RESUMEN
Live, attenuated immunodeficiency virus vaccines, such as nef deletion mutants, are the most effective vaccines tested in the simian immunodeficiency virus (SIV) macaque model. In two independent studies designed to determine the breadth of protection induced by live, attenuated SIV vaccines, we noticed that three of the vaccinated macaques developed higher set point viral load levels than unvaccinated control monkeys. Two of these vaccinated monkeys developed AIDS, while the control monkeys infected in parallel remained asymptomatic. Concomitant with an increase in viral load, a recombinant of the vaccine virus and the challenge virus could be detected. Therefore, the emergence of more-virulent recombinants of live, attenuated immunodeficiency viruses and less-aggressive wild-type viruses seems to be an additional risk of live, attenuated immunodeficiency virus vaccines.
Asunto(s)
Recombinación Genética , Vacunas contra el SIDAS/genética , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/genética , Virus de la Inmunodeficiencia de los Simios/patogenicidad , Animales , Productos del Gen env/genética , Productos del Gen nef/genética , Inmunización , Macaca mulatta , Reacción en Cadena de la Polimerasa , Síndrome de Inmunodeficiencia Adquirida del Simio/prevención & control , Vacunas Atenuadas/genética , Carga Viral , VirulenciaRESUMEN
Live attenuated simian immunodeficiency viruses (SIV), such as nef deletion mutants, are the most effective vaccines tested in the SIV-macaque model so far. To modulate the antiviral immune response induced by live attenuated SIV vaccines, we had previously infected rhesus monkeys with a nef deletion mutant of SIV expressing interleukin 2 (SIV-IL2) (B. R. Gundlach, H. Linhart, U. Dittmer, S. Sopper, S. Reiprich, D. Fuchs, B. Fleckenstein, G. Hunsmann, S. Stahl-Hennig, and K. Uberla, J. Virol. 71:2225-2232, 1997). In the present study, SIV-IL2-infected macaques and macaques infected with the nef deletion mutant SIVDeltaNU were challenged with pathogenic SIV 9 to 11 months postvaccination. In contrast to the results with naive control monkeys, no challenge virus could be isolated from the SIV-IL2- and SIVDeltaNU-infected macaques. However, challenge virus sequences could be detected by nested PCR in some of the vaccinated macaques. To determine the role of immune responses directed against Env of SIV, four vaccinated macaques were rechallenged with an SIV-murine leukemia virus (MLV) hybrid in which the env gene of SIV had been functionally replaced by the env gene of amphotropic MLV. All vaccinated macaques were protected from productive infection with the SIV-MLV hybrid in the absence of measurable neutralizing antibodies, while two naive control monkeys were readily infected. Since the SIV-MLV hybrid uses the MLV Env receptor Pit2 and not CD4 and a coreceptor for virus entry, chemokine inhibition and receptor interference phenomena were not involved in protection. These results indicate that the protective responses induced by live attenuated SIV vaccines can be independent of host immune reactions directed against Env.
Asunto(s)
Genes env , Virus de la Inmunodeficiencia de los Simios/inmunología , Vacunas Virales/inmunología , Animales , Anticuerpos Antivirales/análisis , Anticuerpos Antivirales/inmunología , Secuencia de Bases , Línea Celular , Cartilla de ADN , Interleucina-2/genética , Interleucina-2/fisiología , Virus de la Leucemia Murina/inmunología , Macaca mulatta , Virus de la Inmunodeficiencia de los Simios/genética , Virus de la Inmunodeficiencia de los Simios/fisiología , Vacunas Virales/genética , Replicación ViralRESUMEN
Live attenuated simian immunodeficiency virus (SIV) vaccines, like nef deletion mutants, have been the most effective vaccines tested in the SIV/macaque model so far. The efficacy of live attenuated SIV vaccines in therapeutic vaccination and postexposure prophylaxis has not been determined. Inoculation of macaques with a pathogenic challenge virus and an attenuated SIV vaccine at the same time mimics postexposure vaccination, whereby vaccination with the attenuated virus is performed as rapidly as possible after exposure to pathogenic SIV. In the study presented here, four rhesus macaques were coinfected with pathogenic SIV and a nearly 3000-fold excess of a nef deletion mutant of SIV. Four macaques received pathogenic SIV and an approximately 200-fold excess of a nef deletion mutant expressing interleukin 2 (IL-2). The IL-2-expressing SIV had been previously constructed to enhance the immunogenicity of live attenuated SIV vaccines. All coinfected macaques had a high viral load, and some of them developed AIDS-like symptoms and pathological alterations rapidly. In the presence of pathogenic SIV, both live attenuated SIV vaccines did not protect from disease in this postexposure vaccination model.
Asunto(s)
Productos del Gen nef/genética , Productos del Gen nef/inmunología , Vacunas contra el SIDAS/inmunología , Síndrome de Inmunodeficiencia Adquirida del Simio/genética , Síndrome de Inmunodeficiencia Adquirida del Simio/inmunología , Virus de la Inmunodeficiencia de los Simios/genética , Virus de la Inmunodeficiencia de los Simios/inmunología , Vacunación/métodos , Vacunas Atenuadas/inmunología , Animales , Antígenos CD4/inmunología , Relación CD4-CD8 , División Celular , Células Cultivadas , Citometría de Flujo , Interleucina-2/genética , Interleucina-2/inmunología , Leucocitos Mononucleares , Macaca mulatta , Reacción en Cadena de la Polimerasa , Eliminación de Secuencia , Síndrome de Inmunodeficiencia Adquirida del Simio/prevención & control , Linfocitos T/citología , Linfocitos T/inmunología , Carga ViralRESUMEN
Baboon bone marrow was grafted into human immunodeficiency virus type 1-infected patients in the course of recent trials for AIDS treatment. Since the baboon genome harbors multiple copies of an endogenous oncovirus, chimeric lenti-oncoviruses could emerge in the xenotransplant recipient. To analyze the potential replication competence of hybrid viruses between different genera of retroviruses, we replaced most of the env gene of simian immunodeficiency virus with the env gene of an amphotropic murine leukemia virus. The hybrid virus could be propagated in human T-cell lines, in peripheral blood mononuclear cells of rhesus macaques, and in CD4- B-cell lines. Because of the expanded cell tropism, the hybrid virus might have a selective advantage in comparison to parental viruses. Therefore, emerging chimeric viruses may be considered a serious risk of xenotransplantation. A note of caution is also suggested for the use of pseudotyped lentiviral vectors for human gene therapy.
