RESUMEN
Preexisting immunity to adenovirus serotype 5 (Ad5) has been shown to suppress the immunogenicity of recombinant Ad5 (rAd5) vector-based vaccines for human immunodeficiency virus type 1 (HIV-1) in both preclinical studies and clinical trials. A potential solution to this problem is to utilize rAd vectors derived from rare Ad serotypes, such as Ad35. However, rAd35 vectors have appeared less immunogenic than rAd5 vectors in preclinical studies to date. In this study, we explore the hypothesis that the differences in immunogenicity between rAd5 and rAd35 vectors may be due in part to differences between the fiber proteins of these viruses. We constructed capsid chimeric rAd35 vectors containing the Ad5 fiber knob (rAd35k5) and compared the immunogenicities of rAd5, rAd35k5, and rAd35 vectors expressing simian immunodeficiency virus Gag and HIV-1 Env in mice and rhesus monkeys. In vitro studies demonstrated that rAd35k5 vectors utilized the Ad5 receptor CAR rather than the Ad35 receptor CD46. In vivo studies showed that rAd35k5 vectors were more immunogenic than rAd35 vectors in both mice and rhesus monkeys. These data suggest that the Ad5 fiber knob contributes substantially to the immunogenicity of rAd vectors. Moreover, these studies demonstrate that capsid chimeric rAd vectors can be constructed to combine beneficial immunologic and serologic properties of different Ad serotypes.
Asunto(s)
Infecciones por Adenoviridae/inmunología , Adenoviridae/inmunología , Proteínas de la Cápside/genética , Vacunas Virales , Adenoviridae/clasificación , Adenoviridae/genética , Animales , Epítopos/química , Epítopos/inmunología , Inmunización , Macaca mulatta , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Serotipificación , Replicación ViralRESUMEN
Plasmid DNA vaccines elicit potent and protective immune responses in numerous small-animal models of infectious diseases. However, their immunogenicity in primates appears less potent. Here we investigate a novel approach that optimizes regulatory elements in the plasmid backbone to improve the immunogenicity of DNA vaccines. Among various regions analyzed, we found that the addition of a regulatory sequence from the R region of the long terminal repeat from human T-cell leukemia virus type 1 (HTLV-1) to the cytomegalovirus (CMV) enhancer/promoter increased transgene expression 5- to 10-fold and improved cellular immune responses to human immunodeficiency virus type 1 (HIV-1) antigens. In cynomolgus monkeys, DNA vaccines containing the CMV enhancer/promoter with the HTLV-1 R region (CMV/R) induced markedly higher cellular immune responses to HIV-1 Env from clades A, B, and C and to HIV-1 Gag-Pol-Nef compared with the parental DNA vaccines. These data demonstrate that optimization of specific regulatory elements can substantially improve the immunogenicity of DNA vaccines encoding multiple antigens in small animals and in nonhuman primates. This strategy could therefore be explored as a potential method to enhance DNA vaccine immunogenicity in humans.
Asunto(s)
Vacunas contra el SIDA/inmunología , Genes Reguladores/fisiología , VIH-1/inmunología , Virus Linfotrópico T Tipo 1 Humano/genética , Secuencias Repetidas Terminales , Vacunas de ADN/inmunología , Células 3T3 , Animales , Inmunización , Interferón gamma/biosíntesis , Macaca fascicularis , Ratones , Ratones Endogámicos BALB C , Plásmidos , Replicación ViralRESUMEN
The utility of recombinant adenovirus serotype 5 (rAd5) vector-based vaccines for HIV-1 and other pathogens will likely be limited by the high prevalence of pre-existing Ad5-specific neutralizing Abs (NAbs) in human populations. However, the immunodominant targets of Ad5-specific NAbs in humans remain poorly characterized. In this study, we assess the titers and primary determinants of Ad5-specific NAbs in individuals from both the United States and the developing world. Importantly, median Ad5-specific NAb titers were >10-fold higher in sub-Saharan Africa compared with the United States. Moreover, hexon-specific NAb titers were 4- to 10-fold higher than fiber-specific NAb titers in these cohorts by virus neutralization assays using capsid chimeric viruses. We next performed adoptive transfer studies in mice to evaluate the functional capacity of hexon- and fiber-specific NAbs to suppress the immunogenicity of a prototype rAd5-Env vaccine. Hexon-specific NAbs were remarkably efficient at suppressing Env-specific immune responses elicited by the rAd5 vaccine. In contrast, fiber-specific NAbs exerted only minimal suppressive effects on rAd5 vaccine immunogenicity. These data demonstrate that functionally significant Ad5-specific NAbs are directed primarily against the Ad5 hexon protein in both humans and mice. These studies suggest a potential strategy for engineering novel Ad5 vectors to evade dominant Ad5-specific NAbs.
