Pegivirus humano: potencial patogénico y riesgo de desarrollo de linfoma no Hodgkin / Human Pegivirus: pathogenic potential and non-Hodgkin lymphoma development risk

Resumen El pegivirus humano (HPgV) es un virus ARN que fue identificado en el año 1995. Actualmente se encuentra clasificado dentro de la familia Flaviviridae, género Pegivirus, relacionado filogenéticamente con el virus de la hepatitis C (VHC). El HPgV es un virus linfotrópico, con replicación en médula ósea, tejidos linfoides, y en células mononucleares de sangre periférica. Este virus se transmite por vía parenteral y sexual. Según estimaciones realizadas, en el mundo existen alrededor de 750 millones de personas infectadas por este agente. Se ha evidenciado que hasta en 25% de los casos se presenta una infección persistente, y aunque se considera que el HPgV es un virus no patogénico, existen evidencias epidemiológicas que sugieren una relación con el desarrollo de desórdenes linfoproliferativos, particularmente linfoma no Hodgkin (LNH). Algunos estudios han reportado una alta prevalencia de HPgV en pacientes con LNH comparado con donantes de sangre y/o pacientes con enfermedades hematológicas no malignas, lo que se asocia a un incremento en el riesgo relativo para el desarrollo de LNH en personas infectadas. De otra parte, existen estudios epidemiológicos que contradicen esta asociación, por lo que el rol de HPgV en la aparición de desórdenes lifoproliferativos es un tema actual de debate. En el presente manuscrito se discute el potencial patogénico derivado de los mecanismos de infección persistente del HPgV, así como las principales evidencias sobre la relación entre el HPgV y el riesgo de desarrollo de LNH.

The human pegivirus (HPgV), classified in the Flaviviridae family - Pegivirus genus, is an RNA virus identified in 1995. HPgV is a lymphotrophic virus, with replication sites in bone marrow and lymphoid tissue, as well as in peripheral blood mononuclear cells (PBMCs). Transmission is through sexual and parenteral routes, and recent estimations suggest nearly 750 million people are infected with HPgV worldwide. Almost 25% of infected individuals can develop persistent infection. Until now, HPgV has been considered a non-pathogenic virus; however, epidemiological studies suggest a potential role in lymphoproliferative diseases, particularly in the development of non-Hodgkin lymphoma (NHL). The evidence of this is controversial and the role of HPgV in lymphomagenesis has not yet been demonstrated. Several studies report a high prevalence of HPgV infection in patients with NHL compared to controls and patients with other hematological diseases. Therefore, analytic studies show that HPgV could be related to an increased risk of NHL development. Conversely, other studies indicate no association between HPgV and NHL, so the role of HPgV in lymphomagenesis is not clear. This review summarizes the main findings related to HPgV's pathogenic potential and association with NHL.

Hepatitis G virus infection in India: prevalence and phylogenetic analysis based on 5' non-coding region.

OBJECTIVES: To determine the prevalence of hepatitis G virus (HGV) infection in western India and to carry out phylogenetic analysis of HGV isolates. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) assay was used to detect HGV RNA in serum samples obtained from paid plasma donors, patients with hemophilia and voluntary blood donors. Nine Indian and one Kenyan HGV RNA-positive samples were sequenced in the 5' non-coding region (5'-NCR). Phylogenetic analysis based on the comparison of a 101 nucleotide fragment from a large number of HGV isolates from 22 countries (including Indian and Kenyan sequences obtained during the present study) was carried out. RESULTS: HGV RNA positivity rates among paid plasma donors from a commercial plasmapheresis unit (7/43, 16.3%) and patients with hemophilia (5/44, 11.4%) were significantly higher than that in voluntary blood donors (0/51; p=0.003 and 0.019, respectively). Among patients with acute non-A to E hepatitis and fulminant hepatic failure, 1 of 50 and 1 of 28 were HGV RNA-positive, whereas 6 of 49 (12%) patients with chronic liver disease had circulating HGV RNA. All Indian isolates belonged to genotype 2, whereas the Kenyan isolate formed a distinct branch within genotype 1 consisting of African isolates. CONCLUSION: Our results suggest existence of parenteral transmission of HGV in the Indian population. HGV was not an important cause of acute non-A to E hepatitis or fulminant hepatic failure among the patients investigated. Genotype 2 seems to be the most prevalent genotype in western India.

