Hepatitis C virus-specific reactivity of CD4+-lymphocytes in children born from HCV-infected women

Evidence for B cell maturation but not trained immunity in uninfected infants exposed to hepatitis C virus

OBJECTIVES

Vertical transmission of hepatitis C virus (HCV) is rare compared with other chronic viral infections, despite that newborns have an immature, and possibly more susceptible, immune system. It further remains unclear to what extent prenatal and perinatal exposure to HCV affects immune system development in neonates.

DESIGN

To address this, we studied B cells, innate immune cells and soluble factors in a cohort of 62 children that were either unexposed, exposed uninfected or infected with HCV. Forty of these infants were followed longitudinally from birth up until 18 months of age.

RESULTS

As expected, evidence for B cell maturation was observed with increased age in children, whereas few age-related changes were noticed among innate immune cells. HCV-infected children had a high frequency of HCV-specific IgG-secreting B cells. Such a response was also detected in some exposed but uninfected children but not in uninfected controls. Consistent with this, both HCV-exposed uninfected and HCV-infected infants had evidence of early B cell immune maturation with an increased proportion of IgA-positive plasma cells and upregulated CD40 expression. In contrast, actual HCV viraemia, but not mere exposure, led to alterations within myeloid immune cell populations, natural killer (NK) cells and a distinct soluble factor profile with increased levels of inflammatory cytokines and chemokines.

CONCLUSION

Our data reveal that exposure to, and infection with, HCV causes disparate effects on adaptive B cells and innate immune cell such as myeloid cells and NK cells in infants.

Anti-envelope antibody responses in highly exposed seronegative individuals may be associated with protection from HCV infection

In rare cases, individuals with a history of long-term injecting drug use remain seronegative and aviraemic, despite prolonged and likely repeated exposure to Hepatitis C virus (HCV) through high-risk behaviour. We describe anti-HCV Envelope (E) antibody responses in a prospective cohort of carefully defined highly exposed but uninfected subjects (HESN) and comparison subjects who were also high risk and uninfected, but rapidly became HCV infected (Incident). Longitudinally collected samples from HESN cases (n = 22) were compared to Incident controls (n = 22). IgG, IgM and IgA from sera were tested by ELISA to genotype 1a and 3a E glycoproteins, and recombinant genotype 1a E2 antigen. IgG subclass isotyping was performed for those positive for IgG. Virus-neutralizing activity was assessed on HCV pseudoparticles, and HCV E-specific B cells analysed using flow cytometry. A significant minority of HESN cases (n = 10; 45%) had anti-E, predominantly in the IgG2 subclass, which was not found in the pre-infection time point of the Incident cases (n = 1; 5%). A subset of the HESN subjects also had neutralizing activity and HCV-specific B cells detected significantly more than Incident cases pre-infection. In conclusion, the HESN phenotype is associated with IgG2 anti-E antibodies, neutralization activity and HCV E-specific memory B cells. These findings suggest that HESN subjects may be resistant to HCV infection through humoral immune-mediated mechanisms.

Perinatal transmission of hepatitis C virus: an update

Infection with hepatitis C virus (HCV) is a major health problem worldwide. A large proportion of perinatal HCV infections are silent and may present later in adulthood with long-term complications. HCV has no effective immune prophylaxis and hence appropriate follow-up of all infants born to HCV-infected mothers is necessary. Universal antenatal screening for HCV is largely debatable. Intrauterine and partum transmission of HCV are both possible and higher rates are associated with a high maternal serum viral load (> 106 copies per milliliter), concomitant HIV infection, prolonged or difficult delivery, and invasive fetal monitoring during delivery. Infection during pregnancy and infancy needs to be investigated more in order to design management strategies for perinatal transmission of HCV most effectively. The recently approved new-generation, oral, direct-acting antiviral drugs may open a new era in HCV therapy for pregnant women and infected infants if proved to be safe during conception and infancy.

