Vaccines are the most cost-effective strategy to prevent and suppress global infections, such as viral pathogens.
Conventional vaccines are classified under three categories: live, attenuated or non-live. Conventional vaccines have shown utility in irradicating smallpox and slowing the spread of other diseases, such as polio, measles, mumps and rubella over past decades.1 However, producing these attenuated vaccines is complex and time-consuming; creating new vaccines is estimated to take 5-10 years and costs over $500 million, with additional costs associated with manufacturing and equipment.2
Pandemic-era vaccine manufacturing and beyond
The established methods of conventional vaccine production are no longer adequate to identify and produce new vaccines to ensure global protection.
Technology utilizing mRNA promises to change the current paradigm for vaccine development, as the platform allows the production of vaccine candidates in as little as a few weeks by altering just the viral RNA sequence.3,4
While the mRNA vaccine technology allowed the production of a vaccine against SARS-CoV-2 in just one year, global vaccination efforts were severely strained by the capacity to manufacture.
These bottlenecks were caused by a lack of manufacturing facilities, tech-transfer personnel as well as shortages in raw materials.5 It is now apparent that there is a need for more resilience and robustness to allow for rapid, safe and large-scale production of vaccines, especially in developing countries. The COVID-19 mRNA vaccine has sparked a movement to advance mRNA technology into other therapeutic avenues and to develop better manufacturing technology and practices.
Model-based assessment of the mRNA vaccine manufacturing pipeline
As the COVID-19 vaccine was the first authorized vaccine to use mRNA technology and be mass-produced, little data was available regarding the economic production of mRNA-based therapeutics. The vaccine production started “at risk”, before the completion of clinical trials and before the optimization or scale-up of the product process, which had led to uncertainties in the substrate amount required for dose and the number of doses that would be required.6
Now, data from this experience can be used to model the manufacturing process.
Dr. Zoltán Kis, lecturer and assistant professor of chemical and biological engineering at the University of Sheffield is working to better understand and optimize the mRNA manufacturing landscape. Kis’ research focuses on experimental and modeling techniques to produce platform processes that enable the rapid development and mass manufacturing of RNA vaccines.
In a recent paper, Kis sought to build a model-based assessment to understand vaccine production better.7 “We ran a global sensitivity analysis to evaluate key performance indicators on different vaccine production platforms, namely adenovirus vectors vaccines, mRNA vaccines and saRNA vaccines to assess baseline performance of the production process,” Kis says. Certain inputs such as scale, titers, failure rates, dose size, labor rates and failure rates were used. The model sampled 10,000 simulations and plotted these inputs against key performance indicators to understand how each input affects production.
“In terms of mRNA production, we found that the process was sensitive to a few process specifics, primarily the substrate dose, batch lead times and the production scale. The main driver is the amount of mRNA per dose as well as production scale and titer,” explains Kis. The key takeaways of mRNA manufacturing that should be noted moving forward are:
- To increase annual mRNA production, the dose amount needs to be decreased
- The mRNA production process can be increased as they have a low footprint with low fixed costs and high variable costs (meaning that during surge production, the process is most efficient)
- The main process bottleneck lies in the formulation, specifically encapsulation into the lipid nanoparticle (LNP). This bottleneck can be removed by either equipment scale-up or scale-out.
“We believe that producing an mRNA platform technology for vaccine production will help alleviate many issues. This would mean using the same production platform [equipment] and only changing the RNA that is encapsulated for different diseases. Facilitating the move from batch processing to an efficient continuous process would also speed up production,” Kis says.
These insights are useful not only for the production of vaccines against emerging SARS-CoV-2 variants, but to also better understand the mRNA production process as technology becomes more efficient.8
Engineering better LNPs for mRNA vaccines
Using vaccines to induce a highly potent immune response, such as the production of neutralizing antibodies, is an urgent need. With mRNA technology, scientists are looking into building a mechanistic insight into the function of LNP-mRNA vaccines and engineering them to be more immunologically potent.
“For future vaccine development and manufacturing, we need to look at lowering vaccination dose while maintaining or enhancing vaccination efficacy,” says Dr. Yizhou Dong, professor in the Icahn Genomics Institute at the Icahn School of Medicine at Mount Sinai. The Dong lab focuses on designing and developing biotechnology platforms for treating cancers, infectious diseases and genetic disorders.
