A phase I randomized, double-blind, placebo-controlled study to evaluate the safety, tolerability, and immunogenicity of a live-attenuated quadrivalent dengue vaccine in flavivirus-naïve and flavivirus-experienced healthy adults

Subgenomic flavivirus RNA as key target for live-attenuated vaccine development

Live-attenuated flavivirus vaccines confer long-term protection against disease, but the design of attenuated flaviviruses does not follow a general approach. The non-coding, subgenomic flavivirus RNA (sfRNA) is produced by all flaviviruses and is an essential factor in viral pathogenesis and transmission. We argue that modulating sfRNA expression is a promising, universal strategy to finetune flavivirus attenuation for developing effective flavivirus vaccines of the future.

Immunogenicity and Vaccine Shedding After 1 or 2 Doses of rVSVΔG-ZEBOV-GP Ebola Vaccine (ERVEBO®): Results From a Phase 2, Randomized, Placebo-controlled Trial in Children and Adults

BACKGROUND

The rVSVΔG-ZEBOV-GP vaccine (ERVEBO®) is a single-dose, live-attenuated, recombinant vesicular stomatitis virus vaccine indicated for the prevention of Ebola virus disease (EVD) caused by Zaire ebolavirus in individuals 12 months of age and older.

METHODS

The Partnership for Research on Ebola VACcination (PREVAC) is a multicenter, phase 2, randomized, double-blind, placebo-controlled trial of 3 vaccine strategies in healthy children (ages 1-17) and adults, with projected 5 years of follow-up (NCT02876328). Using validated assays (GP-ELISA and PRNT), we measured antibody responses after 1-dose rVSVΔG-ZEBOV-GP, 2-dose rVSVΔG-ZEBOV-GP (given on Day 0 and Day 56), or placebo. Furthermore, we quantified vaccine virus shedding in a subset of children's saliva using RT-PCR.

RESULTS

In total, 819 children and 783 adults were randomized to receive rVSVΔG-ZEBOV-GP (1 or 2 doses) or placebo. A single dose of rVSVΔG-ZEBOV-GP increased antibody responses by Day 28 that were sustained through Month 12. A second dose of rVSVΔG-ZEBOV-GP given on Day 56 transiently boosted antibody concentrations. In vaccinated children, GP-ELISA titers were superior to placebo and non-inferior to vaccinated adults. Vaccine virus shedding was observed in 31.7% of children, peaking by Day 7, with no shedding observed after Day 28 post-dose 1 or any time post-dose 2.

CONCLUSIONS

A single dose of rVSVΔG-ZEBOV-GP induced robust antibody responses in children that was non-inferior to the responses induced in vaccinated adults. Vaccine virus shedding in children was time-limited and only observed after the first dose. Overall, these data support the use of rVSVΔG-ZEBOV-GP for the prevention of EVD in at-risk children. Clinical Trials Registration. The study is registered at ClinicalTrials.gov (NCT02876328), the Pan African Clinical Trials Registry (PACTR201712002760250), and the European Clinical Trials Register (EudraCT number: 2017-001798-18).

Fully automated high-throughput immuno-µPlaque assay for live-attenuated tetravalent dengue vaccine development

Dengue fever has remained a continuing global medical threat that impacts half of the world's population. Developing a highly effective dengue vaccine, with live-attenuated tetravalent vaccines as leading candidates, remains essential in preventing this disease. For the development of live virus vaccines (LVVs), potency measurements play a vital role in quantifying the active components of vaccine drug substance as well as drug product during various stages of research, development, and post-licensure evaluations. Traditional plaque-based assays are one of the most common potency test methods, but they generally take up to weeks to complete. Less labor and time-intensive potency assays are thus called for to aid in the acceleration of vaccine development, especially for multivalent LVVs. Here, we introduce a fully automated, 96-well format µPlaque assay that has been optimized as a high-throughput tool to evaluate process and formulation development of a live-attenuated tetravalent dengue vaccine. To the best of our knowledge, this is the first report of a miniaturized viral plaque method for dengue with full automation via an integrated robotic system. Compared to the traditional manual plaque assay, this newly developed method substantially reduces testing time by approximately half and allows for the evaluation of over ten times more samples per run. The fully automated workflow, from cell culture to plaque counting, significantly minimizes analyst hands-on time and improves assay repeatability. The study presents a pioneering solution for the rapid measurement of LVV viral titers, offering promising prospects for advancing vaccine development through high-throughput analytics.