Neonatal Exposure to Hepatitis C Virus Antigens in Uninfected Children Born to Infected Mothers

OBJECTIVE

Vertical transmission of hepatitis C virus (HCV) infection is uncommon and occurs in approximately 5% of births from HCV-infected mothers. The reason for the low transmission rate is unclear. We aimed to investigate whether there is evidence of HCV exposure also in the noninfected children born to HCV-infected mothers by the presence of a detectable immune response.

METHODS

Serum and peripheral blood mononuclear cells from 9 HCV vertically infected children, 32 uninfected children born to HCV infected mothers, and 15 HCV chronically infected mothers, were analyzed. HCV-RNA-negative adults and children were used as controls. HCV-specific T cell responses were analyzed by interferon gamma using an enzyme-linked immunospot assay and 3H-thymidine incorporation assay. HCV antibodies were also analyzed.

RESULTS

An HCV-specific T cell response was detected in 73% (11/15) of the HCV-infected mothers, 67% (6/9) of the vertically infected children, 56% (18/32) of the exposed but uninfected children and in 10% and 20% of the control groups, respectively. The 2 groups of HCV-exposed children both had a significantly higher proportion of HCV-specific T cell responders compared to pediatric controls (P = 0.01 and P = 0.02).

CONCLUSIONS

HCV-specific immune responses were more common in children born to HCV-infected mothers, regardless of the presence of HCV RNA. We conclude that noninfected children born to HCV-infected mothers may have been exposed to HCV antigens.

Lack of Association Between Interleukin 28B Polymorphism and Vertical Transmission of Hepatitis C

OBJECTIVES

Single genetic nucleotide polymorphism (rs12979860) near the gene for interleukin 28B (IL28B) is known to be of importance for frequency of spontaneous clearance and treatment outcome in interferon-based therapies in patients with hepatitis C virus (HCV) infection. The aim of the present study was to investigate whether IL28B polymorphism in children and/or their mothers plays a role in vertical transmission of HCV (HCV-VT).

METHODS

Plasma samples from 59 infected women, 76 uninfected children born to infected mothers, and 47 children with known vertically transmitted HCV infection, were analysed for IL28B polymorphism and classified by the IL28B genotype (C/C, C/T, and T/T) and by viral genotype.

RESULTS

The proportion of children with genotype C/C was the same in the vertically infected (36%, 17/47) and the exposed uninfected children (38%, 29/76). No difference was seen when stratifying for viral genotype. There was no association between mothers' IL28B genotype and the risk of vertical transmission.

CONCLUSIONS

Regardless of viral genotype we found no association between IL28B genotype and the risk of HCV-VT. The IL28B genotype CC, which has been shown to be favourable in other settings, was not protective of HCV-VT. Thus, other factors possibly associated with the risk of HCV-VT need to be explored.

CD4+ and CD8+ T Cell Activation in Children with Hepatitis C

OBJECTIVES

To assess if peripheral T cell populations in children with chronic hepatitis C virus (HCV) infection would show evidence of activation/exhaustion and an attenuated functional response.

STUDY DESIGN

Compared with adults, children with HCV infection have a higher rate of spontaneous viral clearance. In adults, chronic HCV has been linked to T cell exhaustion. Little is known of the immune status of children with HCV. Peripheral blood mononuclear cells were isolated from 16 children with HCV (6 males, 10 females; mean age 8.6 years, range 2-17), 16 age- and sex-matched control children without HCV infection, and 20 adults with chronic HCV. Multiparameter flow cytometry was performed to characterize T cell differences across the 3 groups.

RESULTS

Controls and children with HCV had similar levels of CD4(+), CD8(+), and γδ(+) T cells. Children with HCV demonstrated a decrease in naïve T cells compared with control children and increased activation/exhaustion marker expression on both CD8(+) and CD4(+) T cells. Transcription factor analysis suggested functional activation of T cells in children with HCV; however, only the CD4(+) subset had enhanced cytokine production (interferon gamma and interleukin-2) compared with control children.

