The squalene molecule is widely used in the personal care and cosmetics industries and is increasingly included as an immunological adjuvant in vaccines. Currently, the majority of the world’s supply of this highly demanded product comes from the livers of deep-sea sharks. However, squalene is rare and more sustainable alternative sources are desperately needed to meet demand and protect shark populations.
Two companies passionate about improving this situation – Synshark and Phylloceuticals – recently entered into a strategic partnership to produce pharmaceutical squalene from plants. Through this partnership, the two companies will develop manufacturing processes for the production of squalene by Lemna sp. (duckweed) and Nicotiana benthamiana (N. benthamiana), a small Australian ornamental plant.
Technology networks spoke with Jason Ornstein, Executive Director of SynShark, and Barry Holtz, PhD, Chief Scientific Officer of Phylloceuticals, to learn more about the collaboration and how it could help address current challenges associated with supply and access to squalene.
Anna MacDonald (AM): Can you give us an overview of what squalene is and the role it plays in vaccines?
Jason Ornstein (JO): Squalene is a molecule present in most living organisms but in trace amounts. It is a long chain hydrocarbon that is created in the human liver and transferred through our bloodstream to our skin where it plays a role in our natural protection against the sun’s ultraviolet rays. As an antioxidant, it also helps humans protect against pollutants on the skin. Industrially, it is used as an emollient in personal care products because it is colorless and odorless. Unfortunately, the most abundant source of industrial squalene is the liver of deep-sea sharks.
A squalene vaccine adjuvant is delivered as nanodroplets emulsified by a phospholipid or non-ionic surfactant by injection, which increases cellular uptake of the antigen into the vaccine. Once present, squalene recruits immune cells to the site, transporting the antigen into the lymphatic system and eliciting an aggressive response. It is the “why” of the immune system’s response to squalene that remains unknown. Although there are other adjuvants, squalene is the only perfectly biocompatible adjuvant ingredient.
AM: What are the current challenges associated with sourcing and accessing squalene? Are there initiatives in place to address these issues? Can you tell us more about the use of plants to produce squalene?
OJ: Most of the volume of industrial squalene comes from shark livers. While many personal care consumers are unaware of this, environmentalists have raised awareness and many cosmetic companies have sought alternative sources. A natural source is the by-product of olive oil production. This is limited to the total harvest of each year. To qualify for medical use regulated by the United States Food and Drug Administration (FDA) as an adjuvant, this source would require indoor olive growing, which is limited by the years required to develop an olive grove and the duration total harvest.
Another initiative is the new Amyris product of synthetic squalane (an oxidized version of squalene). Unfortunately, this compound lacks the bioactivity of squalene. Amyris offered its compounds for adjuvant use but was rejected by pharmaceutical companies. There is a desperate search for a new plant source of squalene that can be harvested indoors and quickly.
AM: Why were tobacco and duckweed species chosen for this initiative? Why are both transgenic and transient approaches being developed?
Barry Holtz (BH): Both species have inherent advantages in expressing certain types of heterologous proteins. Since both have nearly identical downstream purification steps, it is prudent to evaluate both species.
In general, it is customary to use the transgenic approach in Lemna sp. since the inherent genetic stability allows constant recycling of part of the biomass as inoculum in a continuous flow system. Typically, N.benthAmiana uses fast and stable transient system. Only five to seven days are needed to achieve maximum expression. However, for complex polygenic systems, part of the genetic information may be a permanent transformant and additional genetic input may be inserted as a transient construct.
AM: What are the advantages of manufacturing products like squalene in this way? Are there any challenges to overcome?
BH: The production of several products, in particular a lipid intermediate metabolite and a protein in the same plant by several directed organelles (MODa ) biosynthesis, represents huge upstream cost savings and high yield through low cost of goods.
We have developed a proprietary separation technique at the start of the process that separates discrete sub-cellular fractions so that multiple products can be concentrated and sent on their individual process paths.
AM: What about the regulations? How long could addiction to unsustainable sources of squalene become a thing of the past?
OJ: The product would be regulated by the FDA and with the experience of the Phylloceuticals team, plans are in place to develop the regulatory pathway. During the current pandemic, the FDA has actively prioritized vaccine tools such as this one that could increase the potency of SARS-CoV-2 vaccines. It is well known that the European Union is considering regulations against squalene from sharks.
Jason Ornstein and Dr. Barry Holtz were talking to Anna MacDonald, science writer for Technology Networks.