Structure-based evaluation of the envelope domain III-nonstructural protein 1 (EDIII-NS1) fusion as a dengue virus vaccine candidate

The lack of effective medicines or vaccines, combined with climate change and other environmental factors, annually subjects a significant proportion of the world's inhabitants to the risk of dengue virus (DENV) infection. These conditions increase the likelihood of exposure to mosquito-borne diseases such as dengue fever. Hence, many research approaches tend to develop efficient vaccine candidates against the dengue virus. Therefore, we used immunoinformatics and bioinformatics to design a construction for developing a candidate vaccine against dengue virus serotypes. In this study, the in silico structure, containing the non-structural protein 1 region (NS1) (consensus and epitope), the envelope domain III protein (EDIII) as the structural part of the virus construction, and the bc-loop of envelope domain II (EDII) as the neutralizing and protected epitope, were employed. We utilized in silico tools to enhance the immunogenicity and effectiveness of dengue virus vaccine candidates. Evaluations included refining and validating physicochemical characteristics, B and T-cell epitopes, homology modeling, and the three-dimensional structure to assess the designed vaccine's quality. In silico results for tertiary structure prediction and validation revealed high-quality modeling for all vaccine constructs. Additionally, the instructed model demonstrated stability throughout molecular dynamics simulation. The results of the immune simulation suggested that the titers of IgG and IgM could be raised to desirable values following injection into in vivo models. It can be concluded that the designed construct effectively induce humoral and cellular immunity and can be proposed as effective vaccine candidate against four dengue serotypes.Communicated by Ramaswamy H. Sarma.

Live, Attenuated, Tetravalent Butantan-Dengue Vaccine in Children and Adults

BACKGROUND

Butantan-Dengue Vaccine (Butantan-DV) is an investigational, single-dose, live, attenuated, tetravalent vaccine against dengue disease, but data on its overall efficacy are needed.

METHODS

In an ongoing phase 3, double-blind trial in Brazil, we randomly assigned participants to receive Butantan-DV or placebo, with stratification according to age (2 to 6 years, 7 to 17 years, and 18 to 59 years); 5 years of follow-up is planned. The objectives of the trial were to evaluate overall vaccine efficacy against symptomatic, virologically confirmed dengue of any serotype occurring more than 28 days after vaccination (the primary efficacy end point), regardless of serostatus at baseline, and to describe safety up to day 21 (the primary safety end point). Here, vaccine efficacy was assessed on the basis of 2 years of follow-up for each participant, and safety as solicited vaccine-related adverse events reported up to day 21 after injection. Key secondary objectives were to assess vaccine efficacy among participants according to dengue serostatus at baseline and according to the dengue viral serotype; efficacy according to age was also assessed.

RESULTS

Over a 3-year enrollment period, 16,235 participants received either Butantan-DV (10,259 participants) or placebo (5976 participants). The overall 2-year vaccine efficacy was 79.6% (95% confidence interval [CI], 70.0 to 86.3) - 73.6% (95% CI, 57.6 to 83.7) among participants with no evidence of previous dengue exposure and 89.2% (95% CI, 77.6 to 95.6) among those with a history of exposure. Vaccine efficacy was 80.1% (95% CI, 66.0 to 88.4) among participants 2 to 6 years of age, 77.8% (95% CI, 55.6 to 89.6) among those 7 to 17 years of age, and 90.0% (95% CI, 68.2 to 97.5) among those 18 to 59 years of age. Efficacy against DENV-1 was 89.5% (95% CI, 78.7 to 95.0) and against DENV-2 was 69.6% (95% CI, 50.8 to 81.5). DENV-3 and DENV-4 were not detected during the follow-up period. Solicited systemic vaccine- or placebo-related adverse events within 21 days after injection were more common with Butantan-DV than with placebo (58.3% of participants, vs. 45.6%).