CONCLUSIONS

The HCV response in children is characterized by several changes in T cell phenotype. Many of these changes, such as increased T cell expression of programmed cell death-1, are similar to responses in adults. Of note, cytokine production by CD4(+) helper T cells is increased in children with HCV compared with age- and sex-matched control children, which may influence long-term prognosis in children with HCV.

Analysis of peripheral blood dendritic cells as a non-invasive tool in the follow-up of patients with chronic hepatitis C

Hepatitis C virus (HCV) has a high propensity to establish chronic infections. Failure of HCV-infected individuals to activate effective antiviral immune responses is at least in part related to HCV-induced impairment of dendritic cells (DCs) that play a central role in activating T cell responses. Although the impact of HCV on DC phenotype and function is likely to be more prominent in the liver, major HCV-induced alterations are detectable in peripheral blood DCs (pbDCs) that represent the most accessible source of DCs. These alterations include numerical reduction, impaired production of inflammatory cytokines and increased production of immunosuppressive IL10. These changes in DCs are relevant to our understanding the immune mechanisms underlying the propensity of HCV to establish persistent infection. Importantly, the non-invasive accessibility of pbDCs renders the analysis of these cells a convenient procedure that can be serially repeated in patient follow-up. Accordingly, the study of pbDCs in HCV-infected patients during conventional treatment with pegylated interferon and ribavirin indicated that restoration of normal plasmacytoid DC count may represent an additional mechanism contributing to the efficacy of the dual therapy. It also identified the pre-treatment levels of plasmacytoid DCs and IL10 as putative predictors of response to therapy. Treatment of chronic HCV infection is changing, as new generation direct-acting antiviral agents will soon be available for use in interferon-free therapeutic strategies. The phenotypic and functional analysis of pbDCs in this novel therapeutic setting will provide a valuable tool for investigating mechanisms underlying treatment efficacy and for identifying predictors of treatment response.

Monocyte-derived dendritic cells in children with chronic hepatitis C: correlation with interferon and ribavirin therapy

BACKGROUND

Hepatitis C virus (HCV) infection is a major health problem worldwide. Defective dendritic cell (DC) activation of T cells may underlie poor T-cell responsiveness in HCV infection.

OBJECTIVE

To evaluate the DCs' functions in chronically infected HCV patients and its correlation with the response to therapy.

PATIENTS AND METHODS

This prospective study included 30 chronic hepatitis C (CHC) patients and 30 healthy age-matched and sex-matched controls. The first group received combined pegylated interferon-α-2b (Peg-IFN-α2b)/ribavirin therapy for 48 weeks. A quantitative HCV-RNA PCR was performed for all patients before treatment and at 12, 24, 48, and 24 weeks after treatment. To clarify the functions of DCs, we induced maturation of peripheral DCs from blood samples of CHC patients and healthy controls using Resiquimod (R848). The functions of DCs were assessed by measurement of the levels of IFN-γ and interleukin-10 (IL-10).

RESULTS

Sixteen (53.3%) of the patients were treatment responders and the other 14 (46.4%) were nonresponders. The current study showed a statistically significant difference between CHC patients and the control group in IFN-γ production, which was higher in the control group (1.53±0.38 IU/ml) than in the CHC patients (1.19±0.21 IU/ml); in contrast, IL-10 was higher in CHC (249.4±27.6 pg/ml) than the control group (217.0±29.9 pg/ml). However, there was no significant difference between treatment responders and nonresponders in both IFN-γ and IL-10 levels.

CONCLUSION

HCV infection is associated with impaired production of IFN-γ, which may be an indication of a defect in DC function.