Asunto(s)
Virus de la Leucemia Murina/fisiología , Virus Reordenados/fisiología , Virus de la Inmunodeficiencia de los Simios/fisiología , Animales , Línea Celular , Células Cultivadas , Productos del Gen env/genética , Humanos , Virus de la Leucemia Murina/genética , Leucocitos Mononucleares/citología , Macaca mulatta , Ratones , Virus Reordenados/genética , Virus de la Inmunodeficiencia de los Simios/genética , Linfocitos T/virología , Replicación ViralRESUMEN
To study the effect of interleukin-2 (IL-2) on simian immunodeficiency virus (SIV) replication, pathogenesis, and immunogenicity, we replaced the nef gene of SIVmac239 by the IL-2 coding region. The virus, designated SIV-IL2, stably expressed high levels of IL-2 in cell culture. In comparison to SIVmac239, SIV-IL2 replicated more efficiently in peripheral blood mononuclear cells in the absence of exogenously added IL-2. To determine whether this growth advantage would be of relevance in vivo, four juvenile rhesus monkeys were infected with SIV-IL2 and four monkeys were infected with a nef deletion mutant of SIV (SIVdeltaNU). After a peak in the cell-associated viral load 2 weeks postinfection, the viruses could barely be isolated 3 to 7 months postinfection. Mean capsid antigen levels were higher in the SIV-IL2 group than in the nef deletion group 2 weeks postinfection. Viruses reisolated from the SIV-IL2-infected animals expressed high levels of IL-2 during the acute phase of infection. Deletions in the IL-2 coding region of SIV-IL2 were observed in two of the SIV-IL2-infected macaques 3 months postinfection. Urinary neopterin levels, a marker for unspecific immune stimulation, were higher in the SIV-IL2-infected macaques than in SIVdeltaNU-infected animals during the acute phase of infection. The SIV-specific T-cell-proliferative response and antibody titers were similar in both groups. Cytotoxic T cells directed against viral antigens were detected in all SIV-IL2-infected macaques and in two of the SIVdeltaNU-infected animals. Expression of IL-2 did not seem to alter the attenuated phenotype of nef deletion mutants fundamentally, although there might have been a slight increase in virus replication and immune stimulation during the acute phase of infection. Deletion of the viral IL-2 gene 3 months postinfection could be a consequence of a selective disadvantage due to local coexpression of viral antigen and IL-2 in the presence of an antiviral immune response.
Asunto(s)
Productos del Gen nef/inmunología , Interleucina-2/inmunología , Síndrome de Inmunodeficiencia Adquirida del Simio/inmunología , Virus de la Inmunodeficiencia de los Simios/inmunología , Animales , Secuencia de Bases , Línea Celular , ADN Viral , Eliminación de Gen , Productos del Gen nef/genética , Vectores Genéticos , Humanos , Interleucina-2/genética , Macaca mulatta , Datos de Secuencia Molecular , Proteínas Recombinantes de Fusión/genética , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/aislamiento & purificación , Virus de la Inmunodeficiencia de los Simios/fisiología , Replicación ViralRESUMEN
A new approach to T cell epitope determination is presented. Critical amino acids for the induction of cytotoxic T cell responses were identified using synthetic peptide libraries with single defined sequence positions combined with randomized sequence positions. Sequences for potential T cell epitopes were deduced from scan profiles using combinations of the active amino acids. Highly potent epitopes for cytotoxic T lymphocytes were obtained. Epitopes defined by this approach are, as shown in this communication, not necessarily the natural epitopes and, therefore, were named synthetic epitopes. They can serve effectively for the development of vaccines or for the determination of T cell receptor antagonists.
Asunto(s)
Epítopos/inmunología , Péptidos/inmunología , Linfocitos T/inmunología , Secuencia de Aminoácidos , Animales , Citotoxicidad Inmunológica , Biblioteca de Genes , Ratones , Datos de Secuencia Molecular , Péptidos/síntesis química , Ratas , Linfocitos T Citotóxicos/inmunologíaRESUMEN
Random peptide libraries were employed to investigate the specificity of Ag recognition by H-3-specific, H-2K(b)-restricted CTL clones. The peptide libraries consist of octapeptides with one defined sequence position and mixtures of 19 amino acids (all proteinogenic amino acids except for cysteine) in the remaining seven sequence positions. The complete set of 152 peptide libraries includes all octapeptides possible with these amino acids. Responses of the CTL clones to these peptide libraries reveal patterns of preferred epitope amino acids. Depending on the CTL clone tested, varying numbers of different amino acids were identified for the different sequence positions indicating degeneracy of Ag recognition. Sequences for synthetic epitopes active at low pM concentrations could be deduced from these patterns. They confirm that TCRs of CTL clones do not exhibit specificity for unique ligand structures but rather can interact with sets of ligands. The sequences of peptides recognized by a single clone exhibit great sequence heterogeneity.