RESUMEN
UNLABELLED: Although antibodies to the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein have been studied extensively for their ability to block viral infectivity, little data are currently available on nonneutralizing functions of these antibodies, such as their ability to eliminate virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC). HIV-1 Env-specific antibodies of diverse specificities, including potent broadly neutralizing and nonneutralizing antibodies, were therefore tested for ADCC against cells infected with a lab-adapted HIV-1 isolate (HIV-1NL4-3), a primary HIV-1 isolate (HIV-1JR-FL), and a simian-human immunodeficiency virus (SHIV) adapted for pathogenic infection of rhesus macaques (SHIVAD8-EO). In accordance with the sensitivity of these viruses to neutralization, HIV-1NL4-3-infected cells were considerably more sensitive to ADCC, both in terms of the number of antibodies and magnitude of responses, than cells infected with HIV-1JR-FL or SHIVAD8-EO ADCC activity generally correlated with antibody binding to Env on the surfaces of virus-infected cells and with viral neutralization; however, neutralization was not always predictive of ADCC, as instances of ADCC in the absence of detectable neutralization, and vice versa, were observed. These results reveal incomplete overlap in the specificities of antibodies that mediate these antiviral activities and provide insights into the relationship between ADCC and neutralization important for the development of antibody-based vaccines and therapies for combating HIV-1 infection. IMPORTANCE: This study provides fundamental insights into the relationship between antibody-dependent cell-mediated cytotoxicity (ADCC) and virus neutralization that may help to guide the development of antibody-based vaccines and immunotherapies for the prevention and treatment of HIV-1 infection.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Anticuerpos Neutralizantes/inmunología , Citotoxicidad Celular Dependiente de Anticuerpos , Anticuerpos Anti-VIH/inmunología , VIH-1/inmunología , Productos del Gen env del Virus de la Inmunodeficiencia Humana/inmunología , Vacunas contra el SIDA/inmunología , Animales , Anticuerpos Monoclonales/metabolismo , Anticuerpos Neutralizantes/metabolismo , Especificidad de Anticuerpos , Sitios de Unión de Anticuerpos , Células HEK293 , Infecciones por VIH/prevención & control , Infecciones por VIH/terapia , Infecciones por VIH/virología , VIH-1/aislamiento & purificación , Humanos , Macaca mulatta , Pruebas de Neutralización , Virus de la Inmunodeficiencia de los Simios/inmunología , Productos del Gen env del Virus de la Inmunodeficiencia Humana/metabolismoRESUMEN
Tetherin is an IFN-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. HIV-1 overcomes this restriction factor by expressing HIV-1 viral protein U (Vpu), which down-regulates and degrades tetherin. We report that mutations in Vpu that impair tetherin antagonism increase the susceptibility of HIV-infected cells to antibody-dependent cell-mediated cytotoxicity (ADCC), and conversely that RNAi knockdown of tetherin, but not other cellular proteins down-modulated by Vpu, decreases the susceptibility of HIV-infected cells to ADCC. These results reveal that Vpu protects HIV-infected cells from ADCC as a function of its ability to counteract tetherin. By serving as link between innate and adaptive immunity, the antiviral activity of tetherin may be augmented by virus-specific antibodies, and hence much greater than previously appreciated.
