Lyophilized yeast powder for adjuvant free thermostable vaccine delivery

Abstract

Thermolabile nature of commercially available vaccines necessitates their storage, transportation, and dissemination under refrigerated condition. Maintenance of continuous cold chain at every step increases the final cost of vaccines. Any breach in the cold chain even for a short duration results in the need to discard the vaccines. As a result, there is a pressing need for the development of thermostable vaccines. In this proof-of-concept study, we showed that E. coli curli-green fluorescent fusion protein remains stable in freeze-dried yeast powder for more than 18 and 12 months when stored at 30 °C and 37 °C respectively. Stability of the heterologous protein remains unaffected during the process of heat-inactivation and lyophilization. The mass of lyophilized yeast powder remains almost unchanged during the entire period of storage and expressed protein remains intact even after two cycles of freeze and thaws. The protease-deficient strain appears ideal for the development of whole recombinant yeast-based vaccines. The cellular abundance of expressed antigen in dry powder after a year was comparable to freshly lyophilized cells. Scanning electron microscopy showed the intact nature of cells in powdered form even after a year of storage at 30 °C. Observation made in this study showed that freeze-dry yeast powder can play a vital role in the development of thermostable vaccines. Key Points • Yeast-based vaccines can overcome problem of cold chain associated with conventional vaccines • Lyophilized yeast powder can be a simple way for long-term storage of immunogen(s) • Protease deficient strain is important for whole recombinant yeast-based vaccines

Yeast-Based Screening of Anti-Viral Molecules

“…Despite this, almost all the commercially available vaccines, including recently introduced mRNA vaccines against coronavirus infection, have several issues, including their thermolabile nature [ 39 , 40 ]. Different issues associated with presently available vaccines and different ways to tackle them are discussed elsewhere [ 39 , 41 , 42 , 43 , 44 ]. Although their thermolabile nature and the strict requirement of following the cold chain (the need to store and transport vaccines either frozen or at 4 °C) are of concern, frequent mutations in the surface immunogenic proteins further complicate the future of subunit vaccines.…”

Yeast-Based Virus-like Particles as an Emerging Platform for Vaccine Development and Delivery

“…A continuous cold chain is needed to maintain the efficacy or potency of vaccines. To tackle this, researchers are exploring further advancements to fix the problem associated with the thermolabile nature of vaccines and minimize the requirement of a cold chain, as discussed elsewhere [ 14 , 24 , 25 ].…”

“…In most of the studies using K. phaffii , the authors used the GS115 strain. However, using protease-deficient strains (for example, SMD1163) to minimize the degradation of an expressed protein is recommended [ 24 ]. Intracellular degradation of an expressed protein can affect the assembly and recovery of VLPs.…”

Enhancing TB Vaccine Efficacy: Current Progress on Vaccines, Adjuvants and Immunization Strategies

“…Thus, enhancing the thermal stability of mRNA vaccines is an urgent concern. Freeze-dried recombinant yeast vaccines, storable at room temperature, maintain vaccine antigenic capacity for up to one year [ 78 ]. Yeast cell walls contain substantial amounts of β-1,3-glucan and mannoprotein, which modulate the body’s inflammatory response and activate cytokines and steroids, promoting specific immune responses.…”