Zeta Potential and Aggregation of Virus-Like Particle of Human Norovirus and Feline Calicivirus Under Different Physicochemical Conditions

Abstract

Although the spread of human norovirus reportedly depends on its ability to bind to food materials, the mechanism of the phenomenon remains unknown. Since protein size and electrical charge are reportedly important parameters in their adsorption, the current work is focused on determining human noroviruses isoelectric point (IEP), electrical charge and aggregate size at different pH, ionic strength (IS), and temperature. Using the baculovirus expression vector system, we produced and purified virus-like particles (VLPs) of GI.1 and GII.4 noroviruses and feline calicivirus, determined their IEP, and examined their size and electrical charge using a Zetasizer Nano ZS apparatus. Shape and size were also visualized using transmission electron microscopy. IEPs were found close to pH 4. Net charge increased as the pH deviated from the IEP. VLPs were negatively charged at all IS tested and showed a gradual decrease in charge with increasing IS. At low temperature, VLPs were 20-45 nm in diameter at pH far from their IEP and under almost all IS conditions, while aggregates appeared at or near the IEP. At increased temperatures, aggregates appeared at or near the IEP and at high IS. Aggregation at the IEP was also confirmed by microscopy. This suggests that electrostatic interactions would be the predominant factor in VLPs adhesion at pH far from 4 and at low ionic strength. In contrast, non-electrostatic interactions would prevail at around pH 4 and would be reinforced by aggregates, since size generally favors multiple bonding with sorbents.

Adsorption of norovirus and ostreid herpesvirus type 1 to polymer membranes for the development of passive samplers

“…electric charge, hydrophobicity) and aqueous solution characteristics (pH, ionic strength) (Gerba 1984;da Silva et al 2011). It is known that NoV particles aggregate at pH around the isoelectric point (around pH 4) at room temperature, while individual particles are observed at pH's above their isoelectric point (Samandoulgou et al 2015a). Therefore, for sewage or seawater with a pH of about 6-7, NoVs are negatively charged which explains their adsorption on the electropositive zetapor membrane.…”

Stability of Secondary and Tertiary Structures of Virus-Like Particles Representing Noroviruses: Effects of pH, Ionic Strength, and Temperature and Implications for Adhesion to Surfaces

“…in the food sector (25). Virus adhesion to hydrophobic surfaces appeared to be positively correlated with increasing ionic strength and temperature.…”

Virus Type-Specific Removal in a Full-Scale Membrane Bioreactor Treatment Process

“…NoV GI and GII have different adsorption efficiencies to particles in untreated wastewater, and their binding capacity depends on pH and solution chemistry (da Silva et al, 2008;da Silva et al, 2011). Therefore, we speculated that the surface charge may be the key factor modulating the different behaviors observed in the monitoring and bench-scale experiments, as different isoelectric points (pI) were reported for NoV GI.1 (4.3−6.0) and GII.4 (4.2−6.9) (Michen and Graule, 2010;Samandoulgou et al, 2015), porcine SaV Cowden (5.4) (Wang et al, 2012), and simian RV SA11 (8.0) (Michen and Graule, 2010).…”