Hepatitis C virus vaccines in the era of new direct-acting antivirals

Hepatitis C Virus Infection and Vaccine Development

In the twenty-seven years since the discovery of hepatitis C virus (HCV) the majority of individuals exposed to HCV establish a persistent infection, which is a leading cause of chronic liver disease, cirrhosis and hepatocellular carcinoma. In developed nations, the cure rates of HCV infection could be over 90% with direct-acting antiviral (DAA) regimens, which has made the great progress in global eradication. However, the cost of these treatments is so expensive that the patients in developing nations, where the disease burden is the most severe, could not afford it, which highly restricted its access. Additionally, the largely asymptomatic nature of infection facilitates continued transmission in risk groups due to limited surveillance. Consequently a protective vaccine and likely emergence of drug-resistant viral variants call for further studies of HCV biology. In the current review, the development and the progress of preventive and therapeutic vaccines against the HCV have been reviewed in the context of peptide vaccines, recombinant protein vaccines, HCV-like particle, DNA vaccines and viral vectors expressing HCV genes.

Deciphering molecular properties and docking studies of hepatitis C and non-hepatitis C antiviral inhibitors - A computational approach

BACKGROUND

Hepatitis C is an infectious liver disease with high mortality rate which is caused by Hepatitis C virus. Several treatment methods have been applied to combat this deadly virus including interferons, vaccine and direct acting antivirals (DAAs). However, the later shows promising effects in HCV treatment with lower adverse effect. Specifically, the DAAs target the non-structural proteins (NS3 and NS5B).

PURPOSE

The objective of the present study is to hypothesize an alternative antiviral inhibitor for HCV from the available other antivirals.

METHODS

Computation of 2D molecular descriptors for the selected antiviral inhibitors followed by clustering the descriptor features. The closely clustered compounds were subjected to the interaction studies against the HCV target protein to validate the cluster result.

RESULTS AND DISCUSSION

The clustering result showed that indinavir (HIV inhibitor) and AT130 (HBV inhibitor) molecule are close to the HCV inhibitor. The indinavir complexed with NS3 protein shows -5.33kcal/mol and AT-130 complexed with NS5B protein possess the binding energy of -8.87kcal/mol. The docking interaction study indicated a better binding affinity than other viral inhibitors.

CONCLUSION

From the descriptor based feature similarity analysis and the interaction study, it can be concluded that indinavir and AT-130 could be a potential alternative agent for HCV treatment.

Status of hepatitis C virus vaccination: Recent update

Hepatitis C virus (HCV) infection is still a major public health problem worldwide since its first identification in 1989. At the start, HCV infection was post-transfusion viral infection, particularly in developing countries. Recently, due to iv drug abuse, HCV infection became number one health problem in well-developed countries as well. Following acute HCV infection, the innate immune response is triggered in the form of activated coordinated interaction of NK cells, dendritic cells and interferon α. The acquired immune response is then developed in the form of the antibody-mediated immune response (ABIR) and the cell-mediated immune response (CMIR). Both are responsible for clearance of HCV infection in about 15% of infected patients. However, HCV has several mechanisms to evade these antivirus immune reactions. The current review gives an overview of HCV structure, immune response and viral evasion mechanisms. It also evaluates the available preventive and therapeutic vaccines that induce innate, ABIR, CMIR. Moreover, this review highlights the progress in recent HCV vaccination studies either in preclinical or clinical phases. The unsatisfactory identification of HCV infection by the current screening system and the limitations of currently available treatments, including the ineligibility of some chronic HCV patients to such antiviral agents, mandate the development of an effective HCV vaccine.

Immune responses against hepatitis C virus genotype 3a virus-like particles in mice: A novel VLP prime-adenovirus boost strategy

Chronic hepatitis C virus (HCV) infection represents a major health threat to global population. In India, approximately 15-20% of cases of chronic liver diseases are caused by HCV infection. Although, new drug treatments hold great promise for HCV eradication in infected individuals, the treatments are highly expensive. A vaccine for preventing or treating HCV infection would be of great value, particularly in developing countries. Several preclinical trials of virus-like particle (VLP) based vaccine strategies are in progress throughout the world. Previously, using baculovirus based system, we have reported the production of hepatitis C virus-like particles (HCV-LPs) encoding structural proteins for genotype 3a, which is prevalent in India. In the present study, we have generated HCV-LPs using adenovirus based system and tried different immunization strategies by using combinations of both kinds of HCV-LPs with other genotype 3a-based immunogens. HCV-LPs and peptides based ELISAs were used to evaluate antibody responses generated by these combinations. Cell-mediated immune responses were measured by using T-cell proliferation assay and intracellular cytokine staining. We observed that administration of recombinant adenoviruses expressing HCV structural proteins as final booster enhances both antibody as well as T-cell responses. Additionally, reduction of binding of VLP and JFH1 virus to human hepatocellular carcinoma cells demonstrated the presence of neutralizing antibodies in immunized sera. Taken together, our results suggest that the combined regimen of VLP followed by recombinant adenovirus could more effectively inhibit HCV infection, endorsing the novel vaccine strategy.

Modeling hepatitis C virus transmission among people who inject drugs: Assumptions, limitations and future challenges

The discovery of highly effective hepatitis C virus (HCV) treatments has led to discussion of elimination and intensified interest in models of HCV transmission. In developed settings, HCV disproportionally affects people who inject drugs (PWID), and models are typically used to provide an evidence base for the effectiveness of interventions such as needle and syringe programs, opioid substitution therapy and more recently treating PWID with new generation therapies to achieve specified reductions in prevalence and / or incidence. This manuscript reviews deterministic compartmental S-I, deterministic compartmental S-I-S and network-based transmission models of HCV among PWID. We detail typical assumptions made when modeling injecting risk behavior, virus transmission, treatment and re-infection and how they correspond with available evidence and empirical data.