Virus-Specific Cellular Response in Hepatitis C Virus Infection

Studies performed on chimpanzees and humans have revealed that strong, multispecific and sustained CD4(+) and CD8(+) T cell immune responses is a major determinant of hepatitis C virus (HCV) clearance. However, spontaneous elimination of the virus occurs in minority of infected individuals and cellular response directed against HCV antigens is not persistent in individuals with chronic infection. This review presents characteristics of the HCV-specific T cell response in patients with different clinical course of infection, including acute and chronic infection, persons who spontaneously eliminated HCV and non-infected subjects exposed to HCV. Detection of HCV-specific response, especially in non-infected subjects exposed to HCV, may be indicative of HCV prevalence in population and rate of spontaneous viral clearance. Understanding the mechanisms and role of HCV-specific cellular immune response would contribute to better understanding of HCV epidemiology, immunopathogenesis and may help to design an effective vaccine.

Resistance to hepatitis C virus: potential genetic and immunological determinants

Studies of individuals who were highly exposed but seronegative (HESN) for HIV infection led to the discovery that homozygosity for the Δ32 deletion mutation in the CCR5 gene prevents viral entry into target cells, and is associated with resistance to infection. Additionally, evidence for protective immunity has been noted in some HESN groups, such as sex workers in The Gambia. Population studies of individuals at high risk for hepatitis C virus infection suggest that an HESN phenotype exists. The body of evidence, which suggests that protective immunity allows clearance of hepatitis C virus without seroconversion is growing. Furthermore, proof-of-principle evidence from in-vitro studies shows that genetic polymorphisms can confer resistance to establishment of infection. This Review discusses the possibility that genetic mutations confer resistance against hepatitis C virus, and also explores evidence for protective immunity, including via genetically programmed variations in host responses. The data generally strengthens the notion that investigations of naturally arising polymorphisms within the hepatitis C virus interactome, and genetic association studies of well characterised HESN individuals, could identify potential targets for vaccine design and inform novel therapies.

Protection against hepatitis C infection via NK cells in highly-exposed uninfected injecting drug users

BACKGROUND & AIMS

HCV seroprevalence surveys in longstanding injecting drug users (IDUs) reveal a small minority who remain seronegative, with some exhibiting HCV-specific cellular immunity. This study aimed to characterise this immunity, assess associations with risk behaviours and protection against infection.

METHODS

A nested case-control series from a prospective cohort of seronegative IDUs was selected with incident cases (IN; n = 28) matched by demographics and risk behaviour to exposed uninfected (EU) subjects (n = 28). Samples were assayed for natural killer (NK) cell phenotypes and function, HCV-specific IFNγ in ELISpot, and HCV-specific CD4 T effector responses. IL28B and HLA-C/KIR2DL3 genotypes were tested.

RESULTS

Numbers of activated (CD69(+)) NK cells in the mature CD56(dim)CD16(+) subset, and cytotoxic (NKp30(+)) cells in the CD56(bright)CD16(+) subset were higher in the EU subjects (p = 0.040, p = 0.038 respectively). EU subjects had higher frequencies of interferon gamma (IFNγ) producing NK cells, and lower frequencies of CD107a expression (p = 0.003, p = 0.015 respectively). By contrast, the frequency, magnitude, and breadth of HCV-specific CD4 and CD8 T cell responses did not differ, nor did IL28B, HLA-C, or KIR2DL3 allele frequencies.

CONCLUSIONS

Sustained NK cell activation contributes to protection against HCV infection. HCV-specific cellular immunity is prevalent in EU subjects but does not appear to be protective.

Correlates and characteristics of hepatitis C virus-specific T-cell immunity in exposed uninfected high-risk prison inmates

