RESUMO
The prophylactic efficacies of several multivalent replication-incompetent adenovirus serotype 5 (Ad5) vaccines were examined in rhesus macaques using an intrarectal high-dose simian immunodeficiency virus SIVmac239 challenge model. Cohorts of Mamu-A*01(+)/B*17(-) Indian rhesus macaques were immunized with one of several combinations of Ad5 vectors expressing Gag, Pol, Nef, and Env gp140; for comparison, a Mamu-A*01(+) cohort was immunized using the Ad5 vector alone. There was no sign of immunological interference between antigens in the immunized animals. In general, expansion of the antigen breadth resulted in more favorable virological outcomes. In particular, the order of efficacy trended as follows: Gag/Pol/Nef/Env approximately Gag/Pol > Gag approximately Gag/Pol/Nef > Nef. However, the precision in ranking the vaccines based on the study results may be limited by the cohort size, and as such, may warrant additional testing. The implications of these results in light of the recent discouraging results of the phase IIb study of the trivalent Ad5 HIV-1 vaccine are discussed.
Assuntos
Adenoviridae/imunologia , Vacinas contra a SAIDS/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios , Vírus da Imunodeficiência Símia/imunologia , Vacinas contra a AIDS/imunologia , Adenoviridae/genética , Animais , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/imunologia , Ensaios Clínicos Fase II como Assunto , Humanos , Macaca mulatta/imunologia , Macaca mulatta/virologia , Testes de Neutralização , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/genética , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/imunologia , Carga Viral , Viremia/imunologiaRESUMO
A series of 4-oxo-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxamides was synthesized and tested for their inhibition of HIV-1 integrase catalytic activity and HIV-1 replication in cells. Structure-activity studies around lead compound 5 indicated that a coplanar relationship of metal-binding heteroatoms provides optimal binding to the integrase active site. Identification of potency-enhancing substituents and adjustments in lipophilicity provided 17b which inhibits integrase-catalyzed strand transfer with an IC(50) value of 74 nM and inhibits HIV-1 replication in cell culture in the presence of 50% normal human serum with an IC(95) value of 63 nM.
Assuntos
Inibidores de Integrase de HIV/química , Inibidores de Integrase de HIV/farmacologia , Integrase de HIV/efeitos dos fármacos , Pirazinas/química , Pirazinas/farmacologia , Catálise , Linhagem Celular , Integrase de HIV/metabolismo , Inibidores de Integrase de HIV/síntese química , HIV-1/enzimologia , HIV-1/fisiologia , Pirazinas/síntese química , Relação Estrutura-Atividade , Replicação Viral/efeitos dos fármacosRESUMO
A series of 10-hydroxy-7,8-dihydropyrazino[1',2':1,5]pyrrolo[2,3-d]pyridazine-1,9(2H,6H)-diones was synthesized and tested for their inhibition of HIV-1 replication in cell culture. Structure-activity studies indicated that high antiviral potency against wild-type virus as well as viruses containing integrase mutations that confer resistance to three different structural classes of integrase inhibitors could be achieved by incorporation of small aliphatic groups at certain positions on the core template. An optimal compound from this study, 16, inhibits integrase strand-transfer activity with an IC(50) value of 10 nM, inhibits HIV-1 replication in cell culture with an IC(95) value of 35 nM in the presence of 50% normal human serum, and displays modest pharmacokinetic properties in rats (i.v. t(1/2)=5.3 h, F=17%).
Assuntos
Química Farmacêutica/métodos , Integrase de HIV/síntese química , Integrase de HIV/farmacologia , Integrases/genética , Mutação , Administração Oral , Animais , Antivirais/farmacologia , Disponibilidade Biológica , Desenho de Fármacos , Humanos , Concentração Inibidora 50 , Modelos Químicos , Ratos , Relação Estrutura-Atividade , Replicação ViralRESUMO
A series of potent novel 8-hydroxy-3,4-dihydropyrrolo[1,2-a]pyrazine-1(2H)-one HIV-1 integrase inhibitors was identified. These compounds inhibited the strand transfer process of HIV-1 integrase and viral replication in cells. Compound 12 is active against replication of HIV-1 in cell culture with a CIC(95) of 0.31microM. Further SAR exploration led to the preparation of pseudosymmetrical tricyclic pyrrolopyrazine inhibitors 23 and 24 with further improvement in antiviral activity.
