Hepatitis C virus-multispecific T-cell responses without viremia or seroconversion among Egyptian health care workers at high risk of infection

Where to Next? Research Directions after the First Hepatitis C Vaccine Efficacy Trial

Thirty years after its discovery, the hepatitis C virus (HCV) remains a leading cause of liver disease worldwide. Given that many countries continue to experience high rates of transmission despite the availability of potent antiviral therapies, an effective vaccine is seen as critical for the elimination of HCV. The recent failure of the first vaccine efficacy trial for the prevention of chronic HCV confirmed suspicions that this virus will be a challenging vaccine target. Here, we examine the published data from this first efficacy trial along with the earlier clinical and pre-clinical studies of the vaccine candidate and then discuss three key research directions expected to be important in ongoing and future HCV vaccine development. These include the following: 1. design of novel immunogens that generate immune responses to genetically diverse HCV genotypes and subtypes, 2. strategies to elicit broadly neutralizing antibodies against envelope glycoproteins in addition to cytotoxic and helper T cell responses, and 3. consideration of the unique immunological status of individuals most at risk for HCV infection, including those who inject drugs, in vaccine platform development and early immunogenicity trials.

Association of the polymorphism of the Toll-like receptor (TLR)-3 and TLR-9 genes with hepatitis C virus-specific cell-mediated immunity outcomes among Egyptian health-care workers

Variations in the immune response could explain resistance to hepatitis C virus (HCV) infection. Toll-like receptor gene (TLR)-3 is an innate detector of dsRNA viruses, and the TLR-9 gene recognizes bacterial and viral unmethylated cytosine-phosphate-guanosine (CpG) motifs. We previously reported that the TLR-3.rs3775290 CC genotype was associated with HCV chronicity and that the TLR-9 gene played no major role in this infection. This study identified the role of TLR-3.rs3775290 (c.1377C/T), TLR-9.rs5743836 (-1237T→C) and TLR-9.rs352140 (G2848A) gene polymorphisms in predicting the outcome of HCV-specific cell-mediated immunity (CMI) among Egyptian health-care workers (HCWs). We enrolled 265 HCWs in this study and divided them into four groups. Group 1: 140 seronegative-aviraemic HCWs; group 2: 20 seronegative-viraemic HCWs; group 3: 35 subjects with spontaneously resolved HCV infection; and group 4: 70 chronic HCV HCWs (patients). All subjects were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis for the TLR-3.rs3775290, TLR-9.rs5743836 and TLR-9.rs352140 single nucleotide polymorphisms (SNPs). We also quantified HCV-specific CMI in the four groups using an interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) assay in response to nine HCV genotype 4a, overlapping 15mer peptide pools covering the whole viral genome. No statistically significant difference was found between CMI-responding subjects with different HCV states and TLR-3.rs3775290 or TLR-9.rs352140 genotypes. However, there was a significant relationship between the outcome of the HCV-specific CMI and the TLR-9.rs5743836 genotype among the responding subjects (P = 0·005) and the chronic HCV patients (P = 0·044). In conclusion, TLR-9.rs5743836 SNP, but not TLR-3.rs3775290 or TLR-9.rs352140 genotypes, could predict the outcome of HCV-specific CMI responses among Egyptians infected with genotype-4.

Association of Toll-like receptor 3 and Toll-like receptor 9 single-nucleotide polymorphisms with hepatitis C virus persistence among Egyptians

