The inactivation of single stranded RNA viruses by ultra violet light

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Jones, D.B., 1977. The inactivation of single stranded RNA viruses by ultra violet light. PhD, Nottingham Trent University.

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Abstract

A review of the literature shows that there is variation in the published rates of inactivation for many viruses by UV.

UV equipment was constructed to investigate several aspects of inactivation of viruses by UV. A Bausch and Lomb monochromator in conjunction with e, 750 watts mercury discharge lamp driven at 750 watts gave an output of 1.6 ergs mm-2 sec-1 at 253.7nm, as measured by actinometry. A surface steriliser at 253.7nm had an output of up to 175 ergs mm-2 sec-1. A British Rail UV steriliser was calibrated and had an output of 165 ergs mm-2 sec-1 at a flow ratio of 1.4 1 min-1 and was judged to give a satisfactory treatment at 6 1 min-1 flow.

MS2 and poliovirus were concentrated by a polyethylene glycol tvro phase system and purified by caesium chloride density gradient separation.

Inactivation of MS2 and QB and poliovirus with 253.7nm UV gave a biphasic inactivation rate. The D37 of the sensitive population of MS2 and QB was 720 ergs mm-2, while that of the resistant population was 1,100 ergs mm-2. The D37 of the sensitive polioviruses was 410 ergs mm-2 and that of the resistant, 680 ergs mm-2.

The phenomenon of biphasic inactivation was investigated and multiplicity reactivation, photoreversal, variabilty of data, shielding and attachment of viruses to vessel walls were all investigated and found not to explain the data. The two populations, sens and res, were not genetically distinct. X-radiation showed that sens had a greater cross sectional area of inactivation than res. Sens was also more sensitive to heat.

Two densities of MS2 were isolated that had the same UV sensitivities as sens and res. Sens had a density of 1.46 g cc-3 and res density of 1.44 g cc-3. The two populations also had different iso-electric points, sens at pH 4.0 and res at pH 7.0.

Resistant MS2, expanded at 45°0 0.15 M Na.Cl and re-contracted was converted to sensitive UV resistance.

QB and poliovirus were also shown to have two densities, two iso-electric points and two phase inactiviation.

It is postulated that MS2 has two structures, one in which the RNA is tightly bound and is in stable contact with the coat - the sens form, and one in which the HKA is loosely hound and stretches the capsid - the res form.