Potential cellular receptors involved in hepatitis C virus entry into cells

Lectibodies as antivirals

Growing concerns regarding the emergence of highly transmissible viral diseases highlight the urgent need to expand the repertoire of antiviral therapeutics. For this reason, new strategies for neutralizing and inhibiting these viruses are necessary. A promising approach involves targeting the glycans present on the surfaces of enveloped viruses. Lectins, known for their ability to recognize specific carbohydrate molecules, offer the potential for glycan-targeted antiviral strategies. Indeed, numerous studies have reported the antiviral effects of various lectins of both endogenous and exogenous origins. However, many lectins in their natural forms, are not suitable for use as antiviral therapeutics due to toxicity, other unfavorable pharmacological effects, and/or unreliable manufacturing sources. Therefore, improvements are crucial for employing lectins as effective antiviral therapeutics. A novel approach to enhance lectins' suitability as pharmaceuticals could be the generation of recombinant lectin-Fc fusion proteins, termed "lectibodies." In this review, we discuss the scientific rationale behind lectin-based antiviral strategies and explore how lectibodies could facilitate the development of new antiviral therapeutics. We will also share our perspective on the potential of these molecules to transcend their potential use as antiviral agents.

CD81+ Exosomes Play a Pivotal Role in the Establishment of Hepatitis C Persistent Infection and Contribute Toward the Progression of Hepatocellular Carcinoma

CD81 serves as an immune modulator, playing its role in tumor growth and metastasis of hepatitis C virus (HCV)-mediated hepatocellular carcinoma (HCC). CD81 serves as a coreceptor of viral entry and is found to be enriched in exosomes. HCV E2 protein when associated with CD81 may be responsible for B cell lymphoproliferative disorders, as extrahepatic manifestation. Studies predict that HCV association with exosomes, leads to the establishment of persistent infection, through immune evasion. Herein, we confirm the association of HCV particles with CD81⁺ exosomes. Breifly, exosomes were enriched from peripheral blood of chronic HCV patients who have developed HCC. Sideways, exosomes were also enriched from peripheral blood of healthy individuals, who exhibited normal liver function test profile and had no known infection. Isolation of subpopulation of CD81⁺ exosomes was performed through immunocapture, followed by detection using FACS. Scanning electron microscopy confirmed the physical association of a fraction of exosome with HCV. CD81⁺ exosomes from chronic HCV patients with HCC were more granulated and larger when compared with those enriched from a healthy individual and HCV RNA was also detected in enriched fractions of CD81⁺ exosomes from HCV-positive HCC patients only, through real-time quantitative polymerase chain reaction. We concluded that CD81⁺ exosomes carry HCV particles and the association plays a pivotal role in establishing persistent infection, through immune evasion, thus leading to HCC progression. Exosomal CD81 and its interacting proteins might, therefore, serve as a potential prognostic marker and therapeutic target in HCV progression mediated by active HCV infection.

Vertical Hepatitis C Virus Transmission is not Related to Mother-Child Class-1 HLA Concordance

Mother-child human leukocyte antigen (HLA) diversity is protective for vertical transmission of some viruses. The aim of this study is to evaluate the role of mother-child HLA diversity on hepatitis C virus (HCV) vertical transmission. Forty consecutive HCV infected and 46 consecutive control uninfected children born to HCV-RNA positive mothers were evaluated for HLA class-1 type concordance with their mothers. No significant difference in the degree of HLA concordance was found between HCV infected and uninfected children both when A, B, C ( p=0.30) and when only A and B alleles were evaluated ( p=0.59). Mother-infant HLA concordance does not affect HCV vertical transmission.

The individual and combined influence of HIV and hepatitis C virus on dyslipidaemia in a high-risk Hispanic population

OBJECTIVES

To assess the effects of chronic hepatitis C (HCV) and HIV infection on dyslipidaemia in a Hispanic population at high risk of insulin resistance.

METHODS

We compared serum lipids and C-reactive protein (CRP) in 257 Hispanic adults including 47 HIV- mono-infected, 43 HCV-mono-infected and 59 HIV/HCV-co-infected individuals as well as 108 healthy controls. We also assessed the effect of HCV on lipid alterations associated with antiretroviral therapy (ART), and the impact of HCV and HIV on the associations among insulin resistance, triglycerides and cholesterol.

