Is there still hope for the prophylactic hepatitis C vaccine? A review of different approaches.

Despite remarkable progress in the treatment of hepatitis C virus (HCV) infection, it remains a significant global health burden, necessitating the development of an effective prophylactic vaccine. This review paper presents the current landscape of HCV vaccine candidates and approaches, including more traditional, based on inactivated virus, and more modern, such as subunit protein, vectored, based on nucleic acids (DNA and mRNA) and virus-like particles. The concept of the HCV vaccine is first put in the context of viral genetic diversity and adaptive responses to HCV infection, an understanding of which is crucial in guiding the development of an effective vaccine against such a complex virus. Because ethical dimensions are also significant in vaccine research, development, and potential deployment, we also address them in this paper. The road to a safe and effective vaccine to prevent HCV infection remains bumpy due to the genetic variation of HCV and its ability to evade immune responses. The progress in cell-culture systems allowed for the production of an inactivated HCV vaccine candidate, which can induce cross-neutralizing antibodies in vitro, but whether this could prevent infection in humans is unknown. Subunit protein vaccine candidates that entered clinical trials elicited HCV-specific humoral and cellular responses, though it remains to be shown whether they translate into effective prevention of HCV infection or progression of infection to a chronic state. Such responses were also induced by a clinically tested vector-based vaccine candidate, which decreased the viral HCV load but did not prevent chronic HCV infection. These disappointments were not readily predicted from preclinical animal studies. The vaccine platforms employing virus-like particles, DNA, and mRNA provide opportunities for the HCV vaccine, but their potential in this context has yet to be shown. Ensuring the designed vaccine is based on conserved epitope(s) and elicits broadly neutralizing immune responses is also essential. Given failures in developing a prophylactic HCV vaccine, it is crucial to continue supporting national strategies, including funding for screening and treatment programs. However, these actions are likely insufficient to permanently control the HCV burden, encouraging further mobilization of significant resources for HCV vaccine research as a missing element in the elimination of viral hepatitis as a global public health.

Hepatitis C elimination: amplifying the role of primary care nurses in Australia.

Background Australia's commitment to eliminate hepatitis C by 2030 is underpinned by the mobilisation of the primary care sector. Primary care nurses are well placed to contribute to achieving elimination given their unique access to people with/at risk of hepatitis C and their person-centred approach to care delivery. This study examines the enablers to primary care nurse involvement in elimination efforts. Methods Primary care nurses involved in the care of people with/at risk of hepatitis C were recruited through two national nursing organisations. Participants provided verbal consent to participate in an electronically recorded, semi-structured interview. Interview data were transcribed verbatim, coded and analysed using a thematic analysis. Results Sixteen interviews were conducted with nurses working in general practice, community health, alcohol and other drug services, and custodial settings, with the findings framed using a social-ecological model. The study identified individual attributes, such as empathy and advocacy for clients deemed 'too hard for everyone else'. Interpersonal enablers included participants' ability to effectively communicate with clients and colleagues, and using trusted professional relationships to improve client access to care. Public policy that addressed community factors, including stigma and confidentiality, were seen as supportive. Conclusions This study identified the critical and varied role primary care nurses play in hepatitis C elimination. Effective scale up of hepatitis C care involves recognising the pivotal role of primary care nurses, which will help to create an enabling environment that supports nurses to work to their full scope of practice and enhance their contribution to the elimination response.

Modeling the impact of a supervised consumption site on HIV and HCV transmission among people who inject drugs in three counties in California, USA.

