher risk of acquiring SEN virus than are nontransfused ones.[6]
Two SEN virus strains (D and H) were shown to be significantly associated with posttransfusion non-A to E hepatitis.[1,7] SEN virus-D and SEN virus-H were also detected more frequently in patients with chronic liver disease and hepatocellular carcinoma than in healthy adults.[8,9] However, the causal relation of these viruses to hepatic disease has not yet been proven. Hepatitis C virus (HCV) is a major cause of posttransfusion hepatitis and chronic liver disease.[10] More than half of patients with acute HCV infection develop chronic hepatitis that leads to cirrhosis and hepatocellular carcinoma, and at least 20% develop both.[11] Among patients with acute or chronic HCV infection, 22% to 85% were reported to be coinfected with SEN virus.[7,12–14] Although coinfection of HCV and SEN virus is common, the contribution of SEN virus infection to the course of HCV infection still requires clarification.
Patients undergoing long-term hemodialysis are considered to be at risk for infection by blood-borne viruses because that procedure is often associated with bleeding and blood transfusion.[15] These patients may also show hepatic dysfunction consistent with viral hepatitis, even without documented hepatitis A to E infection.[16]
The aim of the present study was to determine the prevalence of SEN virus infection among Egyptian patients with HCV-related chronic liver disease and uremic patients undergoing maintenance hemodialysis. We also sought to demonstrate the clinical effect of SEN virus infection on coexistent hepatitis C in terms of severity and probability of developing hepatocellular carcinoma.
Patients and Methods
Patients and serum samples
The study group consisted of 119 patients who were consecutively examined and followed up at Theodor Bilharz Research Institute in Giza, Egypt. Seventy-four patients had HCV-related chronic liver disease, and 45 patients had uremia and were undergoing maintenance hemodialysis. The chronic liver disease group comprised 49 males and 25 females, with a mean age (standard deviation) of 46 ± 11 years (range, 13–72 years).
Diagnosis of chronic HCV infection was based on the following criteria: 1) detection of HCV RNA or continuous positivity for antibody to HCV (anti-HCV) in serum for more than 6 months; 2) absence of detectable hepatitis B surface antigen; and 3) exclusion of other causes of chronic liver disease. Diagnosis of chronic liver disease was based on prolonged elevation of serum alanine aminotransferase (ALT) levels for more than 6 months. Liver cirrhosis was diagnosed by histopathologic examination or characteristic clinical signs of advanced liver disease. Hepatocellular carcinoma was diagnosed by histopathologic examination of liver biopsy samples or imaging studies and by serum alpha-fetoprotein levels greater than 400 ng/mL. Serum samples were collected from all patients at the time of clinical evaluation and were stored at −70°C until further testing. Eleven patients were receiving alpha-interferon/ribavirin combination therapy for 24 weeks; their serum samples were available before and 12 weeks after they had received this treatment.
The hemodialysis group comprised 38 men and 7 women; their age ranged from 34 to 72 years (mean ± standard deviation, 56 ± 9 years). The duration of hemodialysis ranged from 0.5 to 16 years. A history of blood transfusion was recorded for 34 (66.7%) patients. Maintenance hemodialysis had been performed 3 times a week by using disposable dialyzers with standard acetate dialysate. Serum samples were collected from all patients before the dialysis session and were stored at −70°C.
Twenty-eight healthy volunteers who had no clinical, virologic, or biochemical signs of liver disease provided serum samples and served as a control group.
Methods
All patients were subjected to full clinical assessment, with special emphasis on symptoms and signs of chronic liver disease. Abdominal ultrasonography and upper endoscopy were performed. Liver biopsy specimens were taken from 48 patients for histopathologic examination.
