Ensilicated tetanus antigen retains immunogenicity: in vivo study and time-resolved SAXS characterization

Abstract

our recently developed ensilication approach can physically stabilize proteins in silica without use of a pre-formed particle matrix. Stabilisation is done by tailor fitting individual proteins with a silica coat using a modified sol-gel process. Biopharmaceuticals, e.g. liquid-formulated vaccines with adjuvants, frequently have poor thermal stability; heating and/or freezing impairs their potency. As a result, there is an increase in the prevalence of vaccine-preventable diseases in low-income countries even when there are means to combat them. one of the root causes lies in the problematic vaccine 'cold chain' distribution. We believe that ensilication can improve vaccine availability by enabling transportation without refrigeration. Here, we show that ensilication stabilizes tetanus toxin c fragment (ttcf), a component of the tetanus toxoid present in the diphtheria, tetanus and pertussis (Dtp) vaccine. experimental in vivo immunization data show that the ensilicated material can be stored, transported at ambient temperatures, and even heat-treated without compromising the immunogenic properties of TTCF. To further our understanding of the ensilication process and its protective effect on proteins, we have also studied the formation of ttcf-silica nanoparticles via time-resolved Small Angle X-ray Scattering (SAXS). Our results reveal ensilication to be a staged diffusion-limited cluster aggregation (DLcA) type reaction. An early stage (tens of seconds) in which individual proteins are coated with silica is followed by a subsequent stage (several minutes) in which the protein-containing silica nanoparticles aggregate into larger clusters. our results suggest that we could utilize this technology for vaccines, therapeutics or other biopharmaceuticals that are not compatible with lyophilization. Biopharmaceuticals are biologically derived active compounds intended for therapeutic or diagnostic usage. Examples include monoclonal antibodies, vaccines, cells and blood components. Many of these are proteins and not stable ex vivo. They must be stabilised to increase their shelf-life. The main approach in stabilisation of biopharmaceuticals is regulating temperature. Maintaining low (2-8 °C) temperatures retains native states of these compounds. Many protein-based biopharmaceuticals are vulnerable not only to heating but also to freezing 1-3 , which can disrupt protein structure and lead to denaturation on thawing. Within cold chain transportation 1,2,4-7 , from manufacturing to endpoint destination, temperature control has proven challenging. Fluctuations in temperature, heating/freezing 1 , can affect biopharmaceuticals resulting in aggregation and protein unfolding, leading to loss of potency. This is a serious issue in global public health 8-10

Thermal resilience of ensilicated lysozyme via calorimetric and in vivo analysis

“…An earlier study into the mechanism of ensilication showed a diffusion limited (controlled) cluster aggregation (DLCA) type process. 10 This means the more silica added to the reaction, the faster the ensilication will occur because of the abundance of polymeric silica. 33,34 This was observed by FE-SEM (Fig.…”

“…6,7 Ultimately, this study aims to further support the future application of ensilication as a novel approach to biopharmaceutical stabilisation. [8][9][10] In order to remain biologically active, the majority of protein-based biopharmaceuticals must be stored and distributed between 2-8 C in what is referred to as the 'cold chain'. Changes in temperature outside this range lead to inactivation due to cold chain failures that can oen be observed in low-income countries.…”

Assembly of cellulose nanocrystals and clay nanoplatelets studied by time-resolved X-ray scattering

“…45 At volume fractions above 24.0%, the reduced SAXS data was fitted to a ''broad-peak'' function (Fig. 1d), see eqn (2): 46,47 IðqÞ…”

Human Vaccines & Immunotherapeutics: news

“…An ensilicated vaccine retained its immunogenicity after heat treatment or storage at room temperature for three years. 1 The technique uses silica coat to stabilize the tetanus toxoid protein in the diphtheria-tetanus-pertussis vaccine. The vaccine was immunogenic in mice after the vials were shipped within the UK by ordinary post and after heating to 100°C.…”