RESULTS

HCV infection was associated with lower total and low-density lipoprotein (LDL) cholesterol, but not high-density lipoprotein (HDL) cholesterol or triglycerides compared with healthy controls. HIV infection was associated with higher triglycerides and lower HDL, but not total or LDL cholesterol. HCV mitigated the elevation of triglycerides associated with ART. In healthy Hispanic adults, insulin resistance was significantly correlated with higher triglycerides, CRP and lower HDL. HIV infection nullified the association of insulin resistance with triglycerides and HDL, and the association of triglycerides with LDL. HCV infection nullified the association of insulin resistance with triglycerides, HDL and CRP.

CONCLUSIONS

HCV co-infection alters the profile of HIV-associated dyslipidaemia. The clinical significance of these findings for cardiovascular complications in HIV merits further study.

HCV genetic variability: from quasispecies evolution to genotype classification

HCV is a ssRNA virus belonging to the Flaviviruses and is found worldwide worldwide in humans. Following primary infection, persistent infection develops in more than 85% of cases, which in up to 30% of cases, may progress to liver disease, cirrhosis and hepatocellular carcinoma. The virus presents a high degree of genetic variability owing to the combination of a lack of proofreading by the RNA-dependent RNA polymerase and a high level of viral replication. This genetic variability allows the classification of genotypes, subtypes, isolates and quasispecies to which epidemiological and pathogenetic significance may be associated. The features and biological implications of HCV variability and of quasispecies dynamics in infection transmission, mechanisms of chronicity and resistance to antiviral therapy are discussed.

Metabolic profiles in patients with chronic hepatitis C: a case-control study

BACKGROUND

The clinical implications of metabolic profiles in patients with chronic hepatitis C remain controversial. To study the association of metabolic abnormalities with chronic hepatitis C, we conducted a case-control study with special emphasis on serum lipid pattern, fasting blood glucose, and adiponectin.

METHODS

We enrolled 500 patients with chronic hepatitis C and 536 sex and age-matched controls. Unadjusted and adjusted associations of demographic and metabolic variables were estimated.

RESULTS

Chronic hepatitis C patients had higher alanine aminotransferase (ALT) and high-density lipoprotein-cholesterol levels, but lower total cholesterol (TC), triglyceride (TG), and low-density lipoprotein-cholesterol levels than controls. Stratifying ALT level according to its upper limit of normal, HCV infection was associated with younger age, female gender, and higher TC levels in chronic hepatitis C patients with normal ALT levels, but with lower TC and lower TG levels in those with abnormal ALT levels. By using multiple linear regression analyses for subjects with available adiponectin data, presence of HCV infection was independently associated with higher serum adiponectin levels.

CONCLUSIONS

Metabolic profiles of chronic hepatitis C patients are affected by age, gender, serum adiponectin, and ALT levels. Further longitudinal studies are needed to clarify the complex interplay between HCV infection and metabolic profiles.

Higher risk of hepatitis C virus perinatal transmission from drug user mothers is mediated by peripheral blood mononuclear cell infection

Maternal injection drug use and peripheral blood mononuclear cell infection by hepatitis C virus are important risk factors for perinatal transmission of the virus. The aim of present study was to evaluate the independent association of these two factors on perinatal transmission. Forty-eight consecutive mothers who transmitted infection to their offspring and 122 consecutive mothers who did not, together with their children, were examined. Both maternal injection drug use and peripheral blood mononuclear cell infection were significantly more frequent in infected than in uninfected children (respectively P = 0.04; odds ratio 2.33, 95% confidence intervals 1.02-5.42 and P < 10(-6); odds ratio and 95% confidence intervals not calculable due to zero values). Multivariate analysis confirmed the link between maternal peripheral blood mononuclear cell infection and perinatal transmission (P < 10(-6); odds ratio and 95% confidence intervals not calculable due to zero values) but no association was found with maternal injection drug use. The high risk of perinatal transmission found in injection drug use mothers is dependent on maternal peripheral blood mononuclear cell infection by hepatitis C virus. Peripheral blood mononuclear cell infection represents one of the most important risk factors for hepatitis C virus perinatal transmission.

