Immune response to hepatitis C virus core protein in mice

Production and characterization of monoclonal antibodies for the detection of the hepatitis C core antigen

Background: Despite highly effective treatments to cure hepatitis C, almost 80% of chronically HCV-infected people are not treated, as they are unaware of their infection. Diagnostic rates and linkage to care must be substantially improved to reverse this situation. The HCV core antigen (HCVcAg) is a highly conserved protein that can be detected in the blood of HCV-infected patients and indicates active infection. Aim: To produce murine monoclonal antibodies against HCVcAg suitable for rapid and inexpensive tests to detect HCV infection. Methods: BALB/c mice were sequentially inoculated with purified recombinant HCVcAg from Gt1a, Gt3a, Gt4a, and Gt1b genotypes. Hybridomas producing the desired monoclonal antibodies were selected, and the reactivity of antibodies against HCVcAg from various genotypes was tested by Western blotting and dot blotting. The binding kinetics of the antibodies to purified HCVcAg was analyzed by surface plasmon resonance (SPR), and their ability to detect HCVcAg was tested by double antibody sandwich ELISA (DAS-ELISA). Results: Four specific monoclonal antibodies (1C, 2C, 4C, and 8C) were obtained. 1C, 2C, and 4C recognized HCVcAg of all genotypes tested (Gt1a, Gt1b, Gt2a, Gt3a, and Gt4a), while 8C did not recognize the Gt2a and Gt3a genotypes. Based on SPR data, the antibody-HCVcAg complexes formed are stable, with 2C having the strongest binding properties. DAS-ELISA with different antibody combinations easily detected HCVcAg in culture supernatants from HCV-infected cells. Conclusion: Specific and cross-reactive anti-HCVcAg monoclonal antibodies with strong binding properties were obtained that may be useful for detecting HCVcAg in HCV-infected samples.

Impact of IL28 Genotypes and Modeling the Interactions of HCV Core Protein on Treatment of Hepatitis C

BACKGROUND

Mutations in the core CVR region of hepatitis C virus (HCV) and polymorphisms of interleukin 28B (IL28B) are associated with progression toward liver disease and in response to therapy. In addition, interactions of the core protein with some cell interactors can be related to HCV liver damage.

AIM

This study aimed to evaluate the effect of core mutations as well as IL28B polymorphism on clinical features, sustained virological response (SVR) in 1a and 3a HCV genotypes amongst Iranian HCV infected patients, and the impact of mutations on core protein properties, antigenic properties, and interactions with HCV inhibitors, using several bioinformatics tools.

METHODS

Seventy-nine Iranian patients infected with HCV genotypes 1a and 3a and diagnosed with chronic active hepatitis were examined. Plasma viral RNA was used to amplify and sequence the HCV Core gene; also, HCV viral load, molecular genotyping, and the liver enzymes were determined for all samples. The sequencing results were analyzed by several reliable bioinformatics tools to determine the physicochemical properties, B cell epitopes, post-modification changes, and secondary/tertiary structures; and evaluate the interactions with 4 drugs by docking method.

RESULT

There were some substitutions in core CVR related to ALT and AST enzymes that can lead to HCV advanced liver disease. The most prevalent mutation for 3a genotypes was a substitution in aa 162 (I to V) while we did not find any mutation in 1a responder group. Polymorphism of the rs8099917 showed that the majority of patients had TG heterozygous and carried CT genotype at the rs12979860. Analysis indicated several phosphorylation sits for core protein as well as two important disulfide bonds. Immunogenic prediction showed that core protein can strongly induce the immune system. Interaction analysis, using the docking method revealed two potential interactors (Vitronectin and SETD2).

CONCLUSION

Generally, mutations in all core CVR regions in all patients showed a relationship between such substitutions and higher liver enzymes that can result in advanced liver disease progression in HCV infected patients. Furthermore, immunoinformatics analysis determined the possible immunodominant regions to be considered in HCV vaccine designs. Furthermore, no association between SVR and IL28B polymorphism was shown. In silico analysis determined modification sites, structures, B-cell epitopes of core protein and interactions with several interactors can lead to persistent HCV infection in the cell and the progress of liver diseases.