The role of a hepatitis C virus vaccine: modelling the benefits alongside direct-acting antiviral treatments

BACKGROUND

Hepatitis C virus (HCV) elimination is being seriously considered globally. Current elimination models require a combination of highly effective HCV treatment and harm reduction, but high treatment costs make such strategies prohibitively expensive. Vaccines should play a key role in elimination but their best use alongside treatments is unclear. For three vaccines with different efficacies we used a mathematical model to estimate the additional reduction in HCV prevalence when vaccinating after treatment; and to identify in which settings vaccines could most effectively reduce the number of treatments required to achieve fixed reductions in HCV prevalence among people who inject drugs (PWID).

METHODS

A deterministic model of HCV transmission among PWID was calibrated for settings with 25, 50 and 75% chronic HCV prevalence among PWID, stratified by high-risk or low-risk PWID. For vaccines with 30, 60 or 90% efficacies, different rates of treatment and vaccination were introduced. We compared prevalence reductions achieved by vaccinating after treatment to prevent reinfection and vaccinating independently of treatment history in the community; and by allocating treatments and vaccinations to specific risk groups and proportionally across risk groups.

RESULTS

Vaccinating after treatment was minimally different to vaccinating independently of treatment history, and allocating treatments and vaccinations to specific risk groups was minimally different to allocating them proportionally across risk groups. Vaccines with 30 or 60% efficacy provided greater additional prevalence reduction per vaccination in a setting with 75% chronic HCV prevalence among PWID than a 90% efficacious vaccine in settings with 25 or 50% chronic HCV prevalence among PWID.

CONCLUSIONS

Vaccinating after treatment is an effective and practical method of administration. In settings with high chronic HCV prevalence among PWID, even modest coverage with a low-efficacy vaccine could provide significant additional prevalence reduction beyond treatment alone, and would likely reduce the cost of achieving prevalence reduction targets.

Priming with two DNA vaccines expressing hepatitis C virus NS3 protein targeting dendritic cells elicits superior heterologous protective potential in mice

Development an effective vaccine may offer an alternative preventive and therapeutic strategy against HCV infection. DNA vaccination has been shown to induce robust humoral and cellular immunity and overcome many problems associated with conventional vaccines. In this study, mice were primed with either conventional pVRC-based or suicidal pSC-based DNA vaccines carrying DEC-205-targeted NS3 antigen (DEC-NS3) and boosted with type 5 adenoviral vectors encoding the partial NS3 and core antigens (C44P). The prime boost regimen induced a marked increase in antigen-specific humoral and T-cell responses in comparison with either rAd5-based vaccines or DEC-205-targeted DNA immunization in isolation. The protective effect against heterogeneous challenge was correlated with high levels of anti-NS3 IgG and T-cell-mediated immunity against NS3 peptides. Moreover, priming with a suicidal DNA vaccine (pSC-DEC-NS3), which elicited increased TNF-α-producing CD4+ and CD8+ T-cells against NS3-2 peptides (aa 1245-1461), after boosting, showed increased heterogeneous protective potential compared with priming with a conventional DNA vaccine (pVRC-DEC-NS3). In conclusion, a suicidal DNA vector (pSC-DEC-NS3) expressing DEC-205-targeted NS3 combined with boosting using an rAd5-based HCV vaccine (rAd5-C44P) is a good candidate for a safe and effective vaccine against HCV infection.

Combined adenovirus vector and hepatitis C virus envelope protein prime-boost regimen elicits T cell and neutralizing antibody immune responses

Despite the recent progress in the development of new antiviral agents, hepatitis C virus (HCV) infection remains a major global health problem, and there is a need for a preventive vaccine. We previously reported that adenoviral vectors expressing HCV nonstructural proteins elicit protective T cell responses in chimpanzees and were immunogenic in healthy volunteers. Furthermore, recombinant HCV E1E2 protein formulated with adjuvant MF59 induced protective antibody responses in chimpanzees and was immunogenic in humans. To develop an HCV vaccine capable of inducing both T cell and antibody responses, we constructed adenoviral vectors expressing full-length and truncated E1E2 envelope glycoproteins from HCV genotype 1b. Heterologous prime-boost immunization regimens with adenovirus and recombinant E1E2 glycoprotein (genotype 1a) plus MF59 were evaluated in mice and guinea pigs. Adenovirus prime and protein boost induced broad HCV-specific CD8+ and CD4+ T cell responses and functional Th1-type IgG responses. Immune sera neutralized luciferase reporter pseudoparticles expressing HCV envelope glycoproteins (HCVpp) and a diverse panel of recombinant cell culture-derived HCV (HCVcc) strains and limited cell-to-cell HCV transmission. This study demonstrated that combining adenovirus vector with protein antigen can induce strong antibody and T cell responses that surpass immune responses achieved by either vaccine alone.

IMPORTANCE

HCV infection is a major health problem. Despite the availability of new directly acting antiviral agents for treating chronic infection, an affordable preventive vaccine provides the best long-term goal for controlling the global epidemic. This report describes a new anti-HCV vaccine targeting the envelope viral proteins based on adenovirus vector and protein in adjuvant. Rodents primed with the adenovirus vaccine and boosted with the adjuvanted protein developed cross-neutralizing antibodies and potent T cell responses that surpassed immune responses achieved with either vaccine component alone. If combined with the adenovirus vaccine targeting the HCV NS antigens now under clinical testing, this new vaccine might lead to a stronger and broader immune response and to a more effective vaccine to prevent HCV infection. Importantly, the described approach represents a valuable strategy for other infectious diseases in which both T and B cell responses are essential for protection.