Retroviral gene transfer

[William Meikrantz]

We've been doing a lot of work with retroviral gene transfer systems 
based on the LXSN series developed by Dusty Miller and colleagues.  The 
basic strategy is to transfect (by lipofection, electroporation, CaPO4) a 
plasmid containing LTRs, packaging sequence, and the gene of interest 
into a packaging cell line that constituitively expresses gag, pol and 
env.  (It's a bit more complicated than that, but that's the basic 
procedure.)  

Our problem is, now we're trying to produce retroviral vectors that carry 
genes that promote growth arrest--this creates the problem that 
expression from the transfected plasmid carrying the growth 
arrest/cytotoxic gene will halt growth of the packaging cell and thereby 
stop production of virus.

We're beginning to work on putting the growth arrest/cytotoxic genes 
under control of a promoter that will not be expressed in the packaging 
cells, but I was wondering if anyone out there has had any experience in 
dealing with this problem before, and maybe has come up with a solution 
that we've overlooked...

Thanks!

Bill Meikrantz
Molecular and Cellular Toxicology
Harvard School of Public Health
meikrant at husc.harvard.edu