Asunto(s)
Citotoxicidad Celular Dependiente de Anticuerpos/inmunología , Citoprotección , Infecciones por VIH/inmunología , Infecciones por VIH/patología , Proteínas del Virus de la Inmunodeficiencia Humana/metabolismo , Proteínas Reguladoras y Accesorias Virales/metabolismo , Sustitución de Aminoácidos , Citotoxicidad Celular Dependiente de Anticuerpos/efectos de los fármacos , Antígenos CD/metabolismo , Antígenos CD4/metabolismo , Citoprotección/efectos de los fármacos , Proteínas Ligadas a GPI/antagonistas & inhibidores , Proteínas Ligadas a GPI/metabolismo , Eliminación de Gen , Humanos , Interferón-alfa/farmacología , Interferencia de ARN/efectos de los fármacos , Receptores de Superficie Celular/metabolismo , Miembro 1 de la Familia de Moléculas Señalizadoras de la Activación LinfocitariaRESUMEN
UNLABELLED: The cytoplasmic tails of human and simian immunodeficiency virus (HIV and SIV, respectively) envelope glycoproteins contain a highly conserved, membrane-proximal endocytosis motif that prevents the accumulation of Env on the surface of infected cells prior to virus assembly. Using an assay designed to measure the killing of virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC), we show that substitutions in this motif increase the susceptibility of HIV-1- and SIV-infected cells to ADCC in a manner that directly correlates with elevated Env levels on the surface of virus-infected cells. In the case of HIV-1, this effect is additive with a deletion in vpu recently shown to enhance the susceptibility of HIV-1-infected cells to ADCC as a result of tetherin-mediated retention of budding virions on the cell surface. These results reveal a previously unappreciated role for the membrane-proximal endocytosis motif of gp41 in protecting HIV-1- and SIV-infected cells from antibody responses by regulating the amount of Env present on the cell surface. IMPORTANCE: This study reveals an unappreciated role for the membrane-proximal endocytosis motif of gp41 in protecting HIV-1- and SIV-infected cells from elimination by Env-specific antibodies. Thus, strategies designed to interfere with this mechanism of Env internalization may improve the efficacy of antibody-based vaccines and antiretroviral therapies designed to enhance the immunological control of HIV-1 replication in chronically infected individuals.
Asunto(s)
Anticuerpos Antivirales/biosíntesis , Citotoxicidad Celular Dependiente de Anticuerpos/genética , Endocitosis/inmunología , VIH-1/inmunología , Virus de la Inmunodeficiencia de los Simios/inmunología , Productos del Gen env del Virus de la Inmunodeficiencia Humana/inmunología , Secuencia de Aminoácidos , Animales , Anticuerpos Antivirales/genética , Antígenos CD/genética , Antígenos CD/inmunología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/virología , Línea Celular , Membrana Celular/química , Membrana Celular/inmunología , Membrana Celular/virología , Secuencia Conservada , Proteínas Ligadas a GPI/genética , Proteínas Ligadas a GPI/inmunología , Expresión Génica , Proteína gp41 de Envoltorio del VIH/genética , Proteína gp41 de Envoltorio del VIH/inmunología , VIH-1/genética , Interacciones Huésped-Patógeno , Proteínas del Virus de la Inmunodeficiencia Humana/genética , Proteínas del Virus de la Inmunodeficiencia Humana/inmunología , Humanos , Inmunidad Celular , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/virología , Datos de Secuencia Molecular , Estructura Terciaria de Proteína , Alineación de Secuencia , Virus de la Inmunodeficiencia de los Simios/genética , Proteínas Reguladoras y Accesorias Virales/genética , Proteínas Reguladoras y Accesorias Virales/inmunología , Productos del Gen env del Virus de la Inmunodeficiencia Humana/genéticaRESUMEN
The resistance of human immunodeficiency virus type 1 (HIV-1) to antibody-mediated immunity often prevents the detection of antibodies that neutralize primary isolates of HIV-1. However, conventional assays for antibody functions other than neutralization are suboptimal. Current methods for measuring the killing of virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC) are limited by the number of natural killer (NK) cells obtainable from individual donors, donor-to-donor variation, and the use of nonphysiological targets. We therefore developed an ADCC assay based on NK cell lines that express human or macaque CD16 and a CD4(+) T-cell line that expresses luciferase from a Tat-inducible promoter upon HIV-1 or simian immunodeficiency virus (SIV) infection. NK cells and virus-infected targets are mixed in the presence of serial plasma dilutions, and ADCC is measured as the dose-dependent loss of luciferase activity. Using this approach, ADCC titers were measured in plasma samples from HIV-infected human donors and SIV-infected macaques. For the same plasma samples paired with the same test viruses, this assay was approximately 2 orders of magnitude more sensitive than optimized assays for neutralizing antibodies-frequently allowing the measurement of ADCC in the absence of detectable neutralization. Although ADCC correlated with other measures of Env-specific antibodies, neutralizing and gp120 binding titers did not consistently predict ADCC activity. Hence, this assay affords a sensitive method for measuring antibodies capable of directing ADCC against HIV- or SIV-infected cells expressing native conformations of the viral envelope glycoprotein and reveals incomplete overlap of the antibodies that direct ADCC and those measured in neutralization and binding assays.