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I'm wondering about the carrying capacity also referred to packaging capacity or loading capacity (how many base pairs can be packed efficiently into virions) of the pseudotyped rabies virus SAD-dG as described in the Wickersham, Callaway publications.

Wickersham, I. R., Finke, S., Conzelmann, K.-K., & Callaway, E. M. (2006). Retrograde neuronal tracing with a deletion-mutant rabies virus. Nature methods, 4(1), 47–49. doi:10.1038/nmeth999

Wickersham, I. R., Lyon, D. C., Barnard, R. J. O., Mori, T., Finke, S., Conzelmann, K.-K., et al. (2007). Monosynaptic Restriction of Transsynaptic Tracing from Single, Genetically Targeted Neurons. Neuron, 53(5), 639–647. doi:10.1016/j.neuron.2007.01.033

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up vote 2 down vote accepted

I have gone through quite a number of papers using this virus, but I haven't found any definite answer on the maximum insert length. There is an indirect answer, though. The two articles cited below both report possible insert length of up to 3.7kb without any experimental problems. This insert length results in a viral genome which is about 1.9kb longer than naturally occurring. So at least 3.7kb insert length are possible, if longer inserts can also be used, needs to be tested.


  1. Design and generation of recombinant rabies virus vectors.
  2. New rabies virus variants for monitoring and manipulating activity and gene expression in defined neural circuits.
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