T-Max™ DNA T Cell Vaccine Technology Q&A

What is the T-Max DNA vaccine platform?
MBFT’s T-Max™ DNA vaccine platform is a proprietary process from discovery to commercialization of protective vaccines that identifies clinically relative pathogen antigens and delivers them in proprietary formulations to stimulate durable and potent T cell immune responses. Four components differentiate the platform: i) a novel antigen selection process to identify multiple clinically relevant antigens to create cross-protective ”universal” vaccines; ii) cloning into proprietary plasmids containing a non-antibiotic selection system; iii) one or more immunomodulators that stimulate an innate immune response; and iv) formulation in proprietary CaptaVax™ nanoparticles that deliver plasmids directly to dendritic cells to stimulate durable memory T cell responses to viral antigens present in natural disease.

What is the difference between humoral (B cell) and cellular (T cell) immunity?
B cells secrete antibodies, proteins that bind to free pathogens circulating throughout the body and provide the signal for other immune cells to kill and eliminate the circulating pathogen. Many pathogens, including PRRSV, influenza and African Swine Fever Virus, enter into host cells in as few as 10 minutes after infection. Once inside, they are no longer accessible to antibodies until the virus replicates and releases new particles into circulation and repeats the infection cycle. T cells have a different role. Cytotoxic, or killer T cells detect and eliminate infected cells that harbor pathogens to stop viral replication by clearing virus from the body. Infected host cells display a ‘kill me signature’ on their surfaces composed of fragments of pathogen antigens that distinguishes them from healthy, normal cells. Cytotoxic T cells ‘trained’ by vaccination to recognize the ‘kill me’ signature bind to and directly kill infected cells to eliminate virus from the body. We believe that a strong T-cell response is particularly important for ASF.

Describe components that differentiate T max vaccines from other vaccines?
A major advantage of T-Max plasmid DNA is large antigen payload capacity and the flexibility to carry one or more antigen genes on a single plasmid. Multiple plasmids can be combined in a single vaccine to broaden the immune response to provide cross-protection and/or produce polyvalent vaccines for multiple diseases i.e., SARS CoV2, PRRS, Influenza and ASF. The CaptaVax calcium phosphate nanoparticle delivery system is non-viral, biocompatible and biodegradable. Calcium phosphate nanoparticles are excellent transmucosal adjuvants that cause less irritation than traditional alum-based adjuvants (alum-based adjuvants cannot be delivered intranasally). Use of particles in the 50 nm to 200 nm range combined with innate immune cell activators enhance activation and processing of antigens by dendritic cells that in turn stimulate potent T cell responses.

How are clinically relevant T cell antigens identified? How are antigens selected for incorporation into the vaccine?
Clinically relevant antigens are the subset of all viral proteins made by a pathogen (or tumor cells) that are displayed to T cells in natural disease. We use the natural host response to the disease to select candidate antigens that are then evaluated in challenge studies to assess protection from disease. Other considerations include the function and timing of expression in the pathogen life cycle and internal vs surface proteins, among other factors. The final vaccine is a mixture of more than one antigen to broaden the immune response and minimize any effects of mutations associated with pathogen genetic diversity.

What are the manufacturing advantages of the T-Max DNA vaccine platform compared to conventional live attenuated and killed virus vaccines?
Plasmid DNA manufacturing has several advantages over traditional roller bottle production of viral vaccines. Roller bottle production requires optimized immortal cell lines for viral replication. The use of complex biological media poses an inherent risk of contamination with adventitial organisms that are a risk to recipients of the vaccine. Other environmental and safety concerns inherent to production and culture of live viruses are reversion to virulence of an attenuated or incompletely attenuated viruses that can cause disease rather than prevent it –as demonstrated by the adverse consequences of virus reversion with increasing use of illegal attenuated vaccines for African Swine Fever Virus in China. The T-Max platform does not use live or attenuated virus in any part of the production process and no live or attenuated virus is present in T Max vaccines, making it impossible for T Max vaccines to cause disease.

