Photodynamic viral inactivation

Gadolinium(III) Texaphyrins Photodynamic Therapy and Photodynamic Viral Inactivation... 

In the present study we have investigated the process of photodynamic inactivation of influenza vims in the allantoic fluid of chicken embryos. This inactivation has been realized by C60 water suspension used as a photosensitizer. Similar studies have been carried out previously by Kaserman and Kempf (1997, 1998). Unlike the latter studies, in which viruses were inactivated in salt solutions (buffer), our experiments were performed in a natural biological fluid that contains all typical components (proteins, lipids, salts, etc.). Comparing the viral inactivation over time in our experiments with previous results we conclude that the process described by Kaserman and Kempf (1997, 1998) was more time-consuming, a fact that may significantly restrict its practical use. 

Units and methods are developed to study the effect of active forms of oxygen on fullerene-based photosensitizers. The kinetics of the inactivation of influenza vims in saline and allantoic fluid during the course of photodynamic treatment using fullerene preparations is studied. Optimization of conditions has been conducted for viral inactivation (irradiation, doses, concentration of fullerene, and intensity of oxygen flow). Experiments are performed for inactivation of vims in blood semm. 

Photodynamic ACT (PACT), similar to photodynamic therapy (PDT) described in Chapter 17, utilizes photosensitizers and visible or UV light in order to induce a phototoxic response, usually via oxidative damage. For some time the disinfection of blood products, particularly for viral inactivation, has been the major use of PACT, although more and more clinically based protocols are being developed, eg in the treatment of oral infections. The technique has been shown to be effective in vitro against bacteria (including drug resistance strains), yeasts, viruses, and parasites. 

Although HIV infection inhibition is mainly due to interaction of fullerene derivatives with viral enzymes, it is necessary to consider that this is not the only exploitable mechanism. In fact, the photodynamic inactivation of influenza vims has also been proposed (Zarubaev et al., 2007). The outer viral membrane is destroyed, while it seems that the protein profile of allantoic fluid, in which the vims was propagated, remains unchanged, confirming one more time the great potentiality of fullerene. 

Currently, all donors and blood preparations undergo multistage and expensive control to ensure the absence of viral contamination In this respect, the development of affordable methods of inactivation of viruses could be an important step toward safety in hemotransfusion. Currently used treatments such as UV irradiation damage therapeutic components of the blood (Williamson and Cardigan, 2003), so alternative selective approaches are needed for this purpose. Among them, chemotherapy, photochemotherapy (PCT), and photodynamic antibacterial therapy should be noted (Mohr, 2000). 

The course of viral photodynamic inactivation in allantoic fluid is probably directed by the following process the initial period of induction is a result of the quenching of singlet oxygen (or other reactive forms of oxygen) by natural antioxidants present in the fluid (Kolb, 1991). Subsequently, a dramatic drop in the viral titer was observed. This then reached a plateau due to the consumption of the active fraction of the fullerene. This may be indirectly confirmed by the results of viral titration after the addition of a new portion of fullerene when the process of inactivation was observed again. 

Photodynamic treatment equally affects viral particles and protein components in biological fluid, but virions, being large supramolecular structures, are more vulnerable compared to protein molecules. For this reason, damage to one of the components of a virion leads to inactivation of the entire viral particle without affecting the growth properties of semm or the electrophoretic pattern of the proteins. 

The photodynamic action of these dyes was first observed in terms of inactivation of biological activity, and of changes in the physical properties of polynucleotides. For example, the infectivity of viral RNA is destroyed by the photodynamic action of acridine orange129 and the transforming ability of DNA (see Glossary) is similarly destroyed by the similar action of a variety of dyes.130... 

The first cell localization study, involving mononuclear cells, was carried out as a complement to the anti-viral photodynamic work. Here, the basic motivation for the study derived from the realization that HIV-1 replicates in human T-4 lymphocytes and that, as such, selective light-derived inactivation of such cells would be of benefit in possible photodynamic blood purification processes (see Sect. 12). Texaphyrin proved to be quite effective in the photodestruction of mononuclear cells. In fact it was found that the cadmium texaphyrin complex 116 is as effective on a per mole basis as the dihematoporphyrin ether (DHE) and slightly more so on a per photon basis. 

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