Clinical implications of hepatitis G virus (HGV) infection in patients of acute viral hepatitis & fulminant hepatic failure.

BACKGROUND & OBJECTIVES: Viral hepatitis is a major public health problem especially in developing countries such as India. Hepatitis viruses A, B, C, D and E are all well characterized and molecularly defined agents with unequivocal association with human liver disease but there is evidence of hepatitis in humans caused by certain transmissible agents which cannot be classified with the above hepatotoric viruses. The role of recently discovered hepatitis G virus (HGV/GBV-C) as an independent heaptitis agent is controversial. Recently, we have shown a relatively high frequency of HGV infection in fulminant hepatic failure but the virus was often detected in co-infection with hepatitis B or E virus. The present study has therefore been carried out to evaluate the clinical significance of HGV infection in acute viral hepatitis (AVH) and fulminant hepatic failure (FHF) through follow up of HGV positive patients till their clinical and biochemical recovery. METHODS: The study included 50 patients comprising 35 of AVH and 15 of FHF. These patients were evaluated on the basis of history, physical examination, liver function profile and serological markers for hepatitis A, B, C and E. Those patients serologically negative for HBV and HCV infection were further screened for HBV DNA and HCV RNA by PCR. All the samples were screened for presence of HGV-RNA by RT-PCR using inner and outer primers sequences selected from NS3 helicase region of the HGV genome. FHF patients who died were subjected to postmortem liver biopsy and these biopsy specimens were also screened for HGV-RNA. Repeat detection of HGV-RNA was done after clinical and biochemical recovery of the patients. RESULTS: Of 35 AVH patients, HGV infection was detected in 5 patients (14.3%) while 4 of 15 patients (26.6%) in the FHF group were positive for HGV-RNA. Five HGV positive AVH patients were followed till clinical and biochemical recovery and all of them tested positive for HGV-RNA at follow up (6 weeks to 6 months). Out of 4 HGV positive FHF patients, only one survived and his repeat sample after clinical and biochemical recovery tested positive for HGV-RNA. INTERPRETATION & CONCLUSIONS: The results suggest that HGV infection does occur in patients of AVH and FHF and HGV viraemia persists for a long time even after clinical and biochemical recovery. These observations point towards a possible non-pathogenic role of hepatitis G virus infection.

Prevalence of hepatitis G virus in Pakistani children with transfusion dependent beta- thalassemia major.

We ought to obtain data on the prevalence of the newly discovered tranfusion transmittable hepatitis G virus in polytransfused b- thalassemia major children. Each individual had received multiple blood transfusions, from 12 to 36 per year. No documentation of prior hepatic infection was available. Serum samples were collected prospectively from the randomly selected subjects and were analyzed for HGV RNA by polymerase chain reaction using primer specific for two different regions of the HGV genome. Among the 100 individuals examined 21 were positive for HGV RNA. Four patients had evidence of dual infection, both HGV RNA and HCV RNA were isolated from their sera. While in one sample presence of both HGV RNA and HBV DNA was established. Only one child was positive for hepatitis E antibodies. The sera of 10 children were reactive for hepatitis B surface antigen whereas 35 individuals were positive for hepatitis C virus antibody. The ALT levels were variable in HGV infected children. Four out of 16 (25%) showed peak ALT levels of 218 IU/I, 8/16 (50%) children demonstrated slightly elevated ALT levels whereas 25% individuals showed normal ALT levels. Alkaline Phosphatase levels were elevated in 90% of the children and 20% patients of this series also had higher GGT levels. The observed AP levels were not statistically different among HGV, HGV/HCV or HGV/HBV groups. Even though the ALT levels were deranged in the children with HGV alone but none of the children had demonstrated symptoms of liver disease, their direct and total bilirubin levels were normal and no complain of jaundice was recorded. In conclusion, our findings suggested that like other blood borne hepatic viruses, HGV is also prevalent in the high risk group of multiple transfused patients in Pakistan but our results support the absence of any causal relationship between HGV and hepatitis.

