Lyophilized yeast powder for adjuvant free thermostable vaccine delivery

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 vaccine. 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-GFP fusion protein remains stable in freeze-dried yeast powder for more than a 13 and 6 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. 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. SEM 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.

Effect of Extended Transit and Temperature Variations on EID50 Values of Thermostable NDVI-2 Vaccines

Temperature alterations due to poor cold keeping condition have consistently posed a challenge to vaccines dose EID50 titre value. The sensitivity of Newcastle disease vaccine to temperature variations due to poor cold storage condition in rural settings, led to the development of the NDVI-2 thermostable vaccine, which is known to exhibit a thermostability of 3 hours at 56 °C. In this study, three Newcastle disease vaccines (NDVI-2) with EID50 titre per dose values of log10 EID50 7.7, 7.6 and 6.75 respectively from vaccine production facility at the National Veterinary Research Institute (NVRI), Vom Nigeria, were sent for certification at African Union laboratory at Debre Zeit, Ethiopia under cold condition; using ice packs for cold chain maintenance. Tracking of the vaccine in the course of freight to the certifying laboratory revealed changes in the original transit route by the airline and delay by custom at the receiving country port. Thus, a 12 hours transit freight was delayed for over 7 days before arrival at the certifying laboratory. Though, the EID50 titre per dose values of these vaccines were originally well above recommended EID50 5.5 per dose value by log 2.2, log 2.1 and log 1.25 for NDVI-2 respectively. Comparing these vaccines EID50 values obtained from the certifying laboratory in relation to values initially obtained by the Quality Control Division of the producing Institute (NVRI), revealed loss of EID50 titre per dose value by log101.2, and log10 0.8 among two of the certified vaccine batches; with one of the certified vaccines retaining its original EID50 titre per dose value. This result attest that NDVI-2 thermostable vaccine produced at NVRI, Vom Nigeria are robust and of high quality. Thus, the findings of this study have further demonstrated that temperature variations, prolonged vaccine transportation under poor cold chain can affect the EID50 per dose value of a wholesome, field fit vaccine irrespective of the vaccine thermostability.

A self-aggregating peptide: Implications for the development of thermostable vaccine candidates

Background: The use of biomaterials has been expanded to improve the characteristics of vaccines. Recently we have identified that the peptide PH(1-110) from polyhedrin self-aggregates and incorporates foreign proteins to form particles. We have proposed that this peptide can be used as an antigen carrying system for vaccines. However, the immune response generated by the antigen fused to the peptide has not been fully characterized. In addition, the adjuvant effect and thermostability of the particles has not been evaluated. Results: In the present study we demonstrate the use of a system developed to generate nano and microparticles carrying as a fusion protein peptides or proteins of interest to be used as vaccines. These particles are purified easily by centrifugation. Immunization of animals with the particles in the absence of adjuvant result in a robust and long-lasting immune response. Proteins contained inside the particles are maintained for over one year at ambient temperature, preserving their immunological properties. Conclusion: The rapid and efficient production of the particles in addition to the robust immune response they generate position this system as an excellent method for the rapid response against emerging diseases. The thermostability conferred by the particle system facilitates the distribution of the vaccines in developing countries or areas with no electricity.

Thermostable Vaccines: Past, Present and Future Perspectives

Vaccines stability has a major role in the success of immunization programs and saves millions of livesevery year. To stabilize vaccines cold chains are developed for storage and transport, as efficiency ofvaccines is hampered if they are not kept under proper temperature. Aluminum is used for making vaccinethermostable. The development of vaccine formulation is a critical part of overall development cycle ofapproving, testing and producing new vaccines. However, Liquid vaccine formulation is still preferred overdry formulation because of ease in using, packaging and manufacturing. Other approaches have beenused to make vaccine thermostable. This study demonstrates those processes, used to develop thermosensitivevaccines into thermostable vaccine and also describes vaccine formulation designing and useof heat shock protein including mHSP70 and mHSP65 to generate innate and adaptive immune response.

Phosphoprotein Contributes to the Thermostability of Newcastle Disease Virus

Newcastle disease (ND), caused by Newcastle disease virus (NDV), is highly contagious and represents a major threat to the poultry industry. The thermostable vaccines are not insensitive to heat and ease of storage and transportation, but the mechanism of NDV thermostability remains unknown. The phosphoprotein (P), fusion protein (F), hemagglutinin-neuraminidase protein (HN), and large polymerase protein (L) are associated with NDV virulence. The association between F, HN, or L and viral thermostability has been, respectively, studied in different reports. However, the effects of P on NDV thermostability have not been demonstrated. Here, we utilized an existing reverse genetics system in our laboratory, to generate chimeric viruses by exchanging the P protein between the thermostable NDV4-C strain and the thermolabile LaSota strain. Chimeric viruses were found to possess similar growth properties, passage stability, and virulence, as compared to those of these parental strains. Interestingly, the thermostability of the chimera with P derived from the thermolabile LaSota strain was reduced compared to that of the parental virus, and P of the thermostable NDV4-C strain enhanced chimeric virus thermostability. Our data demonstrate that P is an important factor for the thermostability of NDV and provides information regarding the molecular mechanism of NDV thermostability; moreover, these results suggest a theoretical basis for using the NDV4-C strain as a thermostable vaccine.