Toll-like receptors (TLRs) give the innate immune system a considerable specificity for a large range of pathogens. TLR3 detects dsRNA of viruses while TLR9 recognizes bacterial and viral unmethylated CpG motifs. This study examined whether there is a potential association between single-nucleotide polymorphisms (SNPs) in the TLR3.rs3775290 (c.1377C/T), TLR9.rs5743836 (-1237T→C) and TLR9.rs352140 (G2848A) genes and HCV infection among Egyptian patients and healthcare workers (HCWs). We enrolled 546 subjects (409 HCWs and 137 patients) divided into four groups: group 1 included 265 seronegative, aviremic subjects; group 2 included 25 seronegative, viremic subjects; group 3 included 87 subjects with spontaneously resolved HCV infection; and group 4 included 169 chronic HCV patients. All subjects were genotyped for TLR3.rs3775290, TLR9.rs5743836 and TLR9.rs352140 SNPs by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. TLR3.rs3775290 "CC" genotype was associated with chronic HCV infection, where there was a significantly greater frequency of this genotype among chronic patients when compared to subjects with spontaneously resolved infection (63.9% vs. 51.9%; p = 0.033; OR = 1.639 and 95% CI = 0.94-2.84). However, this SNP did not correlate with the HCV RNA load among the chronic subjects (p > 0.05). There was no significant difference in TLR9.rs5743836 and TLR9.rs352140 genotype distribution between groups (p > 0.05). Lack of association between the three SNPs was found, as the three SNPs are located on two different chromosomes. In conclusion, the TLR3.rs3775290 "CC" genotype was associated with HCV chronicity, while the TLR9 gene may not play a major role in HCV infection.

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.

Cytomegalovirus driven immunosenescence-An immune phenotype with or without clinical impact?

The continuous emerging increase in life span has led to vulnerability to a number of different diseases in the elderly. Some of these risks may be attributed to specific changes in the immune system referred to as immunoscenescence. This term aims to describe decreased immune functions among elderly individuals, and is characterized to be harmful age-associated changes in the immune system that lead to its gradual immune dysfunction. An impaired function of the immune system may increase susceptibility to various diseases in the elderly population such as infections, cardiovascular diseases and cancer. Although it is unclear how this immune phenotype develops, emerging evidence suggest that it may reflect an exhaustion of the immune system, possibly caused by one or several chronic infections. The main candidate is human cytomegalovirus (CMV), which can induce immune dysfunctions observed in immunoscenescence. Although the immune system is currently considered to be exhausted in CMV positive elderly individuals, it is not known whether such dysfunction of the immune system is a main reason for increased susceptibility to other diseases, or if direct effects of the virus in disease pathogenesis reflect the increased vulnerability to them. These aspects will be discussed in this review.

Cellular immune response to hepatitis-C-virus in subjects without viremia or seroconversion: is it important?

Hepatitis C Virus (HCV) causes chronic infection and represents a global health burden. To date, there is no licensed vaccine for HCV. The high viral replication rate and the existence of several HCV genotypes and quasispecies hamper the development of an effective universal vaccine. In this regard, the current HCV vaccine candidates show genotype-specific protection or narrow cross reactivity against other genotypes. Importantly, HCV spontaneous clearance occurs in 15-50 % of infected subjects, indicating that natural resistance to chronic infection exists. This phenomenon was demonstrated among humans and chimpanzees and continues to motivate researchers attempting to develop an effective HCV vaccine. However, what constitutes a protective immune response or correlate of protection against HCV infection is still vague. Additionally, the mechanisms behind successful HCV clearance suggest the coordination of several arms of the immune system, with cell-mediated immunity (CMI) playing a crucial role in this process. By contrast, although neutralizing antibodies have been identified, they are isolate-specific and poorly correlate with viral clearance. Antigen-specific CD4 T cells, instead, correlate with transient decline in HCV viremia and long-lasting control of the infection. Unfortunately, HCV has been very successful in evading host immune mechanisms, leading to complications such as liver fibrosis, cirrhosis and hepatocellular carcinoma. Interestingly, CMI to HCV antigens were shown among exposed individuals without viremia or seroconversion, suggesting the clearance of prior HCV infection(s). These individuals include family members living with HCV-infected subjects, healthcare workers, IV drug users, and sexual contacts. The correlates of protection could be closely monitored among these individuals. This review provides a summary of HCV-specific immune responses in general and of CMI in particular in these cohorts. The importance of these CMI responses are discussed.