Some hepatitis C (HCV)-uninfected, high-risk individuals have HCV-specific cellular immunity without viraemia or seroconversion. The characteristics of these responses and the risk behavioural associations were studied in 94 subjects in a prospective cohort of recently seronegative prisoners reporting injecting drug use (IDU). Detailed behavioural data were collected. HCV antibody and PCR testing were performed. ELISpot assays for HCV-induced interferon (IFN)-γ and interleukin (IL)-2 production by T lymphocytes, as well as multiplex in vitro cytokine production assays, were performed. Seventy-eight subjects remained antibody and PCR negative and 16 seroconverted. Of the seronegative group, 22 (28%) had IFN-γ ELISpot responses in comparison with 13 of the 16 seroconverters (82%). This seronegative immune status was associated positively with injecting anabolic steroids and negatively with a recent break from IDU. The IFN-γ ELISpot responses involved both CD4 and CD8 T lymphocytes and were comparable in magnitude, but narrower in specificity, in uninfected subjects than in seroconverters. A subset of seronegative subjects had HCV-induced cytokine production patterns comparable with the seroconverters with increased production of IFN-γ, IL-2 and tumour necrosis factor (TNF)-α and reduced IL-10 in response to nonstructural peptides. In conclusion, comparable patterns of HCV-specific cellular immunity are found in recently infected subjects and in a minority of high-risk, uninfected subjects. Further characterization of these responses and their protective efficacy will inform HCV vaccine development.

Hepatitis C virus in pregnancy

Despite recent advances in the pathogenesis, treatment, and public health response to hepatitis C virus (HCV), HCV as it specifically relates to pregnancy has been a neglected condition. HCV-monoinfected pregnant women have a 2-8% risk of viral transmission to their infant, but the mechanism and timing of mother to child transmission (MTCT) are not fully understood, nor is the natural history of the illness in pregnant women and their offspring. Recognition of HCV-infected pregnant women is relevant because of the long-term health implications for the mother, potential adverse effects of infection on pregnancy outcomes, and the possibility of transmission to their infants. Certain risk factors for MTCT of HCV appear similar to those for human immunodeficiency virus (HIV); however, unlike HIV, effective methods for prevention of HCV vertical transmission have not been developed. It is possible that a better understanding of HCV MTCT and pathogenesis in pregnancy will guide development of useful prevention strategies, particularly as we enter an era where interferon-free drug cocktails may emerge as viable treatment options for HCV.

Hepatitis C virus-specific cell-mediated immune responses in children born to mothers infected with hepatitis C virus

OBJECTIVE

To investigate the association between hepatitis C virus (HCV)-specific cell-mediated immunity (CMI) responses and viral clearance in children born to mothers infected with HCV.

STUDY DESIGN

A cross-sectional study of children from a mother-infant cohort in Egypt were enrolled to detect CMI responses to recombinant core and nonstructural HCV antigens (nonstructural segments NS3, NS4a/b, and NS5 of the HCV genome) using an interferon-gamma enzyme-linked immunospot assay. Children born to mothers with chronic HCV were enrolled into 3 groups: transiently viremic (n = 5), aviremic (n = 36), and positive control (n = 6), which consisted of 1 child with chronic HCV from this cohort and another 5 children with chronic HCV from a companion study. Children without HCV born to mothers without HCV (n = 27) served as a negative control group. Wilcoxon rank sum test was used to compare the magnitude of CMI responses between groups.

RESULTS

None of the 6 control children who were positive for HCV responded to any HCV antigen, and 4 (80%) of 5 children with transient viremia responded to at least one HCV antigen, compared with 5 (14%) of 36 and 3 (11%) of 27 children in the aviremic and negative control groups, respectively. Children with transient viremia elicited stronger responses than did negative controls (P = .005), positive controls (P = .011), or children without HCV viremia (P = .012), particularly to nonstructural antigens.

CONCLUSIONS

HCV-specific CMI responses were significantly higher in magnitude and frequency among transiently infected children compared with those persistently infected. This suggests CMI responses may be associated with past viral clearance and can identify children at high risk of infection, who can be targeted for health education, screening, and follow-up.

