Inactivation of MS-2 phage and poliovirus in groundwater

Since temperature affects the inactivation rate of viruses in natural water systems, the aim of this study was to determine if a temperature shift cou ld influence the structural integrity of model viruses. When crude lysates of MS-2 phage were seeded into groundwater microcosms and incubated at 27%C , complete virus inactivation took place in eight days. The temperature was then shifted to 4%C. Three days after the temperature shift, a two-log inc rease in virus titer (reactivation) occurred. However, when purified MS-2 l ysates were added to groundwater microcosms, no reactivation was obtained. No reactivation of poliovirus took place when similar microcosm experiments were done. The sedimentation coefficients of MS-2 shifted from 80S to 58S, 48S, 37S, 32S, and 18S as inactivation proceeded in groundwater and distil led water controls. Similarly, the sedimentation coefficients of poliovirus es changed from 156S to 142S, 135S, 117S, 105S, 95S, and 80 S as inactivati on took place. There was no correlation between % virus inactivation and % decrease in virions with intact sedimentation coefficients, as reported ear lier for poliovirus inactivated by chlorine. The results presented support our hypothesis that virus inactivation proceeds gradually, involving the re arrangement and (or) loss of capsomere components that may eventually lead to the ejection of nucleic acids. The intermediate particles generated as i nactivation proceeds may be in a reversibly inactivated state, and may reve rt back to a fully infectious state when chemical components stabilize the virus particle.