Four COVID-19 Vaccine Approaches, With Profoundly Different Safety Implications
Summary
- Categorizing vaccine candidates by their Method of Action (MOA) provides valuable insights for investors.
- The potential for benefit from a multi-modal approach is intriguing.
- An introduction to Inovio’s co-founder, Dr. Joseph Weiner.
To say that progress in developing a COVID-19 vaccine is unprecedentedly rapid is an understatement. It is also safe to say that understanding the differences in the individual vaccine candidates can be bewildering. To face this challenge, a good place to begin is to look at the WHO draft landscape of Covid-19 vaccine candidates.
For the purposes of this report, we will focus mainly on publicly traded companies whose candidate vaccines are in advanced human trials or in the case of Janssen/Johnson & Johnson, who have received substantial U.S. government funding.
Method of Action | Company/Organization | Transfection Boost Strategy |
|---|---|---|
Group 1: Antigen plus Adjuvant | Novavax GSK/Sanofi | Quillalasaponin/cholesterol/phospholipid Monophosphoryl lipid/squalene/Vit E/oil in water |
Group 2: Virus Mediated | AstraZeneca/Oxford Janssen/Johnson&Johnson MerckShaprDohme/Pitt | Chimp adenovirus vector Non replicating viral vector Live attenuated measles |
Group 3: Cationic Phospholipid | Moderna BioNTech/Pfizer CureVac Arcturus | Lipid nanoparticle envelope Lipid nanoparticle envelope Lipid nanoparticle or "carrier molecule" envelope Lipid nanoparticle envelope |
Group 4: Electroporation | Inovio Pharmaceuticals Genexine/Binex (S. Korea) | Localized electrical pulse Localized electrical pulse |
In this table, vaccine candidates are grouped by the different methods of action that their therapeutic strategies employ, with special attention to potential safety and toxicity issues.
Antigen Plus Adjuvant
In this group we see a traditional approach to vaccine development. Antigen transfection is boosted by adjuvants. By antigen, we refer to viral protein material which is injected into recipients with the objective of stimulating their immune systems to produce humoral or cell-mediated immunity like that developed in patients during an infection with the virus itself.
When these elements are sufficiently present in a subject’s bloodstream, whether because of surviving the disease or as a result of receiving a vaccine, immunity can be said to have been achieved.
Humoral immunity refers to antibodies, also known as immunoglobulins, which are relatively large Y-shaped proteins produced mainly by plasma cells.
Antibodies work by binding to an invading virus, and if by doing so they can block the ability of the virus to bind to cellular walls they are referred to as neutralizing antibodies.
Cell-mediated immunity refers to phagocytes (cells which can engulf and absorb viruses and other pathogenic elements) and antigen-specific cytotoxic T-lymphocytes (a class of white blood cells) which function by releasing various cytokines in response to the presence of viral antigens.
The term adjuvant is used broadly to describe any pharmacological or immunological agent that improves the immune response of a vaccine. They are added to the antigen component of a vaccine to boost the immune response to produce higher levels of humoral and cell-mediated immunity. Adjuvants are generally considered useful in that they allow for longer lasting immunity and a minimization of the dose of antigen needed.
However, despite its friendly-sounding name, (“adjuvant” is derived from the Latin ad-jurare, meaning “to help”), there is reason for concern based on its safety profile.
From Figure 2 (above) we see two vaccine candidates that employ the basic strategy termed Antigen + Adjuvant.
Novavax uses a patented saponin-based adjuvant called Matrix M. It is composed of 40 nanometer particles based on saponin together with cholesterol and phospholipid.
Saponins are foaming glycoside-sugar compounds found in plants. Their ability to foam rests on the hydrophobic, fat soluble glycoside element which is attached to hydrophilic, or water soluble, sugar chains.