Assuntos
Inibidores de Integrase de HIV/química , Integrase de HIV , Pirazinas/química , Linhagem Celular Tumoral , Integrase de HIV/fisiologia , Inibidores de Integrase de HIV/farmacologia , Humanos , Pirazinas/farmacologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/enzimologia , Linfócitos T/virologiaRESUMO
OBJECTIVE: To assess responses to indinavir (IDV)-ritonavir (RTV)-based regimens among HIV-1 infected patients with prior failure of protease inhibitors, and to assess the effects of adherence to therapy and pre-existing genotypic and phenotypic resistance on this response. METHODS: Twenty-eight patients initiating salvage regimens with IDV-RTV (800 mg and 200 mg twice daily, respectively) plus one or more reverse transcriptase inhibitor (RTI) were identified retrospectively. Genotypic and phenotypic susceptibilities to multiple antiretroviral agents were determined on viral samples collected at initiation of the salvage regimens, and adherence to therapy was determined through patient self-reporting. Response to therapy (viral RNA = 400 copies/ml) was assessed at the end of and beyond 6 months of follow-up. RESULTS: Based on responses measured in the first 6 months of follow-up, 16 responders and 12 non-responders were identified without differences in baseline demographic factors, laboratory parameters, extent of prior antiretroviral therapy, or characteristics of the RTI components of the new IDV-RTV-based regimens. Adequate adherence was associated with virologic responses (P = 0.005). There were trends for genotypic and phenotypic resistance to be associated with adequate adherence, and, surprisingly, phenotypic resistance to IDV was associated with virologic response rather than with therapeutic failure (P = 0.02). Beyond 6 months of follow-up (mean follow-up 69 weeks), adequate adherence was still associated with virologic response (P = 0.001), but genotypic or phenotypic resistance to IDV were not associated with therapeutic failure. CONCLUSIONS: These results suggest that IDV-RTV-based regimens may be able to overcome IDV resistance. This underscores the importance of drug adherence, potency, and exposure in determining virologic responses to antiretroviral therapy.
Assuntos
Infecções por HIV/tratamento farmacológico , Inibidores da Protease de HIV/uso terapêutico , HIV-1 , Indinavir/uso terapêutico , Ritonavir/uso terapêutico , Farmacorresistência Viral , Quimioterapia Combinada , Feminino , Seguimentos , Genótipo , Infecções por HIV/virologia , Protease de HIV/genética , HIV-1/efeitos dos fármacos , HIV-1/genética , Humanos , Masculino , Cooperação do Paciente , Fenótipo , Estudos Retrospectivos , Terapia de Salvação/métodos , Falha de Tratamento , Carga ViralRESUMO
The blockade of the HIV protease has become a major target in the search for an effective therapy for AIDS.1 While many reports of potent HIV-1 inhibitors have appeared recently, the compound Ro 31-8959 remains the least selective for the HIV-1 and HIV-2 proteases.2 This property may result in reduced susceptibility to resistance since these represent the genetically most divergent strains of HIV presently known to exist.
RESUMO
The design, synthesis, and biological evaluation of a series of HIV-1 protease inhibitors [(-)-6, (-)-7, (-)-23, (+)-24] based upon the 3,5,5-trisubstituted pyrrolin-4-one scaffold is described. Use of a monopyrrolinone scaffold leads to inhibitors with improved cellular transport properties relative to the earlier inhibitors based on bispyrrolinones and their peptide counterparts. The most potent inhibitor (-)-7 displayed 13% oral bioavailability in dogs. X-ray structure analysis of the monopyrrolinone compounds cocrystallized with the wild-type HIV-1 protease provided valuable information on the interactions between the inhibitors and the HIV-1 enzyme. In each case, the inhibitors assumed similar orientations for the P2'-P1 substituents, along with an unexpected hydrogen bond of the pyrrolinone NH with Asp225. Interactions with the S2 pocket, however, were not optimal, as illustrated by the inclusion of a water molecule in two of the three inhibitor-enzyme complexes. Efforts to increase affinity by displacing the water molecule with second and third generation inhibitors did not prove successful. Lack of success with this venture is a testament to the difficulty of accurately predicting the many variables that influence and build binding affinity. Comparison of the inhibitor positions in three complexes with that of Indinavir revealed displacements of the protease backbones in the enzyme flap region, accompanied by variations in hydrogen bonding to accommodate the monopyrrolinone ring. The binding orientation of the pyrrolinone-based inhibitors may explain their sustained efficacy against mutant strains of the HIV-1 protease enzyme as compared to Indinavir.