Cell surface expression of LDL receptor in chronic hepatitis C: correlation with viral load

The LDL receptor (LDL-R) has been proposed as the viral receptor for Hepatitis C virus (HCV). This hypothesis has been based exclusively on in vitro studies. In human mononuclear cells, LDL-R gene expression has been demonstrated to be parallel and be coordinately regulated to gene expression in the human liver. The purpose of the current study was to determine the mononuclear cell surface expression of the LDL receptor in patients with HCV chronic infection according to viral load. Sixty-eight consecutive untreated chronic hepatitis C patients were studied to determine the mononuclear cell surface expression of the LDL-R. LDL-Rs were quantified at the surface of mononuclear cells in fresh blood samples taken after fasting using flow cytometry. LDL-R expression was significantly associated with LDL-cholesterol (r = -0.25; P = 0.03) and HCV-viral load (r = 0.37, P = 0.002). In multivariate analysis, the LDL-R expression was significantly associated with HCV viral load, whereas genotype, age, body mass index, and fibrosis were not. In conclusion, our data provided by a human study, suggest that the LDL-R may be one of the receptors implicated in HCV replication.

How does hepatitis C virus enter cells?

Hepatitis C virus (HCV) exists in different forms in the circulation of infected people: lipoprotein bound and lipoprotein free, enveloped and nonenveloped. Viral particles with the highest infectivity are associated with lipoproteins, whereas lipoprotein-free virions are poorly infectious. The detection of HCV's envelope proteins E1 and E2 in lipoprotein-associated virions has been challenging. Because lipoproteins are readily endocytosed, some forms of HCV might utilize their association with lipoproteins rather than E1 and E2 for cell attachment and internalization. However, vaccination of chimpanzees with recombinant envelope proteins protected the animals from hepatitis C infection, suggesting an important role for E1 and E2 in cell entry. It seems possible that different forms of HCV use different receptors to attach to and enter cells. The putative receptors and the assays used for their validation are discussed in this review.

Extrahepatic replication of HCV: insights into clinical manifestations and biological consequences

An estimated 170 million persons are infected with the hepatitis C virus (HCV) worldwide. While hepatocytes are the major site of infection, a broad clinical spectrum of extrahepatic complications and diseases are associated with chronic HCV infection, highlighting the involvement of HCV in a variety of non-hepatic pathogenic processes. There is a growing body of evidence to suggest that HCV can replicate efficiently in extrahepatic tissues and cell types, including peripheral blood mononuclear cells. Nonetheless, laboratory confirmation of HCV replication in extrahepatic sites is fraught with technical challenges, and in vitro systems to investigate extrahepatic replication of HCV are severely limited. Thus, future studies of extrahepatic replication should combine innovative in vitro assays with a prospective cohort design to maximize our understanding of this important phenomenon to the pathogenesis and treatment response rates of HCV.

Lack of association between microsomal triglyceride transfer protein gene polymorphism and liver steatosis in HCV-infected patients

OBJECTIVES

It has been shown that the HCV-core protein reduces the activity of microsomal triglyceride transfer protein (MTP) and could lead to steatosis in HCV-infected patients. The aim of our study was to investigate the influence of a functional polymorphism in the promoter region of the MTP gene (493G/T) on the development of HCV-related steatosis.

METHODS

Eighty-six chronic hepatitis C patients were studied to assess: the effects of body mass index, age, HCV genotype, and 493G/T MTP polymorphism on steatosis.

RESULTS

Steatosis was observed in 39 patients (45.3%). The 493G/T MTP polymorphism were not related to the development of steatosis.

CONCLUSION

The functional G/T MTP polymorphism do not seem to play any role in the development of steatosis in chronic hepatitis C.