Typical Saponin Structure
(Water soluble zone to the left; fat soluble zone to the right)
The makeup of the compound gives it the ability to emulsify, which means it allows for mixing of hydrophylic and lipophylic moities. Since cell walls consists of lipids and other hydrophobic compounds surrounded by the aqueous environment of the bloodstream and the aqueous cytosolic environment in the cell’s interior, it is expected that saponins would align themselves with the cell wall where interactions could allow for increased cellular wall permeability to the COVID glycoproteins that the Novavax vaccine employs as its antigen.
In the case of the Glaxo Smith Kline/Sanofi partnership, each company provides a different component to the vaccine candidate. Sanofi provides its recombinant S-protein antigen while GSK supplies the adjuvant.
Working at developing adjuvants for decades, GSK has created at least 4 different formulations where different adjuvants are combined. They call these Adjuvant Systems, and number them sequentially:
AS01 (MPLA + QS21 in liposomes)
AS02 (MPLA + QS21 in oil-in-water emulsion)
AS03 (squalene + alpha-tocopherol+ polysorbate 80 in an oil-in-water emulsion
AS04 (MPL + alum).
Of these Adjuvant Systems, it could be likely that the AS03 will be employed in the GSK/Janssen vaccine candidate.
This is because AS03 is the Adjuvant System supplied by GSK to the Chinese firm, Clover Biopharmaceuticals, which is already in clinical trials with its own COVID-19 vaccine candidate.
A literature review suggests that GSK considers AS03 to induce a marked antibody response and thus be especially useful in situations where anti-body mediated protection is important. As a fat-soluble vitamin, alpha tocopherol (Vitamin E) has known toxic side effects, mainly bleeding, if excess doses are given orally.
Because GSK has used adjuvant systems in several widely used licensed vaccines targeting various types of viruses, there is extensive data collected both on vaccine effectiveness and unwanted toxic sequelae. For example, an increased risk of narcolepsy was observed in Europe after AS03-adjuvanted 2009 H1N1 influenza vaccine was administered to 25,000 subjects in Finland.
Although the mode of action of the vaccine’s side effect is debated, the association with narcolepsy suggests that adjuvanted vaccines are interacting with neural tissue.
Candidate Vaccines Grouped by Method of Action, Intrinsic Toxicity, and Public Acceptance Issues
Group 1 | Group 2 | Group 3 | Group 4 | |
|---|---|---|---|---|
Transfection Boost Strategy | Adjuvant | Virus | Lipid Envelope | Electroporation |
Company/Organization | Novavax GSK/Sanofi | AstraZeneca/Oxford Janssen/J&J MerckSharpDohme/Pitt | Moderna BioNTech/Pfizer CureVac | Inovio Pharmaceuticals Genexine/Binex |
Pros | Venerable; more than 100 years experience. Big Pharma resources. Operation Warp Speed. | Reliable; good history of success. Big Pharma resources. Operation Warp Speed. | Rapidly adaptive platform. No adjuvant risk. No virus vector risk. Substantial Big Pharma resources. Operation Warp Speed. | Rapidly adaptive platform. No adjuvant risk. No virus vector risk. No transfection boost. Stable at room temperature. Supported by Bill Gates, Elon Musk. |
Cons | More than 100 years old. Linked to narcolepsy side effect. Systemic transfection boost. | Potential to develop immunity to vaccine. Flu-like symptoms. PR challenge, as developed from fetal cell line. Transverse myelitis risk. Systemic transfection boost. | Marginal history of success. Long term storage challenge. Systemic transfection boost. | Marginal history of success. Flagging progress in trials after initial good start. Delay of publication of data. Skepticism of electroporation. Snubbed by national media/Dr. Scott Gottlieb. Operation Warp Speed minor league. |
Typical Fringe/Anti-Vaxer Response | "So you put soap in my veins and then I can't wake up? Or I get ADHD if I do?" | "So I get this shot made from aborted babies and then I go straight to Hell?" "Have no clue about transverse myelitis but you won't catch me catch me catching it." | "So while those guys are busy choosing tuxedos for the Billionaire Boy's Club gala, the Chinese hack their computers and switch the vaccine recipe to poison?" | "So this is how Bill and Melinda Gates inject their mind-control chips into the entire human race?" |
Insanity Quotient of Response | One Star Hyperbolic, maybe just ironic? Not that far off the mark. | Two Star Paranoic. Never make medical choices on the advice of Bishop or cult leader. | Three Star Losing contact with reality? The Chinese are trying to steal our science not start Armageddon. But still responding rationally to incredible hubris. | Four Star Bonkers! You're hallucinating devils while looking at saints. Their only mind chip is for giving the gift of sight to the blind. |
Virus Mediation of Transfection
In this Group of COVID-19 vaccines, viral vectors are employed to accomplish transfection.