Hepatitis G virus (HGV) infection & its pathogenic significance in patients of cirrhosis.

In the present study the hepatitis G virus (HGV) infection and its pathogenic significance in patients of cirrhosis were assessed using reverse transcription plus nested polymerase chain reaction (RT-PCR). Serum samples were collected from a total of 50 patients of histologically proven non-alcoholic cirrhosis and from a control group consisting of 50 healthy voluntary blood donors. HGV RNA was detected by RT-PCR using primer sequences located in the conserved NS3 helicase region of HGV genome. Serological evaluation for markers of chronic infection with HBV (HBsAg, IgG anti-HBc, HBeAg) and HCV (anti-HCV) was carried out using commercially available kits. HBV DNA and HCV RNA were also tested by PCR in those samples that were found to be non-B, non-C by serological assays. Serological evidence of exposure to HBV was found in 31 (62%) and to HCV in 15 (30%) patients. HGV RNA was detected in 6 (12%) cirrhosis patients and in 2 (4%) healthy blood donors but the difference between the two groups was not statistically significant. Of the 6 HGV positive patients, 2 were coinfected with HBV, 1 with HCV, while the remaining 3 belonged to non-B, non-C category. No significant difference was observed in the clinical and biochemical profiles of HGV-positive and HGV-negative patients except that a history of blood transfusion was significantly (P < 0.005) more common in the former. The findings indicate that the HGV infection is commonly observed in both cirrhosis patients as well as healthy blood donors. A significant association of the virus with blood transfusion is indicative of a parenteral route of transmission. The observations of this study also suggest that the pathogenic role of HGV in the causation of liver disease may be insignificant.

Hepatitis G infection and therapeutic response to interferon in HCV-related chronic liver disease.

Circulating HGV-RNA was determined in 117 patients with HCV-related chronic liver disease and in 200 healthy blood donors. The patients, aged 50.8+/-13.8 years, were classified as chronic hepatitis (CH; n = 82), liver cirrhosis (n = 25) and hepatocellular carcinoma (HCC; n = 10). HGV-RNA was detected in 5 (4.3%) patients, all with CH and in 10 (5%) of blood donors. The majority of all groups (52% to 70%) were infected with HCV genotype II/1b, including 4/5 patients with HGV co-infection. Of 5 patients with HGV co-infection, 4 were positive for anti-HBs and anti-HBc and none exhibited jaundice. A 24-week course of interferon treatment with 12-month follow-up was achieved in 27 patients with chronic active hepatitis, including 3 with HGV co-infection. Of these, 55.6% responded to the therapy, but only 6/27 (22.2%) patients were sustained responders. The majority of sustained responders were HCV genotype III/2a (4/6) while genotype II/1b was found in the majority of patients with relapse (7/9) and non-responders (9/12). At the 48- month follow up, 2/6 sustained responders (one with HGV co-infection) became HCV RNA positive. These results show that the prevalence of HGV infection in HCV-related chronic liver disease is low, as in the general population, and is found in younger patients with chronic hepatitis. HGV coinfection does not interfere with clinical severity, disease progression or response to interferon in patients with HCV-related chronic liver disease. The favorable factors ofinterferon treatment for HCV infection are young age, low HCV-RNA levels and HCV genotype III/2a.

Hepatitis GBV-C infection in intravenous drug users.

Our group has investigated 204 intravenous drug users for the presence of GBV-C-RNA by means of reverse transcriptase polymerase chain reaction (RT-PCR). The majority of the individuals tested were male, their age ranging from 16 to 63 years, and the duration of intravenous drug use from one to 40 years. We detected GBV-C-RNA in 46 of the 204 IVDUs (22.5%) with its prevalence peaking in the age group between 21 to 30 years while decreasing with advancing age. Similarly, its frequency was found in inverted relation to the duration of drug use. The present findings strongly hint at the host's immune system's capacity to clear hepatitis GBV-C as opposed to the other blood-borne hepatitis viruses. From the liver function tests performed we could not detect any statistically significant difference regarding ALT elevation observed in GBV-C-positive as compared to GBV-C-negative individuals. To date, GBV-C in most cases does not appear to cause any serious liver disease.

