Vaccinia Virus Expression System


Replication‐competent Vaccinia virus was used as the vaccine in the campaign to eradicate smallpox. After the disease was eradicated, recombinant Vaccinia viruses were created that were capable of expressing foreign genes. This made Vaccinia‐based systems available for mammalian cell expression of recombinant protein, an advantage of which, similar to other mammalian expression systems, is authentic posttranslational modification. Generation of recombinant Vaccinia also provided an opportunity for developing Vaccinia‐based vaccines for use against nonpoxvirus diseases. In this respect, recombinant Vaccinia virus and recombinant versions of an attenuated derivative, Modified Vaccinia virus Ankara (MVA) have been extensively studied. Today, there are recombinant Vaccinia viruses expressing foreign antigens in phases I–III clinical trials relating to viral, bacterial, parasitic and cancer‐related diseases, and a licensed veterinary vaccine.

Key Concepts

  • Smallpox was eradicated following a vaccination campaign in which live Vaccinia virus was used as the vaccine.
  • Foreign genes can be inserted into the Vaccinia virus genome to create recombinant Vaccinia virus strains.
  • The Vaccinia virus expression system allows for mammalian cell expression of recombinant protein, an advantage of which is authentic posttranslational modification.
  • Recombinant Vaccinia can deliver vaccine antigens and evoke potent cell‐mediated and humoral responses specific to the inserted gene.
  • Vaccination with recombinant organisms can confer protection against viral, bacterial, parasitic and cancer‐related diseases.

Keywords: Vaccinia virus; recombinant virus; expression system; viral vector; vaccine

Figure 1. Overview of the vaccinia virus life cycle. Four types of vaccinia virion are formed during each round of replication. Intracellular mature virus (IMV) is released on cell lysis. Cell‐associated enveloped virus (CEV) is responsible for cell‐to‐cell spread and extracellular enveloped virus (EEV) for longer range dissemination. The intracellular enveloped virus (IEV) represents an IMV–CEV/EEV intermediate (Smith et al., ). Adapted from Hall Y and Carroll MW Recombinant MVA vaccines: optimization, preclinical, and product development. In: Morrow WJW, Sheikh NA, Schmidt CS, Davies HD (eds) Vaccinology Principles and Practice, pp. 209–223. Chichester: Wiley‐Blackwell.
Figure 2. Immunostained plaques. BHK‐21 and CEF monolayers were infected with MVA. After 24 h, cells were fixed and immunostained using antivaccinia antibody to visualise infected cells.
Figure 3. Typical features of a transfer plasmid. Left and right flanks homologous to the vaccinia genome determine the point and orientation of insertion for the recombinant cassette. The gene of interest (GOI) and a selection marker, green fluorescent protein (GFP), are inserted, each with its own vaccinia promoter (P) for control of gene expression.
Figure 4. Detection of recombinant vaccinia expression. CEF cell lysate samples were separated by SDS PAGE, transferred to nitrocellulose via Western Blot and then subjected to immunodetection using antibody specific for the recombinant insert. Each sample had been infected with a different recombinant MVA (rMVA) strain: (1) rMVA expressing gene A (48 kDa); (2) rMVA expressing gene B (83 kDa) and (3) multiple‐rMVA expressing two inserts, gene A and gene B.


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Further Reading

Cotter CA, Earl PL, Wyatt LS and Moss B (2017) Preparation of cell cultures and Vaccinia virus stocks. Current Protocols in Molecular Biology 117: 16.1–16.8.

Cottingham MG and Carroll MW (2013) Recombinant MVA vaccines: dispelling the myths. Vaccine 31 (39): 4247–4251.

Gilbert SC (2013) Clinical development of Modified Vaccinia virus Ankara vaccines. Vaccine 31 (39): 4241–4246.

Moss B (2007) Poxviridae: the viruses and their replication. In: Fields BN, Knipe DM and Howley PM (eds) Fields Virology, pp. 2905–2946. Philadelphia: Lippincott‐Raven Publishers.

Wyatt LS, Earl PL and Moss B (2017) Generation of Recombinant Vaccinia Viruses. Current Protocols in Molecular Biology 117: 16.7.1–16.7.8.

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Hall, Yper, and Carroll, Miles W(Jan 2018) Vaccinia Virus Expression System. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0002659.pub4]