Mechanism of bio-macromolecule denaturation on solid-liquid surface of ion-exchange chromatographic media - A case study for inactivated foot-and-mouth disease virus

Highly pure measles virus generated by combination of salt-active nuclease treatment and heparin affinity chromatography

Highly purified virus preparations are essential for accurate activity and potency determination. This requires simple and efficient purification methods, especially in the early stages of research and development. While heparin affinity chromatography has been already successfully used for the purification of several enveloped viruses and virus-like particles, we extended its use to purification of very sensitive measles virus. The performance of heparin and heparin-like affinity chromatography was evaluated for the purification of recombinant measles virus, a large and labile enveloped virus used as vaccine or cancer therapy. Since DNA, particularly in the form of chromatin is a critical impurity in enveloped virus preparations, the effect of integration of an endonuclease (Benzonase® or M-SAN) treatment prior to chromatography was also investigated. Both, Capto™ DeVirS (heparin-like) and Capto™ Heparin were able to capture measles viruses directly from clarified cell culture supernatant. Despite capturing 100 % of infectious measles virus, low recovery (8 %) was observed for Capto™ DeVirS. For Capto™ Heparin recoveries up to 85 % were observed. The combination of M-SAN with Capto™ Heparin enabled the production of highly purified measles virus with a yield of 62 % and a final purity of 10.2 ng dsDNA per dose (1 × 105), outperforming the processes without endonuclease treatment with a yield of 18 %, and a purity of 66.7 ng dsDNA/dose or using Benzonase® with a yield of 38 % and a purity of 21.2 ng dsDNA/dose. As the developed method is simple and scalable it could also be integrated in a downstream process train for measles virus manufacturing.

Adeno-associated viral capsid stability on anion exchange chromatography column and its impact on empty and full capsid separation

Recombinant adeno-associated viral vector (rAAV) mediated gene therapy is gaining traction in treating genetic disorders. Current rAAV production systems yield a mixture of capsids largely devoid of the transgene (empty capsid) compared with the desired therapeutic product (full capsid). Anion exchange chromatography (AEX) is an attractive method for separating empty and full AAV capsids because of its scalability. Resin types and buffer composition are key considerations for AEX and must support capsid stability to be suitable for downstream processing. We examined the impact of binding durations (0-8 h) using various binding ionic strengths (15-75 mM), pH (7.5-9.0), resin chemistry (POROS XQ, POROS HQ, POROS I, and BIA QA monolith), and proprietary Q resins with different ligand densities for effects on capsid stability. Empty capsids were altered upon extended binding, leading to retention time shifts and loss of resolution between empty and full capsids. Viral capsid protein analysis reveals that full capsids have more viral capsid protein 3 (VP3) proteins than empty capsids. Analytical hydrophilic liquid chromatography showed that empty capsid retention time shift is accompanied by changes to the empty capsid's native VP3 protein. Among the potential stabilizing additives considered, magnesium chloride was the most effective at reducing negative impacts caused by extended binding.

The SARS-CoV-2 Hydra, a tiny monster from the 21st century: Thermodynamics of the BA.5.2 and BF.7 variants

SARS-CoV-2 resembles the ancient mythical creature Hydra. Just like with the Hydra, when one head is cut, it is followed by appearance of two more heads, suppression of one SARS-CoV-2 variant causes appearance of newer variants. Unlike Hydra that grows identical heads, newer SARS-CoV-2 variants are usually more infective, which can be observed as time evolution of the virus at hand, which occurs through acquisition of mutations during time. The appearance of new variants is followed by appearance of new COVID-19 pandemic waves. With the appearance of new pandemic waves and determining of sequences, in the scientific community and general public the question is always raised of whether the new variant will be more virulent and more pathogenic. The two variants characterized in this paper, BA.5.2 and BF.7, have caused a pandemic wave during the late 2022. This paper gives full chemical and thermodynamic characterization of the BA.5.2 and BF.7 variants of SARS-CoV-2. Having in mind that Gibbs energy of binding and biosynthesis represent the driving forces for the viral life cycle, based on the calculated thermodynamic properties we can conclude that the newer variants are more infective than earlier ones, but that their pathogenicity has not changed.

Biothermodynamics of Viruses from Absolute Zero (1950) to Virothermodynamics (2022)

Biothermodynamics of viruses is among the youngest but most rapidly developing scientific disciplines. During the COVID-19 pandemic, it closely followed the results published by molecular biologists. Empirical formulas were published for 50 viruses and thermodynamic properties for multiple viruses and virus variants, including all variants of concern of SARS-CoV-2, SARS-CoV, MERS-CoV, Ebola virus, Vaccinia and Monkeypox virus. A review of the development of biothermodynamics of viruses during the last several decades and intense development during the last 3 years is described in this paper.