Laboratory tests
Liver biochemical tests, including ALT, aspartate aminotransferase, and total bilirubin, were done by using an autoanalyzer. Commercially available enzyme-linked immunosorbent assays were used to measure serum alpha-fetoprotein levels (DiaMetra, Milano, Italy), hepatitis B surface antigen, antihepatitis B core antibody (DiaSorin, Saluggia, Italy), and third-generation anti-HCV antibody (version 4 from the same laboratory); HCV serotyping (serotypes 1 to 6) was also done (Murex-Biotech Ltd, Dartford, United Kingdom). HCV RNA and hepatitis G virus RNA were detected by means of qualitative reverse transcriptase polymerase chain reaction (RT-PCR) with primers in the 5′ noncoding region, as reported elsewhere.[17,18] TTV DNA was detected by nested PCR using primers as designated by Takahashi and colleagues.[19]
Detection of SEN virus DNA by PCR
Total DNA was extracted from 100 µL of serum, as previously described by Boom and colleagues.[20] The extracted DNA was resuspended in 60 µL TE buffer. The oligonucleotide primers used were according to the method of Tanaka and colleagues.[4] For PCR, 50 µL of reaction mixture containing 10 µL of the DNA sample, 1X PCR buffer (10 mM Tris-h ydrochloride [pH, 9.0], 50 mM potassium chloride, 1.5 mM magnesium chloride, 0.01% gelatin, and 0.1% TritonX-100), 200 µM of each deoxyribonucleotide triphosphate, 20 pmol of each primer (sense primer for SEN virus-D, 5′-GTAACTTTGCGGTCAACTGCC-3′; sense primer for SEN virus-H, 5′-GGTGCCCCTWGTYAGTTGGCGGTT-3′ [W = A or T]; universal antisense primer, 5′-CCTCGGTTKSAAAKGTYTGATAGT-3′ [K = G or T, S = C or G, and Y= C or T]), and 1.5 U of Taq DNA polymerase were amplified in a thermal cycler (PTC- 200,MJ Research, St Bruno, Quebec, Canada) for 40 cycles. Each cycle consisted of denaturation at 95°C for 60 seconds, primer annealing at 55°C for 30 seconds, and extension at 72°C for 60 seconds, with a final extension step at 72°C for 10 minutes.[8] The amplified products (231 base pairs for SEN virus-D and 230 base pairs for SEN virus-H) were separated by using 3% agarose gel electrophoresis, stained with 0.3 µg/mL ethidium bromide, and visualized by using an ultraviolet transilluminator.
All methods were performed according to the principles outlined in the Declaration of Helsinki.[21] Institutional review board approval was obtained.
Statistical analysis
Numeric data were compared by using a Mann-Whitney U test, and categorical data were compared by using a chi-square test. A P value of .05 or less was considered to represent a statistically significant difference. Data analysis was performed using by SPSS software, version 10 (SPSS Inc, Chicago, Illinois).
Results
Table 1 shows the prevalence of SEN virus DNA among the 3 study groups. SEN virus-D/H DNA was detected in 13.5% of patients with chronic liver disease, 11.1% of patients undergoing hemodialysis, and 7.1% of healthy controls, with no significant differences between patients and the control group. SEN virus-D genotype was detected in 10 (59%) of 17 SEN virus-positive cases, and SEN virus-H genotype was detected in 7 (41%) cases. Distribution of SEN virus-D and SEN virus-H did not significantly differ between patients and the control group. Figure 1 shows the PCR findings for SEN virus genotype H.
Table 1.
Prevalence of SEN Virus Infection (Genotypes D and H)
| Group | Genotype D | Genotype H | Total |
|---|---|---|---|
| Chronic liver disease (n = 74) | 6 (8.1)* | 4 (5.4)* | 10 (13.5)* |
| Hemodialysis (n = 45) | 2 (4.4)* | 3 (6.7)* | 5 (11.1)* |
| Healthy control (n = 28) | 2 (7.1) | 0 (0) | 2 (7.1) |
Values are the number (percentage) of participants.
P > .05 relative to healthy control group.
Figure 1.
Agarose gel electrophoresis of PCR-amplified 230-base pair fragment of SEN virus-H (M = molecular size marker [Amplisize; Bio-Rad, Hercules, California], lanes 1 and 3 = positive samples, lane 2 = negative sample, lane 4 = positive control, and lane 5 = negative control.)
On the basis of clinical, ultrasonographic, and histopathologic findings, 39 (52.7%) of patients with chronic liver disease were given a diagnosis of chronic hepatitis; 35 (47.3%) were cirrhotic. Serotyping for HCV was done on 29 serum samples from patients with chronic liver disease. Serotype 4 was detected in 20 (69%) samples, and other serotypes (1, 3, and mixed) were detected in 9 (31%) samples. Although SEN virus coinfection was more associated with HCV serotype 4, no statistically significant differences were found in the distribution of different serotypes among SEN virus-infected and noninfected patients. Demographic, virologic, and clinical data of the patients with chronic liver disease were compared according to the status of SEN virus infection. Mean age, sex distribution, mean serum ALT levels, and virologic and clinical features did not significantly differ between SEN virus-infected and noninfected patients (Table 2).
