Lyophilization to enable distribution of ChAdOx1 and ChAdOx2 adenovirus-vectored vaccines without refrigeration

Development of a thermal stabilizer formulation optimized by response surface methodology for Senecavirus A antigen

Numerous members of the family Picornaviridae, such as the Senecavirus A (SVA) and foot-and-mouth disease virus (FMDV), exhibit thermal instability, resulting in the dissociation of viral particles, which affects the insufficient potency of the vaccine. Based on this characteristic, this study aimed to maintain the thermal stability of SVA by supplementing it with a stabilizer. Excipients, such as sucrose, mannitol, sorbitol, polyethylene glycol (PEG), L-arginine (L-Arg), glutamic acid (Glu), polyvinyl pyrrolidone (PVP), bovine serum albumin (BSA), and potassium chloride (KCl) dissolved in Tris-HCl buffer solution, retained the infectivity of SVA in the thermostability assay. Thermal stability formulations were developed by combining different excipients in disaccharide polyol systems and optimizing formulations using the Box-Behnken experimental design (BBD) combined with response surface methodology (RSM). Three significant factors were studied: sucrose 9.9%, sorbitol 9.9%, and L-Arg 0.06 mol/L against virus titer of thermal-resistance of SVA as a response. The formulation improved the stability of SVA, whose viral infectivity titer decreased by 101.0 TCID50/mL at 4°C, 25°C, and 37°C, respectively, until it decreased by 101.21 TCID50/mL at 7 d of incubation at 42°C. The combinational thermal stabilizer generated in this study enabled the stabilization of the SVA, which might contribute to storage and transportation when the cold chain is unavailable, especially in rural areas. Therefore, the thermal stabilizer is an efficient candidate stabilizer for picornavirus formulations, which keep picornavirus infectivity at various temperatures. Further optimization of this approach will provide new opportunities for the generation of stabilizer formulation from different stabilizers.

A lyophilised formulation of chimpanzee adenovirus vector for long-term stability outside the deep-freeze cold chain

BACKGROUND

The adenovirus-vaccine platform has come to prominence with the COVID-19 vaccination campaigns. The objective of this study was to validate a formulation that was suitable for lyophilisation and long-term storage at 5 (2-8) °C.

METHODS

Vaccine stability was assessed up to five years at 5 °C using a lyophilised formulation of the chimpanzee-adenovirus vector ChAd155 encoding a respiratory syncytial virus (RSV) antigen. Vaccine potency was assessed by functional infectivity assay. Other assessments of vaccine stability included those for capsid integrity, particle content, and DNA release. Vaccine efficacy and safety were assessed after two years in a murine model of RSV challenge and a rabbit toxicology model, respectively.

RESULTS

Here, we show that the potency loss from lyophilisation was 0.12 log10. The potency loss over five years at 5 °C was estimated at 0.21 log10 (95%CI 0.10-0.30). This coincides with a 25% increase in the ratio of non-infectious particles/infectious particles. After two years of storage at 5 °C, (i) the loss of infectivity was 0.17 log10; (ii) the vaccine remained immunogenic and effective at clearing RSV from the lungs in a mouse-challenge model; and (iii) the vaccine was not associated with any adverse safety signal in a rabbit toxicology model.

CONCLUSIONS

The 5-year stability of the lyophilised adenovirus-vector vaccine is within our acceptable limit ( < 0.3 log10 decrease). Its formulation process is amenable to manufacturing scale-up and should help in providing adenovirus-based vaccines where the cold chain is problematic, such as in low-income countries, and in pre-epidemic stockpiling.

Challenges and strategies in the soluble expression of CTA1-(S14P5)4-DD and CTA1-(S21P2)4-DD fusion proteins as candidates for COVID-19 intranasal vaccines

