DCs pulsed with novel HLA-A2-restricted CTL epitopes against hepatitis C virus induced a broadly reactive anti-HCV-specific T lymphocyte response

Combination of three adjuvants enhances the immunogenicity of a recombinant protein containing the CTL epitopes of non-structural proteins of hepatitis C virus

Hepatitis C virus (HCV) can cause chronic infection and evade the immune response. The generation and maintenance of an effective T-cell response is important for immune-mediated control of HCV infection. The purpose of this study was to obtain recombinant mosaic proteins containing the cytotoxic T lymphocyte (CTL) epitopes of HCV fused with different adjuvants and analyse their immunogenicity. A recombinant polyepitope protein comprising HLA-A2-restricted CTL epitopes of the NS3, NS4ab and NS5a proteins of HCV was designed. Adjuvant compounds, the T-helper (Th) epitope PADRE, lipopeptide from Neisseria meningiditis and interleukin 2 (IL-2) were included in the fusion proteins. Three proteins differing in their adjuvant content were expressed in Escherichia coli and purified. The purified proteins formed nanosized particles. The proteins were characterized by their ability to cause proliferation of spleen cells, induce expression of cytokine genes and production of interferon gamma by T lymphocytes of immunized mice. The obtained recombinant vaccine proteins effectively stimulate dendritic cells, which in turn specifically activate Th1 and Th2 lymphocytes. Adjuvant components act additively to enhance the stimulation of dendritic cells and polarize them in the direction of Th1 lymphocyte activation. Analysis of spleen cell proliferation, expression of Th1 and Th2 cytokines and production of interferon gamma by lymphocytes of immunized mice after specific stimulation in vitro revealed that recombinant protein comprising CTL epitopes of HCV, Th epitope PADRE, lipoprotein and IL-2 induced the highest response of T-lymphocytes.

Hepatitis C Virus E2 Envelope Glycoprotein Induces an Immunoregulatory Phenotype in Macrophages

A comprehensive strategy to control hepatitis C virus (HCV) infection needs a vaccine. Our phase I study with recombinant HCV E1/E2 envelope glycoprotein (EnvGPs) as a candidate vaccine did not induce a strong immune response in volunteers. We analyzed the interactions of HCV EnvGPs with human monocyte-derived macrophages as antigen-presenting cells. HCV E2 induced immune regulatory cytokine interleukin (IL)-10 and soluble CD163 (sCD163) protein expression in macrophages from 7 of 9 blood donors tested. Furthermore, HCV E2 enhanced Stat3 and suppressed Stat1 activation, reflecting macrophage polarization toward M2 phenotype. E2-associated macrophage polarization appeared to be dependent of its interaction with CD81 leading endothelial growth factor receptor (EGFR) activation. Additionally, E2 suppressed the expression of C3 complement, similar to HCV-exposed dendritic cells (DCs), implying potential impairment of immune cell priming. Conclusion: Our results suggest that E2 EnvGP may not be an ideal candidate for HCV vaccine development, and discrete domains within E2 may prove to be more capable of elliciting a protective immune response. (Hepatology 2018).

Abnormal phenotypic features of IgM+B cell subsets in patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is associated with B cell abnormality; however the phenotypic profiles of immunoglobulin (Ig)M+B cell subsets in patients with HCV infection remain unclear. In the current study, the effect of HCV infection on IgM+B cell subsets was evaluated. The percentages, as well as the differentiation and activation features of peripheral IgM+B naive subsets [cluster of differentiation (CD)27-IgM+B cells] and IgM+B memory subsets (CD27+IgM+B cells) were assessed using flow cytometry in 27 patients with chronic hepatitis C (CHC) and 20 healthy controls (HCs). The frequency of CD27+IgM+B memory subsets detected in patients with CHC was significantly higher than that in HCs (P<0.05). Although the frequency of CD27-IgM+B naive subsets was similar in both groups, there was a significantly higher proportion of CD5+B cells detected in the CD27-IgM+B subsets of patients with CHC compared with HCs (P<0.05). Among CD27-IgM+B subsets, abnormal differentiation was associated with HCV infection, with significantly increased percentages of IgD+B cells and CD38+B cells in patients with CHC compared with HCs (P<0.05). In CD27+IgM+B memory subsets, the abnormality of cell differentiation was associated with a significantly increased percentage of CD38+B cells in patients with CHC compared with HCs (P<0.05). In addition, the percentage of activated CD27+IgM+B subsets in patients with CHC were significantly higher than those observed in HCs (P<0.05). The number of CD27-IgD+IgM+B, CD27-CD38+IgM+B and CD27+CD38+IgM+B cells were negatively correlated with HCV RNA in patients with CHC. These results suggest that HCV infection contributes to abnormalities in the percentage, differentiation and activation of IgM+B cell subsets and may disrupt the immune response mediated by IgM+B cells.

