The combination of marker gene swapping and fluorescence-activated cell sorting improves the efficiency of recombinant modified vaccinia virus Ankara vaccine production for human use.
Modified vaccinia virus Ankara (MVA) is employed as a human vaccine vector for the high expression of heterologous genes and the lack of replication in mammalian cells. This study demonstrates that cells infected by recombinant viruses can be obtained by fluorescence-activated cell sorting. Recombinant viruses are generated by a swapping event between a red fluorescent protein gene in the acceptor virus and a plasmid cassette coding for both a green fluorescent marker and a transgene. To prevent the carry-over of parental virus, due to superinfection of the cells harbouring recombinant viruses, the sorting is performed on cells infected at low m.o.i. in the presence of a reversible inhibitor of viral particle release. Terminal dilution cloning is then used to isolate both green and marker-free recombinant viruses, which can be identified by whole-plate fluoroimaging. The differential visualization of all the viral types involved allows a stepwise monitoring of all recombinations and leads to a straightforward and efficient flow cytometry-based cell sorting purification protocol. As an example of the efficacy of this sorting procedure, the construction of rMVA's coding for the rat nuclear protein HMGB1 and H5N1 influenza A virus hemagglutinin is reported. The entire recombinant MVA production process is carried out in serum-free media employing primary chicken embryo fibroblasts (CEF), which are certified for the preparation of human vaccines. This rMVA production method is faster, simpler and more reliable than any other available procedure for obtaining safe vaccine stocks for human use.
DIBIT-HSR, San Raffaele Scientific Institute, Milano, Italy.
Giulia
G
Di Lullo
Elisa
E
Soprana
Maddalena
M
Panigada
Alessio
A
Palini
Alessandra
A
Agresti
Claudio
C
Comunian
Adelaide
A
Milani
Ilaria
I
Capua
Volker
V
Erfle
Antonio G
AG
Siccardi
D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D016895:Culture Media, Serum-Free; D005347:Fibroblasts / Q000821:virology; D005434:Flow Cytometry / Q000379:methods; D005814:Genes, Viral; D049452:Green Fluorescent Proteins / Q000235:genetics; D024243:HMGB1 Protein / Q000235:genetics; D053124:Influenza A Virus, H5N1 Subtype / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics; D051381:Rats; D011995:Recombination, Genetic; D012900:Smallpox Vaccine; D013194:Staining and Labeling / Q000379:methods; D014616:Vaccinia virus / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification*; D000097573:Red Fluorescent Protein
D016895:Culture Media, Serum-Free; D049452:Green Fluorescent Proteins; D024243:HMGB1 Protein; D008164:Luminescent Proteins; D012900:Smallpox Vaccine; D000097573:Red Fluorescent Protein; C104200:Hbp1 protein, rat