Assuntos
Carbamatos/síntese química , Inibidores da Protease de HIV/síntese química , Protease de HIV/química , Pirróis/síntese química , Animais , Disponibilidade Biológica , Carbamatos/química , Carbamatos/farmacocinética , Cristalografia por Raios X , Cães , Desenho de Fármacos , Protease de HIV/genética , Inibidores da Protease de HIV/química , Inibidores da Protease de HIV/farmacocinética , Modelos Moleculares , Mutação , Ligação Proteica , Pirróis/química , Pirróis/farmacocinética , Pirróis/farmacologiaRESUMO
Naphthyridine 7 inhibits the strand transfer of the integration process catalyzed by integrase with an IC50 of 10 nM and inhibits 95% of the spread of HIV-1 infection in cell culture at 0.39 microM. It does not exhibit cytotoxicity in cell culture at < or =12.5 microM and shows a good pharmacokinetic profile when dosed orally to rats. The antiviral activity of 7 and its effect on integration were confirmed using viruses with specific integrase mutations.
Assuntos
Fármacos Anti-HIV/síntese química , Inibidores de Integrase de HIV/síntese química , HIV-1/efeitos dos fármacos , Naftiridinas/síntese química , Administração Oral , Animais , Fármacos Anti-HIV/química , Fármacos Anti-HIV/farmacologia , Linhagem Celular , Inibidores de Integrase de HIV/química , Inibidores de Integrase de HIV/farmacologia , Humanos , Injeções Intravenosas , Naftiridinas/química , Naftiridinas/farmacologia , Ratos , Relação Estrutura-AtividadeRESUMO
[reaction: see text] A novel approach to alpha,alpha-disubstituted-beta-amino acids (beta(2,2)-amino acids) was employed in the synthesis of a series of 3-(pyrrolidin-1-yl)propionic acids possessing high affinity for the CCR5 receptor and potent anti-HIV activity. The rat pharmacokinetics for these new analogues featured higher bioavailabilities and lower rates of clearance as compared to cyclopentane 1.
Assuntos
Fármacos Anti-HIV/farmacologia , Antagonistas dos Receptores CCR5 , Propionatos/farmacologia , Pirrolidinas/farmacologia , Fármacos Anti-HIV/farmacocinética , Disponibilidade Biológica , Propionatos/farmacocinética , Pirrolidinas/farmacocinéticaRESUMO
We sought to determine how effectively a CD8+ T cell inducing vaccine controls SHIV-89.6P infection in rhesus macaques at a range of challenge times post-vaccination. To this end, twenty eight Mamu-A*01+ rhesus macaques were given replication incompetent human serotype 5 adenovirus vector expressing SIVmac239 gag DNA and boosted 24 weeks later. Groups of 4 monkeys were then challenged with SHIV-89.6P at 1, 3, 6, 12, and 24 weeks after the boost. We compared the kinetics of viral load, CD4+ and virus-specific CD8+ T cells in these macaques. Measurements of CD8+ T cells taken before challenge show an exponential decay between 1 and 12 weeks following vaccination (p<0.0001). After week 12, no further decay was observed. Twenty of 24 vaccinated animals maintained more CD4+ T cells and kept their viral load at least one order of magnitude lower than the control animals throughout the chronic phase of the study. All 24 vaccinated animals survived the duration of the study. The viral and T cell kinetics over the first two weeks differed between the vaccinated groups, with more recent vaccination improving the early control of virus (p-value=0.027). The rates of virus specific CD8+ T cell expansion were greater in animals having higher viral loads at one week (r=0.45, p=0.029), suggesting that the kinetics of early viral load may have a role in virus specific CD8+ T cell generation, although these early differences did not lead to different clinical outcomes within the vaccinated animals.