BACKGROUND: Supervised consumption sites (SCS) have been shown to reduce receptive syringe sharing among people who inject drugs (PWID) in the United States and elsewhere, which can prevent HIV and hepatitis C virus (HCV) transmission. PWID are at risk of disease transmission and may benefit from SCS, however legislation has yet to support their implementation. This study aims to determine the potential impact of SCS implementation on HIV and HCV incidence among PWID in three California counties. METHODS: A dynamic HIV and HCV joint transmission model among PWID (sexual and injecting transmission of HIV, injecting transmission of HCV) was calibrated to epidemiological data for three counties: San Francisco, Los Angeles, and San Diego. The model incorporated HIV and HCV disease stages and HIV and HCV treatment. Based on United States data, we assumed access to SCS reduced receptive syringe sharing by a relative risk of 0.17 (95 % CI: 0.04-1.03). This model examined scaling-up SCS coverage from 0 % to 20 % of the PWID population within the respective counties and assessed its impact on HIV and HCV incidence rates after 10 years. RESULTS: By increasing SCS from 0 % to 20 % coverage among PWID, 21.8 % (95 % CI: -1.2-32.9 %) of new HIV infections and 28.3 % (95 % CI: -2.0-34.5 %) of new HCV infections among PWID in San Francisco County, 17.7 % (95 % CI: -1.0-30.8 %) of new HIV infections and 29.8 % (95 % CI: -2.1-36.1 %) of new HCV infections in Los Angeles County, and 32.1 % (95 % CI: -2.8-41.5 %) of new HIV infections and 24.3 % (95 % CI: -1.6-29.0 %) of new HCV infections in San Diego County could be prevented over ten years. CONCLUSION: Our models suggest that SCS is an important intervention to enable HCV elimination and could help end the HIV epidemic among PWID in California. It could also have additional benefits such facilitating pathways into drug treatment programs and preventing fatal overdose.

Pilot model of hepatitis C virus micro-elimination in high-risk populations in Hong Kong: Barriers and facilitators.

BACKGROUND: Although the general seroprevalence of hepatitis C virus (HCV) infection in Hong Kong is <0.5 %, Hong Kong is still striving for HCV elimination owing to barriers in care cascade encompassing linkage-to-care (LTC), treatment initiation and adherence. We aimed to evaluate the feasibility of a pilot model of micro-elimination to strengthen the HCV care cascade for high-risk groups in Hong Kong. METHODS: We initiated the pilot Conquering Hepatitis vIa Micro-Elimination (CHIME) program which adopts an integrated care approach involving outreach visits to halfway house or drug rehabilitation centers run by non-governmental organizations. Participants with history of injection drug use (PWID), recreational drug use, or imprisonment were included. We performed point-of-care test for anti-HCV with reflex HCV RNA testing. LTC with government-subsidized direct acting antiviral was provided to viremic participants. We compared the impact on the care cascade with a cohort of HCV patients (17.8 % PWID) under usual care. RESULTS: 396 participants (62.9 % PWID) were screened and 187 (47.2 %) were viremic, of which 29.8 % had cirrhosis. Proportion with LTC, treatment initiation and adherence were 76.5 % and 63.7 %, 90.9 % and 85.8 %, and 90.0 % and 92.2 %, for the CHIME program and usual care, respectively. The CHIME program was significantly associated with higher odds of LTC (OR 1.797, 95 % CI 1.221-2.644). Non-engagement in care (affecting 37.9 % participants with HCV viremia) was associated with unemployment (OR 2.165, 95 % CI 1.118-4.190). CONCLUSION: The pilot CHIME program demonstrated feasibility of an integrated approach to consolidate the HCV care cascade in high-risk populations in Hong Kong.

Impact of educational interventions on hepatitis B and C awareness among school students of Delhi NCR, India.

