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Thesis

French

ID: <

10670/1.s0hkjw

>

Where these data come from
Viral inactivation by physical methods

Abstract

The pattern of viability of non-enveloped viruses, minute virus of mice (MVM), coxsackievirus B4 (CVB4), and simian virus 40 (SV40) and enveloped-viruses, influenza A virus (H1N1), and herpes simplex virus type 1 (HSV-1) onto surfaces and their resistance to heating and to ultraviolet C (UVc) exposure have been investigated. To determine the viability of MVM, CVB4, H1N1 and HSV1 on surface, fifty microliters of viral suspension were applied onto petri dish lids and dried under air flow of biosafety cabinet. The recovered viral preparations were titered on appropriate cell cultures. Enveloped viruses persisted for less than 5 days while CVB4 and MVM persisted for weeks. However, repetitive cycles of drying and resuspension had more virucidal effect on CVB4 than on H1N1 and HSV-1. No effect of these repetitive cycles on infectious titer of MVM was recorded. When exposed to drying, initial concentrations of bovine serum albumin, foetal calf and sodium chloride (NaCl) had an impact on the viability of CVB4. In a protein rich medium, CVB4 was more likely inactivated by drying whereas in presence of NaCl, the impact of drying was reduced. Thus, it appears that the resistance of viruses toward drying is not due to a heterogeneity of viral populations, but it can be influenced by media composition and components concentrations.Heat inactivation of viruses was reported, however, the thermal resistance of viruses in droplets has not been studied. We evaluated the pattern of heat resistance of MVM, CVB4, H1N1 and HSV1 contained in droplets. Four microliters droplets containing viruses were applied onto warmed surface obtained by using a self-made heating device. Viral suspensions were exposed to temperatures ranging from 70 to 130°C for 0 to 90 min depending on the virus, and then the recovered viral preparations were titered. Clearly, MVM was more resistant than H1N1 that was more resistant than HSV-1 and CVB4. For the first time, the inactivation of viral particles contained in drops exposed to temperatures higher than 100°C has been investigated. It appears that heating can have an unexpected faster virucidal effect than previously described. The resistance to ultraviolet C (UVc) (254nm) of MVM, CVB4, H1N1, HSV-1 and SV40 contained in droplets has been evaluated. Double-stranded DNA viruses (HSV-1 and SV40) were still infectious after exposure to 60 mJ/cm² UVc, while RNA viruses H1N1, CVB4 and single-stranded DNA virus MVM were fully inactivated when they were exposed to a dose equal to or lower than 35 mJ/cm² UVc. Moreover the effect of UVc (254 nm) combined with heating onto the viability of MVM was determined. The infectious level of MVM suspension droplets applied onto petri dish lids was fully inactivated when exposed to 27 mJ/cm² UVc. Heating (100°C for 20s) provoked a moderate reduction of infectious level (-1.8 log10TCID50) of MVM, whereas heating followed by UVc exposure (17 mJ/cm²) resulted in a full inactivation.In conclusion, our studies show that viruses can persist for days or even weeks on dry hydrophobic surfaces. The pattern of resistance of viruses toward drying is not due to a heterogeneity of viral population as shown by results obtained with CVB4. In so far as media composition play a role in the viability of viruses exposed to drying, the persistence of viruses in natural media (clinical or environmental), instead of defined media, should be investigated. The impact of short time exposure to heat onto the infectivity of viruses contained in a small volume of suspension has been determined. The thermal resistance of H1N1 up to 100°C, higher than the one of HSV1 another enveloped virus, and CVB4 a non-enveloped virus has been observed. An efficient viral inactivation can be obtained by combining UVc exposure and heating as shown by results obtained with MVM.

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