Helper superinfection

An important contribution to the interpretation of dose response, low efficiency, and the specific role of helper phage in transfection was made by Green (1966 a) with SP82 G. He discovered that, in SP82 G transfection performed with helper superinfection, the efficiency of marker rescue decreased exponentially as the time between exposure of cells to wild-type DNA and addition of superinfecting phage increased. This loss of the ability to con-... 

In the second strategy cells are transfected with plasmids that carry the gene of interest under the control of a vaccinia virus promoter and superinfected with a vaccinia helper virus. In this case, expression occurs in trans by factors provided by the helper virus. The advantage of this... 

Deficient viruses viruses which, through mutation, have lost the ability to synthesize certain essential enzymes, e.g. RNA-dependent RNA replicase. The replication cycle can Ik completed only if the cell is superinfected with a helper virus, which carries the gene for the missing protein. D.v. are often so de-... 

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