What is viral transfection or viral transduction?

For cell types not amenable to lipid-mediated transfection, viral vectors are often employed.

Viral transfection offers a means to reach hard-to-transfect cell types for protein overexpression or knockdown and is also the most commonly used method in clinical research [1–2].

Adenoviral, oncoretroviral, and lentiviral vectors have been used extensively for gene delivery in mammalian cell culture and in vivo. Other well-known examples for viral gene transfer include baculovirus and vaccinia virus-based vectors. For more information, explore viral delivery systems and see additional information on viral vectors.

A typical viral transduction protocol involves engineering of the recombinant virus carrying the transgene, amplification of recombinant viral particles in a packaging cell line, purification and titration of amplified viral particles, and subsequent infection of the cells of interest.

Diagram illustrating the basic mechanism of viral transfection

Figure 1. Mechanism of viral transfection. (1) Packaging cells are transfected with plasmids encoding the gene of interest and viral proteins. (2) The virus is assembled, harvested, and purified from the packaging cell. (3) The virus is used to transduce target cells, releasing the gene of interest. (4) In this example, RNA from the lentiviral vector is reverse-transcribed to DNA, which integrates into the host genome for recombinant protein expression.

While the achieved transduction efficiencies in primary cells and cell lines are quite high (~90–100%), only cells carrying the viral-specific receptor can be infected by the virus. It is also important to note that the packaging cell line used for viral amplification needs to be transfected with a non-viral transfection method.

Viral transfection and viral transduction can be used interchangeably and refer to the use of viruses as vectors for transporting nucleic acids into target cells.

Basic steps for performing viral transfection

Generate recombinant virus via gene cloning.

Transfect packaging cell line using a non-viral method to amplify and isolate viral vector.

Purify and titrate the viral vector containing the transgene.

Infect cells of interest (containing viral-specific receptor) at appropriate multiplicity of infection (MOI).

Remove virus from the culture and/or add fresh medium.

Assay transduced cells for gene expression or silencing.

Step 1 : Generate virus

Generate recombinant virus via gene cloning.

Step 2 : Perform non-viral transfection

Transfect packaging cell line using a non-viral method to amplify and isolate viral vector.

Step 3 : Purify viral vector

Purify and titrate the viral vector containing the transgene.

Step 4 : Infect cells & remove virus

Infect cells of interest (containing viral-specific receptor) at appropriate multiplicity of infection (MOI).

Remove virus from the culture and/or add fresh medium.

Step 5 : Assay cells

Assay transduced cells for gene expression or silencing.


Advantages and disadvantages of viral transfection

Viral transfection is advantageous in many ways, including high in vivo transfection efficiency and sustained gene expression due to integration of the viral vector into the host genome, making this system preferred for gene delivery in clinical trials. However, there are also a number of drawbacks to using viral delivery, including biosafety requirements, cytotoxicity, and variations in infectivity among viral vector preparations [1,3,4].

Advantages

  • High in vivo transfection efficiency
  • Works well in difficult cells
  • Can be used for the generation of stable cell lines with integration into the host genome (retroviral vectors) or for transient expression (adenoviral vectors)

Disadvantages

  • Immunogenicity and cytotoxicity
  • Technically challenging and laborious production procedures
  • High costs due to biosafety requirements
  • Low packaging capacity (~10 kb for most viral vectors compared to ~100 kb for non-viral vectors)
  • Variations in infectivity

Visit Transfection Basics to learn more about performing transfection in your lab.

References

  1. Glover DJ, Lipps HJ, Jans DA. Towards safe, non-viral therapeutic gene expression in humans. Nat Rev Genet. 2005 Apr;6(4):299–310. doi: 10.1038/nrg1577. PMID: 15761468. 
  2. Pfeifer A, Verma IM. Gene therapy: promises and problems. Annu Rev Genomics Hum Genet. 2001;2:177–211. doi: 10.1146/annurev.genom.2.1.177. PMID: 11701648. 
  3. Kim TK, Eberwine JH. Mammalian cell transfection: the present and the future. Anal Bioanal Chem. 2010 Aug;397(8):3173–3178. doi: 10.1007/s00216-010-3821-6. Epub 2010 Jun 13. PMID: 20549496; PMCID: PMC2911531. 
  4. Vorburger SA, Hunt KK. Adenoviral gene therapy. Oncologist. 2002;7(1):46–59. doi: 10.1634/theoncologist.7-1-46. PMID: 11854546. 

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