Manufacturing a chimpanzee adenovirus-vectored SARS-CoV-2 vaccine to meet global needs

Optimization of Culture Media and Feeding Strategy for High Titer Production of an Adenoviral Vector in HEK 293 Fed-Batch Culture

Adenoviruses are efficient and safe vectors for delivering target antigens and adenovirus-based vaccines have been used against a wide variety of pathogens, including tuberculosis and COVID-19. Cost-effective and scalable biomanufacturing processes are critical for the commercialization of adenovirus-vectored vaccines. Adenoviral vectors are commonly produced through the infection of batch cultures at low cell density cultures, mostly because infections at high cell densities result in reduced cell-specific virus productivity and does not improve volumetric productivity. In this study, we have investigated the feasibility of improving the volumetric productivity by infecting fed-batch cultures at high cell densities. Four commercial and one in-house developed serum-free media were first tested for supporting growth of HEK 293 cells and production of adenovirus type 5 (Ad5) in batch culture. Two best media were then selected for development of fed-batch culture to improve cell growth and virus productivity. A maximum viable cell density up to 16 × 106 cells/mL was achieved in shake flask fed-batch cultures using the selected media and commercial or in-house developed feeds. The volumetric virus productivity was improved by up to six folds, reaching 3.0 × 1010 total viral particles/mL in the fed-batch culture cultivated with the media and feeds developed in house and infected at a cell density of 5 × 106 cells/mL. Additional rounds of optimization of media and feed were required to maintain the improved titer when the fed-batch culture was scaled up in a bench scale (3 L) bioreactor. Overall, the results suggested that fed-batch culture is a simple and feasible process to significantly improve the volumetric productivity of Ad5 through optimization and balance of nutrients in culture media and feeds.

Bridging upstream and downstream for improved adenovirus 5 bioprocess

Adenoviruses are well-known viral vectors that have been previously used in gene therapy and as a vaccine-delivery vehicle for humans and animals. During the COVID-19 pandemic, it gained renewed attention, but at the same time, it raised concerns due to side effects observed with some of the resulting vaccines administered to patients. It has been indicated that these side effects might be attributed to impurities present in the final product. Therefore, constant enhancement of the vaccine purity and further improvement of impurity detection methods are needed. In this work, we showcase an example of industry-relevant adenovirus bioprocess optimization. Our data show the effect of upstream parameters on the bioburden introduced to the downstream process. We provide an example of process optimization using a combination of the PATfix analytical method, ddPCR, infectivity, total DNA, and total protein analyses to optimize cell density, multiplicity of infection, and length of production. Additionally, we provide data illustrating the robustness of the convective interaction media quaternary amine monolithic chromatography step. This anion exchange strategy was shown to remove over 99% of protein and DNA impurities, including those unable to be addressed by tangential flow filtration, while maintaining high adenovirus recoveries.

Development of Adenovirus-Based Covid-19 Vaccine Candidate in Indonesia

Covid-19 pandemic has struck worldwide by end of 2019 and the use of various vaccine platforms was one of the main strategies to end this. To meet the needs for vaccine technology equality among many countries, we developed adenovirus-based Covid-19 vaccine candidate in Indonesia. SARS-CoV-2 Spike gene (S) was constructed into pAdEasy vector. The recombinant serotype 5 Adenovirus (AdV_S) genome was transfected into AD293 cells to produce recombinant adenovirus. Characterization using PCR confirmed the presence of spike gene. Transgene expression analysis showed the expression of S protein in AdV_S infected AD293 and A549 cells. Optimization of viral production showed the highest titer was obtained at MOI of 0.1 and 1 at 4 days. The in vivo study was performed by injecting Balb/c mice with 3.5 × 107 ifu of purified adenovirus. The result showed that S1-specific IgG was increased up to 56 days after single-dose administration of AdV_S. Interestingly, significant increase of S1 glycoprotein-specific IFN-γ ELISpot was observed in AdV_S treated Balb/c mice. In conclusion, the AdV_S vaccine candidate was successfully produced at laboratory scale, immunogenic, and did not cause severe inflammation in Balb/c mice. This study serves as initial step towards manufacturing of adenovirus-based vaccine in Indonesia.

Contrasting academic approaches to COVID-19 vaccine production and distribution: What can the Oxford and Texas experiences teach us about pandemic response?

This article contrasts the different approaches to COVID-19 vaccine development adopted by Oxford University, on one hand, and Texas Children's Hospital and Baylor College of Medicine (collectively, Texas), on the other hand. Texas was praised widely in the press and academic literature for adopting an "open source" approach to vaccine development. Oxford, however, chose to license its vaccine technology to pharmaceutical manufacturer AstraZeneca and received significant public criticism as a result. Yet the Oxford vaccine reached far more individuals in developing countries than the Texas vaccine. We compare the two vaccines' experiences, drawing attention to a constellation of interrelated elements that contribute to a successful vaccine production program, including not only IP licensing, but also timing, technology transfer, and resource mobilization, all in the context of the prevailing funding environments. This comparative analysis sheds light on how the innovation ecosystem functioned during the COVID-19 pandemic, providing useful insights for policy makers and advocates as they prepare for future pandemics and other global health challenges.

