10. At 18 hours post infection (h p.i.), cell lysates were harvested and expression of the reovirus non-structural protein µNS was analyzed by immunoblotting (Fig. 5C ). As expected, when treated cells were infected with virions, viral protein expression was blocked. In contrast, µNS expression was evident even in the presence of agents that raise pH when infections were initiated with ISVPs or NE-SVPs (Fig. 5C ). Together, these results demonstrate that NE can directly mediate σ3 removal from virions to generate infectious particles that do not require further proteolytic processing by acid-dependent cysteine proteases in L929 cells.