The AstraZeneca/Oxford vaccine candidate employs a chimp adenovirus vector as its method of transfecting a full length structural surface glycoprotein (spike protein) across cell walls.
The Janssen/J&J vaccine utilizes a non-replicating chimp adenovirus to transfect the spike protein across cell walls.
The MerckSharpeDohme/U.Pitt vaccine candidate utilizes a live attenuated measles virus in a similar fashion.
While the viruses employed in these 3 platforms are certainly less pathogenic than native, disease-causing viruses, cell wall integrity is nevertheless violated in each case.
It’s not unreasonable to consider that any agent capable of boosting transfection could cause damage to cellular walls at the site of the interaction. Also, there is risk that an adenovirus vector vaccine’s effectiveness could be mitigated if a treated subject has formed immunity against a related adenovirus encountered previously.
Furthermore, there is some concern that after receiving this type of vaccine, a patient will develop undesired antibodies against the adenovirus vector itself in addition to the desired antibodies targeting the COVID-19 virus. In this event, it could be expected that subsequent doses of that vaccine, such as might be used as a booster shot, could be seriously attenuated.
Despite these drawbacks. Viruses are at least a method of transfection that humans have had a chance to evolve defenses against.
This is not the case with transfection strategies relying on either adjuvants as in Group 1, or lipid nanoparticles as in Group 3.
Cationic Phospholipid Transfection Boost
We will now discuss Group 3, in which members employ Lipid Envelopes in their vaccine candidates’ formulations.
The BioNTech/Pfizer, Moderna, CureVac and Arcturus products are similar in that they all package messenger RNA coding for the spike protein. In the case of the Arcturus candidate, the mRNA is self-replicating.
In order to achieve its desired effect, mRNA requires a means of ingress to the cellular cytosol, where enzymes required for mRNA transcription reside.
Since clinical trials are showing positive results it stands to reason that mRNA is being transfected. The most logical agent responsible for broaching the cell wall is the lipid nanoparticle envelope which carries the dose of mRNA strands through the blood stream.
Since mRNA has an anionic charge, the components of the lipid envelope must be cationic.
In vitro studies of cationic lipid liposomes (another name for lipid envelopes) have shown significant toxicity to phagocytic macrophages in murine systems. Thus, it would not be unreasonable that toxicity could be expected in vaccine platforms utilizing lipid envelopes to achieve transfection of antigen-coding mRNA. And unlike the viral transfection effectors described in Group 2, lipid envelopes employed in Group 3 are completely foreign to living organisms. This perspective implies the potential for unanticipated toxic complications.
Electroporation
The most revolutionary vaccine platform is found in Group 4. Here DNA plasmids act as viral antigen precursors.
While DNA plasmids have been studied for decades, plasmid-based vaccines have generally yielded disappointingly low immunogenicity when administered in pure form.
From his decades of work searching to improve the effectiveness of DNA gene therapy, Dr. Joseph Weiner is considered “the Father of DNA Medicines.” In his role as the co-founder of Inovio Pharmaceuticals, he has been searching for a strategy by which DNA-based vaccines can achieve an improved rate of transfection without a deterioration in the excellent safety profile observed when such agents are administered in pure form.