What are the advantages of pDNA versus mRNA for use in vaccine development?
Two of the most important advantages of DNA vaccines are safety and stability, both are critical for patient acceptance and universal ease of access to lifesaving vaccines. DNA and RNA vaccines share several characteristics that make both attractive for vaccine development. Antigen constructs can be made from template genes and ‘retooled’ rapidly to address evolving pathogen variants and emerging diseases. Both elicit B and T cell responses, and both are made by rapid, well controlled manufacturing processes. However, an important disadvantage of mRNA is inherently lower stability compared to DNA, and from a safety perspective, a greater potential to elicit inflammatory responses as demonstrated by reports of moderate to severe adverse reactions to the Moderna and Pfizer vaccines. Control of mRNA stability and inflammatory responses requires more complex formulations and presents greater logistical complexities of cold to ultracold storage and transport, and the need to administer to patients immediately after thawing. DNA vaccines have a long history of safe use in humans and animals, including immunocompromised patients. Plasmid DNA is very stable; an advantage for construction, purification and handling. DNA vaccine production and packaging are highly cost effective with no special transport or storage conditions required. DNA vaccines can be produced at commercial scale and distributed anywhere in the world. Global distribution is facilitated by the ability to transport and store DNA vaccines under a wide range of temperatures and environmental conditions.

What are the advantages of pDNA formulated in CaptaVax™ nanoparticles in the T-Max platform versus virally vectored DNA?
Virally vectored vaccines, in particular the Oxford SARS CoV2 spike antigen constructed in a first-in-class chimpanzee derivative adenovirus, or the J&J human adenoviral vector, have clear advantages of safety and efficacy: they stimulate B cell and T cell immunity but also have important limitations. Viral vectors themselves are antigenic and cannot be administered more than once because upon reimmunization, the immune system recognizes the vector as foreign and eliminates it from the body preventing payload antigen presentation expression and presentation to immune cells. Vaccines constructed with the endemic human Adenovirus5 (CureVac, CanSino Biologics) appear to have reduced efficacy from the first shot because some immunity to this vector is already present in the population. The viral vector manufacturing process is complex compared to more straightforward and less costly plasmid manufacture. Viral vectors are limited by the antigen payload size, whereas plasmid DNA can carry substantially higher payloads per plasmid and multiple plasmids expressing multiple antigens can be readily formulated into a single vaccine for broader immune coverage and no limitation on the number of times the vaccine can be readministered.

How is the T-Max™ platform used to create vaccines for infectious diseases?
T-Max is a modular design platform that can be rapidly adapted to any disease. Once the organism’s genetic sequence is identified, clinically relevant antigens can be quickly selected, and DNA plasmids constructed and formulated with the CaptaVax delivery/adjuvant component. This is accomplished through a streamlined manufacturing process for rapid delivery and path to commercialization.

What is the evidence that it is possible to make a universal SARS CoV-2 T cell vaccine?
The definition of a universal vaccine is one that protects against multiple strains or variants of the same pathogen and/or against infection by closely related pathogens. Several 2020 studies identified SARS CoV-2-reponsive T cells in 40-60% of SARS CoV-2 unexposed individuals, presenting strong evidence for cross-reactive T cell recognition between SARS CoV-2 and globally circulating ‘‘common cold’’ coronaviruses. SARS CoV-2, common cold coronaviruses, and more virulent relatives, MERS and the now-eradicated SARS CoV-1 all share some common or universal, conserved DNA sequences that translate into proteins- or for purposes of vaccine development- viral antigens that all share common sequences recognized by T cells. The T Max antigen discovery process identifies viral proteins common to SARS CoV-2 variants and related coronaviruses that stimulate T cell responses when they are challenged with exposure to a variety of different, related viral strains. Proprietary plasmids carrying selected, highly conserved genes for these T cell-responsive antigens are combined, formulated, and tested as candidates for vaccine development.

How can MBFTs T-Max platform reduce vaccine hesitancy?
Vaccine hesitancy is a significant issue where people refuse to be vaccinated. The reasons for hesitancy include disbelief that vaccination is needed to prevent disease, fears based on misinformation, and genuine concerns about safety, efficacy, and convenience. Safety raises two main concerns; is the vaccine safe for my child/loved one, and is it safe for me? The safety of DNA vaccines has been demonstrated in animal and human studies over the past several decades. T-Max vaccines are formulated with a non-viral, biologically inert, low reactogenicity delivery adjuvant that stimulates T cell responses and limited but targeted antibody production to reduce the potential for antibody-enhanced disease. T-Max vaccines are expected to provide efficacy equivalent to current mRNA market leaders and cross-protection against evolving strains and variants. One-shot protection against more than one disease is possible, for example a combination vaccine for SARS CoV-2 + Influenza. Convenience will be enhanced, and hesitancy reduced by simple needle-free administration in a nasal spray – potentially by self-administration in a single dose presentation.