One approach is to engineer the LNP delivery system to stimulate multiple immune system pathways and increase therapeutic efficacy. A pathway of interest is the STING pathway, known to active type 1 interferon(IFN) secretion. Type 1 IFN response is critical for expanding and activating CD8+ T-cells against viral infections.9
By integrating an agonist for the STING pathway into the LNP of the SARS-CoV-2 vaccine, the Dong lab produced a vaccine that was more immunologically potent than the LNPs used for the current mRNA vaccines. This was achieved by producing a potent STING agonist with unique physiochemical properties on the LNP, which, when endocytosed, activates the STING pathway, causing the production of INF-β. When the engineered STING agonist LNP (SAL-12) was compared with the ALC-0315 (the lipid used in the COVID mRNA vaccine) in a mouse study, SAL-12 produced an over 15 times better neutralization titer (NT50), and enhanced protection against SARS-CoV-2.10
This work is a proof of concept for using agonists within LNPS to enhance immune response. Solutions like this one open the avenue for next-generation mRNA vaccines.
How can this technology be used in the future? “Well, each disease has its own challenges, and the vaccine will need to be created and studied accordingly. We need to alter the delivery platform or tune the mRNA cargo and final formulation to match the needs of the disease,” Dong says.
Although mRNA-based vaccines are being tested for many different indications, augmenting the immune response by targeting pathways that amplify the therapeutic response can lower the required doses and manufacturing costs.11
Emerging platform for viral-like particle vaccines
Virus-like particles (VLPs) are structures that mimic both the organization and conformation of viruses but lack a viral genome, which renders them non-infectious.
VLPs have structural characteristics that enable a stronger immune response than conventional vaccines.12 VLP-based vaccines are already available against Hepatitis B, zika and malaria. 13
The production of VLP vaccines using genetic engineering has been challenging because of low yields, high costs and complex and time-consuming expression and purification processes. Advancements are needed to produce a more simplified workflow for VLP-based vaccines.
In a recent study a team at Qingdao Municipal Hospital in Qingdao, China, developed a novel VLP platform that mimics infection and confers protection to influenza through fluorination-drive self-assembly.14
Fluorination is a chemical process that involves the introduction of fluorine atoms into a chemical structure. Fluorination promotes cytosolic delivery of both small molecules and macromolecules, and promotes self-assembly.15 Taking advantage of this phenomenon allows for the self-assembly of viral antigens for VLP vaccines.
In viral antigen self-assembly, the viral surface antigens are fluorinated by conjugating them with tridecafluoroheptanoic acid. These virus proteins then self-assemble into VLPs through fluorophilic interactions, which mimic a natural virus structure. Different influenza strains were used such as H1N1, H6N2 and H9N2. Besides the production of single VLPs from each influence strain, a “mosaic” VLP was also produced with surface antigens of all three influenza strains.
Both these mosaic VLPs and individual VLPs from single influence strains provided protection against lethal viral challenges in a mouse model, where mouse body weight change and survival rate were used to test efficacy. Mice were immunized using either the fluorinated VLP influenza vaccine, whole inactivated influenza virus, soluble influenza antigen or with saline. The VLP vaccine demonstrated the most robust protection and survival against other vaccine types and had also showed low viral loads and inflammation in the lungs.
The fluorination process could enhance the breadth of protection offered by vaccines as it enables the targeting of multiple virus strains simultaneously. This could open avenues to produce VLP vaccines against highly mutable viruses. Using this self-assembly approach may also offer a scalable alternative to conventional VLP vaccine production, making it a more attractive option for manufacturing.
Upcoming advancements in vaccine technology and manufacturing
The utility of mRNA and VLPs have shown technology advancements that will alter the vaccine production and manufacturing landscape.
The modularity and quick production of mRNA sequences allow for rapid adaptation to new targets currently being investigated for cancers, viral infections and genetic disorders.16 This technology is still relatively new and suffers from mRNA thermal stability, storage concerns and unwanted immunogenic responses. 17
VLP vaccines are known to produce a strong immune response that closely resemble viral infection. Since VLPs do not contain genetic information, they are neither infectious nor pathogenic. Current research is looking at redefining VLP-based vaccines by altering adjuvants, stabilizers, and delivery vehicles to reduce required dosages and enhance shelf life.
Both mRNA and VLP vaccines represent a significant advancement in vaccine technology and will play a role in protection against infectious diseases. Given the unique advantages of these platforms and ongoing research and development to address drawbacks in their manufacturing, the future of mRNA and VLP-based vaccines holds great promise for production.
Source: Technology Networks
