Prediction and identification-based prediction of Chinese hepatitis C viral-specific cytotoxic T lymphocyte epitopes

IMMUNOGENIC PROPERTIES OF RECOMBINANT MOZAIC PROTEINS BASED ON ANTIGENS NS4A AND NS4B OF HEPATITIS C VIRUS

The aim of the study was to investigate immunogenic properties of mosaic recombinant proteins constructed on the data of hepatitis C virus NS4A and NS4B antigens. Four mosaic recombinant proteins, containing the T and B epitopes of the NS4A and NS4B antigens, were created by genetic engineering methods in the E. coli system. To enhance the immune response they were linked in different variations to the nucleotide sequences of murine interleukin-2 (IL-2), the Neisseria meningiditis lipopeptide, and the T helper epitope of the core protein of hepatitis C virus. The immunogenic properties of these recombinant proteins were analyzed by immunoblotting, ELISA and ELISpot using sera from immunized mice and patients infected with hepatitis C virus. Recombinant proteins specifically reacted with the sera of immunized mice and infected patients in immunoblotting. According to the ELISA data, the predominant formation of antibodies to NS4B was observed when mice were immunized with the recombinant proteins containing both antigens. Analysis of gamma-interferon production by T-lymphocytes upon contact with activated dendritic cells showed in ELISpot that the maximum production of this cytokine was detected when adjuvant components were located at the N- and C-ends of the recombinant protein. The highest level of gamma-interferon production during stimulation with this drug was detected in lymphocytes from the bone marrow and lymph nodes. The recombinant protein containing the T and B epitopes of NS4A and NS4B, murine IL-2 and the lipopeptide Neisseria meningiditis had the greatest immunostimulate effect among the four constructions. This recombinant protein formed nanoparticles of 100-120 nm in size.

Prediction of linear B-cell epitopes of hepatitis C virus for vaccine development

Background

High genetic heterogeneity in the hepatitis C virus (HCV) is the major challenge of the development of an effective vaccine. Existing studies for developing HCV vaccines have mainly focused on T-cell immune response. However, identification of linear B-cell epitopes that can stimulate B-cell response is one of the major tasks of peptide-based vaccine development. Owing to the variability in B-cell epitope length, the prediction of B-cell epitopes is much more complex than that of T-cell epitopes. Furthermore, the motifs of linear B-cell epitopes in different pathogens are quite different (e. g. HCV and hepatitis B virus). To cope with this challenge, this work aims to propose an HCV-customized sequence-based prediction method to identify B-cell epitopes of HCV.

Results

This work establishes an experimentally verified dataset comprising the B-cell response of HCV dataset consisting of 774 linear B-cell epitopes and 774 non B-cell epitopes from the Immune Epitope Database. An interpretable rule mining system of B-cell epitopes (IRMS-BE) is proposed to select informative physicochemical properties (PCPs) and then extracts several if-then rule-based knowledge for identifying B-cell epitopes. A web server Bcell-HCV was implemented using an SVM with the 34 informative PCPs, which achieved a training accuracy of 79.7% and test accuracy of 70.7% better than the SVM-based methods for identifying B-cell epitopes of HCV and the two general-purpose methods. This work performs advanced analysis of the 34 informative properties, and the results indicate that the most effective property is the alpha-helix structure of epitopes, which influences the connection between host cells and the E2 proteins of HCV. Furthermore, 12 interpretable rules are acquired from top-five PCPs and achieve a sensitivity of 75.6% and specificity of 71.3%. Finally, a conserved promising vaccine candidate, PDREMVLYQE, is identified for inclusion in a vaccine against HCV.

Conclusions

This work proposes an interpretable rule mining system IRMS-BE for extracting interpretable rules using informative physicochemical properties and a web server Bcell-HCV for predicting linear B-cell epitopes of HCV. IRMS-BE may also apply to predict B-cell epitopes for other viruses, which benefits the improvement of vaccines development of these viruses without significant modification. Bcell-HCV is useful for identifying B-cell epitopes of HCV antigen to help vaccine development, which is available at http://e045.life.nctu.edu.tw/BcellHCV.