Innovative translational platforms for rapid developing clinical vaccines against COVID-19 and other infectious disease

A vaccine is a biological preparation that contains the antigen capable of stimulating the immune system to form the defense against pathogens. Vaccine development often confronts big challenges, including time/energy-consuming, low efficacy, lag to pathogen emergence and mutation, and even safety concern. However, these seem now mostly conquerable through constructing the advanced translational platforms that can make innovative vaccines, sometimes, potentiated with a distinct multifunctional VADS (vaccine adjuvant delivery system), as evidenced by the development of various vaccines against the covid-19 pandemic at warp speed. Particularly, several covid-19 vaccines, such as the viral-vectored vaccines, mRNA vaccines and DNA vaccines, regarded as the innovative ones that are rapidly made via the high technology-based translational platforms. These products have manifested powerful efficacy while showing no unacceptable safety profile in clinics, allowing them to be approved for massive vaccination at also warp speed. Now, the proprietary translational platforms integrated with the state-of-the-art biotechnologies, and even the artificial intelligence (AI), represent an efficient mode for rapid making innovative clinical vaccines against infections, thus increasingly attracting interests of vaccine research and development. Herein, the advanced translational platforms for making innovative vaccines, together with their design principles and immunostimulatory efficacies, are comprehensively elaborated.

Accelerated and intensified manufacturing of an adenovirus-vectored vaccine to enable rapid outbreak response

The Coalition for Epidemic Preparedness Innovations' "100-day moonshot" aspires to launch a new vaccine within 100 days of pathogen identification, followed by large-scale vaccine availability within the "second hundred days." Here, we describe work to optimize adenoviral vector manufacturing for rapid response, by minimizing time to clinical trial and first large-scale supply, and maximizing output from the available manufacturing footprint. We describe a rapid virus seed expansion workflow that allows vaccine release to clinical trials within 60 days of antigen sequence identification, followed by vaccine release from globally distributed sites within a further 40 days. We also describe a perfusion-based upstream production process, designed to maximize output while retaining simplicity and suitability for existing manufacturing facilities. This improves upstream volumetric productivity of ChAdOx1 nCoV-19 by approximately fourfold and remains compatible with the existing downstream process, yielding drug substance sufficient for 10,000 doses from each liter of bioreactor capacity. This accelerated manufacturing process, along with other advantages such as thermal stability, supports the ongoing value of adenovirus-vectored vaccines as a rapidly adaptable and deployable platform for emergency response.

Recombinant chimpanzee adenovirus expressing spike protein protects chickens against infectious bronchitis virus

Infectious bronchitis (IB) is an acute and highly contagious disease caused by avian infectious bronchitis virus (IBV), resulting in significant economic losses in the global poultry industry. In this study, we utilized a replication-incompetent adenovirus vector derived from chimpanzees for the first time to express the S gene of IBV. The adenovirus was successfully rescued and demonstrated convenient production, good growth performance, and stability on HEK293 A cells. Morphologically, the recombinant adenovirus (named PAD-S) appeared normal under transmission electron microscopy, and efficient expression of the exogenous gene was confirmed through immunofluorescence analysis and immunoblotting. Administration of PAD-S via ocular and nasal routes induced a strong immune response in the chicken population, as evidenced by specific antibody and cytokine measurements. PAD-S was unable to replicate within chickens and showed low pre-existing immunity, demonstrating high safety and environmental friendliness. The robust immune response triggered by PAD-S immunization effectively suppressed viral replication in various tissues, alleviating clinical symptoms and tissue damage, thus providing complete protection against viral challenges in the chicken population. In conclusion, this study successfully developed an IBV candidate vaccine strain that possesses biosafety, high protective efficacy, and ease of production.

Preclinical immunogenicity of an adenovirus-vectored vaccine for herpes zoster

Herpes zoster (HZ) results from waning immunity following childhood infection with varicella zoster virus (VZV) but is preventable by vaccination with recombinant HZ vaccine or live HZ vaccine (two doses or one dose, respectively). Vaccine efficacy declines with age, live HZ vaccine is contraindicated in immunosuppressed individuals, and severe local reactogenicity of recombinant HZ vaccine is seen in up to 20% of older adults, indicating a potential need for new vaccines. Nonreplicating chimpanzee adenovirus (ChAd) vectors combine potent immunogenicity with well-established reactogenicity and safety profiles. We evaluated the cellular and humoral immunogenicity of ChAdOx1 encoding VZV envelope glycoprotein E (ChAdOx1-VZVgE) in mice using IFN-γ ELISpot, flow cytometry with intracellular cytokine staining, and ELISA. In outbred CD-1 mice, one dose of ChAdOx1-VZVgE (1 × 10⁷ infectious units) elicited higher gE-specific T cell responses than two doses of recombinant HZ vaccine (1 µg) or one dose of live HZ vaccine (1.3 × 10³ plaque-forming units). Antibody responses were higher with two doses of recombinant HZ vaccine than with two doses of ChAdOx1-VZVgE or one dose of live HZ vaccine. ChAdOx1-VZVgE boosted T cell and antibody responses following live HZ vaccine priming. The frequencies of polyfunctional CD4+ and CD8+ T cells expressing more than one cytokine (IFN-γ, TNF-α and IL-2) were higher with ChAdOx1-VZVgE than with the conventional vaccines. Results were similar in young and aged BALB/c mice. These findings support the clinical development of ChAdOx1-VZVgE for prevention of HZ in adults aged 50 years or over, including those who have already received conventional vaccines.