Developing intranasal vaccines against pandemics and devastating airborne infectious diseases is imperative. The superiority of intranasal vaccines over injectable systemic vaccines is evident, but developing effective intranasal vaccines presents significant challenges. Fusing a protein antigen with the catalytic domain of cholera toxin (CTA1) and the two-domain D of staphylococcal protein A (DD) has significant potential for intranasal vaccines. In this study, we constructed two fusion proteins containing CTA1, tandem repeat linear epitopes of the SARS-CoV-2 spike protein (S14P5 or S21P2), and DD. Structural predictions indicated that each component of the fusion proteins was compatible with its origin. In silico analyses predicted high solubility for both fusion proteins when overexpressed in Escherichia coli. However, contrary to these predictions, the constructs exhibited limited solubility. Lowering the cultivation temperature from 37°C to 18°C did not improve solubility. Inducing expression with IPTG at the early log phase significantly increased soluble CTA1-(S21P2)4-DD but not CTA1-(S14P5)4-DD. Adding non-denaturing detergents (Nonidet P40, Triton X100, or Tween 20) to the extraction buffer significantly enhanced solubility. Despite this, purification experiments yielded low amounts, only 1-2 mg/L of culture, due to substantial losses during the purification stages. These findings highlight the challenges and potential strategies for optimizing soluble expression of CTA1-DD fusion proteins for intranasal vaccines.

Nucleic Acid Delivery Nanotechnologies for In Vivo Cell Programming

In medicine, it is desirable for clinicians to be able to restore function and imbue novel function into selected cells for therapy and disease prevention. Cells damaged by disease, injury, or aging could be programmed to restore normal or lost functions, such as retinal cells in inherited blindness and neuronal cells in Alzheimer's disease. Cells could also be genetically programmed with novel functions such as immune cells expressing synthetic chimeric antigen receptors for immunotherapy. Furthermore, knockdown or modification of risk factor proteins can mitigate disease development. Currently, nucleic acids are emerging as a versatile and potent therapeutic modality for achieving this cellular programming. In this review, we highlight the latest developments in nanobiomaterials-based nucleic acid therapeutics for cellular programming from a biomaterial design and delivery perspective and how to overcome barriers to their clinical translation to benefit patients.

Clinical and Preclinical Methods of Heat-Stabilization of Human Vaccines

Vaccines have historically faced challenges regarding stability, especially in regions lacking a robust cold chain infrastructure. This review delves into established and emergent techniques to improve the thermostability of vaccines. We discuss the widely practiced lyophilization method, effectively transforming liquid vaccine formulations into a solid powdered state, enhancing storage and transportation ability. However, potential protein denaturation during lyophilization necessitates alternative stabilization methods. Cryoprotectants, namely, starch and sugar molecules, have shown promise in protecting vaccine antigens and adjuvants from denaturation and augmenting the stability of biologics during freeze-drying. Biomineralization, a less studied yet innovative approach, utilizes inorganic or organic-inorganic hybrids to encapsulate biological components of vaccines with a particular emphasis on metal-organic coordination polymers. Encapsulation in organic matrices to form particles or microneedles have also been studied in the context of vaccine thermostability, showing some ability to store outside the cold-chain. Unfortunately, few of these techniques have advanced to clinical trials that evaluate differences in storage conditions. Nonetheless, early trials suggest that alternative storage techniques are viable and emphasize the need for more comprehensive studies. This review underscores the pressing need for heat-stable vaccines, especially in light of the increasing global distribution challenges. Combining traditional methods with novel approaches holds promise for the future adaptability of vaccine distribution and use.

Pre-Clinical Development of an Adenovirus Vector Based RSV and Shingles Vaccine Candidate

Respiratory syncytial virus (RSV) infection and shingles are two viral diseases that affect older adults, and a combined vaccine to protect against both could be beneficial. RSV infection causes hospitalisations and significant morbidity in both children and adults and can be fatal in the elderly. The RSV fusion (F) envelope glycoprotein induces a strong RSV-neutralising antibody response and is the target of protective immunity in the first RSV vaccine for older adults, recently approved by the FDA. An initial childhood infection with the varicella zoster virus (VZV) results in chickenpox disease, but reactivation in older adults can cause shingles. This reactivation in sensory and autonomic neurons is characterized by a skin-blistering rash that can be accompanied by prolonged pain. The approved protein-in-adjuvant shingles vaccine induces VZV glycoprotein E (gE)-fspecific antibody and CD4+ T cell responses and is highly effective. Here we report the evaluation of RSV/shingles combination vaccine candidates based on non-replicating chimpanzee adenovirus (ChAd) vectors. We confirmed the cellular and humoral immunogenicity of the vaccine vectors in mice using T cell and antibody assays. We also carried out an RSV challenge study in cotton rats which demonstrated protective efficacy following a homologous prime-boost regimen with our preferred vaccine candidate.