Ascoviruses (AVs) are double-stranded DNA viruses causing a fatal disease in lepidopteran host larvae. A unique feature of AV infection is cleavage of host cells into membrane bound vesicles containing the virions. A recent study showed that a caspase from Spodoptera frugiperda AV (SfAV) is directly involved in initiation of apoptosis and eventually cell cleavage. Results shown here indicate that Heliothis virescens AV does not induce apoptosis in host cells. HvAV codes for a caspase-like protein but no apoptosis was observed when the gene was expressed in vitro. RNAi studies indicated that the gene is essential for virus replication. (C) 2007 Elsevier B.V. All rights reserved.