Intranasally Delivered Adenoviral Vector Protects Chickens against Newcastle Disease Virus: Vaccine Manufacturing and Stability Assessments for Liquid and Lyophilized Formulations

Newcastle disease (ND) remains a critical disease affecting poultry in sub-Saharan Africa. In some countries, repeated outbreaks have a major impact on local economies and food security. Recently, we developed an adenovirus-vectored vaccine encoding the Fusion protein from an Ethiopian isolate of Newcastle disease virus (NDV). The adenoviral vector was designed, and a manufacturing process was developed in the context of the Livestock Vaccine Innovation Fund initiative funded by the International Development Research Centre (IDRC) of Canada. The industrially relevant recombinant vaccine technology platform is being transferred to the National Veterinary Institute (Ethiopia) for veterinary applications. Here, a manufacturing process using HEK293SF suspension cells cultured in stirred-tank bioreactors for the vaccine production is proposed. Taking into consideration supply chain limitations, options for serum-free media selection were evaluated. A streamlined downstream process including a filtration, an ultrafiltration, and a concentration step was developed. With high volumetric yields (infectious titers up to 5 × 109 TCID50/mL) in the culture supernatant, the final formulations were prepared at 1010 TCID50/mL, either in liquid or lyophilized forms. The liquid formulation was suitable and safe for mucosal vaccination and was stable for 1 week at 37 °C. Both the liquid and lyophilized formulations were stable after 6 months of storage at 4 °C. We demonstrate that the instillation of the adenoviral vector through the nasal cavity can confer protection to chickens against a lethal challenge with NDV. Overall, a manufacturing process for the adenovirus-vectored vaccine was developed, and protective doses were determined using a convenient route of delivery. Formulation and storage conditions were established, and quality control protocols were implemented.

Humoral immunity to phlebovirus infection

Phleboviruses are zoonotic pathogens found in parts of Africa, Asia, Europe, and North America and cause disease symptoms ranging from self-limiting febrile illness to severe disease, including hemorrhagic diathesis, encephalitis, and ocular pathologies. There are currently no approved preventative vaccines against phlebovirus infection or antivirals for the treatment of the disease. Here, we discuss the roles of neutralizing antibodies in phlebovirus infection, the antigenic targets present on the mature polyproteins Gn and Gc, progress in vaccine development, and the prospects of identifying conserved neutralizing epitopes across multiple phleboviruses. Further research in this area will pave the way for the rational design of pan-phlebovirus vaccines that will protect against both known phleboviruses but also newly emerging phleboviruses that may have pandemic potential.

mRNA and Adenoviral Vector Vaccine Platforms Utilized in COVID-19 Vaccines: Technologies, Ecosystem, and Future Directions

New technological platforms, such as mRNA and adenoviral vector vaccines, have been utilized to develop coronavirus disease 2019 (COVID-19) vaccines. These new modalities enable rapid and flexible vaccine design and cost-effective and swift manufacturing, effectively combating pandemics caused by mutating viruses. Innovation ecosystems, including universities, startups, investors, and governments are crucial for developing these cutting-edge technologies. This review summarizes the research and development trajectory of these vaccine technologies, their investments, and the support surrounding them, in addition to the technological details of each technology. In addition, this study examines the importance of an innovation ecosystem in developing novel technologies, comparing it with the case of Japan, which has lagged behind in COVID-19 vaccine development. It also explores the direction of vaccine development in the post-COVID-19 era.

Vaccine value profile for leishmaniasis

Leishmania infections are global, occurring in 98 countries and all World Health Organization (WHO) regions with 600 million to 1 billion people at risk of infection. Visceral leishmaniasis is associated with almost 20,000 reported deaths annually, with children under 5 years of age being at the greatest risk of mortality. Amongst WHO-recognised Neglected Tropical Diseases (NTDs), leishmaniasis is one of the most important in terms of mortality and morbidity. With an increasing global burden of disease and a growing threat from climate change, urbanisation and drug resistance, there remains an imperative to develop leishmaniasis vaccines. New tools to understand correlates of protection and to assess vaccine efficacy are being developed to ease the transition into larger scale efficacy trials or provide alternate routes to licensure. Early indications suggest a diverse portfolio of manufacturers exists in endemic countries with an appetite to develop leishmaniasis vaccines. This Vaccine Value Profile (VVP) provides a high-level, comprehensive assessment of the currently available data to inform the potential public health, economic, and societal value of leishmaniasis vaccines. The leishmaniasis VVP was developed by a working group of subject matter experts from academia, public health groups, policy organizations, and non-profit organizations. All contributors have extensive expertise on various elements of the leishmaniasis VVP and have collectively described the state of knowledge and identified the current gaps. The VVP was developed using only existing and publicly available information.

Pre-Clinical Development of an Adenovirus Vector Based RSV and Shingles Vaccine Candidate

Respiratory syncytial virus (RSV) infection and shingles are two viral diseases that affect older adults, and a combined vaccine to protect against both could be beneficial. RSV infection causes hospitalisations and significant morbidity in both children and adults and can be fatal in the elderly. The RSV fusion (F) envelope glycoprotein induces a strong RSV-neutralising antibody response and is the target of protective immunity in the first RSV vaccine for older adults, recently approved by the FDA. An initial childhood infection with the varicella zoster virus (VZV) results in chickenpox disease, but reactivation in older adults can cause shingles. This reactivation in sensory and autonomic neurons is characterized by a skin-blistering rash that can be accompanied by prolonged pain. The approved protein-in-adjuvant shingles vaccine induces VZV glycoprotein E (gE)-fspecific antibody and CD4+ T cell responses and is highly effective. Here we report the evaluation of RSV/shingles combination vaccine candidates based on non-replicating chimpanzee adenovirus (ChAd) vectors. We confirmed the cellular and humoral immunogenicity of the vaccine vectors in mice using T cell and antibody assays. We also carried out an RSV challenge study in cotton rats which demonstrated protective efficacy following a homologous prime-boost regimen with our preferred vaccine candidate.