Bioinformatics Analysis of Domain 1 of HCV-Core Protein: Iran

Hepatitis C virus (HCV) infection is a serious global health problem and a cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). Bioinformatics software has been an effective tool to study the HCV genome as well as core domains. Our research was based on employing several bioinformatics software applications to find important mutations in domain 1 of core protein in Iranian HCV infected samples from 2006 to 2017, and an investigation of general properties, B-cell and T-cell epitopes, modification sites, and structure of domain 1. Domain 1 sequences of 188 HCV samples isolated from 2006 to 2017, Iran, were retrieved from NCBI gene bank. Using several tools, all sequences were analyzed for determination of mutations, physicochemical analysis, B-cell epitopes prediction, T-cell and CTL epitopes prediction, post modification, secondary and tertiary structure prediction. Our analysis determined several mutations in some special positions (70, 90, 91, and 110) that are associated with HCC and hepatocarcinogenesis, efficacy of triple therapy and sustained virological response, and interaction between core and CCR6. Several B-cell, T-cell, and CTL epitopes were recognized. Secondary and tertiary structures were mapped fordomain1 and core proteins. Our study, as a first report, offered inclusive data about frequent mutation in HCV-core gene domain 1 in Iranian sequences that can provide helpful analysis on structure and function of domain 1 of the core gene.

The Immunogenicity in Mice of HCV Core Delivered as DNA Is Modulated by Its Capacity to Induce Oxidative Stress and Oxidative Stress Response

HCV core is an attractive HCV vaccine target, however, clinical or preclinical trials of core-based vaccines showed little success. We aimed to delineate what restricts its immunogenicity and improve immunogenic performance in mice. We designed plasmids encoding full-length HCV 1b core and its variants truncated after amino acids (aa) 60, 98, 152, 173, or up to aa 36 using virus-derived or synthetic polynucleotides (core191/60/98/152/173/36_191v or core152s DNA, respectively). We assessed their level of expression, route of degradation, ability to trigger the production of reactive oxygen species/ROS, and to activate the components of the Nrf2/ARE antioxidant defense pathway heme oxygenase 1/HO-1 and NAD(P)H: quinone oxidoreductase/Nqo-1. All core variants with the intact N-terminus induced production of ROS, and up-regulated expression of HO-1 and Nqo-1. The capacity of core variants to induce ROS and up-regulate HO-1 and Nqo-1 expression predetermined their immunogenicity in DNA-immunized BALB/c and C57BL/6 mice. The most immunogenic was core 152s, expressed at a modest level and inducing moderate oxidative stress and oxidative stress response. Thus, immunogenicity of HCV core is shaped by its ability to induce ROS and oxidative stress response. These considerations are important in understanding the mechanisms of viral suppression of cellular immune response and in HCV vaccine design.

Comparative Immunogenicity in Rabbits of the Polypeptides Encoded by the 5' Terminus of Hepatitis C Virus RNA

Recent studies on the primate protection from HCV infection stressed the importance of immune response against structural viral proteins. Strong immune response against nucleocapsid (core) protein was difficult to achieve, requesting further experimentation in large animals. Here, we analyzed the immunogenicity of core aa 1–173, 1–152, and 147–191 and of its main alternative reading frame product F-protein in rabbits. Core aa 147–191 was synthesized; other polypeptides were obtained by expression in E. coli. Rabbits were immunized by polypeptide primes followed by multiple boosts and screened for specific anti-protein and anti-peptide antibodies. Antibody titers to core aa 147–191 reached 10⁵; core aa 1–152, 5 × 10⁵; core aa 1–173 and F-protein, 10⁶. Strong immunogenicity of the last two proteins indicated that they may compete for the induction of immune response. The C-terminally truncated core was also weakly immunogenic on the T-cell level. To enhance core-specific cellular response, we immunized rabbits with the core aa 1–152 gene forbidding F-protein formation. Repeated DNA immunization induced a weak antibody and sustained proliferative response of broad specificity confirming a gain of cellular immunogenicity. Epitopes recognized in rabbits overlapped those in HCV infection. Our data promotes the use of rabbits for the immunogenicity tests of prototype HCV vaccines.

Additives and protein-DNA combinations modulate the humoral immune response elicited by a hepatitis C virus core-encoding plasmid in mice

Humoral and cellular immune responses are currently induced against hepatitis C virus (HCV) core following vaccination with core-encoding plasmids. However, the anti-core antibody response is frequently weak or transient. In this paper, we evaluated the effect of different additives and DNA-protein combinations on the anti-core antibody response. BALB/c mice were intramuscularly injected with an expression plasmid (pIDKCo), encoding a C-terminal truncated variant of the HCV core protein, alone or combined with CaCl2, PEG 6000, Freund's adjuvant, sonicated calf thymus DNA and a recombinant core protein (Co. 120). Mixture of pIDKCo with PEG 6000 and Freund's adjuvant accelerated the development of the anti-core Ab response. Combination with PEG 6000 also induced a bias to IgG2a subclass predominance among anti-core antibodies. The kinetics, IgG2a/IgG1 ratio and epitope specificity of the anti-core antibody response elicited by Co. 120 alone or combined with pIDKCo was different regarding that induced by the pIDKCo alone. Our data indicate that the antibody response induced following DNA immunization can be modified by formulation strategies.