Highly-Immunogenic Virally-Vectored T-cell Vaccines Cannot Overcome Subversion of the T-cell Response by HCV during Chronic Infection

An effective therapeutic vaccine for the treatment of chronic hepatitis C virus (HCV) infection, as an adjunct to newly developed directly-acting antivirals (DAA), or for the prevention of reinfection, would significantly reduce the global burden of disease associated with chronic HCV infection. A recombinant chimpanzee adenoviral (ChAd3) vector and a modified vaccinia Ankara (MVA), encoding the non-structural proteins of HCV (NSmut), used in a heterologous prime/boost regimen induced multi-specific, high-magnitude, durable HCV-specific CD4+ and CD8+ T-cell responses in healthy volunteers, and was more immunogenic than a heterologous Ad regimen. We now assess the immunogenicity of this vaccine regimen in HCV infected patients (including patients with a low viral load suppressed with interferon/ribavirin therapy), determine T-cell cross-reactivity to endogenous virus, and compare immunogenicity with that observed previously in both healthy volunteers and in HCV infected patients vaccinated with the heterologous Ad regimen. Vaccination of HCV infected patients with ChAd3-NSmut/MVA-NSmut was well tolerated. Vaccine-induced HCV-specific T-cell responses were detected in 8/12 patients; however, CD4+ T-cell responses were rarely detected, and the overall magnitude of HCV-specific T-cell responses was markedly reduced when compared to vaccinated healthy volunteers. Furthermore, HCV-specific cells had a distinct partially-functional phenotype (lower expression of activation markers, granzyme B, and TNFα production, weaker in vitro proliferation, and higher Tim3 expression, with comparable Tbet and Eomes expression) compared to healthy volunteers. Robust anti-vector T-cells and antibodies were induced, showing that there is no global defect in immunity. The level of viremia at the time of vaccination did not correlate with the magnitude of the vaccine-induced T-cell response. Full-length, next-generation sequencing of the circulating virus demonstrated that T-cells were only induced by vaccination when there was a sequence mismatch between the autologous virus and the vaccine immunogen. However, these T-cells were not cross-reactive with the endogenous viral variant epitopes. Conversely, when there was complete homology between the immunogen and circulating virus at a given epitope T-cells were not induced. T-cell induction following vaccination had no significant impact on HCV viral load. In vitro T-cell culture experiments identified the presence of T-cells at baseline that could be expanded by vaccination; thus, HCV-specific T-cells may have been expanded from pre-existing low-level memory T-cell populations that had been exposed to HCV antigens during natural infection, explaining the partial T-cell dysfunction. In conclusion, vaccination with ChAd3-NSmut and MVA-NSmut prime/boost, a potent vaccine regimen previously optimized in healthy volunteers was unable to reconstitute HCV-specific T-cell immunity in HCV infected patients. This highlights the major challenge of overcoming T-cell exhaustion in the context of persistent antigen exposure.

CD4+CXCR5+ T cells activate CD27+IgG+ B cells via IL-21 in patients with hepatitis C virus infection

BACKGROUND

Chronic hepatitis C virus (HCV) infection causes the skewing and activation of B cell subsets, but the characteristics of IgG+ B cells in patients with chronic hepatitis C (CHC) infection have not been thoroughly elucidated. CD4+CXCR5+ follicular helper T (Tfh) cells, via interleukin (IL)-21 secretion, activate B cells. However, the role of CD4+CXCR5+ T cells in the activation of IgG+ B cells in CHC patients is not clear.

METHODS

The frequency of IgG+ B cells, including CD27-IgG+ B and CD27+IgG+ B cells, the expression of the activation markers (CD86 and CD95) in IgG+ B cells, and the percentage of circulating CD4+CXCR5+ T cells were detected by flow cytometry in CHC patients (n=70) and healthy controls (n=25). The concentrations of serum IL-21 were analyzed using ELISA. The role of CD4+CXCR5+ T cells in the activation of IgG+ B cells was investigated using a co-culture system.

RESULTS

A significantly lower proportion of CD27+IgG+ B cells with increased expression of CD86 and CD95 was observed in CHC patients. The expression of CD95 was negatively correlated with the percentage of CD27+IgG+ B cells, and it contributed to CD27+IgG+ B cell apoptosis. Circulating CD4+CXCR5+ T cells and serum IL-21 were significantly increased in CHC patients. Moreover, circulating CD4+CXCR5+ T cells from CHC patients induced higher expressions of CD86 and CD95 in CD27+IgG+ B cells in a co-culture system; the blockade of the IL-21 decreased the expression levels of CD86 and CD95 in CD27+IgG+ B cells.

