Influence of HLA class I, HLA class II and KIRs on vertical transmission and chronicity of hepatitis C virus in children

Hepatitis B and C in Children

Hepatitis B and hepatitis C are a global burden and underscore the impact of preventable acute and chronic diseases on personal as well as population level health. Caring for pediatric patients with hepatitis B and C requires a deep understanding of the pathophysiology of viral processes. Insight into the epidemiology, transmission, and surveillance of these infections is critical to prevention and therapy. Extensive research in recent years has created a growing number of treatments, changing the landscape of the medical field's approach to the viral hepatitis pandemic.

Hepatitis C: Current State of Treatment in Children

Hepatitis C in children is on the rise due to perinatal transmission from infected mothers, and high-risk practices in adolescents and young adults. Prevalence remains underestimated because children at high risk are often not screened. Treatment has evolved over the past decade with the advent of new drugs, and global elimination is now possible. Direct-acting antiviral combinations are safe and effective, with sustained viral suppression rate >90%, and Food and Drug Administration-approved for children ≥3 years old. Although challenging, efficient screening and treatment of chronic hepatitis C virus early is cost-effective and reduces burden of disease and its complications.

Hepatitis C in 2020: A North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition Position Paper

In 1989, a collaboration between the Centers for Disease Control (CDC) and a California biotechnology company identified the hepatitis C virus (HCV, formerly known as non-A, non-B hepatitis virus) as the causative agent in the epidemic of silent posttransfusion hepatitis resulting in cirrhosis. We now know that, the HCV genome is a 9.6 kb positive, single-stranded RNA. A single open reading frame encodes a 3011 amino acid residue polyprotein that undergoes proteolysis to yield 10 individual gene products, consisting of 3 structural proteins (core and envelope glycoproteins E1 and E2) and 7 nonstructural (NS) proteins (p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B), which participate in posttranslational proteolytic processing and replication of HCV genetic material. Less than 25 years later, a new class of medications, known as direct-acting antivirals (DAAs) which target these proteins, were introduced to treat HCV infection. These highly effective antiviral agents are now approved for use in children as young as 3 years of age and have demonstrated sustained virologic responses exceeding 90% in most genotypes. Although tremendous scientific progress has been made, the incidence of acute HCV infections has increased by 4-fold since 2005, compounded in the last decade by a surge in opioid and intravenous drug use. Unfortunately, awareness of this deadly hepatotropic virus among members of the lay public remains limited. Patient education, advocacy, and counseling must, therefore, complement the availability of curative treatments against HCV infection if this virus is to be eradicated.

Human leucocyte antigen but not KIR alleles and haplotypes associated with chronic HCV infection in a Chinese Han population

The host immune system plays a key role in the elimination of infected cells which depend on killer-cell immunoglobulin-like receptors (KIR), human leucocyte antigen (HLA) class I molecules and their combinations. To evaluate the roles of HLAclass I, KIR genes and their combination in Chronic hepatitis C virus (HCV) infection (CHC), a total of 301 CHCs and 239 controls in a Chinese Han population were included for HLA and KIR genotyping using next-generation sequencing and multiplex PCR sequence-specific priming, respectively. The allele frequency of HLA-C*08:01 was significantly higher in the CHCs than that of the controls (0.088 vs. 0.040, OR = 2.332, 95%CI: 1.361-3.996, p = 0.022), while the frequencies of B*13:01 (0.032 vs. 0.084, OR = 0.357, 95%CI: 0.204-0.625, p = 0.009) and C*08:04 (0.008 vs. 0.038, OR = 0.214, 95%CI: 0.079-0.581, p = 0.022) were significantly lower in the CHCs. The frequencies of haplotype A*11:01-C*08:01 were higher in the CHCs (0.058 vs. 0.019, OR = 3.096, 95%CI: 1.486-6.452, p = 0.026), while haplotype B*13:01-C*03:04 were lower in the CHCs compared to the controls (0.028 vs. 0.071, OR = 0.377, 95%CI: 0.207-0.685, p = 0.012). No association of CHC with KIR genes, genotypes, or haplotypes, as well as HLA/KIR combinations was observed. Our results indicated that HLA-C*08:01 was a risk factor for CHC, while HLA-C*08:04 and HLA-B*13:01 were protective factors against CHC. Haplotypes HLA-A*11:01-C*08:01 could increase susceptibility to CHC, while HLA-B*13:01-C*03:04 could be protective against CHC in the Chinese Han population.

HLA-B, HLA-C and KIR improve the predictive value of IFNL3 for Hepatitis C spontaneous clearance

IFNL3 is the strongest predictor of spontaneous resolution (SR) of hepatitis C virus (HCV), however, consideration of IFNL3 genotype alone is of limited clinical value for the prediction of SR or chronic HCV infection. The objective of this study was to analyze the impact of HLA-B, HLA-C and KIRs on SR, as well as their additive effects on the predictive value of the IFNL3 genotype. We conducted a retrospective study of HIV patients that included both SR and chronic HCV patients. In our study, 61.6% of patients with IFNL3 CC achieved SR, and 81.5% with non-CC genotypes did not achieve SR. HLA-B*44, HLA-C*12, and KIR3DS1 were identified as predictive factors for SR, with percentages of 77.4%, 85.7% and 86.2%, respectively, for patients who did not experience SR. The presence of at least one of these three markers, defined as a genetically unfavorable profile (GUP), combined with the IFNL3 non-CC genotype showed a value of 100% for non-SR. The absence of the three markers, defined as a genetically favorable profile (GFP), in addition to the IFNL3 CC genotype showed a percentage of 74.1% for SR. The combination of these markers in addition to the IFNL3 genotype improves the predictive value of IFNL3 for SR of acute HCV infection in HIV patients, which would be clinically valuable.

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.