Comparison of Post-Vaccination Response between mRNA and Vector Vaccines against SARS-CoV-2 in Terms of Humoral Response after Six Months of Observation

BACKGROUND

The emergence of the SARS-CoV-2 (COVID-19) pandemic has accelerated work on the creation of effective vaccines, both in terms of previously known vector vaccines and new-generation (mRNA) vaccines. The scientific research on vaccination against COVID-19 infection is limited; therefore, understanding how the immune system responds to vaccines is critical. In our study, we conducted a long-term analysis of the presence and persistence of the immune response via chemiluminescence, analyzing the level of IgG antibodies and neutralizing antibodies in subjects vaccinated with two types of mRNA (Comirnaty) and vector (Vaxzevria) vaccines.

MATERIALS AND METHODS

Healthcare workers and a group of teachers were recruited for this study according to the 2021 government-launched vaccination calendar. They received two doses of the Comirnaty or Vaxzevria vaccine. SRBD (spike-receptor binding domain) IgG antibody levels were measured monthly for 6 consecutive months with a chemiluminescent assay (CLIA) and neutralizing antibodies for two periods-1 and 5 months from the completion of the vaccination course.

RESULTS

168 people were recruited for this study: 135 people for the mRNA vaccine group and 33 people for the vector vaccine group. Comparing the serum IgG levels between the two types of vaccines, a significant difference in median values can be noted at all time points. In consecutive months, the mRNA-vaccinated group exhibited significantly higher SRBD levels compared to the vector group, with peak concentrations at one month after the complete vaccination cycle (745 AU/mL vs. 15.44 AU/mL; p < 0.001). Peak antibody concentration for the vector vaccine was observed one month later, at the third follow-up visit; however, the median IgG concentration was almost 7.7 times higher for the Comirnaty group. Both products were effective in stimulating neutralizing antibody production after vaccination. Higher median values were observed for the mRNA vaccines in both evaluations. At first evaluation, the median value for NA concentration in the Comirnaty group was 6 times higher than in the Vaxzevria group (median value 12.23 [IQR 27.3] vs. 1.7 [IQR 3.3]; p < 0.001.

CONCLUSIONS

People vaccinated with the mRNA vaccine (Comirnaty) showed a stronger immune response to the vaccination than the group of people administered the vector vaccine (Vaxzevria). The Comirnaty group showed higher levels of IgG, including neutralizing antibodies, at all time points during the follow-up period, and this was independent of having had a SARS-CoV-2 infection. A natural decrease in antibody levels was seen within 6 months. A booster vaccination may be required. No serious side effects were observed in either group.

COVID-19 vaccine booster doses provide increased protection against COVID-19 hospitalization compared with previously vaccinated individuals: Interim findings from the REFORCO-Brazil real-world effectiveness study during Delta and Omicron

BACKGROUND

Although COVID-19 booster vaccination is widely recommended, there is limited long-term, population-level, real-world evidence on the magnitude of improved protection against severe COVID-19 conferred by boosting with monovalent COVID-19 vaccines developed against ancestral SARS-CoV-2, especially in low- or middle-income countries. We present interim results from the first large-scale assessment of the relative vaccine effectiveness (rVE) of first and second booster doses against severe COVID-19 in a low-/middle-income country.

METHODS

REFORCO-Brazil is an ongoing, test-negative case-control study (NCT05697705) utilizing Brazil national severe acute respiratory syndrome (SARS) surveillance and vaccination data. In SARS hospitalizations from August 1, 2021 to July 31, 2022, we matched test-positive (via SARS-CoV-2 antigen/reverse transcription polymerase chain reaction [RT-PCR]) cases and test-negative case-controls (via RT-PCR) based on admission date, preceding vaccinations, and age. We evaluated the rVEs of four monovalent COVID-19 vaccines (AZD1222, Ad26.COV2.S, CoronaVac, and BNT162b2) as second boosters compared with any first boosters received ≥4 months previously, and as first boosters compared with primary-series vaccinations completed ≥4 months previously.

RESULTS

The overall rVE of second boosters, from 5668 (2238 test-positive) evaluated hospitalizations, was 24.7 % (95 % confidence interval [CI]: 12.6-35.1); the overall rVE of first boosters, from 30,272 (12,063 test-positive) hospitalizations, was 46.8 % (95 % CI: 43.3-50.0). The rVEs of AZD1222 and BNT162b2 were similar: 29.4 % (95 % CI: 8.6-45.5) and 25.5 % (95 % CI: 4.2-42.2), respectively, for second boosters; and 42.5 % (95 % CI: 28.0-54.0) and 50.8 % (95 % CI: 47.5-54.0), respectively, for first boosters. In general, rVEs were higher in elderly (≥80 years) and immunocompromised/high-risk individuals.

CONCLUSIONS

Our results support the use of AZD1222 and other adenoviral/mRNA vaccine boosters to maintain protection against COVID-19 hospitalization from Omicron subvariants, including in elderly and immunocompromised individuals at increased risk of accelerated waning or severe outcomes.

Safety and immunogenicity of a ChAdOx1 vaccine against Rift Valley fever in UK adults: an open-label, non-randomised, first-in-human phase 1 clinical trial

BACKGROUND

Rift Valley fever is a viral epidemic illness prevalent in Africa that can be fatal or result in debilitating sequelae in humans. No vaccines are available for human use. We aimed to evaluate the safety and immunogenicity of a non-replicating simian adenovirus-vectored Rift Valley fever (ChAdOx1 RVF) vaccine in humans.

