RESUMEN
Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract illness in infants, the elderly, and other high-risk individuals. Despite years of research in this field, there is no effective licensed vaccine to prevent RSV infection. We have generated candidate RSV vaccines using a recombinant vesicular stomatitis virus (rVSV) replicon in which the attachment and fusion domains of the VSV glycoprotein (G) have been deleted (rVSV-Gstem), rendering the virus propagation-defective except in the presence of complementing VSV G provided in trans. A form of this vector encoding the RSV fusion protein (F) gene expressed high levels of F in vitro and elicited durable neutralizing antibody responses as well as complete protection against RSV challenge in vivo. Mice vaccinated with rVSV-Gstem-RSV-F replicons also developed robust cellular responses characterized by both primary and memory Th1-biased CD8+ and CD4+ T cells. Furthermore, a single high dose of the Gstem-RSV-F replicon was effective against challenge with both RSV A and B subgroup viruses. Finally, addition of an RSV glycoprotein (G)-expressing Gstem vector significantly improved the incomplete protection achieved with a single low dose of Gstem-RSV-F vector alone.
Asunto(s)
Vectores Genéticos/genética , Vectores Genéticos/inmunología , Inmunidad Celular , Inmunidad Humoral , Infecciones por Virus Sincitial Respiratorio/inmunología , Virus Sincitiales Respiratorios/genética , Virus Sincitiales Respiratorios/inmunología , Vesiculovirus/genética , Animales , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Modelos Animales de Enfermedad , Femenino , Orden Génico , Vectores Genéticos/administración & dosificación , Humanos , Inmunización , Memoria Inmunológica , Ratones , Infecciones por Virus Sincitial Respiratorio/prevención & control , Células TH1/inmunología , Proteínas Virales de Fusión/genética , Proteínas Virales de Fusión/inmunologíaRESUMEN
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.