Envelope targeting: hemagglutinin attachment specificity rather than fusion protein cleavage-activation restricts Tupaia paramyxovirus tropism.
To engineer a targeting envelope for gene and oncolytic vector delivery, we characterized and modified the envelope proteins of Tupaia paramyxovirus (TPMV), a relative of the morbilli- and henipaviruses that neither infects humans nor has cross-reactive relatives that infect humans. We completed the TPMV genomic sequence and noted that the predicted fusion (F) protein cleavage-activation site is not preceded by a canonical furin cleavage sequence. Coexpression of the TPMV F and hemagglutinin (H) proteins induced fusion of Tupaia baby fibroblasts but not of human cells, a finding consistent with the restricted TPMV host range. To identify the factors restricting fusion of non-Tupaia cells, we initially analyzed F protein cleavage. Even without an oligo- or monobasic protease cleavage sequence, TPMV F was cleaved in F1 and F2 subunits in human cells. Edman degradation of the F1 subunit yielded the sequence IFWGAIIA, placing the conserved phenylalanine in position 2, a novelty for paramyxoviruses but not the cause of fusion restriction. We then verified whether the lack of a TPMV H receptor limits fusion. Toward this end, we displayed a single-chain antibody (scFv) specific for the designated receptor human carcinoembryonic antigen on the TPMV H ectodomain. The H-scFv hybrid protein coexpressed with TPMV F mediated fusion of cells expressing the designated receptor, proving that the lack of a receptor limits fusion and that TPMV H can be retargeted. Targeting competence and the absence of antibodies in humans define the TPMV envelope as a module to be adapted for ferrying ribonucleocapsids of oncolytic viruses and gene delivery vectors.
Springfeld
Christoph
C
Mayo Clinic Rochester, Molecular Medicine Program, Guggenheim 1838, 200 First St. SW, Rochester, MN 55902, USA.
von Messling
Veronika
V
Tidona
Christian A
CA
Darai
Gholamreza
G
Cattaneo
Roberto
R
D000595:Amino Acid Sequence; D000818:Animals; D005822:Genetic Vectors / Q000502:physiology*; D016679:Genome, Viral; D006389:Hemagglutinins, Viral / Q000502:physiology*; D006801:Humans; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D010252:Paramyxoviridae / Q000235:genetics / Q000502:physiology*; D011991:Receptors, Virus / Q000502:physiology; D018523:Tropism; D014417:Tupaia / Q000821:virology*; D014760:Viral Fusion Proteins / Q000378:metabolism*
D006389:Hemagglutinins, Viral; D011991:Receptors, Virus; D014760:Viral Fusion Proteins