Attenuation of Recombinant Vesicular Stomatitis Virus-Human Immunodeficiency Virus Type 1 Vaccine Vectors by Gene Translocations and G Gene Truncation Reduces Neurovirulence and Enhances Immunogenicity in Mice

Abstract

Recombinant vesicular stomatitis virus (rVSV) has shown great potential as a new viral vector for vaccination. However, the prototypic rVSV vector described previously was found to be insufficiently attenuated for clinical evaluation when assessed for neurovirulence in nonhuman primates. Here, we describe the attenuation, neurovirulence, and immunogenicity of rVSV vectors expressing human immunodeficiency virus type 1 Gag. These rVSV vectors were attenuated by combinations of the following manipulations: N gene translocations (N4), G gene truncations (CT1 or CT9), noncytopathic M gene mutations (Mncp), and positioning of the gag gene into the first position of the viral genome (gag1). The resulting N4CT1-gag1, N4CT9-gag1, and MncpCT1-gag1 vectors demonstrated dramatically reduced neurovirulence in mice following direct intracranial inoculation. Surprisingly, in spite of a very high level of attenuation, the N4CT1-gag1 and N4CT9-gag1 vectors generated robust Gag-specific immune responses following intramuscular immunization that were equivalent to or greater than immune responses generated by the more virulent prototypic vectors. MncpCT1-gag1 also induced Gag-specific immune responses following intramuscular immunization that were equivalent to immune responses generated by the prototypic rVSV vector. Placement of the gag gene in the first position of the VSV genome was associated with increased in vitro expression of Gag protein, in vivo expression of Gag mRNA, and enhanced immunogenicity of the vector. These findings demonstrate that through directed manipulation of the rVSV genome, vectors that have reduced neurovirulence and enhanced immunogenicity can be made.

Safety Studies on Intrahepatic or Intratumoral Injection of Oncolytic Vesicular Stomatitis Virus Expressing Interferon-β in Rodents and Nonhuman Primates

“…Intranasal instillation of VSV into mice leads to initial infection of olfactory receptor neurons and then the olfactory bulb, and this is followed by acute infection of the CNS, breakdown of the blood-brain barrier, and the death of mice (Forger et al, 1991;Bi et al, 1995). Data indicate that attenuation of VSV can occur through genetic modifications of the viral genome (Cooper et al, 2008). Thus, although all four cynomolgus macaques inoculated intrathalamically with 10 7 PFU of wild-type VSV developed signs of neurological disease by days 6-7 after virus inoculation (head tilt, irregular gait, tremors, and ataxia), only one of four macaques receiving recombinant VSV developed clinical and histological signs similar to the wild-type VSV group ( Johnson et al, 2007).…”

Re-engineering Vesicular Stomatitis Virus to Abrogate Neurotoxicity, Circumvent Humoral Immunity, and Enhance Oncolytic Potency

“…We removed the VSV glycoprotein G, the key neurovirulence determinant (20)(21)(22), and replaced it with the arenavirus glycoprotein LCMV-GP (23)(24)(25)(26), thereby generating rVSV(GP). While there are no doses at which wtVSV can be safely introduced into rodent brains, we found that rVSV(GP) caused no significant neurotoxicity even at doses of 10 8 plaque-forming units (PFU).…”

The vesicular stomatitis virus-based Ebola virus vaccine: From concept to clinical trials

“…4 Multiple strategies have been developed to achieve attenuation of the VSV vaccine vector, including truncation of the cytoplasmic tail of the VSV glycoprotein (G) to reduce virulence, as well as modification of other structural proteins. 5 , 6 Alternatively, when the antigen expressed is a glycoprotein that facilitates cell entry, removal and replacement of VSV G with a different viral glycoprotein can occur while preserving the immunogenicity of a replication-competent vector. 7 This strategy has proven effective for the VSV-EBOV vaccine, in which the EBOV glycoprotein (GP) is inserted into a VSV vector from which the G open reading frame is deleted (VSV-ΔG), resulting in a replication-competent virus particle exhibiting rhabdovirus morphology with EBOV GP expressed on its surface (Fig.…”