Table 2.
Demographic, Virologic, and Clinical Features of Patients with HCV-Related Chronic Liver Disease Relative to SEN Viremia
| Patients with Chronic Liver Disease (n = 74) | |||
|---|---|---|---|
| Characteristic | SEN Virus Positive (n = 10) | SEN Virus Negative (n = 64) | P Value |
| Mean age ± SD (y) | 45 ± 10 | 46 ± 12 | NS |
| Men/women (n/n) | 5/5 | 44/20 | NS |
| Mean ALT level ± SD (IU/L) | 58 ± 22 | 61 ± 23 | NS |
| Virologic features | |||
| HCV | |||
| Anti-HCV-positive | 10 (100) | 64 (100) | NS |
| HCV RNA-positive | 5 (50) | 39 (61) | NS |
| Serotype 4* | 3/3 (100) | 17/26 (65) | NS |
| Other serotypes (1, 3, mixed)* | 0/3 (0) | 9/26 (34.6) | NS |
| TTV DNA-positive | 3 (30) | 18 (28.1) | NS |
| HGV RNA-positive | 1 (10) | 11 (17.1) | NS |
| Clinical features | |||
| Chronic hepatitis | 3 (30) | 36 (56.3) | NS |
| Cirrhosis | 7 (70) | 28 (43.8) | NS |
Unless otherwise noted, values are the number (percentage) of patients.
ALT = alanine aminotransferase; HBcAb = hepatitis B core antibody; HCV = hepatitis C virus; HGV = hepatitis G virus; NS = not significant; SD = standard deviation; TTV = TT virus.
The data are the number of positive samples/number of tested samples (percentage).
A subgroup analysis of 74 patients with chronic liver disease showed that 15 of these patients had hepatocellular carcinoma and 59 did not. The rate of SEN virus positivity was significantly higher in patients with chronic liver disease patients and hepatocellular carcinoma (33.3%) than in those with chronic liver disease only (8.5%) (P < .05) (Figure 2). However, no significant differences were noted between SEN virus-infected and noninfected patients (Table 3).
Figure 2.
Prevalence of SEN V infection among patients with chronic liver disease who did and did not have hepatocellular carcinoma. HCC = hepatocellular carcinoma. P < .05.
Table 3.
Demographic, Virologic, and Clinical Features of Patients with Chronic Liver Disease with and without Hepatocellular Carcinoma Relative to SEN Virus Infection
| Patients with Hepatocellular Carcinoma (n = 15) | Patients without Hepatocellular Carcinoma (n = 59) | |||||
|---|---|---|---|---|---|---|
| Characteristic | SEN Virus Positive (n = 5) | SEN Virus Negative (n = 10) | P Value | SEN virus Positive (n = 5) | SEN Virus Negative (n = 54) | P Value |
| Mean age ± SD (y) | 46 ± 14 | 58 ± 8 | NS | 43 ± 4 | 44 ± 11 | NS |
| Men/women (n/n) | ¼ | 6/4 | NS | 4/1 | 38/16 | NS |
| Mean ALT level ± SD (IU/L) | 54 ± 19 | 52 ± 18 | NS | 53 ± 12 | 62 ± 31 | NS |
| Virologic features | ||||||
| HCV | ||||||
| Anti-HCV-positive | 5 (100) | 10 (100) | NS | 5 (100) | 54 (100) | NS |
| HCV RNA-positive | 3 (60) | 5 (50) | NS | 2 (40) | 34 (63) | NS |
| Serotype 4* | 2/2 (100) | 4/4 (100) | NS | 1/1 (100) | 13/22 (59) | NS |
| Other serotypes (1, 3, mixed)* | 0/2 (0) | 0/4 (0) | NS | 0/1 (0) | 9/22 (41) | NS |
| HBcAb-positive | 1 (20) | 5 (50) | NS | 2 (40) | 18 (33.3) | NS |
| TTV DNA-positive | 3 (60) | 3 (30) | NS | 0 (0) | 15 (27.8) | NS |
| HGV RNA-positive | 0 (0) | 0 (0) | NS | 1 (20) | 11 (20.4) | NS |
| Clinical features | ||||||
| Chronic hepatitis | 1 (20) | 3 (30) | NS | 2 (40) | 33 (61) | NS |
| Cirrhosis | 4 (80) | 7 (70) | NS | 3 (60) | 21 (38.9) | NS |
Unless otherwise noted, values are the number (percentage) of patients.
