Proteomic and Molecular Study to Identify the Inactivation Mechanisms of a Norovirus Surrogate by Cold Plasma Exposure

Introduction: Non-thermal decontamination of fresh-eaten foods and food-contact surfaces from foodborne viruses, particularly human norovirus (NoV), is of great interest to food industry personnel. Recently, we reported complete inactivation of feline calicivirus (FCV), a surrogate of human NoV, by 15 second exposure in water to Ar+1%O₂ cold atmospheric pressure gaseous plasma (CAGP).

Purpose: In the present study, we studied the mechanism of virucidal activity of CAGP to understand how viruses are being affected by cold plasma.

Methods: Cultural, proteomic, molecular, and morphologic comparisons of CAGP-inactivated FCV and non-exposed virus were undertaken.

Results: The reactive oxygen and nitrogen species of plasma oxidized specific amino acids (i.e., histidine, methionine, and tryptophan) located in the shell (S) and protrusion (P) domains, the dimeric interface regions, and movable- flexible hinge region linked between S and P domains of the major capsid protein (VP1) of the virus. This led to: 1) loss of the structural integrity and damage to viral capsid in the exposed virions, 2) hindrance in viral attachment to the functional receptor (fJAM-A) of the host cells, and 3) cleavage in the viral RNA once it becomes uncoated because of the damage to the viral capsid. The former effect is not the key role in virus inactivation as the infectivity of the virus is lost by the capsid damage even if the RNA is left intact after plasma exposure.

Significance: The high similarity between the capsid structures of NoV and FCV and the high histidine, methionine, and tryptophan- content of human NoV capsid protein indicate that similar mechanisms may apply to CAGP’s effect on NoV. This understanding of how the virus is being affected by plasma and what plasma species are most effective against the virus led us to design a new cold plasma unit, which is more efficient against foodborne viruses.