SEN virus infection in patients with hepatocellular carcinoma

The Role of Emerging and Neglected Viruses in the Etiology of Hepatitis

PURPOSE OF REVIEW

In this review, we present the overview of emerging and neglected viruses associated with liver involvement.

RECENT FINDINGS

Hepatitis E virus (HEV) emerged in the last two decades, causing hepatitis in many parts of the world. Moreover, liver involvement was also described in some emerging arboviral infections. Many reports showed dengue-associated liver injury; however, chikungunya, West Nile, tick-borne encephalitis, and Zika virus are rarely associated with clinically manifest liver disease. In addition, some neglected highly prevalent viruses such as adenoviruses and parvovirus B19 are capable of causing hepatitis in specific population groups. Anelloviruses (torque teno virus/torque teno mini virus/torque teno midi virus, SEN virus), human bocavirus, pegiviruses, and lymphocytic choriomeningitis virus have shown a little potential for causing hepatitis, but their role in the etiology of liver disease remains to be determined. In addition to the well-known hepatotropic viruses, many emerging and neglected viruses have been associated with liver diseases. The number of emerging zoonotic viruses has been increasingly recognized. While zoonotic potential of HEV is well documented, the recent identification of new hepatitis-related animal viruses such as HEV strains from rabbits and camels, non-primate hepaciviruses in domestic dogs and horses, as well as equine and porcine pegivirus highlights the possible zoonotic transmission in the context of "One Health." However, zoonotic potential and hepatotropism of animal hepatitis viruses remain to be determined.

Cloning and expression of N22 region of Torque Teno virus (TTV) genome and use of peptide in developing immunoassay for TTV antibodies

BACKGROUND

Torque Teno Virus (TTV) is a DNA virus with high rate of prevalence globally. Since its discovery in 1997, several studies have questioned the role of this virus in causing disease. However, it still remains an enigma. Although methods are available for detection of TTV infection, there is still a need for simple, rapid and reliable method for screening of this virus in human population. Present investigation describes the cloning and expression of N22 region of TTV-genome and the use of expressed peptide in development of immunoassay to detect anti-TTV antibodies in serum. Since TTV genotype-1 is more common in India, the serum positive for genotype-1 was used as source of N22 for expression purpose.

METHODS

Full length N22 region of ORF1 from TTV genotype-1 was amplified and cloned in pGEM®-T Easy vector. After cloning, the amplicon was transformed and expressed as a fusion protein containing hexa-histidine tag in pET-28a(+) vector using BL21 E. coli cells as host. Expression was conducted both in LB medium as well as ZYP-5052 auto-induction medium. The expressed peptide was purified using metal-chelate affinity chromatography and used as antigen in developing a blot immunoassay.

RESULTS

Analysis of translated product by SDS-PAGE and western blotting demonstrated the presence of 25 kDa polypeptide produced after expression. Solubility studies showed the polypeptide to be associated with insoluble fraction. The use of this peptide as antigen in blot assay produced prominent spot on membrane treated with sera from TTV-infected patients. Analysis of sera from 75 patients with liver and renal diseases demonstrated a successful implication of N22 polypeptide based immunoassay in screening sera for anti-TTV antibodies. Comparison of the immunoassay developed using expressed N22 peptide with established PCR method for TTV-DNA detection showed good coherence between TTV-DNA and presence of anti-TTV antibodies in the sera analysed.

CONCLUSIONS

This concludes that TTV N22 region may be expressed and safely used as antigen for blot assay to detect anti-TTV antibodies in sera.

Hepatitis viruses (other than hepatitis B and C viruses) as causes of hepatocellular carcinoma: an update

Chronic hepatitis B and C virus infections are universally accepted as causes of hepatocellular carcinoma in humans. Hepatitis A and E viruses cause only acute self-limiting infections of the liver. Of the remaining hepatitis viruses - Delta hepatitis, hepatitis G (GB-C), TT and SEN - all have at some time been incriminated as causes of hepatocellular carcinoma. Delta hepatitis virus requires helper functions from hepatitis B virus to become invasive. Chronic Delta/hepatitis B viral co-infection runs a more severe course than that resulting from chronic hepatitis B virus infection alone, with progression to cirrhosis being more likely and more rapid. A substantial majority of the early studies did not find an increased incidence of hepatocellular carcinoma in co-infected individuals. But more recently, an increased incidence of the tumour has been recorded more often than no increase. Further studies are needed to draw a firm conclusion with regard to the hepatocarcinogenic effect of dual Delta/hepatitis B virus co-infection. With one exception, no published study (of 13) has incriminated chronic infection with hepatitis G virus as a cause of hepatocellular carcinoma. The dissenting study, published in 1999, was the only one performed in the United States. Fewer studies of the hepatocarcinogenic effect of TT virus have been performed. Apart from one study, published in 1999, no convincing evidence is available that supports a causal role for TT virus in hepatocarcinogenesis. The exception was in Japanese patients with high hepatitis C viral loads but independent of chronic hepatitis C virus infection. No evidence has been produced to indicate that SEN virus causes hepatocellular carcinoma.

Prevalence and determinants of SENV viremia among adolescents in an endemic area of chronic liver diseases

BACKGROUND

SENV is a potential causative agent responsible for chronic liver diseases (CLDs) that are precipitated in early life. SENV prevalence in adolescents is unknown and its transmission route is uncertain.

METHODS

We randomly selected 824 serum samples from a cohort of 2383 adolescents aged 15-17 years who resided in Hualien County, an endemic area of liver diseases. Serum SENV genotype-D and genotype-H DNA were assayed by seminested polymerase chain reaction.

RESULTS

The positive rates for SENV-D and SENV-H DNA were 25.1% and 30.6%, respectively. Amis adolescents had a significantly higher rate of SENV-D viremia than Han Chinese adolescents (31.0%vs 22.2%; P = 0.025). Adolescents residing in rural or mountainous areas had significantly higher rates of SENV-H viremia than those residing in urban areas. There was no difference in the positive rates of SENV-D and SENV-H DNA among adolescents with or without hepatitis B virus (HBV) or hepatitis C virus (HCV) infection or history of hospitalization, surgery or blood transfusion. In multivariate analyses, males and adolescents residing in rural or mountainous areas had significantly higher risks of SENV-H viremia. As compared with those residing in urban areas, the multivariate-adjusted odds ratio (OR) for rural and mountainous areas were 1.49 (95% confidence interval [CI], 1.08-2.07) and 2.16 (95% CI, 1.32-3.53), respectively.

CONCLUSION

SENV-D and SENV-H infection were frequent among adolescents in eastern Taiwan. SENV was unlikely to be transmitted via the parenteral route and factors associated with level of urbanization were probably the major determinants of SENV infection.