Analysis of two potential shuttle vectors containing herpes simplex virus defective DNA.

Two potential shuttle vectors which contained the identical herpes simplex virus type 1 (HSV-1) defective particle DNA (dDNA), but prokaryotic DNA of different origins, were examined for their stability when propagated in eukaryotic cells, and for their efficiency as shuttle vectors. Each chimeric molecule contained a 9.5 kilobase-pair (kb) EcoRI fragment (HSV12-7) representing a single unit of a class I HSV-1 dDNA. This dDNA was cloned into the bacteriophage lambda (lambda) vector lambda gtWES X lambda B' to create a 45.3 kb chimeric molecule (lambda gtWES::12-7), and into the plasmid vector pBR325, resulting in a 15.5 kb recombinant DNA molecule (pBR325::12-7). Each of these DNA molecules was transfected independently into African green monkey kidney cells which were then infected with wild-type HSV-1 helper virus. Both chimeric molecules were replicated and packaged into HSV-1 virions. However, regions of the lambda gtWES::12-7 chimeric DNA were rapidly deleted and rearranged, whereas the plasmid/HSV-1 DNA molecules were less rearranged. No intact lambda gtWES::12-7 DNA was recovered from HSV-1 virions as detected by infectivity of in vitro packaged DNA. However, pBR325::12-7 DNA isolated from HSV-1 virions was able to transform E. coli to ampicillin resistance. These results suggest additional considerations when designing single units of HSV-1 dDNA for use as vectors to accommodate large fragments of DNA.