BACKGROUND: Viral hepatitis, particularly B and C, is a major cause of liver cirrhosis and cancer, leading to about 1.4 million deaths annually. Alarmingly, less than 20% of those with hepatitis are aware of their status, with only 6.3% receiving treatment. School children can play a pivotal role in raising awareness and preventing the spread of infections. This intervention study focuses on understanding and enhancing the knowledge, attitudes, and practices related to Hepatitis B and C, among school children in Delhi NCR to foster dialogue and awareness. METHODS: An intervention study was conducted in selected schools across Delhi NCR between September and October 2022 to assess baseline knowledge, attitudes, and practices related to Hepatitis B and C. Three of seven schools were randomly selected by probability sampling, representing 9-12 grade students, and 901 students participated. Following this, an educational interventional program was conducted using educational material, interactive sessions, and audiovisual aids. Post-intervention assessments were done to measure the impact on knowledge improvement. RESULTS: The study is expected to provide insights into the current level of awareness regarding Hepatitis B and C. Furthermore, the intervention's effectiveness was analysed using the pre-formed questionnaire. The average pre-test knowledge score was 8.9 ± 3.2, while the post-test average was 15.6 ± 4.4, indicating a substantial increase of 6.7 ± 4.7 points (+ 75.2%). There was a positive correlation of 0.240 between pre and post-test scores. Attitude change before and after the session showed a positive percentage change of + 38.0% with a correlation of 0.351. The study indicated substantial improvements in knowledge about hepatitis B and C, notably regarding awareness about transmission methods and risk factors. CONCLUSION: This interventional study seeks to bridge the knowledge gap among school children regarding Hepatitis B and C in Delhi NCR, fostering a proactive approach towards prevention, detection, and treatment. The considerable rise in awareness and favourable changes in perspectives post-intervention say that specific health education initiatives are pivotal in raising awareness and comprehension of infectious diseases, ultimately contributing to improving community health.

Progress Toward the Elimination of Hepatitis B and Hepatitis C in the Country of Georgia, April 2015-April 2024.

Hepatitis B and hepatitis C are leading causes of cirrhosis and liver cancer and caused 1.3 million deaths worldwide in 2022. Hepatitis B is preventable with vaccination, and hepatitis C is curable with direct-acting antivirals. In 2015, in collaboration with CDC and other partners, Georgia, a country at the intersection of Europe and Asia, launched a hepatitis C elimination program to reduce the prevalence of chronic hepatitis C; at that time, the prevalence was 5.4%, more than five times the global average of 1.0%. In 2016, the World Health Assembly endorsed a goal for the elimination of viral hepatitis as a public health problem by 2030. In 2024, 89% of the Georgian adult population have received screening for hepatitis C, 83% of persons with current chronic HCV infection have received a diagnosis, and 86% of those with diagnosed hepatitis C have started treatment. During 2015-2023, vaccination coverage with the hepatitis B birth dose and with 3 doses of hepatitis B vaccine among infants exceeded 90% for most years. In 2021, the prevalence of hepatitis B surface antigen was 0.03% among children and adolescents aged 5-17 years and 2.7% among adults. Georgia has demonstrated substantial progress toward hepatitis B and hepatitis C elimination. Using lessons from the hepatitis C elimination program, scale-up of screening and treatment for hepatitis B among adults would prevent further viral hepatitis-associated morbidity and mortality in Georgia and would accelerate progress toward hepatitis B and hepatitis C elimination by 2030.

Update on Hepatitis C Vaccine: Results and Challenges.

Therapy against the Hepatitis C virus (HCV) has significantly improved with the introduction of direct-acting antiviral drugs (DAAs), achieving over 95% sustained virological response (SVR). Despite this, the development of an effective anti-HCV vaccine remains a critical challenge due to the low number of patients treated with DAAs and the occurrence of HCV reinfections in high-risk groups. Current vaccine strategies aim to stimulate either B-cell or T-cell responses. Vaccines based on E1 and E2 proteins can elicit broad cross-neutralizing antibodies against all major HCV genotypes, though with varying efficiencies and without full protection against infection. In humans, the neutralizing antibodies induced by such vaccines mainly target the AR3 region, but their levels are generally insufficient for broad neutralization. Various HCV proteins expressed through different viral vectors have been utilized to elicit T cell immune responses, showing sustained expansion of HCV-specific effector memory T cells and improved proliferation and polyfunctionality of memory T cells over time. However, despite these advancements, the frequency and effectiveness of T-cell responses remain limited.