Assuntos
Macaca mulatta/imunologia , Vacinas contra a SAIDS/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Vírus da Imunodeficiência Símia/imunologia , Carga Viral , Animais , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Humanos , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Síndrome de Imunodeficiência Adquirida dos Símios/virologia , Vírus da Imunodeficiência Símia/genética , Fatores de Tempo , VacinaçãoRESUMO
A series of HIV protease inhibitors with modifications on the P3 position have been designed and synthesized. These compounds exhibit excellent antiviral activity against both the wild type enzyme and PI-resistant clinical viral isolates. The synthesis and biological activity of the compounds are described.
Assuntos
Inibidores da Protease de HIV/síntese química , Inibidores da Protease de HIV/farmacologia , HIV-1/efeitos dos fármacos , Linhagem Celular , Farmacorresistência Viral , Infecções por HIV/tratamento farmacológico , Infecções por HIV/virologia , Humanos , Indicadores e Reagentes , Indinavir/síntese química , Indinavir/farmacologia , Relação Estrutura-AtividadeRESUMO
Lack of virus specific antibody response is commonly observed in both HIV-1-infected humans and SIV-infected monkeys with rapid disease progression. However, the mechanisms underlying this important observation still remain unclear. In a titration study of a SIVmac239 viral stock, three out of six animals with viral inoculation rapidly progressed to AIDS within 5 months. Unexpectedly, there was no obvious depletion of CD4(+) T cells in both peripheral and lymph node (LN) compartments in these animals. Instead, progressive depletion of proliferating B cells and disruption of the follicular dendritic cell (FDC) network in germinal centers (GC) was evident in the samples collected at as early as 20 days after viral challenge. This coincided with undetectable, or weak and transient, virus-specific antibody responses over the course of infection. In situ hybridization of SIV RNA in the LN samples revealed a high frequency of SIV productively infected cells and large amounts of accumulated viral RNA in the GCs in these animals. Early severe depletion of GC proliferating B cells and disruption of the FDC network may thus result in an inability to mount a virus-specific antibody response in rapid progressors, which has been shown to contribute to accelerated disease progression of SIV infection.
Assuntos
Linfonodos/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Vírus da Imunodeficiência Símia , Animais , Anticorpos Antivirais/sangue , Linfócitos B/citologia , Biópsia , Contagem de Células , Progressão da Doença , Centro Germinativo/imunologia , Centro Germinativo/virologia , Hiperplasia/patologia , Linfonodos/patologia , Macaca mulatta , Masculino , Síndrome de Imunodeficiência Adquirida dos Símios/diagnóstico , Síndrome de Imunodeficiência Adquirida dos Símios/patologia , Vírus da Imunodeficiência Símia/imunologia , Carga ViralRESUMO
A series of potent novel dihydroxypyridopyrazine-1,6-dione HIV-1 integrase inhibitors was identified. These compounds inhibited the strand transfer process of HIV-1 integrase and viral replication in cells. Compound 6 is active against replication of HIV with a CIC(95) of 0.31 microM and exhibits no shift in potency in the presence of 50% normal human serum. It displays a good pharmacokinetic profile when dosed in rats and no covalent binding with microsomal proteins in both in vitro and in vivo models.
Assuntos
Inibidores de Integrase de HIV/química , Inibidores de Integrase de HIV/farmacologia , Pirazinas/química , Pirazinas/farmacologia , Animais , Benzeno/química , Linhagem Celular , HIV/efeitos dos fármacos , HIV/enzimologia , HIV/fisiologia , Inibidores de Integrase de HIV/síntese química , Inibidores de Integrase de HIV/farmacocinética , Humanos , Microssomos Hepáticos/efeitos dos fármacos , Modelos Moleculares , Estrutura Molecular , Pirazinas/síntese química , Pirazinas/farmacocinética , Ratos , Relação Estrutura-Atividade , Replicação Viral/efeitos dos fármacosRESUMO
A series of monopyrrolinone-based HIV-1 protease inhibitors possessing rationally designed P2' side chains have been synthesized and evaluated for activity against wild-type HIV-1 protease. The most potent inhibitor displays subnanomolar potency in vitro for the wild-type HIV-1 protease. Additionally, the monopyrrolinone inhibitors retain potency in cellular assays against clinically significant mutant forms of the virus. X-ray structures of these inhibitors bound in the wild-type enzyme reveal important insights into the observed biological activity.