CONCLUSIONS

A single dose of Butantan-DV prevented symptomatic DENV-1 and DENV-2, regardless of dengue serostatus at baseline, through 2 years of follow-up. (Funded by Instituto Butantan and others; DEN-03-IB ClinicalTrials.gov number, NCT02406729, and WHO ICTRP number, U1111-1168-8679.).

In situ process analytical technology for real time viable cell density and cell viability during live-virus vaccine production

Viable cell density (VCD) and cell viability (CV) are key performance indicators of cell culture processes in biopharmaceutical production of biologics and vaccines. Traditional methods for monitoring VCD and CV involve offline cell counting assays that are both labor intensive and prone to high variability, resulting in sparse sampling and uncertainty in the obtained data. Process analytical technology (PAT) approaches offer a means to address these challenges. Specifically, in situ probe-based measurements of dielectric spectroscopy (also commonly known as capacitance) can characterize VCD and CV continuously in real time throughout an entire process, enabling robust process characterization. In this work, we propose in situ dielectric spectroscopy as a PAT tool for real time analysis of live-virus vaccine (LVV) production. Dielectric spectroscopy was collected across 25 discreet frequencies, offering a thorough evaluation of the proposed technology. Correlation of this PAT methodology to traditional offline cell counting assays was performed, in which VCD and CV were both successfully predicted using dielectric spectroscopy. Both univariate and multivariate data analysis approaches were evaluated for their potential to establish correlation between the in situ dielectric spectroscopy and offline measurements. Univariate analysis strategies are presented for optimal single frequency selection. Multivariate analysis, in the form of partial least squares (PLS) regression, produced significantly higher correlations between dielectric spectroscopy and offline VCD and CV data, as compared to univariate analysis. Specifically, by leveraging multivariate analysis of dielectric information from all 25 spectroscopic frequencies measured, PLS models performed significantly better than univariate models. This is particularly evident during cell death, where tracking VCD and CV have historically presented the greatest challenge. The results of this work demonstrate the potential of both single and multiple frequency dielectric spectroscopy measurements for enabling robust LVV process characterization, suggesting that broader application of in situ dielectric spectroscopy as a PAT tool in LVV processes can provide significantly improved process understanding. To the best of our knowledge, this is the first report of in situ dielectric spectroscopy with multivariate analysis to successfully predict VCD and CV in real time during live virus-based vaccine production.

A Phase 1, double-blind, randomized, placebo-controlled study to evaluate the safety and immunogenicity of a tetravalent live attenuated dengue vaccine in adults

BACKGROUND

Dengue fever is an important public health problem, especially in Asia and South America. A tetravalent live attenuated dengue vaccine was manufactured in India after receipt of vaccine strains from NIAID, NIH, USA.

METHODS

This was a Phase 1, double-blind, randomized, placebo-controlled study performed in 60 healthy adults of 18 to 45 years. Participants were randomized 2:1 to receive a single subcutaneous injection of either a tetravalent live attenuated dengue vaccine or placebo. Safety was assessed by unsolicited adverse events (AEs) and solicited reactions through 21 days after vaccination and serious adverse events (SAEs) through the entire study period of 180 days. Dengue viremia was assessed at baseline and on day 9, 11 and 13 post-vaccination using a plaque assay. Immunogenicity was assessed using the plaque reduction neutralization test (PRNT) assay using vaccine-matched wild virus serotypes (DENV 1, DENV 2, DENV 3 and DENV 4) at baseline and on 56-, 84- and 180-days post-vaccination. PRNT assay using circulating wild type DENV 1, DENV 2, DENV 3 and DENV 4 were done on day 1 and day 85 for a subset of 31 participants.

