Photodynamic inactivation of bacteriophage MS2: The A-protein is the target of virus inactivation

Abstract

Singlet oxygen mediated oxidation has been shown to be responsible for photodynamic inactivation (PDI) of viruses in solution with photosensitisers such as 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin tetra p-toluenesulfonate (TMPyP). The capsids of non-enveloped viruses, such as bacteriophage MS2, are possible targets for viral inactivation by singlet oxygen oxidation. Within the capsid (predominantly composed of coat protein), the A-protein acts as the host recognition and attachment protein. The A-protein has two domains; an α-helix domain and a β-sheet domain. The α-helix domain is attached to the viral RNA genome inside the capsid while the β-sheet domain, which is on the surface of the capsid, is believed to be the site for attachment to the host bacteria pilus during infection. In this study, 4 sequence-specific antibodies were raised against 4 sites on the A-protein. Changes induced by the oxidation of singlet oxygen were compared to the rate of PDI of the virus. Using these antibodies, our results suggest that the rate of PDI is relative to loss of antigenicity of two sites on the A-protein. Our data further showed that PDI caused aggregation of MS2 particles and crosslinking of MS2 coat protein. However, these inter- and intra-capsid changes did not correlate to the rate of PDI we observed in MS2. Possible modes of action are discussed as a means to gaining insight to the targets and mechanisms of PDI of viruses.

Photodynamic inactivation of non-enveloped RNA viruses

“…Sample treatments are indicated on the right-hand panel. Scale bars are shown underneath each micrograph column.Unlike previously reported aggregation of MS2(Majiya et al, 2018) Q BEV-2 did not…”

“…Previously, we reported that a minimum dose of 0.2 µM TMPyP in solution under light (32 mW cm -2 ) inactivated MS2 within one minute (Majiya et al, 2017). We also showed that the A-protein of MS2 was the PDI target and aggregation of the viral particles after sixty minutes of PDI treatment (Majiya et al, 2018). Although MS2 remains a useful and relevant virus for study, it is also necessary to investigate human (or closely related animal) viruses to accurately model inactivation of human viruses under relevant experimental conditions.…”

“…Previously, we showed that TMPyP-PDI may affect the integrity of the MS2 capsid and may result in aggregation of viral particles (Majiya et al, 2018). We therefore sought to investigate the structural effects of TMPyP PDI-treatment on the capsid integrity of other viruses using negative stain electron microscopy.…”

“…Owing to the capsid breathing phenomenon common to icosahedral viruses (Bothner et al, 2005, Lewis et al, 1998, Jaegle et al, 1988, Witz and Brown, 2001), we previously suggested that there could be effects of PDI on inner residues of the viral capsid protein and the viral genome (Majiya et al, 2018). Here, using MNV-1 as a study model, we sought to investigate the effect of PDI on the encapsidated viral genome.…”

Trends and targets in antiviral phototherapy

“…Such PSs are used to target the outer structures of the virus, i.e., unsaturated lipids as well as envelope proteins. 10,62,86,98 Virus proteins typically undergo structural modifications such as protein cross-linking. Particularly, the photooxidative damage occurs at oxidation-sensitive amino acids such as tryptophan, methionine, cysteine, histidine and tyrosine.…”