On-line separation and quantification of virus antigens of different serotypes in multivalent vaccines by capillary zone electrophoresis: A case study for quality control of foot-and-mouth disease virus vaccines

Accurate quantification of effective antigens of different serotypes is crucial for quality control of multivalent vaccines but challenging. A simple and rapid capillary zone electrophoresis (CZE) method was developed for on-line separation and quantification of foot-and-mouth disease virus (FMDV) antigens in monovalent and bivalent FMDV vaccines. The FMDV peak identity in CZE was demonstrated by the study of FMDV dissociation combined with high performance size exclusion chromatography (HPSEC) analysis. After optimizing CZE conditions including UV detecting wavelength, injection volume, and separation voltage, both serotype A and O FMDV showed good reproducibility (RSD <5%) and linear responses (R²=0.999) between the peak area and FMDV content in the concentration range of 15-400 μg/mL. The two serotypes of FMDV with similar size had different migration time in CZE according to their different zeta potential, which allows them to be separated and quantified, with accuracy of <10% relative error. CZE was then successfully applied for antigen quantification of commercial O monovalent and A/O bivalent FMDV vaccines. Compared with HPSEC, CZE was not only able to quantify each serotype of FMDV, but also free from interference of nucleic acids impurities. In summary, the CZE can be a simple, rapid, and reliable tool for quality control of monovalent and bivalent FMDV vaccines. The CZE method can also be further extended to the quality control of other multivalent virus and virus like particle vaccines.

Characterization and stabilization in process development and product formulation for super large proteinaceous particles

Super large proteinaceous particles (SLPPs) such as virus, virus like particles, and extracellular vesicles have successful and promising applications in vaccination, gene therapy, and cancer treatment. The unstable nature, the complex particulate structure and composition are challenges for their manufacturing and applications. Rational design of the processing should be built on the basis of fully understanding the characteristics of these bio-particles. This review highlights useful analytical techniques for characterization and stabilization of SLPPs in the process development and product formulations, including high performance size exclusion chromatography, multi-angle laser light scattering, asymmetrical flow field-flow fractionation, nanoparticle tracking analysis, CZE, differential scanning calorimetry, differential scanning fluorescence, isothermal titration calorimetry , and dual polarization interferometry. These advanced analytical techniques will be helpful in obtaining deep insight into the mechanism related to denaturation of SLPPs, and more importantly, in seeking solutions to preserve their biological functions against deactivation or denaturation. Combination of different physicochemical techniques, and correlation with in vitro or in vivo biological activity analyses, are considered to be the future trend of development in order to guarantee a high quality, safety, and efficacy of SLPPs.

A Novel Particulate Delivery System Based on Antigen-Zn2+ Coordination Interactions Enhances Stability and Cellular Immune Response of Inactivated Foot and Mouth Disease Virus

The interactions between antigen and adjuvant were among the most significant factors influencing the immunogenicity of vaccines, especially for unstable antigens like inactivated foot and mouth disease virus (iFMDV). Here we propose a novel antigen delivery pattern based on the coordination interaction between transition metal ions Zn²⁺ chelated to chitosan nanoparticles and iFMDV, which is known to be rich in histidine. The zinc chelated chitosan particles (CP-PEI-Zn) were prepared by cross-linking chitosan particles (CP) with sodium tripolyphosphate (TPP), modifying with metal chelator polyethylenimine (PEI), and subsequent chelating of Zn²⁺. The coordination interaction was confirmed by analyzing the adsorption and desorption behavior of iFMDV on CP-PEI-Zn by high-performance size exclusion chromatography (HPSEC), while the CP-PEI without chelating Zn²⁺ loads iFMDV mainly through electrostatic interactions. The iFMDV loaded on CP-PEI-Zn showed better thermal stability than that on CP-PEI, as revealed by a slightly higher transition temperature (T_m) related to iFMDV dissociation. After subcutaneous immunization in female Balb/C mice, antigens loaded on CP-PEI and CP-PEI-Zn all induced higher specific antibody titers, better activation of B lymphocytes, and more effector-memory T cells proliferation than the free antigen and iFMDV adjuvanted with ISA 206 emulsion did. Moreover, CP-PEI-Zn showed superior efficacy to CP-PEI in promoting the proliferation of effector-memory T cells and secretion of cytokines, indicating a more potent cellular immune response. In summary, the CP-PEI-Zn stabilized the iFMDV after loading and promoted both humoral and cellular immune responses, thus reflecting its potential to be a promising adjuvant for the iFMDV vaccine and other unstable viral antigens.