Assuntos
Inibidores da Protease de HIV , Protease de HIV/efeitos dos fármacos , Pirrolidinonas , Animais , Bovinos , Cristalografia por Raios X , Desenho de Fármacos , Inibidores da Protease de HIV/síntese química , Inibidores da Protease de HIV/química , Inibidores da Protease de HIV/farmacologia , Humanos , Técnicas In Vitro , Testes de Sensibilidade Microbiana , Modelos Moleculares , Conformação Molecular , Mutação , Pirrolidinonas/síntese química , Pirrolidinonas/química , Pirrolidinonas/farmacologia , Relação Estrutura-AtividadeRESUMO
A series of 5-amino derivatives of 8-hydroxy[1,6]-naphthyridine-7-carboxamide exhibiting sub-micromolar potency against replication of HIV-1 in cell culture was identified. One of these analogs, compound 12, displayed excellent pharmacokinetic properties when dosed orally in rats and in monkeys. This compound was demonstrated to be efficacious against replication of simian-human immunodeficiency virus (SHIV) 89.6P in infected rhesus macaques.
Assuntos
Inibidores de Integrase de HIV/síntese química , Inibidores de Integrase de HIV/farmacologia , Naftiridinas/química , Naftiridinas/farmacologia , Aminação , Inibidores de Integrase de HIV/química , Estrutura Molecular , Naftiridinas/síntese química , Relação Estrutura-AtividadeRESUMO
Peptides from the N-heptad repeat region of the HIV gp41 protein can inhibit viral fusion, but their potency is limited by a low tendency to form a trimeric coiled-coil. Accordingly, stabilization of N peptides by fusion with the stable coiled-coil IZ yields nanomolar inhibitors [Eckert, D. M. & Kim, P. S. (2001) Proc. Natl. Acad. Sci. USA 98, 11187-11192]. Because the antiviral potency of IZN17 is limited by self-association equilibrium, we covalently stabilized the peptide by using interchain disulfide bonds. The resulting covalent trimer, (CCIZN17)3, has an extraordinary thermodynamic stability that translates into unprecedented antiviral potency: (CCIZN17)3 (i) inhibits fusion in a cell-cell fusion assay (IC50 = 260 pM); (ii) is the most potent fusion inhibitor described to date (IC50 = 40-380 pM) in a single-cycle infectivity assay against HIV(HXB2), HIV(NL4-3), and HIV(MN-1); (iii) efficiently neutralizes acute viral infection in peripheral blood mononuclear cells; and (iv) displays a broad antiviral profile, being able to neutralize 100% of a large panel of HIV isolates, including R5, X4, and R5/X4 strains. In all of these assays, the potency of N-peptide inhibitor (CCIZN17)3 was equal to or more than the C-peptide inhibitor in clinical use, DP178 (also known as Enfuvirtide and Fuzeon). More importantly, we show that the two inhibitors, which have different targets in gp41, synergize when used in combination. These features make (CCIZN17)3 an attractive lead to develop as an antiviral drug, alone or in combination with DP178, as well as a promising immunogen to elicit a fusion-blocking neutralizing antibody response.
Assuntos
Fármacos Anti-HIV/química , Fármacos Anti-HIV/farmacologia , Proteína gp41 do Envelope de HIV/química , Proteína gp41 do Envelope de HIV/farmacologia , HIV-1/efeitos dos fármacos , HIV-1/fisiologia , Fármacos Anti-HIV/metabolismo , Fusão Celular , Dicroísmo Circular , Cisteína/química , Cisteína/metabolismo , Dissulfetos/química , Dissulfetos/metabolismo , Enfuvirtida , Proteína gp41 do Envelope de HIV/genética , Proteína gp41 do Envelope de HIV/metabolismo , Infecções por HIV/tratamento farmacológico , Infecções por HIV/virologia , Humanos , Concentração Inibidora 50 , Fusão de Membrana/efeitos dos fármacos , Testes de Neutralização , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/farmacologia , Desnaturação Proteica , Estrutura Quaternária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Recombinantes de Fusão/farmacologia , Relação Estrutura-Atividade , Temperatura , TermodinâmicaRESUMO
Efforts directed to identifying potent HIV protease inhibitors (PI) have yielded a class of compounds that are not only very active against wild-type (NL4-3) HIV virus but also very potent against a panel of PI-resistant viral isolates. Chemistry and biology are described.
