Another commonly used adjuvant in veterinary and human vaccines is the yellow powder produced from a tree native to South America, specifically in Chile. They are extensively used as a foaming agent in root beer, slurpees, swine food, and vaccines. Also known as the soapbark tree, Quillaja Saponaria is the source of material for some saponins.
The discovery of vaccine adjuvants dates to a French veterinarian named Gaston Ramon in the 1920s. His discovery showed that co-administration of his newly invented diphtheria toxoid and other compounds such as tapioca, lecithin, agar, starch oil, Saponin, or breadcrumbs increased antitoxin responses. Following the adjuvant research, British researchers tested aluminum salts, and many others used “something” to help the immune system produce more antibodies after vaccination.
Not every vaccine needs an adjuvant, especially veterinary vaccines, since they are often not purified and contain “impurities” that help the immune system to increase its immune response. For example, clostridium vaccines for cattle sometimes have more than 6 to 7 toxins and whole-cell bacteria combined with aluminum hydroxide or Alumen in their formulation, making them very immunogenic.
The most potent saponin fraction currently available is QS 21, which is known to be more immunogenic than QS7, QS17, and QS18. However, the immunogenic fraction is obtained from the tree Quillaja extract using biomass. In our experience, some companies use food-grade Saponin without purification in some vaccines, containing approximately 10 to 30% of QS-21, and other companies purify themselves to reduce costs.
The use of Saponin in some vaccines can help boost the immune system and reduce the quantity of antigen needed per dose of the vaccine; in our experience, Saponin is associated with a reduced variability of the immune response.
Often, I have seen manufacturers use high quantities of Saponin (with or without purification), hoping you will still have a robust immune response even with a poorly immunogenic antigen; however, this is an incorrect assumption.
Recently, Saponin has been a significant issue due to the sustainability of its production. With the recent pandemic, companies rushed to purchase Saponin for human vaccines, leaving a gap in the veterinary vaccine market; however, in Chile, there is a call for sustainable extraction of Saponin, which many researchers call ECOSAPONIN.
For years now, several universities and companies have been trying to synthesize Saponin in the laboratory, cultivate it on a large scale, and or find different sources for the adjuvant, especially in the potential of its use for COVID vaccines; however, to our knowledge, we were still looking for a commercially suitable replacement for such raw material.
The research is advanced, and we will soon be able to synthesize and produce not only the QS-21 fraction but also the complete Saponin on a large scale.
It’s uncertain whether this synthetic compound will be affordable for veterinary vaccines; however, sustainable alternatives must be found for such an important raw material.