Apolipoprotein epsilon3 allele is associated with persistent hepatitis C virus infection

BACKGROUND

Host genetic factors may significantly influence the ability to clear hepatitis C virus (HCV) following infection. HCV is associated with very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in the host's circulation. Apolipoprotein E (APOE) is found in VLDL and binds to potential receptors involved in HCV entry into cells, the LDL receptor, and the scavenger receptor protein SR-B1. The APOE gene is polymorphic with three alleles coding for three isoforms: Apo-epsilon2, Apo-epsilon3, and Apo-epsilon4. The aim of this study was to assess if these functional polymorphisms determine disease outcome in HCV infected individuals.

METHODS

The APOE genotype was determined in 420 Northern European patients with evidence of exposure to HCV. Genotype and allele distribution were compared with those of 288 healthy controls and progression of liver disease and viral clearance were analysed according to APOE allele status.

RESULTS

The APOE*E2 and APOE*E4 alleles were both associated with a reduced likelihood of chronic infection (odds ratio (OR) 0.39 (95% confidence interval (CI) 0.211-0.728), p = 0.003; and OR 0.6 (95% CI 0.38-0.96), p = 0.032) and there was a notable absence of the E2E2 genotype in the HCV antibody positive group compared with the control population (p = 0.0067). Overall the genotypes carrying the E2 allele (E2,E3 and E2,E4) were associated with the equivalent of a 3-5-fold reduction in the risk of chronic HCV infection (genotype relative risk 0.36 and 0.20, respectively).

CONCLUSION

This study indicates that functional APOE gene polymorphisms may be a determinant of outcome in HCV infection. We hypothesise that the E2 allele may protect against viral persistence via defective binding of HCV lipoviral particles to the cellular receptors involved in entry of these infectious particles.

Antibody to E1 peptide of hepatitis C virus genotype 4 inhibits virus binding and entry to HepG2 cells in vitro

AIM

To analyze the neutralizing activity of antibodies against E1 region of hepatitis C virus (HCV). Specific polyclonal antibody was raised via immunization of New Zealand rabbits with a synthetic peptide that had been derived from the E1 region of HCV and was shown to be highly conserved among HCV published genotypes.

METHODS

Hyper-immune HCV E1 antibodies were incubated over night at 4 degree Celsius with serum samples positive for HCV RNA, with viral loads ranging from 615 to 3.2 million IU/ mL. Treated sera were incubated with HepG2 cells for 90 min. Blocking of viral binding and entry into cells by anti E1 antibody were tested by means of RT-PCR and flow cytometry.

RESULTS

Direct immunostaining using FITC conjugated E1 antibody followed by Flow cytometric analysis showed reduced mean fluorescence intensity in samples pre-incubated with E1 antibody compared with untreated samples. Furthermore, 13 out of 18 positive sera (72%) showed complete inhibition of infectivity as detected by RT-PCR.

CONCLUSION

In house produced E1 antibody, blocks binding and entry of HCV virion infection to target cells suggesting the involvement of this epitope in virus binding and entry. Isolation of these antibodies that block virus attachment to human cells are useful as therapeutic reagents.

Antibody to E1 peptide of hepatitis C virus genotype 4 inhibits virus binding and entry to HepG2 cells in vitro

AIM

To analyze the neutralizing activity of antibodies against E1 region of hepatitis C virus (HCV). Specific polyclonal antibody was raised via immunization of New Zealand rabbits with a synthetic peptide that had been derived from the E1 region of HCV and was shown to be highly conserved among HCV published genotypes.

METHODS

Hyper-immune HCV E1 antibodies were incubated over night at 4 degree Celsius with serum samples positive for HCV RNA, with viral loads ranging from 615 to 3.2 million IU/ mL. Treated sera were incubated with HepG2 cells for 90 min. Blocking of viral binding and entry into cells by anti E1 antibody were tested by means of RT-PCR and flow cytometry.

RESULTS

Direct immunostaining using FITC conjugated E1 antibody followed by Flow cytometric analysis showed reduced mean fluorescence intensity in samples pre-incubated with E1 antibody compared with untreated samples. Furthermore, 13 out of 18 positive sera (72%) showed complete inhibition of infectivity as detected by RT-PCR.

CONCLUSION

In house produced E1 antibody, blocks binding and entry of HCV virion infection to target cells suggesting the involvement of this epitope in virus binding and entry. Isolation of these antibodies that block virus attachment to human cells are useful as therapeutic reagents.