Acidification induces condensation of the adenovirus core

Impact of concentration, temperature and pH on the virucidal activity of alcohols against human adenovirus

BACKGROUND

Adenoviruses belong to the stable nonenveloped viruses playing an important role in healthcare-associated infections mainly causing respiratory infections and epidemic keratoconjunctivitis. Hand disinfection with alcoholic preparations is therefore one of the most important measures to prevent such viral infections in hospitals and other medical settings.

METHODS

The inactivation of adenovirus type 5 by ethanol, 1- and 2-propanol, and 2 commercially available hand disinfectants was examined at different concentrations, temperatures, and pH-values.

RESULTS

For ethanol and 1-propanol the maximum virus-inactivating properties after 30 seconds exposure were found at a concentration of 60%-70% and 50%-60%, respectively, whereas with 2-propanol no activity was observed. The virucidal activity of all alcohols and the 2 hand disinfectants examined was increased when raising the temperature from 20°C to 25°C. By increasing the pH value to 9, a strong improvement of the activity of ethanol, 1-propanol and 1 hand disinfectant was observed, whereas pH lowering resulted in decrease of activity.

CONCLUSIONS

These results demonstrate the importance of physical parameters in the inactivation of adenoviruses by alcohols and will help to improve measures to reduce adenovirus transmission in healthcare settings.

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.

Adenovirus core protein V reinforces the capsid and enhances genome release from disrupted particles

Out of the three core proteins in human adenovirus, protein V is believed to connect the inner capsid surface to the outer genome layer. Here, we explored mechanical properties and in vitro disassembly of particles lacking protein V (Ad5-ΔV). Ad5-ΔV particles were softer and less brittle than the wild-type ones (Ad5-wt), but they were more prone to release pentons under mechanical fatigue. In Ad5-ΔV, core components did not readily diffuse out of partially disrupted capsids, and the core appeared more condensed than in Ad5-wt. These observations suggest that instead of condensing the genome, protein V antagonizes the condensing action of the other core proteins. Protein V provides mechanical reinforcement and facilitates genome release by keeping DNA connected to capsid fragments that detach during disruption. This scenario is in line with the location of protein V in the virion and its role in Ad5 cell entry.

Surface characterization of alkane viral anchoring films prepared by titanate-assisted organosilanization

Studies of virus adsorption on surfaces with optimized properties have attracted a lot of interest, mainly due to the influence of the surface in the retention, orientation and stability of the viral capsids. Besides, viruses in whole or in parts can be used as cages or vectors in different areas, such as biomedicine and materials science. A key requirement for virus nanocage application is their physical properties, i.e. their mechanical response and the distribution of surface charge, which determine virus-substrate interactions and stability. In the present work we show two examples of viruses exhibiting strong surface interactions on homogeneous hydrophobic surfaces. The surfaces were prepared by titanate assisted organosilanization, a sol-gel spin coating process, followed by a mild annealing step. We show by surface and interface spectroscopies that the process allows trapping triethoxy-octylsilane (OCTS) molecules, exhibiting a hydrophobic alkane rich surface finishing. Furthermore, the surfaces remain flat and behave as more efficient sorptive surfaces for virus particles than mica or graphite (HOPG). Also, we determine by atomic force microscopy (AFM) the mechanical properties of two types of viruses (human adenovirus and reovirus) and compare the results obtained on the OCTS functionalized surfaces with those obtained on mica and HOPG. Finally, the TIPT+OCTS surfaces were validated as platforms for the morphological and mechanical characterization of virus particles by using adenovirus as initial model and using HOPG and mica as standard control surfaces. Then, the same characteristics were determined on reovirus using TIPT+OCTS and HOPG, as an original contribution to the catalogue of physical properties of viral particles.

Seeing and touching adenovirus: complementary approaches for understanding assembly and disassembly of a complex virion

Understanding adenovirus assembly and disassembly poses many challenges due to the virion complexity. A distinctive feature of adenoviruses is the large amount of virus-encoded proteins packed together with the dsDNA genome. Cryo-electron microscopy (cryo-EM) structures are broadening our understanding of capsid variability along evolution, but little is known about the organization of the non-icosahedral nucleoproteic core and its influence in adenovirus function. Atomic force microscopy (AFM) probes the biomechanics of virus particles, while simultaneously inducing and monitoring their disassembly in real time. Synergistic combination of AFM with EM shows that core proteins play unexpected key roles in maturation and entry, and uncoating dynamics are finely tuned to ensure genome release at the appropriate time and place for successful infection.