Virus inactivation at moderately low pH varies with virus and buffer properties

Exploring the effects of excipients on complex coacervation

Complex coacervation is an associative liquid-liquid phase separation phenomenon that takes place due to the electrostatic complexation of oppositely-charged polyelectrolytes and the entropic gains associated with the release of bound counterions and rearrangement of solvent. The aqueous nature of coacervation has resulted in its broad use in systems requiring high biocompatibility. The significance of electrostatic interactions in coacervates has meant that studies investigating the phase behaviors of these systems have tended to focus on parameters such as the charge stoichiometry of the polyions, the solution pH, and the ionic strength. However, the equilibrium that exists between the polymer-rich coacervate phase and the polymer-poor supernatant phase represents a balance among attractive electrostatic interactions and excluded volume repulsions as well as osmotic pressure effects. As such, we hypothesize that it should be possible to tune coacervate phase behavior via the addition of non-electrostatic excipients which would partition between the two phases and potentially alter both the solvent quality and the osmotic pressure balance. In particular, our work focuses on small molecule excipients such as sugars, amino acids, and other additives that have a history of use in vaccine formulation. We quantified the ability of these excipients to partition into the coacervate phase, and their potential for destabilizing the phase separation. Furthermore, we demonstrate that these additives can be combined with complex coacervation in the context of a virus formulation.

Systematic Development of a Detergent Toolbox as an Alternative to Triton X-100

Detergents are routinely included in protein purification processes to inactivate enveloped viruses that may arise from adventitious or endogenous contamination. The detergent Triton X-100 (TX-100) has been widely used as part of the production process for therapeutic proteins. However, recent ecological studies indicate that TX-100 and its metabolites detrimentally impact aquatic organisms, thus alternative detergents for viral inactivation are required. The overall aim of this study was to identify one or more detergents that are a suitable replacement for TX-100 in the viral inactivation step. In stage one, 16 potential alternatives were identified and screened against TX-100 using multiple criteria such as solubility, feasibility of virus inactivation, critical micelle concentration, and storage conditions. The multi-criteria decision analysis (MCDA) methodology was used to identify four candidates for the second stage assessment. In stage two, a detailed evaluation was undertaken and two candidates C16-AO, and C11/15-sEO9, were found to be practical alternatives to TX-100 for use in protein therapeutic production processes for inactivating enveloped viruses. In addition, C13-EO8 demonstrated good viral inactivation capability and warrants further investigation in detergent clearance and impact on product quality.

Impact of Eco-Friendly Surfactant Structure and Class on Enveloped Virus Inactivation

BACKGROUND

Sustainable and effective strategies for virus inactivation are crucial for ensuring the safety and quality of biological products. The European Union's (EU) 2021 ban on Triton X-100 for viral inactivation in biomanufacturing has pushed the field to find sustainable alternatives with equal effectiveness. We aim to increase the sustainability of biopharmaceutical production by ensuring the effectiveness of eco-friendly surfactant-mediated virus inactivation by comparing the antiviral efficacy of Triton X-100 to glucosides and amine oxides.

RESULTS

Surfactants were evaluated for antiviral efficacy against herpes viruses, SuHV and HSV, and the retrovirus XMuLV. The surfactants demonstrated equivalent or superior inactivation efficacy compared to Triton X-100. Herpes viruses were inactivated similarly with all surfactants. For XMuLV, surfactants with longer alkyl chains achieved maximum log reduction values (LRV) at 1x CMC, outperforming Triton X-100, which required 2x CMC for comparable efficacy. Surfactants with bulky headgroups, such as LAPAO, showed lower efficacy against XMuLV. At a salt concentration of 2 M ionic strength, the antiviral efficacy of Triton X-100 and TDAO decreased for the herpes viruses. Variability in inactivation was observed among the surfactants at 0.5x CMC, indicating that surfactant characteristics influence their antiviral performance below CMC.

CONCLUSIONS

Adding salt enhanced the antiviral efficacy of surfactants by lowering their CMC while maintaining consistent virus inactivation. Among the surfactants tested, the glucoside with a longer tail, n-nonyl-β-D-glucoside (NG), emerged as the most robust and could function as an eco-friendly surfactant for virus inactivation in bioprocessing. For NG, virus inactivation was independent of all variables tested.

