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°C treatment for 2 h at pH 8.5. It also resisted pH 8.5–5 at 45°C for 2 h. 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°C (simulated field conditions), with 0.1 and 1.0% alcalase. At pH 6.0 and 15°C, 0.1% alcalase reduced SA-11 titer by 0.75 log in 24 h, and by 1.25 log in 120 h. At 25°C and pH 6.0, 0.1% alcalase reduced the titer by 2.25 log after 24 h, and by 2.75 log in 120 h. At pH 6.0 and 15°C, 1% alcalase reduced SA-11 titer by 1.50 log in 24 h and by 1.75 log in 120 h. At the same enzyme concentration and pH, but at 25°C the titer was reduced by 2.75 log in the first 24 h and by 3.25 log at 120 h. 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.