Increased proportions of dendritic cells and recovery of IFNγ responses in HIV/HCV co-infected patients receiving ART

Dendritic cell (DC) numbers and functions can be affected by HIV and HCV disease, but the effects of antiretroviral therapy (ART) on DC and the implications of these changes are unclear. We examined circulating DC in samples from Indonesian patients beginning ART with advanced HIV disease and documented mild/moderate HCV hepatitis. Frequencies of myeloid and plasmacytoid DC increased after 6 months on ART, but frequencies of DC producing IL-12 or IFNα following stimulation with TLR agonists (CL075, CpG) did not change. IFNγ responses to CL075, HCV and other antigens rose over this period. Hence increased IFNγ responses during ART may be associated with increased DC frequencies rather than changes in their functional capacity.

Differential distribution of IL28B.rs12979860 single-nucleotide polymorphism among Egyptian healthcare workers with and without a hepatitis C virus-specific cellular immune response

The CC genotype of the interleukin (IL)-28B.rs12979860 gene has been associated with spontaneous hepatitis C virus (HCV) clearance and treatment response. The distribution and correlation of an IL28B.rs12979860 single-nucleotide polymorphism (SNP) with HCV-specific cell-mediated immune (CMI) responses among Egyptian healthcare workers (HCWs) is not known. We determined this relationship in 402 HCWs who serve a patient cohort with ~85% HCV prevalence. We enrolled 402 HCWs in four groups: group 1 (n = 258), seronegative aviremic subjects; group 2 (n = 25), seronegative viremic subjects; group 3 (n = 41), subjects with spontaneously resolved HCV infection; and group 4 (n = 78), chronic HCV patients. All subjects were tested for an HCV-specific CMI response using an ex-vivo interferon-gamma (IFNγ) ELISpot assay with nine HCV genotype-4a overlapping 15-mer peptide pools corresponding to all of the HCV proteins. All subjects were tested for IL28B.rs12979860 SNP by real-time PCR. An HCV-specific CMI was demonstrated in ~27% of the seronegative aviremic HCWs (group 1), suggesting clearance of infection after low-level exposure to HCV. The frequency of IL28B.rs12979860 C allele homozygosity in the four groups was 49%, 48%, 49%, and 23%, while that of the T allele was 14%, 16%, 12 and 19%, respectively, suggesting differential distributions among subjects with different HCV status. As reported, IL28B.rs12979860 predicted the outcome of HCV infection (p < 0.05), but we did not find any relationship between the IL28B genotypes and the outcome of HCV-specific CMI responses in the four groups (p > 0.05). The data show differential IL28B.rs12979860 genotype distribution among Egyptian HCWs with different HCV status and could not predict the outcome of HCV-specific CMI responses.

Discordant humoral and cellular immune responses to Cytomegalovirus (CMV) in glioblastoma patients whose tumors are positive for CMV

Background. Glioblastoma (GBM) is the most common malignant brain tumor in adults and is nearly always fatal. Emerging evidence suggests that human Cytomegalovirus (HCMV) is present in 90-100% of GBMs and that add-on antiviral treatment for HCMV show promise to improve survival. Methods. In a randomized, placebo-controlled trial of valganciclovir in 42 GBM patients, blood samples were collected for analyses of HCMV DNA, RNA, reactivity against HCMV peptides, IgG, and IgM at baseline and at 3, 12, and 24 weeks of treatment. Results. All 42 tumors were positive for HCMV protein. All patients examined had at least one blood sample positive for HCMV DNA, 63% were HCMV RNA positive, and 21% were IgM positive. However, 29% of GBM patients were IgG negative for HCMV. Five of these samples were positive in an enzyme-linked immunosorbent assay (ELISA) that used antigens derived from a clinical isolate. Blood T cells from 11 of 13 (85%) HCMV IgG-negative GBM patients reacted against HCMV peptides. Valganciclovir did not affect IgG titers, DNA, or RNA levels of the HCMV immediate early (HCMV IE) gene in blood. Conclusion. In GBM patients, HCMV activity is higher than in healthy controls and serology is a poor test to define previous or active HCMV infection in these patients.