Several strategies can be conceived to approach the challenge of enhancing DNA-plasmid transfection. One intriguing approach is being pursued in by the Anges /Osaka U. consortium. Their ongoing Covid-19 vaccine trial in humans employs the strategy of utilizing DNA plasmids coding for appropriate viral proteins. Their strategy to enhance drug effectiveness employs the addition of adjuvant to their antigen precursor.
While better results might be expected when DNA plasmid transfection is enhanced by adjuvant, this transfection enhancer is given parenterally and thus systemically.
A breakthrough localized, non-systemic transfection enhancement strategy was developed, to a great extent, by Dr. Weiner and his team at Inovio. It employs electroporation at the vaccine injection site. In their technique, although a dose of DNA plasmids would be delivered parenterally, and thus systemically, their non-pharmacological transfection enhancement system is non-systemic, being that it is confined to the injection site at the arm.
Electroporation was developed in the laboratory decades ago and has revolutionized transfection in tissue culture systems. Electroporation is achieved by exposing living cells to a pulsed electrical charge.Through trial and error scientists learned to tune the pulses so that target cells achieved sufficient disruption of cell wall integrity to allow for effective transfection, even at energy levels low enough that the transfected cells were able to reproduce.
Further investigation showed that the increase in cell wall permeability associated with exposure to short electric field pulses is related to the formation of nanoscale defects or pores in the cell membranes.
This is how electroporation got its name.
The abundance of electroporators on the market points to the continuing utility and popularity of this approach for in vitro applications.
The first demonstration of the use of electroporation to transfect DNA into tissues of living mice was published in 1991. Eventually, it was ascertained that two mechanisms contribute to transfection of DNA by electroporation:
a) transient permeabilization (pore formation) and
b) an electrophoretic effect on DNA, which would lead the polyanionic molecule to move toward or across the transiently destabilized membrane.
Trials studying the utility of electroporation to enhance vaccine transfection of DNA medications are currently underway in clinical trials in both China and the U.S., as well as pre-clinically in Scandinavia and Thailand.
While these studies imply serious international interest in the use of electroporation in DNA vaccine therapy, acceptance of the technique has not been universal. Of course slow approval and even disdain for therapeutic innovation is not unprecedented.
The recent description of electroporation as a “gimmick” in a New York Times article is reminiscent of the famous 1802 “cow pox” cartoon which satirized Jenner’s seminal breakthrough when he essentially created the field of vaccinology by developing the very first vaccine.
Jenner demonstrated that inoculation with the relatively mild cow pox virus conferred immunity against the deadly small pox virus. Vaccines got their name from the latin vacca for cow.
Currently anticipated is the release of Inovio’s ongoing COVID-19 vaccine trial report. The preliminary data of the Phase 1 trial were encouraging but scant. While the report is complete and submitted to a prestigious journal, we hear no prediction of its release date. (Some journals take eight weeks to publish submissions).
What seems likely from Inovio’s preliminary report is that a robust elaboration of cell mediated immunity may be expected with strong immunogenicity demonstrated broadly in the group over all. Even if elaboration of humoral (i.e. antibody-mediated) immunity lags other candidates, the safety advantages associated with the Inovio product would provide a role for INO-4800 in multimodal strategies, as described below.
At least one health care expert, former FDA Deputy Commissioner, has opined that the difference in the COVID-19 race is that the winner is not the first to cross the line.
Everyone who crosses the line is a winner.
Although Dr. Gottlieb now delivers nearly daily reports regarding Covid-19 vaccine development on CNBC’s Squawk Box, he has adroitly avoided discussion of DNA vaccines.
The differences in the approach pursued by Inovio compared with alternative efforts may be usefully considered when the promising strategy of multi-modal vaccine therapy is contemplated.
If these vaccines turn out to be inadequate, one option is to combine them..."