ALT = alanine aminotransferase; HBcAb = hepatitis B core antibody; HCV = hepatitis C virus; HGV = hepatitis G virus; NS = not significant; SD = standard deviation; TTV = TT virus.
The data are the number of positive samples/number of tested samples (percentage).
Coinfection with SEN virus was detected in 1 of 11 patients with chronic HCV infection before they received alpha-interferon/ribavirin combination therapy. Clearance of both HCV RNA and SEN virus DNA was observed 12 weeks after the patients had received the treatment.
Table 4 compares the clinical and virologic characteristics of patients undergoing hemodialysis who did and did not have SEN virus infection. Duration of hemodialysis and history of blood transfusion did not significantly differ between infected and noninfected patients. Coinfection with HCV and hepatitis B virus was observed among 80% and 20%, respectively, of SEN virus-infected patients undergoing hemodialysis.
Table 4.
Demographic, Clinical, and Virologic Data of Hemodialysis Patients with and without SEN Virus Infection
| Characteristics | SEN Virus Positive (n = 5) | SEN Virus Negative (n = 40) | P Value |
|---|---|---|---|
| Mean age ± SD (y) | 59 ± 9 | 56 ± 10 | NS |
| Men/women (n/n) | 4/1 | 34/6 | NS |
| Mean ALT level ± SD (IU/L) | 16 ± 12 | 15 ± 8 | NS |
| Mean duration of hemodialysis ± SD (y) | 4.4 ± 3.05 | 7.12 ± 4.37 | NS |
| Transfusion history* | 4 (80) | 26 (65) | NS |
| Virologic features* | |||
| Hepatitis B surface antigen | 1 (20) | 3 (7.5) | NS |
| HCV antibody | 4 (80) | 31 (77.5) | NS |
ALT = alanine aminotransferase; HCV = hepatitis C virus; NS = not significant; SD = standard deviation.
Data are the number (percentage) of patients.
Discussion
The clinical relevance of SEN virus infection alone or in combination with HCV infection remains controversial. Given the high incidence of HCV in Egypt (10%–13%),[22] we investigated the prevalence and clinical effect of SEN virus on coexistent HCV infection. We also determined the prevalence of SEN virus among patients undergoing hemodialysis, a group at high risk of being infected with parenterally transmitted viruses.
Infection with SEN virus has been observed in 22% to 85% of patients with chronic hepatitis C[7,12–14] and in 27% to 61% of uremic patients undergoing maintenance hemodialysis.[16,23–25] We found that the prevalence of SEN virus infection was 13.5% in patients with chronic HCV infection and 11.1% in patients undergoing hemodialysis; these rates were similar to that in healthy controls. The observed differences in the prevalence of SEN virus DNA between our patients and those in previous studies may be attributed to different routes of transmission, such as injection-drug use, or to the use of slightly different primers.[26] The low prevalence of SEN virus infection relative to HCV infection may be attributed to the rate of clearance of the SEN virus. Umemura and colleagues[1] found that about 77% of posttransfusion infected patients cleared the virus within 6 months after being infected and that 13% appeared to have chronic SEN virus infection.
Dual infection with HCV and either hepatitis A or hepatitis B virus has been associated with a more and rapidly progressive disease.[27] In contrast, in our study, clinical and biochemical evaluations of patients with chronic liver disease and patients undergoing hemodialysis did not significantly differ between those infected with HCV alone and those coinfected with HCV and SEN virus. In this and previous studies,[13,28–30] no evidence suggests that SEN virus causes hepatitis when it is the sole agent detected, or worsens the severity or persistence of coexistent chronic HCV. In the present study, coinfection with TTV and hepatitis G virus were detected in 30% and 10% of SEN virus-infected patients, respectively. However, the distribution of TTV or hepatitis G virus did not significantly differ between SEN virus-infected and noninfected patients. Previous studies done in our laboratory found that neither virus was causally associated with chronic liver disease or hepatocellular carcinoma.[31,32] Some authors have suggested a specific link between HCV genotypes 2a and 1b and coinfection with SEN virus among patients with chronic HCV.[14,33] In the present study, the association of SEN virus with HCV serotype 4 may be attributed to the high prevalence of this serotype in Egypt (>90%).[34]
The influence of coinfection with SEN virus on HCV response to combination therapy has been investigated, with contradictory results. Rigas and colleagues[35] reported that coinfection with SEN virus might adversely affect the outcome of combination therapy. However, other studies found that HCV response was not affected by the presence of SEN virus and recorded a significantly higher rate of SEN virus response to combination therapy than the response of HCV.[14,29,33] We could not judge this influence because SEN virus DNA was detected in only 1 patient before receipt of combination therapy. However, clearance of both HCV RNA and SEN virus DNA was observed after 12 weeks of treatment. Additional studies using a large number of patients are required to confirm this finding and to document the duration of response and rate of spontaneous clearance of this virus over time.