Going (Anti)Viral: Improving HIV and HCV Screening and HPV Vaccination in Primary Care.

BACKGROUND: Human immunodeficiency virus (HIV) and hepatitis C (HCV) screening and human papillomavirus (HPV) vaccine uptake remain suboptimal. To improve HIV and HCV screening and HPV vaccination, the authors implemented a quality improvement project in three southwestern Pennsylvania family medicine residency practices. METHODS: From June 1 to November 30, 2021, participating practices used universal screening and vaccination guidelines and chose from multiple strategies at the office (for example, standing orders), provider (for example, multiple forms of provider reminders), and patient (for example, incentives) levels derived from published literature and tailored to local context. Age-eligible patients for each recommendation with at least one in-person office visit during the intervention period were included. To assess the interventions' effect, the authors obtained testing and vaccination data from the electronic health record for the intervention period, contrasted it with identical data from June 1 to November 30, 2020, and used logistic regression controlling for patient age, sex, and race to determine differences in screening and vaccination between intervention and baseline periods. RESULTS: A total of 14,920 and 15,523 patients were eligible in the baseline and intervention periods, respectively. Following the intervention, HIV lifetime screening but not first-time screening for patients 13-64 years old was significantly higher (78.9% vs. 76.1%, p = 0.004, and 39.6% vs. 36.6%, p = 0.152, respectively, adjusted odds ratio [aOR] 1.21, 95% confidence interval [CI] 1.06-1.38). HCV lifetime screening for patients 18-79 years old was significantly higher postintervention (62.5% vs. 53.5%, p < 0.001, aOR 1.51, 95% CI 1.4-1.64). For patients 9-26 years old, no change in HPV initiation was observed, but the percentage of patients who completed their HPV vaccinations in the observed period was significantly higher postintervention (7.0% vs 4.6%, p = 0.006, aOR 1.58, 95% CI 1.14-2.2). During the postintervention period, the researchers identified 0 new HIV diagnoses and 48 HCV diagnoses (19 eligible for treatment). CONCLUSION: Family medicine residency office-based multistrategy efforts appear to successfully increase patient uptake of HIV and HCV screenings and maintain HPV vaccination rates.

A community-based participatory research approach to evaluating and improving hepatitis C risk, knowledge, and stigma associations among people who inject substances in Indiana.

OBJECTIVES: To explore hepatitis C risk, knowledge, and stigma among individuals who inject substances in South Central Indiana. DESIGN: A cross-sectional study design was employed using a community-based participatory research approach. The community partner was a grassroots harm reduction organization. SAMPLE: Participants in this study were at least 18 years of age, current residents of Indiana, and self-identified as injection substance users (n = 179). MEASUREMENTS: The survey measured hepatitis C risk, knowledge, and stigma, as well as differences in hepatitis C risk scores among key demographic characteristics. RESULTS: Most participants identified as male (n = 106, 59%), White (n = 139, 78%), and straight (n = 143, 80%). People of color reported lower hepatitis C knowledge than White participants. Women had significantly lower hepatitis C knowledge compared with men. LGBTQ participants reported increased hepatitis C risk compared with straight participants. Increased frequency of substance use was associated with decreased stigma. Unhoused participants demonstrated significantly lower hepatitis C knowledge compared with housing-secure participants. CONCLUSIONS: Our findings increase understanding that knowledge and risk around hepatitis C are associated with demographic characteristics. Results underscore the need for tailored public health interventions to increase hepatitis C knowledge, reduce stigma, and improve testing and treatment among vulnerable populations.

Reverse vaccinology approach for identification of epitopes from E1 protein as peptide vaccine against HCV: A proof of concept.