METHODS

We conducted a phase 1, first-in-human, open-label, dose-escalation trial in healthy adults aged 18-50 years at the Centre for Clinical Vaccinology and Tropical Medicine, Oxford, UK. Participants were required to have no serious comorbidities or previous history of receiving an adenovirus-based vaccine before enrolment. Participants were non-randomly allocated to receive a single ChAdOx1 RVF dose of either 5 × 109 virus particles (vp), 2·5 × 1010 vp, or 5 × 1010 vp administered intramuscularly into the deltoid of their non-dominant arm; enrolment was sequential and administration was staggered to allow for safety to be assessed before progression to the next dose. Primary outcome measures were assessment of adverse events and secondary outcome measures were Rift Valley fever neutralising antibody titres, Rift Valley fever GnGc-binding antibody titres (ELISA), and cellular response (ELISpot), analysed in all participants who received a vaccine. This trial is registered with ClinicalTrials.gov (NCT04754776).

FINDINGS

Between June 11, 2021, and Jan 13, 2022, 15 volunteers received a single dose of either 5 × 109 vp (n=3), 2·5 × 1010 vp (n=6), or 5 × 1010 vp (n=6) ChAdOx1 RVF. Nine participants were female and six were male. 14 (93%) of 15 participants reported solicited local adverse reactions; injection-site pain was the most frequent (13 [87%] of 15). Ten (67%) of 15 participants (from the 2·5 × 1010 vp and 5 × 1010 vp groups only) reported systemic symptoms, which were mostly mild in intensity, the most common being headache (nine [60%] of 15) and fatigue (seven [47%]). All unsolicited adverse events reported within 28 days were either mild or moderate in severity; gastrointestinal symptoms were the most common reaction (at least possibly related to vaccination), occurring in four (27%) of 15 participants. Transient decreases in total white cell, lymphocyte, or neutrophil counts occurred at day 2 in some participants in the intermediate-dose and high-dose groups. Lymphopenia graded as severe occurred in two participants in the 5 × 1010 vp group at a single timepoint, but resolved at the subsequent follow-up visit. No serious adverse events occurred. Rift Valley fever neutralising antibodies were detectable across all dose groups, with all participants in the 5 × 1010 vp dose group having high neutralising antibody titres that peaked at day 28 after vaccination and persisted through the 3-month follow-up. High titres of binding IgG targeting Gc glycoprotein were detected whereas those targeting Gn were comparatively low. IFNγ cellular responses against Rift Valley fever Gn and Gc glycoproteins were observed in all participants except one in the 5 × 1010 vp dose group. These IFNγ responses peaked at 2 weeks after vaccination, were highest in the 5 × 1010 vp dose group, and tended to be more frequent against the Gn glycoprotein.

INTERPRETATION

ChAdOx1 RVF was safe, well tolerated, and immunogenic when administered as a single dose in this study population. The data support further clinical development of ChAdOx1 RVF for human use.

FUNDING

UK Department of Health and Social Care through the UK Vaccines Network, Oak Foundation, and the Wellcome Trust.

TRANSLATION

For the Swahili translation of the abstract see Supplementary Materials section.

Next-generation viral nanoparticles for targeted delivery of therapeutics: Fundamentals, methods, biomedical applications, and challenges

INTRODUCTION

Viral nanoparticles (VNPs) are virus-based nanocarriers that have been studied extensively and intensively for biomedical applications. However, their clinical translation is relatively low compared to the predominating lipid-based nanoparticles. Therefore, this article describes the fundamentals, challenges, and solutions of the VNP-based platform, which will leverage the development of next-generation VNPs.

AREAS COVERED

Different types of VNPs and their biomedical applications are reviewed comprehensively. Strategies and approaches for cargo loading and targeted delivery of VNPs are examined thoroughly. The latest developments in controlled release of cargoes from VNPs and their mechanisms are highlighted too. The challenges faced by VNPs in biomedical applications are identified, and solutions are provided to overcome them.

EXPERT OPINION

In the development of next-generation VNPs for gene therapy, bioimaging and therapeutic deliveries, focus must be given to reduce their immunogenicity, and increase their stability in the circulatory system. Modular virus-like particles (VLPs) which are produced separately from their cargoes or ligands before all the components are coupled can speed up clinical trials and commercialization. In addition, removal of contaminants from VNPs, cargo delivery across the blood brain barrier (BBB), and targeting of VNPs to organelles intracellularly are challenges that will preoccupy researchers in this decade.

An adenoviral-vectored vaccine confers seroprotection against capsular group B meningococcal disease

Adenoviral-vectored vaccines are licensed for prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Ebola virus, but, for bacterial proteins, expression in a eukaryotic cell may affect the antigen's localization and conformation or lead to unwanted glycosylation. Here, we investigated the potential use of an adenoviral-vectored vaccine platform for capsular group B meningococcus (MenB). Vector-based candidate vaccines expressing MenB antigen factor H binding protein (fHbp) were generated, and immunogenicity was assessed in mouse models, including the functional antibody response by serum bactericidal assay (SBA) using human complement. All adenovirus-based vaccine candidates induced high antigen-specific antibody and T cell responses. A single dose induced functional serum bactericidal responses with titers superior or equal to those induced by two doses of protein-based comparators, as well as longer persistence and a similar breadth. The fHbp transgene was further optimized for human use by incorporating a mutation abrogating binding to the human complement inhibitor factor H. The resulting vaccine candidate induced high and persistent SBA responses in transgenic mice expressing human factor H. The optimized transgene was inserted into the clinically relevant ChAdOx1 backbone, and this vaccine has now progressed to clinical development. The results of this preclinical vaccine development study underline the potential of vaccines based on genetic material to induce functional antibody responses against bacterial outer membrane proteins.

