Proteolytic inactivation of simian-11 rotavirus: a pilot study

In an effort to develop alternate disinfectants for rotaviruses, pilot studies were conducted to determine if bacterial proteases could render simian-11 (SA-11) rotavirus non-infectious. SA-11 was found to be fairly temperature resistant, retaining a low-level of infectivity following 65 degrees C treatment for 2h at pH 8.5. It also resisted pH 8.5-5 at 45 degrees C for 2h. Alcalase, an alkaline protease, was the most effective of the various proteases (alcalase, durazym, neutrase, and savinase) tested. To analyze specific parameters for alcalase, SA-11 virus (10(5.5) median tissue culture infective dose/ml original titer) was treated at pH 6, 25 and 15 degrees C (simulated field conditions), with 0.1 and 1.0% alcalase. At pH 6.0 and 15 degrees C, 0.1% alcalase reduced SA-11 titer by 0. 75 log in 24h, and by 1.25 log in 120h. At 25 degrees C and pH 6.0, 0.1% alcalase reduced the titer by 2.25 log after 24h, and by 2.75 log in 120h. At pH 6.0 and 15 degrees C, 1% alcalase reduced SA-11 titer by 1.50 log in 24h and by 1.75 log in 120h. At the same enzyme concentration and pH, but at 25 degrees C the titer was reduced by 2. 75 log in the first 24h and by 3.25 log at 120h. These results show that the alkaline protease alcalase is capable of inactivating SA-11 virus to a certain degree depending on conditions. Further definition of operating parameters, demonstration of inactivation under field conditions and analysis whether the demonstrated degree of inactivation would decrease calf morbidity and mortality remain to be explored at this time.