POTENTIAL REPLICATION OF RECOMBINANT BACULOVIRUSES IN NONTARGET INSECT SPECIES - REPORTER GENE-PRODUCTS AS INDICATORS OF INFECTION

The assessment of environmental risks associated with genetically engi neered baculovirus pesticides depends on an accurate knowledge of the host range of each virus. However, studies of baculovirus host ranges based solely on symptomology may misidentify as nonhosts any species w ith symptomless infections. This project used recombinant viruses that allowed detection of symptomless as well as pathogenic virus infectio ns. Seven recombinant isolates of Autographa californica nuclear polyh edrosis virus (AcMNPV), Bombyx mori nuclear polyhedrosis virus, Lymant ria dispar nuclear polyhedrosis virus (LdMNPV), and Orgyia pseudotsuga ta nuclear polyhedrosis virus were tested by either hemocoelic injecti on or per os inoculation for their potential replication in 23 insect species from eight orders and 17 families. The recombinant viruses con tained genes coding for beta-galactosidase, secreted alkaline phosphat ase (SEAP), or luciferase under the transcriptional control of either the polyhedrin or ETL promoter. Replication was initially assessed bas ed on detection of the reporter gene products. Results obtained with b eta-galactosidase or SEAP as indicators were more consistent but less sensitive than those with luciferase. With all insects tested, much hi gher reporter enzyme activities were found with the beta-galactosidase reporter gene placed under the polyhedrin promoter than under the ETL promoter, As indicated by reporter enzyme activity after injection wi th the budded virus particles, the AcMNPV replicated in more species t han did the other viruses, and the LdMNPV was the most host specific. Most of the insect species tested did not support detectable replicati on of any of the viruses. While an observation of symptoms of viral in fection was usually concurrent with detection of reporter gene activit ies, with certain insect/virus combinations, little or no reporter gen e activity was detected even though the feeding activity and growth ra tes were significantly reduced relative to those of the sham-injected controls. The results of this project provide a database for the estab lishment of future environmental risk assessment protocols and guideli nes with baculovirus pesticides. (C) 1997 Academic Press.