Lyophilization to enable distribution of ChAdOx1 and ChAdOx2 adenovirus-vectored vaccines without refrigeration

Distribution of vaccines which require refrigerated or frozen storage can be challenging and expensive. The adenovirus vector platform has been widely used for COVID-19 vaccines while several further candidate vaccines using the platform are in clinical development. In current liquid formulations, adenoviruses require distribution at 2-8 °C. The development of formulations suitable for ambient temperature distribution would be advantageous. Previous peer-reviewed reports of adenovirus lyophilization are relatively limited. Here, we report the development of a formulation and process for lyophilization of simian adenovirus-vectored vaccines based on the ChAdOx1 platform. We describe the iterative selection of excipients using a design of experiments approach, and iterative cycle improvement to achieve both preservation of potency and satisfactory cake appearance. The resulting method achieved in-process infectivity titre loss of around 50%. After drying, there was negligible further loss over a month at 30 °C. Around 30% of the predrying infectivity remained after a month at 45 °C. This performance is likely to be suitable for 'last leg' distribution at ambient temperature. This work may also facilitate the development of other product presentations using dried simian adenovirus-vectored vaccines.

Vaccine technology transfer in a global health crisis: Actors, capabilities, and institutions

The COVID-19 pandemic, which featured international pharmaceutical firms seeking to build global manufacturing networks to scale-up the supply of vaccines, has generated heightened interest in understanding the role of firm-to-firm technology transfer. While considerable attention has been given to tracking the extent of international vaccine technology transfer, we know little about how partnerships were established and work in practice. Understanding the challenges that such projects face, and how such challenges may be overcome, is crucially important. This paper provides an account of the partnership between the British-Swedish multinational pharmaceutical company AstraZeneca, the vaccine developer that has engaged in the most technology transfer and built the widest global manufacturing network, and Bio-Manguinhos, a public laboratory linked to Brazil's Ministry of Health. The case study demonstrates the importance of capabilities and regulatory flexibility. Moreover, the analysis highlights the role of political factors that affect the process of technology transfer, and innovation more broadly. Because of the risks involved and the need to quickly mobilize existing capabilities and build new ones, as well as the imperatives of coordinating among manufacturing and regulatory processes and allocating resources to make such arrangements feasible, technology transfer projects need to be enabled politically. Looking forward, the case study has implications for initiatives to expand technology transfer for broadened production of vaccines in the Global South.

Measurement of Adenovirus-Based Vector Heterogeneity

Adenovirus vectors have become an important class of vaccines with the recent approval of Ebola and COVID-19 products. In-process quality attribute data collected during Adenovirus vector manufacturing has focused on particle concentration and infectivity ratios (based on viral genome: cell-based infectivity), and data suggest only a fraction of viral particles present in the final vaccine product are efficacious. To better understand this product heterogeneity, lab-scale preparations of two Adenovirus viral vectors, (Chimpanzee adenovirus (ChAdOx1) and Human adenovirus Type 5 (Ad5), were studied using transmission electron microscopy (TEM). Different adenovirus morphologies were characterized, and the proportion of empty and full viral particles were quantified. These proportions showed a qualitative correlation with the sample's infectivity values. Liquid chromatography-mass spectrometry (LC-MS) peptide mapping was used to identify key adenovirus proteins involved in viral maturation. Using peptide abundance analysis, a ∼5-fold change in L1 52/55k abundance was observed between low-(empty) and high-density (full) fractions taken from CsCl ultracentrifugation preparations of ChAdOx1 virus. The L1 52/55k viral protein is associated with DNA packaging and is cleaved during viral maturation, so it may be a marker for infective particles. TEM and LC-MS peptide mapping are promising higher-resolution analytical characterization tools to help differentiate between relative proportions of empty, non-infectious, and infectious viral particles as part of Adenovirus vector in-process monitoring, and these results are an encouraging initial step to better differentiate between the different product-related impurities.

SARS-CoV-2 infection and immune responses

The recent pandemic caused by the SARS-CoV-2 virus continues to be an enormous global challenge faced by the healthcare sector. Availability of new vaccines and drugs targeting SARS-CoV-2 and sequelae of COVID-19 has given the world hope in ending the pandemic. However, the emergence of mutations in the SARS-CoV-2 viral genome every couple of months in different parts of world is a persistent danger to public health. Currently there is no single treatment to eradicate the risk of COVID-19. The widespread transmission of SARS-CoV-2 due to the Omicron variant necessitates continued work on the development and implementation of effective vaccines. Moreover, there is evidence that mutations in the receptor domain of the SARS-CoV-2 spike glycoprotein led to the decrease in current vaccine efficacy by escaping antibody recognition. Therefore, it is essential to actively identify the mechanisms by which SARS-CoV-2 evades the host immune system, study the long-lasting effects of COVID-19 and develop therapeutics targeting SARS-CoV-2 infections in humans and preclinical models. In this review, we describe the pathogenic mechanisms of SARS-CoV-2 infection as well as the innate and adaptive host immune responses to infection. We address the ongoing need to develop effective vaccines that provide protection against different variants of SARS-CoV-2, as well as validated endpoint assays to evaluate the immunogenicity of vaccines in the pipeline, medications, anti-viral drug therapies and public health measures, that will be required to successfully end the COVID-19 pandemic.

Computational framework to understand the clinical stages of COVID-19 and visualization of time course for various treatment strategies

Coronavirus disease 2019 is known to be regulated by multiple factors such as delayed immune response, impaired T cell activation, and elevated levels of proinflammatory cytokines. Clinical management of the disease remains challenging due to interplay of various factors as drug candidates may elicit different responses depending on the staging of the disease. In this context, we propose a computational framework which provides insights into the interaction between viral infection and immune response in lung epithelial cells, with an aim of predicting optimal treatment strategies based on infection severity. First, we formulate the model for visualizing the nonlinear dynamics during the disease progression considering the role of T cells, macrophages and proinflammatory cytokines. Here, we show that the model is capable of emulating the dynamic and static data trends of viral load, T cell, macrophage levels, interleukin (IL)-6 and TNF-α levels. Second, we demonstrate the ability of the framework to capture the dynamics corresponding to mild, moderate, severe, and critical condition. Our result shows that, at late phase (>15 days), severity of disease is directly proportional to pro-inflammatory cytokine IL6 and tumor necrosis factor (TNF)-α levels and inversely proportional to the number of T cells. Finally, the simulation framework was used to assess the effect of drug administration time as well as efficacy of single or multiple drugs on patients. The major contribution of the proposed framework is to utilize the infection progression model for clinical management and administration of drugs inhibiting virus replication and cytokine levels as well as immunosuppressant drugs at various stages of the disease.