The development of effective vaccines against Hepatitis C Virus (HCV) remains a global health priority and challenge. In this study, we employed an integrative approach combining computational epitope prediction with experimental validation to identify immunogenic peptides targeting the E1 glycoprotein of HCV. In the present report, computational data from various epitope prediction algorithms such as IEDB and SYFPEITHI, followed by molecular dynamics (MD) simulations and immuno-informatics analysis is presented. Through computational screening, we identified potential epitope candidates, with QVRNSSGLY (P3) and QLFTFSPRH (P7) emerging as promising candidates. MD simulations revealed stable interactions between these epitopes and MHC molecule, further validated by free energy estimations using MMPBSA method. Immuno-informatics analysis supported these findings, showing high binding potential and immunogenicity scores for the selected peptides. Subsequent synthesis and characterization of epitope peptides confirmed their structural integrity and purity required for conducting immune activation assays. Experimental immunological assays carried out in this study involved epitope peptide induced activation of CD8 + and CD4 + T cells from healthy human subjects and HCV- recovered patients. Data from experimental validation revealed significant cytokine release upon exposure to epitope peptides, particularly TNF-a, IL-6, and GM-CSF, indicative of robust immune responses. Notably, peptides P3 and P7 exhibited the most pronounced cytokine induction profiles, underscoring their potential as vaccine candidates. Further investigations addressing the mechanism of action of these epitope peptides under preclinical and clinical settings may help in developing effective vaccine against HCV.

Prevalence and Modes of Transmission of Hepatitis C Virus Infection: A Historical Worldwide Review.

Hepatitis C virus infection affects over 58 million individuals and is responsible for 290,000 annual deaths. The infection spread in the past via blood transfusion and iatrogenic transmission due to the use of non-sterilized glass syringes mostly in developing countries (Cameroon, Central Africa Republic, Egypt) but even in Italy. High-income countries have achieved successful results in preventing certain modes of transmission, particularly in ensuring the safety of blood and blood products, and to a lesser extent, reducing iatrogenic exposure. Conversely, in low-income countries, unscreened blood transfusions and non-sterile injection practices continue to play major roles, highlighting the stark inequalities between these regions. Currently, injection drug use is a major worldwide risk factor, with a growing trend even in low- and middle-income countries (LMICs). Emerging high-risk groups include men who have sex with men (MSM), individuals exposed to tattoo practices, and newborns of HCV-infected pregnant women. The World Health Organization (WHO) has proposed direct-acting antiviral (DAA) therapy as a tool to eliminate infection by interrupting viral transmission from infected to susceptible individuals. However, the feasibility of this ambitious and overly optimistic program generates concern about the need for universal screening, diagnosis, linkage to care, and access to affordable DAA regimens. These goals are very hard to reach, especially in LMICs, due to the cost and availability of drugs, as well as the logistical complexities involved. Globally, only a small proportion of individuals infected with HCV have been tested, and an even smaller fraction of those have initiated DAA therapy. The absence of an effective vaccine is a major barrier to controlling HCV infection. Without a vaccine, the WHO project may remain merely an illusion.

Development of an evidence-based hepatitis C education program to enhance public health literacy in the Australian prison sector: The Hepatitis in Prisons Education program (HepPEd).

BACKGROUND: Australia's prisons have a high chronic hepatitis C (HCV) prevalence (8 %). Antiviral therapies and prison-based hepatitis services are available, but only a minority of those eligible are being treated. Improving the HCV public health literacy of the prison sector via targeted education may overcome key barriers to scale-up treatment. This paper describes the: i) HCV public health literacy of the prison setting; ii) barriers and solutions for HCV education and service engagement; iii) HCV education program co-design and development processes; and iv) HepPEd resources. METHODS: A national needs assessment was conducted to analyse the HCV public health literacy of the target audience groups in the prisons (healthcare providers; custodial officers; people in prison) to inform development of a prison-specific HCV education program (HepPEd). Structured interviews were conducted with key informants (n = 40). Three National Steering Committees, one for each target group, were convened to co-design and develop HepPEd. RESULTS: Only healthcare providers involved with hepatitis care were considered to have 'good' to 'very good' HCV health literacy (including knowledge, attitudes, and capabilities), with all other groups considered less favourably. Key barriers identified included being time poor (healthcare providers), poor motivation (custodial officers) and stigma (people in prison). Peer education delivery was considered a key facilitator for custodial officers and people in prison. A suite of multi-modal resources addressing the perceived gaps in HCV health literacy was developed, with a broad theme of 'Let's talk about hep C'. Delivery of HepPEd was designed to overcome key barriers and utilise facilitators for each group. CONCLUSIONS: Significant gaps in HCV health literacy were perceived amongst the target audience groups. The comprehensive co-design and development processes utilised in HepPEd suggest the program will be well-placed to improve the HCV public health literacy of the prison sector and thereby enhance HCV testing and treatment rates amongst people in prison.

