Complementing Defective Viruses That Express Separate Paramyxovirus Glycoproteins Provide a New Vaccine Vector Approach

Abstract

Replication-defective vaccine vectors based on vesicular stomatitis virus (VSV) lacking its envelope glycoprotein gene (G) are highly effective in animal models. However, such ⌬G vectors are difficult to grow because they require complementation with the VSV G protein. In addition, the complementing G protein induces neutralizing antibodies in animals and thus limits multiple vector applications. In the process of generating an experimental Nipah virus (a paramyxovirus) vaccine, we generated two defective VSV⌬G vectors, each expressing one of the two Nipah virus (NiV) glycoproteins (G and F) that are both required for virus entry to host cells. These replication-defective VSV vectors were effective at generating NiV neutralizing antibody in mice. Most interestingly, we found that these two defective viruses could be grown together and passaged in tissue culture cells in the absence of VSV G complementation. This mixture of complementing defective viruses was also highly effective at generating NiV neutralizing antibody in animals. This novel approach to growing and producing a vaccine from two defective viruses could be generally applicable to vaccine production for other paramyxoviruses or for other viruses where the expression of at least two different proteins is required for viral entry. Such an approach minimizes biosafety concerns that could apply to single, replicationcompetent VSV recombinants expressing all proteins required for infection.

Identification of a Region in the Stalk Domain of the Nipah Virus Receptor Binding Protein That Is Critical for Fusion Activation

“…1A) were infected with a recombinant vesicular stomatitis virus (VSV) that encodes NiV F but not VSV-G [VSV-F(NiV)], complemented with VSV-G externally and is thus replication deficient. This replication-deficient virus, which carries VSVG and NiV F on its surface but only NiV F in its genome, has been shown to efficiently promote fusion and plaque formation when complemented with NiV G (29). We use this recombinant virus to evaluate the activity of the chimeric receptor proteins in viral plaque enlargement, which has been an accurate marker for the fusion activation properties of several HPIV3 HN proteins (32).…”

Chikungunya, Influenza, Nipah, and Semliki Forest Chimeric Viruses with Vesicular Stomatitis Virus: Actions in the Brain

“…All the chimeric viruses discussed here have shown efficacy in acting in a vaccine capacity to protect against the respective virus antigens, including Nipah virus, chikungunya virus, and influenza virus (44,(46)(47)(48)(49). By virtue of their safety in both adult and developing brains, VSVΔG-CHIKV and VLV showed the least adverse neurotropism among the chimeric viruses tested; these viruses merit further investigation for potential applications, including vaccination.…”

“…The VSV glycoprotein gene was deleted (VSVΔG) in four of the viruses, VSVΔG-CHIKV, VSVΔG-H5N1, VSVΔG-Nipah F, and VSVΔG-Nipah G. VLV was generated from the Semliki Forest virus RNA replicon encoding VSV G and the four nonstructural proteins of SFV but none of the SFV structural proteins (37,39). All four recombinants have been tested as possible vaccine vectors (38,(44)(45)(46)(47)(48)(49). Three additional recombinant VSVs were used for control purposes; all three have been previously used to test intracranial safety (18,41,50).…”

“…Having different VSV recombinants each expressing only one Nipah glycoprotein, however, appears safe. Nonspreading VSVΔG-Nipah F or VSVΔG-Nipah G, used separately, generated a protective immune response against Nipah virus (47,48) and in the absence of ongoing replication would be substantially safer and more viable than the combined VSVΔG-Nipah FϩG.…”

“…VSVΔG-Nipah FϩG is a combination of the two replicationincompetent VSVs that each express a single Nipah glycoprotein, F or G. This was done by adding together the two replication-incompetent viruses (VSVΔG-Nipah F plus VSVΔG-Nipah G). Whereas each separately does not propagate, together the two recombinants complement each other and generate a replication-competent chimeric virus pair that expresses both VSV F and G on the virus surface (47,48) when both viruses infect the same cell. Each of the two chimeric viruses was initially pseudotyped with the VSV glycoprotein by expanding the respective virus in cells that express the VSV glycoprotein on the surface.…”