Enhanced anti-colon cancer immune responses with modified eEF2-derived peptides

Eukaryotic elongation factor-2 (eEF2) is overexpressed in many human cancers and is an attractive target for cancer immunotherapy. The eEF2 derived polypeptides have been shown to be able to induce cytotoxic T lymphocytes from healthy donor. Here, we demonstrate the evidence indicating that modification of a segment of peptides from wild type eEF2-derived immunogenic peptides is able to further enhance its capacity of inducing antigen-specific cytotoxic T lymphocytes (CTLs) against colon cancer cells. Using peptide-MHC binding algorithms, potential HLA-A2.1-restricted epitopes capable of inducing specific CD8(+) CTLs were identified. By analyzing HLA-A2.1 affinity and immunogenicity, we further identified one novel immunogenic peptide, P739-747 (RLMEPIYLV), that elicited specific CTL responses in HLA-A2.1/K(b) transgenic mice and culture with peripheral blood lymphocytes from colon cancer patients. Furthermore, replacing certain amino acids (at positions 1, 3, 7) within the P739-747 sequence improved the immunogenicity against eEF2. Several analogs containing the auxiliary HLA-A*0201 anchor residues were able to stably bind to HLA-A*0201 and enhance CTL responses compared with the native sequence; two of them showed increased anti-tumor effects during the adoptive immunotherapy in vivo. Thus, these results support that modified immunogenic analogs are promising candidates for peptide-based cancer vaccination and immunotherapy.

Therapeutic vaccines against hepatitis C virus

Hepatitis C virus (HCV) is a blood-borne pathogen which has chronically infected about 130-210 million people worldwide. Current standard-of-care (SoC) therapy is an inadequate and expensive treatment with more side effects. Two direct-acting antiviral agents (DAAs) (telaprevir and boceprevir) in combination with SoC therapy have been used in patients infected with HCV genotype 1. Although these drugs result in a shortening of therapy, they also have additional side effects and are expensive. In their stead, several second-generation DAAs are being investigated. What important is that all-oral, interferon (IFN)- and ribavirin-free regimens for the treatment of HCV-infected patients are now being investigated, and will be applied in the next year. Preventive measures against HCV, including vaccine development, are also now in progress. However, no therapeutic vaccine against HCV has been produced to date. An effective vaccine should induce robust and broadly cross-reactive CD4(+), CD8(+)T-cell and neutralising antibody (NAb) responses. Current data indicate that vaccines can usually not completely prevent HCV infection but rather prevent the progression of HCV infection to chronic and persistent infection, which may be a realistic goal. This review discusses the important roles of NAbs and CD8(+)T-cells in the development of therapeutic vaccines, and summarizes some important epitopes of HCV recognized by CD8(+)T-cells and some prospective therapeutic vaccine approaches.

Cellular immunogenicity of a multi-epitope peptide vaccine candidate based on hepatitis C virus NS5A, NS4B and core proteins in HHD-2 mice

To develop a vaccine against hepatitis C virus (HCV), a multi-epitope peptide was synthesized from nonstructural proteins containing HLA-A2 epitopes inducing mainly responses in natural infection. The engineered vaccine candidate, VAL-44, consists of multiple epitopes from the HCV NS5A, NS4B and core proteins. Immunization with the VAL-44 peptide induced higher CTL responses than those by the smaller VL-20 peptide. VAL-44 induced antigen-specific IFN-γ-producing CD4+ T cells and CD8+ T cells. VAL-44 elicited a Th1-biased immune response with secretion of high amounts of IFN-γ and IL-2, compared with VL-20. These results suggest that VAL-44 can elicit strong cellular immune responses. The VAL-44 peptide stimulated IFN-γ production from viral-specific peripheral blood mononuclear cells (PBMCs) of patients infected with HCV. These results suggest that VAL-44 could be developed as a potential HCV multi-epitope peptide vaccine.