Immunogenicity study of a Novel DNA-Based HCV vaccine candidate.

In this study, we aimed to evaluate the immunogenic profile of a chimeric DNA-based hepatitis C virus (HCV) vaccine candidate encoding the full-length viral core-E1-E2 (HCV-CE) fragment. The vaccine candidate was designed to uniformly express the HCV genotype 4 core-E1-E2 protein. The recombinant HCV-CE protein was bacterially expressed in C41 (DE3) cells, and then BALB/c mice were immunized with different combinations of DNA/DNA or DNA/protein prime/boost immunizations. The proper construction of our vaccine candidate was confirmed by specific amplification of the encoded fragments and basic local alignment search tool (BLAST) results of the nucleotide sequence, which revealed a high degree of similarity with several HCV serotypes/genotypes. The platform for bacterial expression was optimized to maximize the yield of the purified recombinant HCV-CE protein. The recombinant protein showed high specific antigenicity against the sera of HCV-infected patients according to the ELISA and western blot results. The predicted B- and T-cell epitopes showed high antigenic and interferon-γ (IFN-γ) induction potential, in addition to cross-genotype conservation and population coverage. The mice antisera further demonstrated a remarkable ability to capture 100% of the native viral antigens circulating in the sera of HCV patients, with no cross-reactivity detected in control sera. In conclusion, the proposed HCV vaccination strategy demonstrated promising potential regarding its safety, immunogenicity, and population coverage.

Potential impact of curative and preventive interventions toward hepatitis C elimination in people who inject drugs-A network modeling study.

BACKGROUND: Injection-equipment-sharing networks play an important role in hepatitis C virus (HCV) transmission among people who inject drugs (PWID). Direct-acting antiviral (DAA) treatments for HCV infection and interventions to prevent HCV transmission are critical components of an overall hepatitis C elimination strategy, but how they contribute to the elimination outcomes in different PWID network settings are unclear. METHODS: We developed an agent-based network model of HCV transmission through the sharing of injection equipment among PWID and parameterized and calibrated the model with rural PWID data in the United States. We modeled curative and preventive interventions at annual coverage levels of 12.5 %, 25 %, or 37.5 % (cumulative percentage of eligible individuals engaged), and two allocation approaches: random vs targeting PWID with more injection partners (hereafter 'degree-based'). We compared the impact of these intervention strategies on prevalence and incidence of HCV infections. We conducted sensitivity analysis on key parameters governing the effects of curative and preventive interventions and PWID network characteristics. RESULTS: Combining curative and preventive interventions at 37.5 % annual coverage with degree-based allocation decreased prevalence and incidence of HCV infection by 67 % and 70 % over two years, respectively. Curative interventions decreased prevalence by six to 12 times more than preventive interventions, while curative and preventive interventions had comparable effectiveness on reducing incidence. Intervention impact increased with coverage almost linearly across all intervention strategies, and degree-based allocation was always more effective than random allocation, especially for preventive interventions. Results were sensitive to parameter values defining intervention effects and network mean degree. CONCLUSION: DAA treatments are effective in reducing both prevalence and incidence of HCV infection in PWID, but preventive interventions play a significant role in reducing incidence when intervention coverage is low. Increasing coverage, including efforts in reaching individuals with the most injection partners, preventing reinfection, and improving compliance and retention in preventive services can substantially improve the outcomes. PWID network characteristics should be considered when designing hepatitis C elimination programs.