CONCLUSIONS

HCV infection increased the frequency of CD4+CXCR5+ T cells and decreased the frequency of CD27+IgG+ B cells. CD4+CXCR5+ T cells activated CD27+IgG+ B cells via the secretion of IL-21.

Identification and retrospective validation of T-cell epitopes in the hepatitis C virus genotype 4 proteome: an accelerated approach toward epitope-driven vaccine development

With over 150 million people chronically infected worldwide and millions more infected annually, hepatitis C continues to pose a burden on the global healthcare system. The standard therapy of hepatitis C remains expensive, with severe associated side effects and inconsistent cure rates. Vaccine development against the hepatitis C virus has been hampered by practical and biological challenges posed by viral evasion mechanisms. Despite these challenges, HCV vaccine research has presented a number of candidate vaccines that progressed to phase II trials. However, those efforts focused mainly on HCV genotypes 1 and 2 as vaccine targets and barely enough attention was given to genotype 4, the variant most prevalent in the Middle East and central Africa. We describe herein the in silico identification of highly conserved and immunogenic T-cell epitopes from the HCV genotype 4 proteome, using the iVAX immunoinformatics toolkit, as targets for an epitope-driven vaccine. We also describe a fast and inexpensive approach for results validation using the empirical data on the Immune Epitope Database (IEDB) as a reference. Our analysis identified 90 HLA class I epitopes of which 20 were found to be novel and 19 more had their binding predictions retrospectively validated; empirical data for the remaining 51 epitopes was insufficient to validate their binding predictions. Our analysis also identified 14 HLA class II epitopes, of which 8 had most of their binding predictions validated. Further investigation is required regarding the efficacy of the identified epitopes as vaccine targets in populations where HCV genotype 4 is most prevalent.

Abnormal CD4 + T helper (Th) 1 cells and activated memory B cells are associated with type III asymptomatic mixed cryoglobulinemia in HCV infection

Background

Mixed cryoglobulinemia (MC) in hepatitis C virus (HCV) infection is associated with abnormal immune responses mediated by T cells and B cells, while the relationships of different subsets of CD4 + T helper (Th) cells, B cells and associated cytokines with type III asymptomatic MC in HCV infection are poorly understood.

Methods

Fifty-four chronic hepatitis C (CHC) patients and 23 healthy controls (HCs) were enrolled in the study. Serum cryoglobulins were detected by cryoprecipitation. The types of cryoglobulin were determined by western blot. The phenotypes and frequencies of Th cell and B cell subsets were detected by flow cytometric analysis. The cytokines IFN-γ, IL-4, IL-17, IL-21, IL-22, and TGF-β were measured by enzyme-linked immunosorbent assay.

Results

Twenty-six CHC patients were detected with type III asymptomatic MC. The frequencies of Th2, Th17, follicular helper T (Tfh cells), Th22, and tissue-like B cells were significantly higher in CHC patients compared to HCs, while these cell subsets were not significantly different between CHC patients and HCV-related MC patients. The frequencies of Th1 and activated memory B cells increased in HCV-related MC patients compared to HCs, although the difference between the two cell subsets in CHC patients and HCs was not significant. The frequency of regulatory T cells (Treg cells) was higher in CHC patients than in HCV-related MC patients and HCs. Higher expressions of serum IFN-γ, IL-17, IL-21, and IL-22 were observed in CHC patients than in HCs, but the differences were not significantly different in CHC patients and HCV-related MC patients. The frequency of Th1 cells was associated with activated memory B cells in HCV-related MC patients, and the frequency of Th1 cells and activated memory B cells was closely related to HCV RNA in HCV-related MC patients.

Conclusions

The increased frequencies of Th17 cells, Tfh cells, Th22 cells, Treg cells, cytokines IL-17, IL-21, IL-22, and tissue-like B cells, were related to HCV infection but not type III asymptomatic MC. Higher frequencies of Th1 cells and activated memory B cells were associated with type III asymptomatic MC in HCV infection.

Phage display--a powerful technique for immunotherapy: 2. Vaccine delivery

Phage display is a powerful technique in medical and health biotechnology. This technology has led to formation of antibody libraries and has provided techniques for fast and efficient search of these libraries. The phage display technique has been used in studying the protein-protein or protein-ligand interactions, constructing of the antibody and antibody fragments and improving the affinity of proteins to receptors. Recently phage display has been widely used to study immunization process, develop novel vaccines and investigate allergen-antibody interactions. This technology can provide new tools for protection against viral, fungal and bacterial infections. It may become a valuable tool in cancer therapies, abuse and allergies treatment. This review presents the recent advancements in diagnostic and therapeutic applications of phage display. In particular the applicability of this technology to study the immunization process, construction of new vaccines and development of safer and more efficient delivery strategies has been described.