OVEREXPRESSION OF BOMBYX-MORI PROTHORACICOTROPIC HORMONE USING BACULOVIRUS VECTORS

Recombinant baculoviruses were constructed that express the cDNA encod ing the prothoracicotropic hormone (PTTH) of Bombyx mori. This hormone stimulates the production of ecdysteroids by the insect's prothoracic glands. Two groups of viruses were constructed, expressing either the entire cDNA encoding prepro-PTTH, or a synthetic chimeric gene encodi ng a signal peptide fused to the mature PTTH subunit. In both cases, t he genes were expressed in wild-type Autographa californica nuclear po lyhedrosis virus (AcMNPV) and in vEGTDEL, an AcMNPV mutant that lacks a functional egt gene. The egt gene is required for viral-mediated ina ctivation of host ecdysteroids. High levels of functional PTTH were pr oduced only by viruses expressing the mature subunit cDNA. This recomb inant PTTH resembled the native hormone by all criteria examined. The overproduction of B. mori PTTH induced higher than normal levels of ha emolymph ecdysteroids but had no observable effects on the development of infected Spodoptera frugiperda larvae. However, expression of PTTH by AcMNPV was found to inhibit the pathogenicity of the virus. This e ffect was particularly marked in the case of viruses lacking a functio nal egt gene.