RESULTS

60 participants were randomized to receive dengue vaccine (n = 40) or placebo (n = 20). 23 participants (59 %) showed DENV vaccine viremia post- vaccination for any of the four serotypes with majority on day 9 and day 11. At baseline, all participants were naïve by dengue PRNT50 for all four serotypes in both the study groups except for four in the dengue vaccine group and two in the placebo group. On day 57, the GMTs of neutralizing antibodies ranged from 66.76 (95 % CI 36.63, 121.69) to 293.84 (95 % CI 192.25, 449.11) for all four serotypes in the dengue vaccine group. On day 181 though the titers declined, they still remained much higher than the baseline. The titers in the placebo group did not change after vaccination. Seroconversion through day 85 ranged from 79.5 % for DENV 1 to 100 % for DENV2 while in the placebo group, no participant showed seroconversion through day 85. Similar trends were noted when PRNT was done using wild DENV serotypes in both vaccine and placebo groups. Among solicited reactions, injection site erythema, rash, headache, fatigue, myalgia and arthralgia were reported more frequently in the vaccine group than placebo group. All solicited reactions were of grade 1 or grade 2 severity and completely resolved. One unrelated serious adverse event was reported in the vaccine group.

CONCLUSION

A single dose of dengue vaccine was safe and well tolerated in adults. The vaccine was highly immunogenic with trivalent or tetravalent seroconversion and seropositivity in most of the participants. The study was funded by Serum Institute of India Pvt. Ltd., Pune, India.

CLINICALTRIALS

gov: NCT04035278.

Insights into dengue immunity from vaccine trials

The quest for an effective dengue vaccine has culminated in two approved vaccines and another that has completed phase 3 clinical trials. However, shortcomings exist in each, suggesting that the knowledge on dengue immunity used to develop these vaccines was incomplete. Vaccine trial findings could refine our understanding of dengue immunity, because these are experimentally derived, placebo-controlled data. Results from these trials suggest that neutralizing antibody titers alone are insufficient to inform protection against symptomatic infection, implicating a role for cellular immunity in protection. These findings have relevance for both future dengue vaccine development and application of current vaccines for maximal public health benefit.

Phase 1 trial to model primary, secondary, and tertiary dengue using a monovalent vaccine

BACKGROUND

The four co-circulating and immunologically interactive dengue virus serotypes (DENV1-4) pose a unique challenge to vaccine design because sub-protective immunity can increase the risk of severe dengue disease. Existing dengue vaccines have lower efficacy in DENV seronegative individuals but higher efficacy in DENV exposed individuals. There is an urgent need to identify immunological measures that are strongly associated with protection against viral replication and disease following sequential exposure to distinct serotypes.

METHODS/DESIGN

This is a phase 1 trial wherein healthy adults with neutralizing antibodies to zero (seronegative), one non-DENV3 (heterotypic), or more than one (polytypic) DENV serotype will be vaccinated with the live attenuated DENV3 monovalent vaccine rDEN3Δ30/31-7164. We will examine how pre-vaccine host immunity influences the safety and immunogenicity of DENV3 vaccination in a non-endemic population. We hypothesize that the vaccine will be safe and well tolerated, and all groups will have a significant increase in the DENV1-4 neutralizing antibody geometric mean titer between days 0 and 28. Compared to the seronegative group, the polytypic group will have lower mean peak vaccine viremia, due to protection conferred by prior DENV exposure, while the heterotypic group will have higher mean peak viremia, due to mild enhancement. Secondary and exploratory endpoints include characterizing serological, innate, and adaptive cell responses; evaluating proviral or antiviral contributions of DENV-infected cells; and immunologically profiling the transcriptome, surface proteins, and B and T cell receptor sequences and affinities of single cells in both peripheral blood and draining lymph nodes sampled via serial image-guided fine needle aspiration.

DISCUSSION

This trial will compare the immune responses after primary, secondary, and tertiary DENV exposure in naturally infected humans living in non-endemic areas. By evaluating dengue vaccines in a new population and modeling the induction of cross-serotypic immunity, this work may inform vaccine evaluation and broaden potential target populations.

