Title: Photoinactivation of viruses by porphyrins
Abstract: Microbial photodynamic inactivation (PDI) has been successfully used to inactivate microorganisms. PDI has already been studied under different conditions for different microorganisms; however, there is still scarce information about bacteriophage inactivation. The goal of this study was to elucidate and evaluate several aspects of viral PDI: (i) effect of different light sources, doses and intensities on phage inactivation; (ii) photoinactivation efficiency on DNA- and RNA-type bacteriophages, (iii) main mechanism by which phage photosensitization takes place, (iv) effect of PDI on phage proteins; and (v) possibility of resistance development and viability recovery after consecutive phototreatments.
From this study it can be concluded that: (i) phage photoinactivation was significantly higher when low fluence rates were used at long irradiation times (Costa et al, 2012b); (ii) phages were efficiently inactivated to the detection limit (reductions of 6-7 log)(Costa et al., 2011); (iii) RNA-type phages were much more easily inactivated than the DNA-type ones (sooner and with ten times less porphyrin concentration than that used for DNA-type phages) (Costa et al., 2012b); (iii) type II mechanism (production of singlet oxygen) was the main mechanism by which photosensitization took place (Costa et al., 2013); (iv) IR spectroscopy represents a promising and fast-screening methodology to study damage induced by photosensitization on phage proteins; and (v) after ten consecutive photodynamic cycles, T4-like phage did not exhibit any resistance to PDI nor recovered its viability (Costa et al., 2010).
In conclusion, viral PDI is a very efficient technology for inactivation of non-enveloped DNA- and RNA-type phages (Costa et al., 2012a); it may be used as an alternative to conventional antiviral treatments, even at low light fluence rates, without emergence of viral resistance.
Acknowledgments: Thanks are due to the Univ. de Aveiro, FCT, FEDER and to CESAM.
Costa L, Faustino MAF, Tomé JPC, Neves MGPS, Tomé AC, Cavaleiro JAS, Cunha A, Almeida A. (2013), Involvement of type I and type II mechanisms on the photoinactivation of non-enveloped DNA and RNA bacteriophages. J. Photochem. Photobiol. B: Biol. 120:10-16.
Costa L, Neves MGPS, Cavaleiro JAS, Cunha A, Faustino MAF, Almeida A.(2012a), Susceptibility of non-enveloped DNA- and RNA-type viruses to photodynamic inactivation. Photoch. Photobio. Sci. 11:1520-1523.
Costa L, Faustino MAF, Neves MGPS, Cunha A, Almeida A. (2012b), Photodynamic inactivation of mammalian viruses and bacteriophages. Viruses 4:1034-1074.
Costa L, Tomé JPC, Neves MGPS, Tomé AC, Cavaleiro JAS, Faustino MAF, Cunha A, Almeida A. (2011), Evaluation of resistance development and viability recovery by a non-enveloped virus after repeated cycles of aPDT. Antiviral Res. 91:278-282.
Costa L, Carvalho CMB, Tomé JPC, Faustino MAF, Neves MGPS, Tomé AC, Cavaleiro JAS, Cunha A, Almeida A. (2010), Sewage bacteriophage inactivation by cationic porphyrins: influence of light parameters. Photoch. Photobio. Sci. 9:1126-1133.
PhD Degree: Biologia, ramo Microbiologia; Year of conlusion: 2012
Institution: Universidade de Aveiro, Portugal
Supervision(s): Adelaide Almeida (Dep. Biologia, Univ Aveiro) and Amparo Faustino (Dep, Química, Univ Aveiro)