Most cases of hepatocellular carcinoma are associated with chronic infection with hepatitis B virus or HCV.[36] In the present study, the prevalence of SEN virus infection was significantly higher in patients with chronic liver disease and hepatocellular carcinoma than in those with chronic liver disease only. This finding may suggest a possible role of SEN virus as a cofactor in the development of hepatocellular carcinoma. However, clinical and virologic measures did not significantly differ between patients with hepatocellular carcinoma who were SEN virus infected and those who were not infected. High prevalence of SEN virus infection among patients with hepatocellular carcinoma may be attributed to increased risk for exposure as a result of multiple medical or radiologic interventions, in addition to the decreased rate of spontaneous clearance due to immunosuppression.[37,38] Whether coexistent SEN virus infection has a role in the etiology of HCV-related hepatocellular carcinoma or is just an innocent bystander requires further investigation.
We found that SEN virus DNA was detected in 7.1% of healthy volunteers, a rate similar to that previously reported in Thailand, Turkey, and Japan (range, 5%–10%)[9,12,30] but higher than that in the United States and Italy (range, 2%–3%)[39,40] and lower than that in China (31%).[7] These data suggest that SEN virus has a global distribution with marked geographic differences in its prevalence. The explanations for these differences are unknown, but they may result from interactions among behavioral, social and biological factors.[41]
Geographic distribution of different SEN virus variants was also noted. Previous studies have shown that SEN virus-D is the predominant genotype in Japan and Greece,[42,43] whereas SEN virus-H genotype is predominant in the United States and Taiwan.[1,8] Our results indicated that SEN virus-D is more prevalent than SEN virus-H among Egyptian patients and healthy controls. This variability in the prevalence of different genotypes may be attributed to different exposure rates or routes of infection or to differing rates of spontaneous clearance between these two strains.[33] Whether differences in SEN virus variants affect the heterogeneity in clinical outcome or response to antiviral therapy in patients with chronic SEN virus infection requires further study.
Previous studies strongly suggest that SEN virus is transmitted through blood transfusion.[1,14,44] However, our results indicate that SEN virus was not absolutely associated with a history of blood transfusion or duration of hemodialysis. In addition, no statistically significant differences were observed for the distribution of HCV or hepatitis B virus (well-known blood-borne viruses) between SEN virus-infected and noninfected hemodialysis patients. A possible explanation is that SEN virus can be transmitted through not only parenteral but also nonparenteral routes. This possibility is supported by the finding that TTV, which is distantly related to SEN virus, can also be transmitted through the fecal-oral route.[45] Recent data suggest that vertical transmission of SEN virus does occur, presumably at delivery, but that it may not induce persistent viremia.[46] Further epidemiologic studies on larger groups of SEN virus-infected patients are recommended.
In conclusion, SEN virus does not seem to be a common infection in Egyptian patients. It has no apparent influence on the severity of coexistent HCV-related chronic liver disease, but it may have a role in the development of hepatocellular carcinoma in these patients. SEN virus is probably transmitted via parenteral and nonparenteral routes. Further studies are needed to define the pathogenic and clinical importance of SEN virus infection.
Funding Information
This work was funded by Hepatitis Research Project number 74D of Microbiology Department, TBRI.
Footnotes
Reader Comments on: SEN Virus Infection in Egyptian Patients With Chronic Hepatitis C and Patients Undergoing Hemodialysis See reader comments on this article and provide your own.
Readers are encouraged to respond to the author at manalkandil@hotmail.com or to Peter Yellowlees, MD, Deputy Editor of The Medscape Journal of Medicine, for the editor's eyes only or for possible publication as an actual Letter in the Medscape Journal via email: peter.yellowlees@ucdmc.ucdavis.edu
Contributor Information
Maisa Omar, Microbiology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Samah Saad El-Din, Microbiology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Nevine Fam, Microbiology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Manal Diab, Microbiology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt Author's email: manalkandil@hotmail.com.