TRIAL REGISTRATION

NCT05691530 registered on January 20, 2023.

Proceedings of the 5th Asia Dengue Summit

The 5th Asia Dengue Summit, themed "Roll Back Dengue", was held in Singapore from 13 to 15 June 2022. The summit was co-convened by Asia Dengue Voice and Action (ADVA), Global Dengue and Aedes transmitted Diseases Consortium (GDAC), Southeast Asian Ministers of Education Tropical Medicine and Public Health Network (SEAMEO TROPMED), and the Fondation Mérieux (FMx). Dengue experts from academia and research and representatives from the Ministries of Health, Regional and Global World Health Organization (WHO), and International Vaccine Institute (IVI) participated in the three-day summit. With more than 270 speakers and delegates from over 14 countries, 12 symposiums, and 3 full days, the 5th ADS highlighted the growing threat of dengue, shared innovations and strategies for successful dengue control, and emphasized the need for multi-sectoral collaboration to control dengue.

Is new dengue vaccine efficacy data a relief or cause for concern?

Dengue is a major global public health problem requiring a safe and efficacious vaccine as the foundation of a comprehensive countermeasure strategy. Despite decades of attempts, the world has a single dengue vaccine licensed in numerous countries, but restrictions and conditions of its use have deterred uptake. Recently, clinical efficacy data has been revealed for two additional dengue vaccine candidates and the data appears encouraging. In this perspective I discuss dengue, the complexities of dengue vaccine development, early development setbacks, and how the latest data from the field may be cause for measured optimism. Finally, I provide some perspectives on evaluating dengue vaccine performance and how the pursuit of the perfect dengue vaccine may prevent advancement of vaccines which are good enough.

Biologics for dengue prevention: up-to-date

INTRODUCTION

Dengue is a worsening global public health problem. The vector-viral-host interactions driving the pathogenesis of dengue are multi-dimensional. Sequential dengue virus (DENV) infections with different DENV types significantly increase the risk of severe disease. Treatment is supportive in nature as there are no licensed anti-DENV antivirals or immuno-therapeutics. A single dengue vaccine has widely been licensed with two others in advanced clinical development. Dengvaxia® has been licensed in numerous countries but uptake has been slow as a result of safety signals noted in the youngest recipients and those who were dengue naïve at the time of vaccination.

AREAS COVERED

In this review, the current state of dengue vaccine and antiviral drug development will be discussed as well as new developments in controlled human infection models to support product development.

EXPERT OPINION

The world needs a safe and efficacious tetravalent dengue vaccine capable of protecting multiple different populations across a broad age range and different flavivirus immunologic backgrounds. Safe and effective antivirals are also needed to prevent or attenuate dengue disease in the unvaccinated, in cases of vaccine failure, or in high-risk populations.

A dengue vaccine whirlwind update

Dengue virus (DENV) is a mosquito-borne single-stranded RNA virus of the Flaviviridae family with four serotypes (DENV1, DENV2, DENV3, and DENV4) circulating many tropical and subtropical regions of the world. Endemic in more than 100 countries, DENV results in over 400 million cases annually, a subset presenting with severe or life-threatening illnesses such as dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). While no specific treatments outside of supportive management exist, vaccines are an area of major research with two vaccines, Dengvaxia^® (CYD-TDV) and Denvax^® (TAK003), recently licensed for clinical use. CYD-TDV is highly efficacious in children 9 years or older who have had prior DENV infection due to the high risk of severe disease in seronegative children aged 2-5 years. Meanwhile, TAK003 has shown efficacy at 97.7% and 73.7% against, DENV2 and DENV1, respectively, in phase 3 clinical trials across Latin America and Asia in healthy children aged 4-16 with virologically confirmed dengue. Other vaccines including TV003 and TV005 continue to be developed across the world, with the hopes of entering clinical trials in the near future. We discuss the current state of vaccine development against dengue, with a focus on CYD-TDV and TAK003 as promising novel vaccines to target this neglected tropical disease (NTD).