Incubation Temperature and Period During Denarase Treatment and Microfiltration Affect the Yield of Recombinant Adenoviral Vectors During Downstream Processing

Adenoviral vectors (AV) are commonly used as vaccine and gene therapy vehicles because of their ease of construction, ability to grow to high titers in the large-scale production process, and safety for human applications. However, the efficiency rate of downstream processes for adenoviral vectors still varies greatly. In the current study, we aimed to investigate the effect of the downstream treatment protocol and microfiltration of the harvested upstream material on viral vector yield. We compared the performance of the repeated freeze-thaw (RFT) and the Tween-20 detergent lysis (DLT) methods. In addition, the effects of the cell lysis method, incubation temperature, and time on viral yield were investigated. The samples were incubated at either room temperature or 37 °C for 1-, 2-, and 4-h periods. Samples were filtered with PES and SFCA membrane. Virus yield and infectivity were assayed by qPCR and immuno-titration. In conclusion, our results suggest that 2-h incubation gives the best results when incubated at 37 °C for denarase activity when Tween-20 is used for virus recovery. If the room temperature is preferred, 4-h incubation could be preferred. A phase 1 clinical trial (NCT05526183, January 21, 2022) was started with the recombinant adenovirus used in the study.

Tolerability and immunogenicity of an intranasally-administered adenovirus-vectored COVID-19 vaccine: An open-label partially-randomised ascending dose phase I trial

BACKGROUND

Intranasal vaccination may induce protective local and systemic immune responses against respiratory pathogens. A number of intranasal SARS-CoV-2 vaccine candidates have achieved protection in pre-clinical challenge models, including ChAdOx1 nCoV-19 (AZD1222, University of Oxford / AstraZeneca).

METHODS

We performed a single-centre open-label Phase I clinical trial of intranasal vaccination with ChAdOx1 nCoV-19 in healthy adults, using the existing formulation produced for intramuscular administration. Thirty SARS-CoV-2 vaccine-naïve participants were allocated to receive 5 × 10⁹ viral particles (VP, n=6), 2 × 10¹⁰ VP (n=12), or 5 × 10¹⁰ VP (n=12). Fourteen received second intranasal doses 28 days later. A further 12 received non-study intramuscular mRNA SARS-CoV-2 vaccination between study days 22 and 46. To investigate intranasal ChAdOx1 nCoV-19 as a booster, six participants who had previously received two intramuscular doses of ChAdOx1 nCoV-19 and six who had received two intramuscular doses of BNT162b2 (Pfizer / BioNTech) were given a single intranasal dose of 5 × 10¹⁰ VP of ChAdOx1 nCoV-19. Objectives were to assess safety (primary) and mucosal antibody responses (secondary).

FINDINGS

Reactogenicity was mild or moderate. Antigen-specific mucosal antibody responses to intranasal vaccination were detectable in a minority of participants, rarely exceeding levels seen after SARS-CoV-2 infection. Systemic responses to intranasal vaccination were typically weaker than after intramuscular vaccination with ChAdOx1 nCoV-19. Antigen-specific mucosal antibody was detectable in participants who received an intramuscular mRNA vaccine after intranasal vaccination. Seven participants developed symptomatic SARS-CoV-2 infection.

INTERPRETATION

This formulation of intranasal ChAdOx1 nCoV-19 showed an acceptable tolerability profile but induced neither a consistent mucosal antibody response nor a strong systemic response.

FUNDING

AstraZeneca.

Safety and immunogenicity of a simian-adenovirus-vectored rabies vaccine: an open-label, non-randomised, dose-escalation, first-in-human, single-centre, phase 1 clinical trial

BACKGROUND

Rabies kills around 60 000 people each year. ChAdOx2 RabG, a simian adenovirus-vectored rabies vaccine candidate, might have potential to provide low-cost single-dose pre-exposure rabies prophylaxis. This first-in-human study aimed to evaluate its safety and immunogenicity in healthy adults.

METHODS

We did a single-centre phase 1 study of ChAdOx2 RabG, administered as a single intramuscular dose, with non-randomised open-label dose escalation at the Centre for Clinical Vaccinology and Tropical Medicine, Oxford, UK. Healthy adults were sequentially allocated to groups receiving low (5 × 109 viral particles), middle (2·5 × 1010 viral particles), and high doses (5 x 1010 viral particles) of ChAdOx2 RabG and were followed up to day 56 after vaccination. The primary objective was to assess safety. The secondary objective was to assess immunogenicity with the internationally standardised rabies virus neutralising antibody assay. In an optional follow-up phase 1 year after enrolment, we measured antibody maintenance then administered a licensed rabies vaccine (to simulate post-exposure prophylaxis) and measured recall responses. The trial is registered with ClinicalTrials.gov, NCT04162600, and is now closed to new participants.