Hepatitis G virus infection in hemodialysis and continuous ambulatory peritoneal dialysis patients

To determine the prevalence and clinical relevance of HGV infection in dialysis patients, we performed a cross-sectional study of 61 HD patients and 79 Continuous Ambulatory Peritoneal Dialysis (CAPD) patients. HGV-RNA was identified by reverse-transcription (RT) polymerase chain reaction (PCR) assay with primers from the 5'-untranslated region of the viral genome. The prevalence of HGV infection was similar in HD and CAPD patients (9.8% vs. 12.7%), while that of HCV infection was significantly higher in HD patients compared to CAPD patients (16.4% vs. 1.3%, p < 0.05). The mean age (49.2 +/- 13.4 vs. 46.7 +/- 13.0 years), male to female ratio (2.4:1 vs. 1.3:1), history of transfusion (62.3% vs. 49.4%), history of hepatitis (27.9% vs. 26.6%), mean ALT level during the previous 6 months (22.4 +/- 37.9 vs. 14.0 +/- 7.4 IU/L), and the prevalence of HBsAg (8.2% vs. 6.3%) showed no difference between HD and CAPD patients. In both HD and CAPD patients, the presence of HGV RNA was not related to age, sex, duration of dialysis, history of transfusion, history of hepatitis, or to the presence of HBV or HCV markers. There was no significant difference in the clinical and biochemical data between patients with isolated HGV infection (n = 12) and patients without viremia (n = 106). The clinical feature of patients coinfected with HGV and HBV (n = 2), or HGV and HCV (n = 2) seemed to be similar to those of patients with isolated HBV (n = 8) or HCV (n = 9) infection. In conclusion, the prevalence of HGV infection was not different between HD and CAPD patients, and HGV infections did not seem to be associated with clinically significant hepatitis. The routes of HGV transmission, other than transfusion or contamination during HD procedure, were suspected.

A proposed rapid method for genomic characterization of GBV-C/hepatitis G virus (HGV)

GBV-C/Hepatitis G virus (HGV) has been identified as an infectious agent for humans although its potential involvement as a pathogenic virus is still controversial. Hitherto, 3 genotypes have been identified worldwide by c-DNA sequencing. This method allows genomic viral RNA clustering according to the geographical source of the strains, but its potential value in type- (or even strain-) specific pathogenesis has only started to be explored. Since this method requires highly specialized laboratories and is rather expensive, we propose a rapid method based on differential restriction fragment lenght polymorphism (RFLP) of 5'NCR amplicons. Using Hinf I, Dra I and Mae II endonucleases, it is possible to obtain different restriction patterns to discriminate among 1a, 1b, 2a, 2b and 3 subtypes/types. This methodology could be useful for large scale molecular epidemiology as well as for studies on viral pathogenesis.

The newly discovered non A-E hepatitis viruses.

Two biotechnology companies have recently announced the discovery of 4 new hepatitis viruses, provisionally named HGV and GBV agents (GBV-A, GBV-B, and GBV-C). Using a molecular biological approach, the genomes of these viruses were identified from non-A-E hepatients patients who had no markers to any previously known hepatitis viruses. The new viruses are members of family Flaviviridae, and are closely related to hepatitis C virus (HCV). Preliminary studies show that the prevalence of GBV agents and HGV are alarmingly high in blood donors in the United States, Europe, Africa and Japan. The viruses are transmitted parenterally, similar to HCV and hepatitis B virus (HBV), Chronic infection is common and can lead to cirrhosis. Some chronic hepatitis cases caused by these viruses respond to interferon treatment. The viruses can coinfect with HCV and/or HBV. A number of questions about these new viruses remain to be answered, including the magnitude of the problems, clinical significance, mode of transmission and populations at risk, as well as the appropriate treatment.