Assuntos
Inibidores da Protease de HIV/química , Inibidores da Protease de HIV/farmacologia , HIV/efeitos dos fármacos , Indinavir/análogos & derivados , Administração Oral , Disponibilidade Biológica , Farmacorresistência Viral , HIV/enzimologia , Protease de HIV/efeitos dos fármacos , Inibidores da Protease de HIV/administração & dosagem , Estrutura MolecularRESUMO
A series of 1,3,4-trisubstituted pyrrolidine CCR5 receptor antagonists containing a variety of fused heterocycles at the 4-position of the piperidine side chain has been discovered, which are orally bioavailable with potent anti-HIV activity.
Assuntos
Fármacos Anti-HIV/química , Antagonistas dos Receptores CCR5 , Compostos Heterocíclicos/química , Pirrolidinas/química , Administração Oral , Animais , Fármacos Anti-HIV/farmacocinética , Células HeLa , Compostos Heterocíclicos/farmacocinética , Humanos , Pirrolidinas/farmacocinética , Ratos , Receptores CCR5/metabolismoRESUMO
Synthesis of analogs containing more rigid bicyclic piperidine replacements for the 4-benzyloxycarbonyl-(ethyl)amino-piperidine moiety of the CCR5 antagonist structure, 1, is described. Although similar binding affinity to the lead was achieved with some analogs they were overall less potent anti-HIV agents suggesting that other features besides CCR5 binding are required for good anti-viral activity.
Assuntos
Fármacos Anti-HIV/síntese química , Antagonistas dos Receptores CCR5 , Sulfonas/síntese química , Fármacos Anti-HIV/farmacologia , Butanos/síntese química , Butanos/farmacologia , Relação Dose-Resposta a Droga , Concentração Inibidora 50 , Piperidinas/síntese química , Piperidinas/farmacologia , Relação Estrutura-Atividade , Sulfonas/farmacologia , Vírus/efeitos dos fármacosRESUMO
Adenovirus 5 (Ad5) vectors show promise as human immunodeficiency virus vaccine candidates. Indian rhesus macaques vaccinated with Ad5-gag controlled simian-human immunodeficiency virus SHIV89.6P viral replication in the absence of Env immunogens that might elicit humoral immunity. Here we immunized 15 macaques using either a homologous Ad5-gag/Ad5-gag (Ad5/Ad5) or a heterologous DNA-gag/Ad5-gag (DNA/Ad5) prime-boost regimen and challenged them with a high dose of simian immunodeficiency virus SIVmac239. Macaques vaccinated with the DNA/Ad5 regimen experienced a brief viral load nadir of less than 10,000 viral copies per ml blood plasma that was not seen in Mamu-A*01-negative DNA/Ad5 vaccinees, Mamu-A*01-positive Ad5/Ad5 vaccinees, or vaccine-naive controls. Interestingly, most of these animals were not durably protected from disease progression when challenged with SIVmac239. To investigate the reasons underlying this short-lived vaccine effect, we investigated breadth of the T-cell response, immunogenetic background, and viral escape from CD8+ lymphocytes that recognize immunodominant T-cell epitopes. We show that these animals do not mount unusually broad cellular immune response, nor do they express unusual major histocompatibility complex class I alleles. Viral recrudescence occurred in four of the five Mamu-A*01-positive vaccinated macaques. However, only a single animal in this group demonstrated viral escape in the immunodominant Gag181-189 CM9 response. These results suggest that viral "breakthrough" in vaccinated animals and viral escape are not inextricably linked and underscore the need for additional research into the mechanisms of vaccine failure.