How can MBFTs T-Max platform address future and current epidemics/pandemics?
The most important way to limit the economic and humanitarian damage from epidemics/pandemics is to rapidly vaccinate the at-risk population with an efficacious product to stop the virus from circulating. The efficacy of T-Max vaccines is assured by the selection of clinically relevant, conserved T cell antigens that can be rapidly incorporated into the delivery/adjuvant system to provide strong cross-protection. The modular design of the T-Max platform means that vaccines can be rapidly re-tooled to respond to new diseases or major changes in an ongoing outbreak. This also facilitates regulatory approval, and the simplified manufacturing process can be ramped up rapidly to meet supply demands. The vaccine will be administered as a single dose, nasal spray that does not require refrigerated transport or storage. In summary, the T-Max platform will deliver a rapid-response, highly efficacious, patient- and distribution-friendly vaccine to rapidly stop circulation of the virus.

Why are you pursuing development of an African Swine Fever vaccine?
The inherent lethality of African Swine Fever (ASF) makes creating an attenuated vaccine that will be consistently safe and that will elicit a protective immune response a challenge, one that has perplexed scientists for years.

Our approach to constructing a protective ASF vaccine is fundamentally different. We never use live virus in the vaccine or in the manufacturing of the vaccine. There is zero risk that our vaccines can cause disease. We use our proprietary antigen selection process to identify core conserved antigens that elicit strong T-cell and B-cell responses. We incorporate multiple antigens and immunomodulators with our proprietary biocompatible CaptaVax delivery system to enhance the T cell immune response to provide broad coverage against divergent ASFV strains. ASF is a respiratory virus, therefore locally active T cell immunity in the upper and lower respiratory system is important for protection. CaptaVax nanoparticles are very effective when delivered mucosally and our ASF vaccine will be delivered intranasally to weanling pigs to stop infection at the site of pathogen entry in the airways. We will also evaluate protection by SC and IM administration as a more conventional route of administration in larger pigs.

What were the results of MBFT’s most recent clinical studies?
We recently completed three clinical studies. One evaluated our proprietary CaptaVax™ nanoparticle delivery system formulated as an autogenous PRRS vaccine. This study in weanling pigs was conducted in collaboration with Smithfield Foods. An important outcome was confirmation that intranasal vaccination is a viable route of administration in weanlings. The other two studies evaluated an experimental protective T cell DNA vaccine for SARS CoV-2. The DNA vaccine constructed with our T-Max™ vaccine platform comprises Spike and three other viral proteins. The vaccine was formulated with CaptaVax nanoparticles and a proprietary immunomodulator delivered to Syrian hamsters. The vaccine elicited robust CD8+ and CD4+ responses. In a third study, we challenged blood samples from recovered Covid19 human donors with the four vaccine antigens and observed strong CD4+ responses that verified the clinical relevance of these antigens, the DNA plasmid design and the CaptaVax nanoparticle delivery adjuvant. Taken together, these two studies validate our T-Max vaccine platform and ability to create protective T cell vaccines.

Can the T-Max platform be used to make immunotherapeutic cancer vaccines?
Yes. Cancer is an example of using vaccination in a therapeutic setting where the patient has a condition that impairs the immune system’s ability to recognize and eliminate cancerous cells. Like infection, tumor cells display ‘altered self signatures’ on their surfaces that we use to create immunotherapeutic vaccines that train T cells to recognize cancer cells while leaving healthy cells unaffected. Tumor cells grow and spread because they have evolved many mechanisms for evading immune recognition. T-Max immunotherapeutic T cell vaccines comprise tumor-specific antigens, immunomodulators to stimulate innate and adaptive responses, and checkpoint inhibitors that relieve immunosuppressive processes and enable T and B cell activation to recognize and kill tumor cells. MBFT’s future plans include development of multiple canine cancer vaccines.