Mohamed Shemis, Biochemistry Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Manar Raafat, Nephrology Department, Theodor Bilharz Research Institute, Al-Azhar University, Giza, Egypt.
Moataz Seyam, Tropical Medicine Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Moataz Hssan, Tropical Medicine Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Afkar Badawy, Pathology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Maha Akl, Pathology Department, Theodor Bilharz Research Institute, Cairo University, Giza, Egypt.
Mohamed Saber, Biochemistry Department, Theodor Bilharz Research Institute, Ain Shams University, Giza, Egypt.
References
- 1.Umemura T, Yeo AE, Sottini A, et al. SEN virus infection and its relation to transfusion-associated hepatitis. Hepatology. 2001;33:1303–1311. doi: 10.1053/jhep.2001.24268. [DOI] [PubMed] [Google Scholar]
- 2.Primi D, Sortini A. Identification and characterization of SEN virus, a family of novel DNA viruses. Antiviral Ther. 2000;5(suppl 1):G.7. (Abstract) [Google Scholar]
- 3.Takahashi K, Iwasa Y, Hijikata M, et al. Identification of a new human DNA virus (TTV-like mini virus, TLMV) intermediately related to TT virus and chicken anaemia virus. Arch Virol. 2000;145:979–993. doi: 10.1007/s007050050689. [DOI] [PubMed] [Google Scholar]
- 4.Tanaka Y, Primi D, Wang RY, et al. Genomic and molecular evolutionary analysis of a newly identified infectious agent (SEN virus) and its relationship to the TT virus family. J Infect Dis. 2001;138:359–367. doi: 10.1086/318091. [DOI] [PubMed] [Google Scholar]
- 5.Kojima H, Kaita KD, Zhang M, et al. Genomic analysis of a recently identified virus (SEN virus) and genotypes D and H by polymerase chain reaction. Antiviral Res. 2003;60:27–33. doi: 10.1016/s0166-3542(03)00133-5. [DOI] [PubMed] [Google Scholar]
- 6.Akiba J, Umemura T, Alter HJ, et al. SEN virus: epidemiology and characteristics of a transfusion transmitted virus. Transfusion. 2005;45:1084–1088. doi: 10.1111/j.1537-2995.2004.00209.x. [DOI] [PubMed] [Google Scholar]
- 7.Mu SJ, Du J, Zhan LS, et al. Prevalence of a newly identified SEN virus in China. World J Gastroenterol. 2004;10:2402–2405. doi: 10.3748/wjg.v10.i16.2402. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Kao JH, Chen W, Chen PJ, et al. Prevalence and implication of a newly identified infectious agent (SEN virus) in Taiwan. J Infect Dis. 2002;185:389–392. doi: 10.1086/338472. [DOI] [PubMed] [Google Scholar]
- 9.Tangkijvanich P, Theamboonlers A, Sriponthong M, et al. SEN virus infection in patients with chronic liver disease and hepatocellular carcinoma in Thailand. J Gastroenterol. 2003;38:142–148. doi: 10.1007/s005350300023. [DOI] [PubMed] [Google Scholar]
- 10.Alter HJ, Seeff LB. Recovery, persistence and sequelae in hepatitis C virus infection: a perspective on long-term outcome. Semin Liver Dis. 2000;20:17–35. doi: 10.1055/s-2000-9505. [DOI] [PubMed] [Google Scholar]
- 11.Lauer GM, Walker BD. Hepatitis C virus infection. N Engl J Med. 2001;345:41–45. doi: 10.1056/NEJM200107053450107. [DOI] [PubMed] [Google Scholar]
- 12.Shibata M, Wang RY, Yoshida M, et al. The presence of a newly identified agent (SEN virus) in patients with liver diseases and in blood donors in Japan. J Infect Dis. 2001;184:400–404. doi: 10.1086/322050. [DOI] [PubMed] [Google Scholar]
- 13.Schréter I, Kristian P, Jarèušaka P, et al. Detection of SEN virus in the general population and different risk groups in Slovakia. Folia Microbiol. 2006;51:223–228. doi: 10.1007/BF02932126. [DOI] [PubMed] [Google Scholar]
- 14.Kao JH, Chen W, Chen PJ, et al. SEN virus infection in patients with chronic hepatitis C: preferential coinfection with hepatitis C genotype 2a and no effect on response to therapy with interferon plus ribavirin. J Infect Dis. 2003;187:307–310. doi: 10.1086/346055. [DOI] [PubMed] [Google Scholar]
- 15.Wreghitt TG. Blood-borne virus infections in dialysis units – a review. Rev Med Virol. 1999;9:101–109. doi: 10.1002/(sici)1099-1654(199904/06)9:2<101::aid-rmv234>3.0.co;2-u. [DOI] [PubMed] [Google Scholar]
