Studies on the attachment of herpes simplex virus. Effect of trypsin treatment

Does Trypsin Oral Spray (Viruprotect®/ColdZyme®) Protect against COVID-19 and Common Colds or Induce Mutation? Caveats in Medical Device Regulations in the European Union

BACKGROUND

nasal or oral sprays are often marketed as medical devices (MDs) in the European Union to prevent common cold (CC), with ColdZyme^®/Viruprotect^® (trypsin/glycerol) mouth spray claiming to prevent colds and the COVID-19 virus from infecting host cells and to shorten/reduce CC symptoms as an example. We analyzed the published (pre)-clinical evidence.

METHODS

preclinical: comparison of in vitro tests with validated host cell models to determine viral infectivity. Clinical: efficacy, proportion of users protected against virus (compared with non-users) and safety associated with trypsin/glycerol.

RESULTS

preclinical data showed that exogenous trypsin enhances SARS-CoV-2 infectivity and syncytia formation in host models, while culture passages in trypsin presence induce spike protein mutants. The manufacturer claims >98% SARS-CoV-2 deactivation, although clinically irrelevant as based on a tryptic viral digest, inserting trypsin inactivation before host cells exposure. Efficacy and safety were not adequately addressed in clinical studies or leaflets (no COVID-19 data). Protection was obtained among 9-39% of users, comparable to or lower than placebo-treated or non-users. Several potential safety risks (tissue digestion, bronchoconstriction) were identified.

CONCLUSIONS

the current European MD regulations may result in insufficient exploration of (pre)clinical proof of action. Exogenous trypsin exposure even raises concerns (higher SARS-CoV-2 infectivity, mutations), whereas its clinical protective performance against respiratory viruses as published remains poor and substandard.

2-deoxy-D-glucose inhibition of herpes simplex virus type-1 receptor expression

Growth of HEp-2 cells in 2-deoxy-D-glucose (2-DOG) supplemented media decreased the cells' binding capacity for herpes simplex virus type-1 KOS(HSV-1) but not vesicular stomatitis virus. HEp-2 cells tolerated up to 30 mM 2-DOG, but 2-DOG was toxic for Vero cells over 2 mM. The reduction in binding was maintained for at least 24 h even after careful removal of the inhibitor and growth in normal media. Complete regeneration of the receptor sites on HEp-2 cells was observed 8 h after mild trypsinization of cells grown in either normal or the 2-DOG supplemented media. Specific glycoprotein characteristics of the HSV-1 binding site were indicated by its inactivation upon trypsinization (0.1 mg per 5 X 10(5) cells for 30 s) and blocking by wheat germ agglutinin but not limulin. These results suggest that 2-DOG inhibits the proper expression of cell surface glycoprotein HSV-1 receptor sites on HEp-2 cells.

Physical integrity of herpes simplex virus following thermal inactivation

The effect of thermal inactivation on the gross physical integrity of herpes simplex virus (HSV) was investigated. Purified preparations of HSV containing 3H-thymidine were subjected to thermal inactivation at 36 degrees C, ph 6.3 and pH 7.8 and then were analysed by sucrose gradient centrifugation. The data indicated that although HSV inactivation at 36 degrees C was significantly greater at pH 7.8 than at 6.3, the gross physical integrity of most of the HSV in both of these inactivated virus populations was maintained. In addition, heat inactivated HSV adsorbed to mammalian cells as readily as non-inactivated HSV. Thus, thermal inactivation of HSV does not result in the physical disassembly of the virion particles or in the destruction of virus receptor activity.