Asunto(s)
Adenovirus Humanos/inmunología , Anticuerpos Antivirales/fisiología , Proteínas de la Cápside/inmunología , Vectores Genéticos/inmunología , Vacunas de ADN/inmunología , Vacunas Virales/inmunología , Adenovirus Humanos/genética , Adulto , Animales , Anticuerpos Antivirales/biosíntesis , Anticuerpos Antivirales/sangre , Proteínas de la Cápside/administración & dosificación , Proteínas de la Cápside/genética , Relación Dosis-Respuesta Inmunológica , Vectores Genéticos/administración & dosificación , Vectores Genéticos/metabolismo , Humanos , Epítopos Inmunodominantes/genética , Epítopos Inmunodominantes/inmunología , Epítopos Inmunodominantes/metabolismo , Inmunosupresores/metabolismo , Inmunosupresores/farmacología , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Pruebas de Neutralización , Estudios Seroepidemiológicos , Vacunas de ADN/administración & dosificación , Vacunas de ADN/genética , Vacunas Virales/administración & dosificación , Vacunas Virales/genéticaRESUMEN
Viral escape from cytotoxic T lymphocytes (CTLs) can undermine immune control of human immunodeficiency virus 1. It is therefore important to assess the stability of viral mutations in CTL epitopes after transmission to naive hosts. Here we demonstrate the persistence of mutations in a dominant CTL epitope after transmission of simian immunodeficiency virus variants to major histocompatibility complex-matched rhesus monkeys. Transient reversions to wild-type sequences occurred and elicited CTLs specific for the wild-type epitope, resulting in immunological pressure that rapidly reselected the mutant viruses. These data suggest that mutations in dominant human immunodeficiency virus 1 CTL epitopes may accumulate in human populations with limited major histocompatibility complex heterogeneity by a mechanism involving dynamic CTL control of transiently reverted wild-type virus.
Asunto(s)
Epítopos de Linfocito T/inmunología , Mutación , Síndrome de Inmunodeficiencia Adquirida del Simio/inmunología , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/genética , Virus de la Inmunodeficiencia de los Simios/inmunología , Linfocitos T Citotóxicos/inmunología , Animales , Epítopos de Linfocito T/genética , Humanos , Epítopos Inmunodominantes/genética , Macaca mulatta , Complejo Mayor de Histocompatibilidad/inmunología , Virus de la Inmunodeficiencia de los Simios/patogenicidadRESUMEN
DCs are critical for priming adaptive immune responses to foreign antigens. However, the utility of harnessing these cells in vivo to optimize the immunogenicity of vaccines has not been fully explored. Here we investigate a novel vaccine approach that involves delivering synergistic signals that both recruit and expand DC populations at the site of antigen production. Intramuscular injection of an unadjuvanted HIV-1 envelope (env) DNA vaccine recruited few DCs to the injection site and elicited low-frequency, env-specific immune responses in mice. Coadministration of plasmids encoding the chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) and the DC-specific growth factor fms-like tyrosine kinase 3 ligand with the DNA vaccine resulted in the recruitment, expansion, and activation of large numbers of DCs at the site of inoculation. Consistent with these findings, coadministration of these plasmid cytokines also markedly augmented DNA vaccine---elicited cellular and humoral immune responses and increased protective efficacy against challenge with recombinant vaccinia virus. These data suggest that the availability of mature DCs at the site of inoculation is a critical rate-limiting factor for DNA vaccine immunogenicity. Synergistic recruitment and expansion of DCs in vivo may prove a practical strategy for overcoming this limitation and potentiating immune responses to vaccines as well as other immunotherapeutic strategies.