Schistosomiasis does not affect the outcome of HCV infection in genotype 4-infected patients

Although reports suggest that Schistosoma mansoni increases hepatitis C virus (HCV) morbidity and chronicity, its impact on HCV spontaneous resolution is not clear. HCV genotype, viral load, abdominal ultrasonographic findings, and HCV-specific cell-mediated immunity (CMI) were examined among 141 healthcare workers infected with HCV (68 workers with and 73 workers without S. mansoni). HCV genotype 4 was dominate, and viral loads were 2.62 ± 0.69 × 10(6) and 4.24 ± 1.4 × 10(6) IU/mL among patients with and without coinfection, respectively (P = 0.309); 23.5% with and 32.9% without coinfection had spontaneously resolved HCV infection (P = 0.297). Interferon-γ spot-forming cells/10(6) peripheral blood mononuclear cells among responding viremic patients with and without coinfection were 716 ± 194 and 587 ± 162, whereas among aviremic patients, it was 794 ± 272 and 365 ± 36 (P > 0.05), respectively. In conclusion, there was no statistical difference in HCV spontaneous resolution, viral load, liver pathology, or CMI in patients with or without S. mansoni coinfection, suggesting that it did not impact the outcome of HCV infection.

Cross reactive cellular immune response to HCV genotype 1 and 4 antigens among genotype 4 exposed subjects

BACKGROUND

Hepatitis C Virus (HCV) infection is a global health burden particularly in Egypt, where HCV genotype 4a (GT-4a) predominates. The prevention and control of HCV infection will remain a challenge until the development of an effective vaccine that protects against different genotypes. Several HCV GT-1-based vaccines are in different stages of clinical trials, but antigenic differences could make protection against other genotypes problematic. In this regard, data comparing the cell-mediated immune (CMI) response to different HCV genotypes are limited. We aimed to ex vivo investigate whether GT-1-based vaccine may protect against HCV GT-4 infections. This was carried out on samples collected from genotype 4 infected/exposed subjects.

METHODS/PRINCIPAL FINDINGS

The CMI responses of 35 subjects; infected with HCV GT-4/or who had spontaneously-resolved the infection and 10 healthy control subjects; to two sets of seven HCV overlapping 15-mer peptide pools derived from both genotypes; and covering most of the viral proteins; were evaluated. This was carried out using an interferon gamma (IFNγ) enzyme-linked immunospot (ELISpot) assay. Peripheral blood mononuclear cells (PBMC) from 17 subjects (48%) responded to at least one peptide pool derived from GT-1b/GT-4a with 13 subjects responding to peptide pools from both genotypes. A strong correlation was found in the responses to both genotypes (r = 0.82, p<0.001; 95% confidence interval = 0.562-0.933). The average IFNγ total spot forming cells (SFC)/10(6) PBMC (±SE) from the responding subjects for GT-1b and GT-4a was 216±56 and 199±55, respectively (p = 0.833). Also, there were no significant differences between those who cleared their HCV infection or who remained HCV-RNA positive (p = 0.8).

CONCLUSION/SIGNIFICANCE

Our data suggest that an effective GT-1b vaccine could protect from GT-4a infection. These data could help in HCV rationale vaccine design and efficacy studies and further our understanding of HCV cross protection against different genotypes.