NASPGHAN practice guidelines: Diagnosis and management of hepatitis C infection in infants, children, and adolescents

Hepatitis C virus (HCV) is an RNA virus that affects >180 million individuals worldwide with a high propensity for chronic infection. Children with HCV infection differ from adults in several ways including some modes of transmission, rates of clearance, progression of fibrosis, and the duration of potential chronic infection when acquired at birth. Since the discovery of HCV in 1989, there have been significant advances in the understanding of the virology and natural history of chronic HCV infection in children. In addition, there are now several treatment options for children with chronic hepatitis C infection and many new therapies on the horizon. As a consequence, the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition brought together experts in pediatric hepatology to review the available data in children and provide clinicians with approaches to the diagnosis, management, and prevention of HCV infection in children and adolescents. The guideline details the epidemiology and natural history of HCV infection in children, the diagnostic workup, monitoring and treatment of disease, and provides an update on future treatment options and areas of research.

Spontaneous clearance of hepatitis C virus in vertically infected children

Spontaneous viral clearance of hepatitis C virus (HCV) has been reported to occur in children with vertical HCV infection. However, factors which are associated with or predispose for clearance are largely unknown. In this case series we retrospectively analyzed laboratory parameters associated with spontaneous clearance of HCV in vertically infected children. The charts of six patients with documented spontaneous viral clearance by the age of 5 years were reviewed regarding clinical course, liver function tests (LFTs) and trend of HCV gene copy numbers. Spontaneous viral elimination was observed between the 25th and 52nd months of age. All patients had elevated LFTs, which peaked before 20 months of life. Peak LFT elevation was followed by normalization of LFTs and decline in viral load. These findings suggest that, in vertically HCV-infected children, a potent inflammatory response in the liver precedes viral clearance. Therefore, temporarily elevated LFTs, followed by a decline of viral load may be indicative of a near viral clearance in early childhood.

CONCLUSION

Further investigations regarding the development of optimal treatment algorithms should take into account factors, which are associated with possible spontaneous viral resolution, such as viral genotype, favourable host factors as well as direct and indirect parameters of antiviral immunity, and the individual course of viral replication.

Strong hepatitis C virus (HCV)-specific cell-mediated immune responses in the absence of viremia or antibodies among uninfected siblings of HCV chronically infected children

BACKGROUND

Cell-mediated immune (CMI) responses to hepatitis C virus (HCV) antigens in adults without seroconversion or viremia are biomarkers for prior transient infection. We investigated HCV-specific CMI responses in seronegative children living with HCV-infected siblings.

METHODS

Children 3-18 years of age living with HCV-infected siblings were screened for HCV antibodies and HCV RNA. Peripheral blood mononuclear cells (PBMCs) were evaluated for HCV-specific CMI responses by interferon γ (IFN-γ) enzyme-linked immunospot assay using 3 recombinant HCV protein antigens. Flow cytometry phenotypically characterized IFN-γ-secreting cells.

RESULTS

Forty-five seronegative children and 5 seropositive viremic siblings had functionally viable PBMCs. Among the 45 seronegative siblings, 15 (33.3%) had positive HCV-specific IFN-γ responses, and subsequent RNA testing revealed that 3 were viremic. Compared with the 5 seropositive viremic children, the median number of HCV-specific spot-forming units was significantly higher in the 12 seronegative aviremic children (P = .002) and in the 3 seronegative viremic children (P = .025). Flow cytometric analysis revealed that IFN-γ was synthesized mainly by CD4(+) T cells.

CONCLUSION

Strong HCV-specific CD4(+) T cell responses were detectable in higher frequency among seronegative, aviremic children compared with persistently infected siblings. Further studies are needed to determine whether these immune responses are protective against HCV infection.

Chronic hepatitis C virus infection in children

The importance of hepatitis C viral infection in the health care of children has grown in recent decades. More is now known about the epidemiology of this infection in children and the progression of disease in the pediatric age group, and the treatment options are increasing. In this review, we update readers on the state of our understanding of hepatitis C infection in children, provide the current recommendations for monitoring and treatment, and discuss emerging therapies.

Age-related lymphocyte and neutrophil levels in children of hepatitis C-infected women

BACKGROUND

Investigation of immunologic values in children vertically exposed to hepatitis C virus (HCV) infection could help explain the higher risk of infection in girls and indicate mechanisms of spontaneous viral clearance and possible long-term immunologic effects.