Using nominal group technique to identify perceived barriers and facilitators to improving uptake of the Prison Needle Exchange Program in Canadian federal prisons by correctional officers and healthcare workers.

BACKGROUND: Elimination of bloodborne viruses including HIV and hepatitis C virus from prisons requires high coverage of evidence-based interventions that prevent bloodborne virus transmission, including needle and syringe programs. Canada launched a Prison Needle Exchange Program (PNEP) in nine federal prisons in 2018; however, uptake among people who inject drugs in prison remains low. We aimed to explore barriers and facilitators to improving PNEP uptake identified by correctional officers and healthcare workers. METHODS: Participants from nine federal prisons with PNEP completed focus groups using nominal group technique, a rapid mixed-method consensus strategy. Responses were generated, rank-ordered, and prioritized by each stakeholder group. We identified the highest-ranking responses (≥10 % of the overall votes) to questions about barriers and facilitators to PNEP uptake. RESULTS: Between September 2023 and February 2024, 16 focus groups were conducted with 118 participants (n = 51 correctional officers; n = 67 healthcare workers). Among correctional officers, the top perceived barriers were bullying from peers (22 %), fear of being targeted by correctional officers (14 %), and fear of repercussions due to drug use (13 %). The top facilitators were safe injection sites (30 %), provision of wrap-around services (16 %), and education of correctional officers (10 %). Among healthcare workers, the top perceived barriers were lack of confidentiality (16 %), fear of being targeted by correctional officers (12 %), and a long and complex application process (11 %). The top facilitators were education of correctional officers (29 %), delivery of PNEP by an external provider (15 %), automatic approval for participation in the PNEP (13 %), and safe injection sites (12 %). CONCLUSION: Multiple modifiable barriers and solutions to improving PNEP uptake in Canadian federal prisons were identified by correctional employees. Both participant groups identified the potential for safe injection sites and education to correctional officers as enabling PNEP uptake. These data will inform Canadian efforts to improve engagement and to expand PNEP coverage.

An in vitro CD8 T-cell priming assay enables epitope selection for hepatitis C virus vaccines.

For the rational design of epitope-specific vaccines, identifying epitopes that can be processed and presented is essential. As algorithm-based epitope prediction is frequently discordant with actually recognized CD8+ T-cell epitopes, we developed an in vitro CD8 T-cell priming protocol to enable the identification of truly and functionally expressed HLA class I epitopes. The assay was established and validated to identify epitopes presented by hepatitis C virus (HCV)-infected cells. In vitro priming of naïve CD8 T cells was achieved by culturing unfractionated PBMCs in the presence of a specific cocktail of growth factors and cytokines, and next exposing the cells to hepatic cells expressing the NS3 protein of HCV. After a 10-day co-culture, HCV-specific T-cell responses were identified based on IFN-γ ELISpot analysis. For this, the T cells were restimulated with long synthetic peptides (SLPs) spanning the whole NS3 protein sequence allowing the identification of HCV-specificity. We demonstrated that this protocol resulted in the in vitro priming of naïve precursors to antigen-experienced T-cells specific for 11 out of 98 SLPs tested. These 11 SLPs contain 12 different HLA-A*02:01-restricted epitopes, as predicted by a combination of three epitope prediction algorithms. Furthermore, we identified responses against 3 peptides that were not predicted to contain any immunogenic HLA class I epitopes, yet showed HCV-specific responses in vitro. Separation of CD8+ and CD8- T cells from PBMCs primed in vitro showed responses only upon restimulation with short peptides. We established an in vitro method that enables the identification of HLA class I epitopes resulting from cross-presented antigens and that can cross-prime T cells and allows the effective selection of functional immunogenic epitopes, but also less immunogenic ones, for the design of tailored therapeutic vaccines against persistent viral infections and tumor antigens.