Between Scylla and Charybdis: The role of the human immune system in the pathogenesis of hepatitis C

Hepatitis C virus (HCV) frequently elicits only mild immune responses so that it can often establish chronic infection. In this case HCV antigens persist and continue to stimulate the immune system. Antigen persistence then leads to profound changes in the infected host’s immune responsiveness, and eventually contributes to the pathology of chronic hepatitis. This topic highlight summarizes changes associated with chronic hepatitis C concerning innate immunity (interferons, natural killer cells), adaptive immune responses (immunoglobulins, T cells, and mechanisms of immune regulation (regulatory T cells). Our overview clarifies that a strong anti-HCV immune response is frequently associated with acute severe tissue damage. In chronic hepatitis C, however, the effector arms of the immune system either become refractory to activation or take over regulatory functions. Taken together these changes in immunity may lead to persistent liver damage and cirrhosis. Consequently, effector arms of the immune system will not only be considered with respect to antiviral defence but also as pivotal mechanisms of inflammation, necrosis and progression to cirrhosis. Thus, avoiding Scylla - a strong, sustained antiviral immune response with inital tissue damage - takes the infected host to virus-triggered immunopathology, which ultimately leads to cirrhosis and liver cancer - the realm of Charybdis.

Occupational exposure to hepatitis C virus: early T-cell responses in the absence of seroconversion in a longitudinal cohort study

BACKGROUND

T-cell responses have been described in seronegative patients who test negative for hepatitis C virus (HCV) RNA despite frequent HCV exposure. However, the cross-sectional design of those studies did not clarify whether T cells were indeed induced by low-level HCV exposure without seroconversion or whether they resulted from regular acute infection with subsequent antibody loss.

METHODS

Over a 10-year period, our longitudinal study recruited 72 healthcare workers with documented HCV exposure. We studied viremia and antibody and T-cell responses longitudinally for 6 months.

RESULTS

All healthcare workers remained negative for HCV RNA and antibodies. However, 48% developed proliferative T-cell response and 42% developed responses in interferon-gamma enzyme-linked immunosorbent spot assays, with 29 healthy HCV-unexposed controls used to define assay cutoffs. The response prevalence was associated with the transmission risk score. T-cell responses peaked at week 4 and returned to baseline by week 12 after exposure. They predominantly targeted nonstructural HCV proteins, which are not part of the HCV particle and thus must have been synthesized in infected cells.

CONCLUSIONS

Subclinical transmission of HCV occurs frequently, resulting in infection and synthesis of nonstructural proteins despite undetectable systemic viremia. T-cell responses are more sensitive indicators of this low-level HCV exposure than antibodies.

TH1 cytokine response to HCV peptides in Egyptian health care workers: a pilot study

Our objective was to elucidate the effects of different HCV peptides on TH1 cytokine synthesis (interleukin 2(IL2), gamma interferon (INFγ) and tumor necrosis factor α (TNF α)), in a proliferative response in a high risk population of HCV seronegative aviremic Egyptian healthcare workers (HCW). We studied the TH1 cytokine response to different HCV peptides among 47 HCW with and without evidence of HCV infection. Participants were classified according to the proliferation index (PI) in a CFSE proliferation assay as an indicator of previous exposure to HCV. Cytokines were analyzed using Luminex xMAP technology. Results showed that positive PI HCW produced a higher IL2 in response to all HCV peptides except NS4, a higher IFNγ response to NS3 and NS4 and no difference in TNFα response when compared to the negative PI HCWs. When compared to chronic HCV HCW, positive PI HCW showed no difference in the IL2 response, a higher IFNγ response to NS4 and NS5 HCV peptides and a higher TNFα response to all peptides. In conclusion the magnitude and type of cytokines produced in HCV infection is critical in determining the outcome of infection. NS4 & NS5 HCV peptides induce a protective TH1 response in positive PI HCW.

Ever closer to a prophylactic vaccine for HCV

Introduction

With 3 – 4 million new infections occurring annually, hepatitis C virus (HCV) is a major global health problem. There is increasing evidence to suggest that HCV will be highly amenable to a vaccine approach, and despite advances in treatment, a vaccine remains the most cost-effective and realistic means to significantly reduce the worldwide mortality and morbidity associated with persistent HCV infection.