METHODS

Prospective study of children born to HCV-infected women. Lymphocyte and neutrophil measurements were age-standardized using the LMS method (this summarizes the changing age distribution of a variable). Associations between maternal and infant characteristics and lymphocyte and neutrophil z-scores were quantified using linear regression allowing for repeated measures.

RESULTS

HCV-infected children, girls, and those born to HCV/human immunodeficiency virus (HIV)-coinfected women had significantly higher lymphocyte z-scores than HCV-uninfected children, boys, and children born to HCV-only-infected women, respectively. Peak absolute lymphocytes were significantly lower for infected children with evidence of viral clearance than for persistently infected children. Girls also had significantly higher neutrophil z-scores than boys but HCV-infected children had significantly lower neutrophil z-scores than uninfected children.

CONCLUSIONS

The gender associations are in line with those observed among children born to HIV-infected women, suggesting general gender-based differences in response to infection. Age-related standards for uninfected children could be used to assess immune function in other pediatric diseases and these results suggest that gender-specific reference values should be used at least for the first 2 years of life.

Decrease and dysfunction of dendritic cells correlate with impaired hepatitis C virus-specific CD4+ T-cell proliferation in patients with hepatitis C virus infection

Through the production of stimulatory and suppressive cytokines, dendritic cells (DCs) regulate virus-specific immune responses that are crucial to virus eradication. To explore a possible role of DCs in the persistence of hepatitis C virus (HCV) infection, in this study we analysed peripheral blood DCs (PBDCs) in patients with chronic hepatitis C (CHC) compared with those in both healthy seronegative (HSN) controls and a group of subjects who had spontaneously resolved infection, defined as healthy HCV-seropositive (HSP), and we evaluated the relationships between PBDCs and HCV-specific CD4(+) T-cell reactivity. The number of PBDCs, their immunophenotype and expression of regulatory cytokines were evaluated by flow cytometry on whole-blood samples. HCV-specific CD4(+) T-cell activation, proliferation and cytokine production were evaluated in cultures of peripheral blood mononuclear cells (PBMCs) stimulated in vitro with HCV peptides. We found that PBDCs from CHC subjects were numerically reduced and showed lower interleukin-12 (IL-12) and higher IL-10 expression than those from HSN controls. PBDCs from HSP subjects were similar to those from HSN controls. HCV-specific CD4(+) T-cell proliferation was less frequent and vigorous in CHC than in HSP patients and was directly related to the number of PBDCs and their IL-12 production but inversely related to their IL-10 production. Taken together, these results seem to suggest that cytokines of DC origin contribute to the regulation of HCV-specific immunity in CHC patients and indicate that PBDCs may represent a novel non-invasive tool for immune monitoring of these patients.

Hepatitis C virus infection

The prevalence of chronic hepatitis C infection in the general paediatric population varies between 0.1 and 15% around the world, with the highest numbers noted in endemic areas of Africa. The risk of viral transmission from an infected mother to her child is approximately 5% and there are currently no effective preventative measures to lower it. All children born to infected mothers should be tested for hepatitis C. The progression to liver damage in infected children is slow. However, in the perspective of 15-20 years of infection or in the presence of other risk factors, such as concomitant chronic disease, a progression to more severe liver damage can be seen. Thus, the use of antiviral treatment may be of importance. Treatment combinations of interferon and ribavirin seem to be at least as effective in children as in adults. However, the negative effect on growth of interferon requires specific attention by paediatricians.

Protective immunity against hepatitis C virus infection

There is increasing evidence that a small percentage of individuals exposed to the hepatitis C virus have the capacity to generate a strong cellular immune response against the virus and avoid persistent infection, and perhaps do so repeatedly after re-exposure. This article reviews the evidence that the responses identified in this unique group of individuals represent the protective immunity that will need to be elicited by hepatitis C virus vaccines.