Asunto(s)
Células Dendríticas/citología , Inmunoterapia/métodos , Vacunas de ADN , Animales , Vacunas contra el Cáncer , Quimiocina CCL3 , Quimiocina CCL4 , Quimiotaxis , Citocinas/metabolismo , ADN Viral , Células Dendríticas/metabolismo , Ensayo de Inmunoadsorción Enzimática , Epítopos/química , VIH-1/genética , Inmunohistoquímica , Proteínas Inflamatorias de Macrófagos/metabolismo , Proteínas de la Membrana/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Plásmidos/metabolismo , Factores de Tiempo , Virus Vaccinia/genéticaRESUMEN
The high prevalence of pre-existing immunity to adenovirus serotype 5 (Ad5) in human populations may substantially limit the immunogenicity and clinical utility of recombinant Ad5 vector-based vaccines for HIV-1 and other pathogens. A potential solution to this problem is to use vaccine vectors derived from adenovirus (Ad) serotypes that are rare in humans, such as Ad35. However, cross-reactive immune responses between heterologous Ad serotypes have been described and could prove a major limitation of this strategy. In particular, the extent of immunologic cross-reactivity between Ad5 and Ad35 has not previously been determined. In this study we investigate the impact of pre-existing anti-Ad5 immunity on the immunogenicity of candidate rAd5 and rAd35 vaccines expressing SIV Gag in mice. Anti-Ad5 immunity at levels typically found in humans dramatically blunted the immunogenicity of rAd5-Gag. In contrast, even high levels of anti-Ad5 immunity did not substantially suppress Gag-specific cellular immune responses elicited by rAd35-Gag. Low levels of cross-reactive Ad5/Ad35-specific CD4(+) T lymphocyte responses were observed, but were insufficient to suppress vaccine immunogenicity. These data demonstrate the potential utility of Ad35 as a candidate vaccine vector that is minimally suppressed by anti-Ad5 immunity. Moreover, these studies suggest that using Ad vectors derived from immunologically distinct serotypes may be an effective and general strategy to overcome the suppressive effects of pre-existing anti-Ad immunity.
Asunto(s)
Infecciones por Adenoviridae/inmunología , Infecciones por Adenoviridae/prevención & control , Adenoviridae/genética , Adenoviridae/inmunología , Vacunas Virales/genética , Vacunas Virales/inmunología , Adenoviridae/clasificación , Secuencia de Aminoácidos , Animales , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Relación Dosis-Respuesta Inmunológica , Mapeo Epitopo/métodos , Epítopos de Linfocito T/sangre , Productos del Gen gag/administración & dosificación , Productos del Gen gag/sangre , Productos del Gen gag/inmunología , Vectores Genéticos , Inmunidad Activa , Esquemas de Inmunización , Inmunización Secundaria , Inyecciones Intramusculares , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Fragmentos de Péptidos/inmunología , Fragmentos de Péptidos/metabolismo , Unión Proteica/inmunología , Serotipificación , Virus de la Inmunodeficiencia de los Simios/inmunología , Vacunas Sintéticas/administración & dosificación , Vacunas Sintéticas/inmunología , Vacunas Virales/administración & dosificaciónRESUMEN
The high prevalence of preexisting immunity to adenovirus serotype 5 (Ad5) in human populations will likely limit the immunogenicity and clinical utility of recombinant Ad5 vector-based vaccines for human immunodeficiency virus type 1 and other pathogens. Ad5-specific neutralizing antibodies (NAbs) are thought to contribute substantially to anti-Ad5 immunity, but the potential importance of Ad5-specific T lymphocytes in this setting has not been fully characterized. Here we assess the relative contributions of Ad5-specific humoral and cellular immune responses in blunting the immunogenicity of a rAd5-Env vaccine in mice. Adoptive transfer of Ad5-specific NAbs resulted in a dramatic abrogation of Env-specific immune responses following immunization with rAd5-Env. Interestingly, adoptive transfer of Ad5-specific CD8(+) T lymphocytes also resulted in a significant and durable suppression of rAd5-Env immunogenicity. These data demonstrate that NAbs and CD8(+) T lymphocytes both contribute to immunity to Ad5. Novel adenovirus vectors that are currently being developed to circumvent the problem of preexisting anti-Ad5 immunity should therefore be designed to evade both humoral and cellular Ad5-specific immune responses.