Environmental Stability and Transmissibility of Enveloped Viruses at Varied Animate and Inanimate Interfaces

Enveloped viruses have been the leading causative agents of viral epidemics in the past decade, including the ongoing coronavirus disease 2019 outbreak. In epidemics caused by enveloped viruses, direct contact is a common route of infection, while indirect transmissions through the environment also contribute to the spread of the disease, although their significance remains controversial. Bridging the knowledge gap regarding the influence of interfacial interactions on the persistence of enveloped viruses in the environment reveals the transmission mechanisms when the virus undergoes mutations and prevents excessive disinfection during viral epidemics. Herein, from the perspective of the driving force, partition efficiency, and viral survivability at interfaces, we summarize the viral and environmental characteristics that affect the environmental transmission of viruses. We expect to provide insights for virus detection, environmental surveillance, and disinfection to limit the spread of severe acute respiratory syndrome coronavirus 2.

Study of Oncolytic Virus Preservation and Formulation

In recent years, oncolytic viruses (OVs) have emerged as an effective means of treating cancer. OVs have multiple oncotherapeutic functions including specifically infecting and lysing tumor cells, initiating immune cell death, attacking and destroying tumor angiogenesis and triggering a broad bystander effect. Oncolytic viruses have been used in clinical trials and clinical treatment as drugs for cancer therapy, and as a result, oncolytic viruses are required to have long-term storage stability for clinical use. In the clinical application of oncolytic viruses, formulation design plays a decisive role in the stability of the virus. Therefore, this paper reviews the degradation factors and their degradation mechanisms (pH, thermal stress, freeze-thaw damage, surface adsorption, oxidation, etc.) faced by oncolytic viruses during storage, and it discusses how to rationally add excipients for the degradation mechanisms to achieve the purpose of maintaining the long-term stability of oncolytic viral activity. Finally, the formulation strategies for the long-term formulation stability of oncolytic viruses are discussed in terms of buffers, permeation agents, cryoprotectants, surfactants, free radical scavengers, and bulking agent based on virus degradation mechanisms.

Virucidal N95 Respirator Face Masks via Ultrathin Surface-Grafted Quaternary Ammonium Polymer Coatings

N95 respirator face masks serve as effective physical barriers against airborne virus transmission, especially in a hospital setting. However, conventional filtration materials, such as nonwoven polypropylene fibers, have no inherent virucidal activity, and thus, the risk of surface contamination increases with wear time. The ability of face masks to protect against infection can be likely improved by incorporating components that deactivate viruses on contact. We present a facile method for covalently attaching antiviral quaternary ammonium polymers to the fiber surfaces of nonwoven polypropylene fabrics that are commonly used as filtration materials in N95 respirators via ultraviolet (UV)-initiated grafting of biocidal agents. Here, C₁₂-quaternized benzophenone is simultaneously polymerized and grafted onto melt-blown or spunbond polypropylene fabric using 254 nm UV light. This grafting method generated ultrathin polymer coatings which imparted a permanent cationic charge without grossly changing fiber morphology or air resistance across the filter. For melt-blown polypropylene, which comprises the active filtration layer of N95 respirator masks, filtration efficiency was negatively impacted from 72.5 to 51.3% for uncoated and coated single-ply samples, respectively. Similarly, directly applying the antiviral polymer to full N95 masks decreased the filtration efficiency from 90.4 to 79.8%. This effect was due to the exposure of melt-blown polypropylene to organic solvents used in the coating process. However, N95-level filtration efficiency could be achieved by wearing coated spunbond polypropylene over an N95 mask or by fabricating N95 masks with coated spunbond as the exterior layer. Coated materials demonstrated broad-spectrum antimicrobial activity against several lipid-enveloped viruses, as well as Staphylococcus aureus and Escherichia coli bacteria. For example, a 4.3-log reduction in infectious MHV-A59 virus and a 3.3-log reduction in infectious SuHV-1 virus after contact with coated filters were observed, although the level of viral deactivation varied significantly depending on the virus strain and protocol for assaying infectivity.