FINDINGS

Between Jan 2 and Oct 28, 2020, 12 adults received low (n=3), middle (n=3), and high doses (n=6) of ChAdOx2 RabG. Participants reported predominantly mild-to-moderate reactogenicity. There were no serious adverse events. Virus neutralising antibody concentrations exceeded the recognised correlate of protection (0·5 IU/mL) in three middle-dose recipients and six high-dose recipients within 56 days of vaccination (median 18·0 IU/mL). The median peak virus neutralising antibody concentrations within 56 days were 0·7 IU/mL (range 0·0-54·0 IU/mL) for the low-dose group, 18·0 IU/mL (0·7-18·0 IU/mL) for the middle-dose group, and 18·0 IU/mL (6·0-486·0 IU/mL) for the high-dose group. Nine participants returned for the additional follow-up after 1 year. Of these nine participants, virus neutralising antibody titres of more than 0·5 IU/mL were maintained in six of seven who had received middle-dose or high-dose ChAdOx2 RabG. Within 7 days of administration of the first dose of a licensed rabies vaccine, nine participants had virus neutralising antibody titres of more than 0·5 IU/mL.

INTERPRETATION

In this study, ChAdOx2 RabG showed an acceptable safety and tolerability profile and encouraging immunogenicity, supporting further clinical evaluation.

FUNDING

UK Medical Research Council and Engineering and Physical Sciences Research Council.

Application of bioreactor technology for cell culture-based viral vaccine production: Present status and future prospects

Bioreactors are widely used in cell culture-based viral vaccine production, especially during the coronavirus disease 2019 (COVID-19) pandemic. In this context, the development and application of bioreactors can provide more efficient and cost-effective vaccine production to meet the global vaccine demand. The production of viral vaccines is inseparable from the development of upstream biological processes. In particular, exploration at the laboratory-scale is urgently required for further development. Therefore, it is necessary to evaluate the existing upstream biological processes, to enable the selection of pilot-scale conditions for academic and industrial scientists to maximize the yield and quality of vaccine development and production. Reviewing methods for optimizing the upstream process of virus vaccine production, this review discusses the bioreactor concepts, significant parameters and operational strategies related to large-scale amplification of virus. On this basis, a comprehensive analysis and evaluation of the various process optimization methods for the production of various viruses (SARS-CoV-2, Influenza virus, Tropical virus, Enterovirus, Rabies virus) in bioreactors is presented. Meanwhile, the types of viral vaccines are briefly introduced, and the established animal cell lines for vaccine production are described. In addition, it is emphasized that the co-development of bioreactor and computational biology is urgently needed to meet the challenges posed by the differences in upstream production scales between the laboratory and industry.

Process- and product-related impurities in the ChAdOx1 nCov-19 vaccine

ChAdOx1 nCov-19 and Ad26.COV2.S are approved vaccines inducing protective immunity against SARS-CoV-2 infection in humans by expressing the Spike protein of SARS-CoV-2. We analyzed protein content and protein composition of ChAdOx1 nCov-19 and Ad26.COV2.S by biochemical methods and by mass spectrometry. Four out of four tested lots of ChAdOx1 nCoV-19 contained significantly higher than expected levels of host cell proteins (HCPs) and of free viral proteins. The most abundant contaminating HCPs belonged to the heat-shock protein and cytoskeletal protein families. The HCP content exceeded the 400 ng specification limit per vaccine dose, as set by the European Medicines Agency (EMA) for this vaccine, by at least 25-fold and the manufacturer’s batch-release data in some of the lots by several hundred-fold. In contrast, three tested lots of the Ad26.COV2.S vaccine contained only very low amounts of HCPs. As shown for Ad26.COV2.S production of clinical grade adenovirus vaccines of high purity is feasible at an industrial scale. Correspondingly, purification procedures of the ChAdOx1 nCov-19 vaccine should be modified to remove protein impurities as good as possible. Our data also indicate that standard quality assays, as they are used in the manufacturing of proteins, have to be adapted for vectored vaccines.

Pandemic-response adenoviral vector and RNA vaccine manufacturing

Rapid global COVID-19 pandemic response by mass vaccination is currently limited by the rate of vaccine manufacturing. This study presents a techno-economic feasibility assessment and comparison of three vaccine production platform technologies deployed during the COVID-19 pandemic: (1) adenovirus-vectored (AVV) vaccines, (2) messenger RNA (mRNA) vaccines, and (3) the newer self-amplifying RNA (saRNA) vaccines. Besides assessing the baseline performance of the production process, impact of key design and operational uncertainties on the productivity and cost performance of these vaccine platforms is quantified using variance-based global sensitivity analysis. Cost and resource requirement projections are computed for manufacturing multi-billion vaccine doses for covering the current global demand shortage and for providing annual booster immunisations. The model-based assessment provides key insights to policymakers and vaccine manufacturers for risk analysis, asset utilisation, directions for future technology improvements and future epidemic/pandemic preparedness, given the disease-agnostic nature of these vaccine production platforms.

Considerations for rapid development and licencing of conventional and platform technology veterinary vaccines

The threat posed by zoonotic diseases and other livestock pathogens has never been greater, and thus we must do all we can to learn from past experience in order to tackle emerging disease threats. The process of developing a new veterinary vaccine involves the generation of a specific set of data in order to meet the strict product licencing requirements of regulatory approval bodies around the globe. As a result, it is important that those embarking on the development of a vaccine using either conventional or novel platform technologies understand these regulations. In addition, there are a number of specific requirements that one needs to take into consideration when developing a product specifically for the commercial poultry market. This paper briefly outlines the veterinary vaccine development process in general and then explores ways in which this process can be accelerated. It also recognises the "one health" lessons that can be learnt from the recent rapid development of vaccines to tackle the COVID-19 pandemic and acknowledges the important measures that regulatory authorities have taken in the creation of an environment to facilitate the licencing of new vaccine platform technologies.