Deletion ofv-chiAfrom a Baculovirus Reduces Horizontal Transmission in the Field

Abstract

ABSTRACTNucleopolyhedroviruses (NPVs) can initiate devastating disease outbreaks in populations of defoliating Lepidoptera, a fact that has been exploited for the purposes of biological control of some pest insects. A key part of the horizontal transmission process of NPVs is the degradation of the larval integument by virus-coded proteins called chitinases, such as V-CHIA produced by thev-chiAgenes. We used recombinant and naturally occurring strains of theLymantria disparNPV (LdMNPV) to test horizontal transmission in the field, release of virus from dead larvae under laboratory conditions, and cell lysis and virus release in cell culture. In the field, strains of LdMNPV lacking functionalv-chiAgenes showed reduced horizontal transmission compared to wild-type or repaired strains. These findings were mirrored by a marked reduction in released virus in laboratory tests and cell culture when the same strains were used to infect larvae or cells. Thus, this study tests the pivotal role of liquefaction and thev-chiAgene in field transmission for the first time and uses complementary laboratory data to provide a likely explanation for our findings.