- 16.Pirovano S, Gregorini G, Malacarne F, et al. High prevalence of SEN virus infection in patients on maintenance haemodialysis: frequent mixed infections with different variants and evidence for nosocomial transmission of the virus. Intervirology. 2005;48:216–222. doi: 10.1159/000084598. [DOI] [PubMed] [Google Scholar]
- 17.Van Doorn LJ. Molecular biology of the hepatitis C virus. J Med Virol. 1994;43:345–356. doi: 10.1002/jmv.1890430406. [DOI] [PubMed] [Google Scholar]
- 18.Schauder GG, Dawson GJ, Simons JN, et al. Molecular and serological analysis in the transmission of the GB hepatitis agents. J Med Virol. 1995;46:81–90. doi: 10.1002/jmv.1890460117. [DOI] [PubMed] [Google Scholar]
- 19.Takahashi K, Hoshino H, Ohta Y, et al. Very high prevalence of TT virus (TTV) infection in general population in Japan revealed by a new set of PCR primers. Hepatol Res. 1998;12:233–239. [Google Scholar]
- 20.Boom R, Sol CJ, Salimans MM, et al. Rapid and simple method for purification of nucleic acid. J Clin Microbiol. 1990;28:495–503. doi: 10.1128/jcm.28.3.495-503.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.World Medical Association. Declaration of Helsinki: ethical principles for medical research involving human subjects. Available at: http://www.wma.net/e/policy/pdf/17c.pdf. Accessed September 4, 2008.
- 22.Mohamed MK. Epidemiology of HCV in Egypt. Afro-Arab Liver J. 2004;3:41–52. [Google Scholar]
- 23.Kobayashi N, Tanaka E, Umemura T, et al. Clinical significance of SEN virus infection in patients on maintenance haemodialysis. Nephrol Dial Transplant. 2003;18:348–352. doi: 10.1093/ndt/18.2.348. [DOI] [PubMed] [Google Scholar]
- 24.Dai CY, Chuang WL, Chang WY, et al. SEN virus infection among patients on maintenance haemodialysis in southern Taiwan. J Infect. 2005;51:110–115. doi: 10.1016/j.jinf.2004.10.007. [DOI] [PubMed] [Google Scholar]
- 25.Hsu BG, Wang LY, Hu CT, et al. SEN virus infection in patients on peritoneal dialysis. Perit Dial. 2007;27:74–78. [PubMed] [Google Scholar]
- 26.Schroter M, Laufs R, Zollner B, et al. Prevalence of SEN-H viraemia among healthy subjects and individuals at risk for parenterally transmitted diseases in Germany. J Viral Hepat. 2002;9:455–459. doi: 10.1046/j.1365-2893.2002.00390.x. [DOI] [PubMed] [Google Scholar]
- 27.Chen YD, Liu MY, Yu WL, et al. Mix-infections with different genotypes of HCV and with HCV plus other hepatitis viruses in patients with hepatitis C in China. World J Gastroenterol. 2003;9:984–992. doi: 10.3748/wjg.v9.i5.984. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Yoshida H, Kato N, Shiratori Y. Weak association between SEN virus viraemia and liver disease. J Clin Microbiol. 2001;40:3140–3145. doi: 10.1128/JCM.40.9.3140-3145.2002. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Sagir A, Adams O, Kirschberg O, et al. SEN virus does not affect treatment response in hepatitis C virus coinfected patients but SEN virus response depends on SEN virus DNA concentration. World J Gastroenterol. 2004;10:1893–1897. doi: 10.3748/wjg.v10.i13.1893. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Serin MS, Koksal F, Oksuz M, et al. SEN virus prevalence among non-B and non-C hepatitis patients with high liver function tests in south of Turkey. Jpn J Infect Dis. 2005;58:349–352. [PubMed] [Google Scholar]
- 31.Omar M, Fam N, Saad El-Dine S, et al. Torque Teno virus (TTV) infection in Egyptian patients with chronic liver disease and hepatocellular carcinoma. Nature Sci. 2006;4:38–45. [Google Scholar]
- 32.Omar M, Fam N, Saad El-Dine S, et al. Impact of hepatitis G virus infection on chronic hepatitis C Egyptian patients: clinical, virological and ultrastructural aspects. Life Sci J. 2006;3:9–17. [Google Scholar]
- 33.Dai CY, Chuang WL, Chang WY. Co-infection of SENV-D among hepatitis C patients treated with combination therapy with high dose interferon-alfa and ribavirin. World J Gastroenterol. 2005;11:4241–4245. doi: 10.3748/wjg.v11.i27.4241. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Mezban ZD, El Wakil A. Hepatitis C in Egypt. Available at: http://www.hcvadvocate.org/hcsp/articles/Egypt_06.html Accessed November 24, 2008.