Areas covered

In this review we discuss immune responses to HCV during natural infection, and describe how they may inform vaccine design. We introduce the current candidate vaccines for HCV and compare how these fare against the expected requirements of an effective prophylactic HCV vaccine in relation to the breadth, functionality, magnitude and phenotype of the vaccine-induced immune response.

Expert opinion

Although the correlates of immune protection against HCV are not completely defined, we now have vaccine technologies capable of inducing HCV-specific adaptive immune responses to an order of magnitude that are associated with protection during natural infection. The challenge next is to i) establish well-characterised cohorts of people at risk of HCV infection for vaccine efficacy testing and ii) to better understand the correlates of protection in natural history studies. If these can be achieved, a vaccine against HCV appears a realistic goal.

Incidence of hepatitis C virus infection among Egyptian healthcare workers at high risk of infection

BACKGROUND

Hepatitis C virus (HCV) is a global health threat with Egypt having the highest worldwide prevalence. Evaluation of the efficacy of a preventive HCV vaccine, such as those currently in Phase I/II trials, requires a cohort with a high-risk exposure to HCV.

OBJECTIVE

To identify a reliable cohort for evaluating preventive HCV vaccines, we studied HCV incidence among HCW in a hospital where almost 85% of patients are HCV-infected.

STUDY DESIGN

Of 717 HCW negative for HCV-antibodies (anti-HCV) at baseline, 651 were followed up and tested for seroconversion twice annually for an average of 504 ± 154 days. Those reporting a needle-stick injury were additionally tested for both HCV antibodies and RNA monthly for a total of four months.

RESULTS

Two subjects (0.31%) had anti-HCV and HCV-RNA seroconversion with an overall incidence of 2.04/1000 person-years and a 4.8% incidence among the 21 subjects who reported a needle-stick injury. Two additional subjects had viremia without detectable anti-HCV. Two of the four subjects were among 21 with reported needle-stick injuries (9.5%) and another had surgery. All four were nurses providing direct patient care.

CONCLUSIONS

Our results show that both transient and persistent viremia were detectable in this high-risk cohort of HCW and suggest that absence of anti-HCV in two of the subjects may be due to low-dose viral exposures. These data indicate that HCV infections acquired from documented injuries during direct patient care are frequent in Egypt and can guide selection of eligible HCW suitable for preventive HCV vaccine trials.

Frequent transient hepatitis C viremia without seroconversion among healthcare workers in Cairo, Egypt

Backgrounds

With 10% of the general population aged 15–59 years chronically infected with hepatitis C virus (HCV), Egypt is the country with the highest HCV prevalence worldwide. Healthcare workers (HCWs) are therefore at particularly high risk of HCV infection. Our aim was to study HCV infection risk after occupational blood exposure among HCWs in Cairo.

Methodology/Principal Findings

The study was conducted in 2008–2010 at Ain Shams University Hospital, Cairo. HCWs reporting an occupational blood exposure at screening, having neither anti-HCV antibodies (anti-HCV) nor HCV RNA, and exposed to a HCV RNA positive patient, were enrolled in a 6-month prospective cohort with follow-up visits at weeks 2, 4, 8, 12 and 24. During follow-up, anti-HCV, HCV RNA and ALT were tested. Among 597 HCWs who reported a blood exposure, anti-HCV prevalence at screening was 7.2%, not different from that of the general population of Cairo after age-standardization (11.6% and 10.4% respectively, p = 0.62). The proportion of HCV viremia among index patients was 37%. Of 73 HCWs exposed to HCV RNA from index patients, nine (12.3%; 95%CI, 5.8–22.1%) presented transient viremia, the majority of which occurred within the first two weeks after exposure. None of the workers presented seroconversion or elevation of ALT.

Conclusions/Significance

HCWs of a general University hospital in Cairo were exposed to a highly viremic patient population. They experienced frequent occupational blood exposures, particularly in early stages of training. These exposures resulted in transient viremic episodes without established infection. These findings call for further investigation of potential immune protection against HCV persistence in this high risk group.

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.