- 35.Rigas B, Hasan I, Rehman R, et al. Effect on treatment outcome of coinfection with SEN viruses in patients with hepatitis C. Lancet. 2001;358:1961–1962. doi: 10.1016/S0140-6736(01)06968-9. [DOI] [PubMed] [Google Scholar]
- 36.Tabor K. Hepatocellular carcinoma: global epidemiology. Digest Liver Dis. 2001;33:115–117. doi: 10.1016/s1590-8658(01)80062-1. [DOI] [PubMed] [Google Scholar]
- 37.Tangkijvanich P, Theamboonlers A, Sriponthong M, et al. SEN virus infection and the risk of hepatocellular carcinoma: a case-control study. Am J Gastroenterol. 2003;28:2500–2504. doi: 10.1111/j.1572-0241.2003.07689.x. [DOI] [PubMed] [Google Scholar]
- 38.Momosaki S, Umemura T, Scudamore CH, et al. SEN virus infection in patients with hepatocellular carcinoma. J Viral Hepat. 2005;12:435–438. doi: 10.1111/j.1365-2893.2005.00618.x. [DOI] [PubMed] [Google Scholar]
- 39.Mushahwar IK. Recently discovered blood-borne viruses: are they hepatitis viruses or merely endosymbionts? J Med Virol. 2000;62:399–404. doi: 10.1002/1096-9071(200012)62:4<399::aid-jmv1>3.0.co;2-u. [DOI] [PubMed] [Google Scholar]
- 40.Bowden S. New hepatitis viruses: contenders and pretenders. J Gastroenterol Hepatol. 2001;16:124–131. doi: 10.1046/j.1440-1746.2001.02405.x. [DOI] [PubMed] [Google Scholar]
- 41.Pfeiffer RM, Tanaka Y, Yeo AE, et al. Prevalence of SEN viruses among injection drug users in the San Francisco Bay area. J Infect Dis. 2003;188:13–18. doi: 10.1086/375740. [DOI] [PubMed] [Google Scholar]
- 42.Umemura T, Alter HJ, Tanaka E, et al. SEN virus: response to interferon alfa and influence on the severity and treatment response of coexistent hepatitis C. Hepatology. 2002;35:953–959. doi: 10.1053/jhep.2002.32536. [DOI] [PubMed] [Google Scholar]
- 43.Umemura T, Tanaka E, Ostapowicz G, et al. Investigation of SEN virus infection in patients with cryptogenic acute liver failure, hepatitis-associated aplastic anaemia, or acute and chronic non-A-E hepatitis. J Infect Dis. 2003;188:1545–1552. doi: 10.1086/379216. [DOI] [PubMed] [Google Scholar]
- 44.Spataro P, Di-Pietro A, Scoglio ME, et al. Prevalence of SENV-H and SENV-D virus: epidemiological study in blood donors and dialysis patients. Ren Fail. 2006;28:441–448. doi: 10.1080/08860220600684225. [DOI] [PubMed] [Google Scholar]
- 45.Okamoto H, Nishizaw T, Kate N, et al. Molecular cloning and characterization of a novel DNA virus (TTV) associated with post-transfusion hepatitis of unknown etiology. Hepatol Res. 1998;10:1–6. [Google Scholar]
- 46.Moriondo M, Resti M, Betti L, et al. SEN virus co-infection among HCV-RNA-positive mothers, risk and outcome of child infection during a 1-year follow-up. J Viral Hepat. 2007;14:355–359. doi: 10.1111/j.1365-2893.2006.00805.x. [DOI] [PubMed] [Google Scholar]
