51
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Burke B, Gómez-Román VR, Lian Y, Sun Y, Kan E, Ulmer J, Srivastava IK, Barnett SW. Neutralizing antibody responses to subtype B and C adjuvanted HIV envelope protein vaccination in rabbits. Virology 2009; 387:147-56. [PMID: 19249806 PMCID: PMC2705626 DOI: 10.1016/j.virol.2009.02.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 12/08/2008] [Accepted: 02/03/2009] [Indexed: 11/30/2022]
Abstract
Improving the potency, breadth, and durability of neutralizing antibody responses to HIV are major challenges for HIV vaccine development. To address these challenges, the studies described evaluate in rabbits the titers, breadth, and epitope specificities of antibody responses elicited by HIV envelope subunit vaccines adjuvanted with MF59 with or without CpG oligodeoxynucleotide (ODN). Animals were immunized with trimeric o-gp140DeltaV2 derived from subtype B HIV-1(SF162) or subtype C HIV-1(TV1), or proteins from both strains. Immunization with SF162 or TV1 with MF59/CpG elicited higher titers of binding and neutralizing antibodies to SF162 than monovalent immunization with MF59 alone (P<0.01). Bivalent immunization increased binding and neutralizing antibody titers over single envelope immunization in MF59 (P<0.01). Bivalent immunization also improved neutralization breadth. Epitope mapping indicated neutralizing activity in rabbits was directed to V3 and V4. Overall, our data suggests that a multivalent vaccination approach with MF59 and CpG can enhance humoral responses to HIV-1.
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Affiliation(s)
- Brian Burke
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | | | - Ying Lian
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | - Yide Sun
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | - Elaine Kan
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | - Jeffrey Ulmer
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | - Indresh K. Srivastava
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
| | - Susan W. Barnett
- Novartis Vaccines and Diagnostics, 4560 Horton Street, Emeryville, California 94608, USA
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52
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Abstract
HIV vaccine research is at a crossroads carefully contemplating on the next path. The unexpected results of the Merck vaccine trial, while providing a stunning blow to a field in dire need of a protective vaccine, has also raised several fundamental questions regarding the candidate immunogen itself, preexisting immunity to vaccine vectors, surrogate assays and animal models used for assessing preclinical protective responses, as well as relevant endpoints to be measured in a clinical trial. As a result, the research community is faced with the daunting task of identifying novel vaccine concepts and products to continue the search. This review highlights and addresses some of the scientific and practical concerns.
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53
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Doria-Rose NA, Klein RM, Manion MM, O'Dell S, Phogat A, Chakrabarti B, Hallahan CW, Migueles SA, Wrammert J, Ahmed R, Nason M, Wyatt RT, Mascola JR, Connors M. Frequency and phenotype of human immunodeficiency virus envelope-specific B cells from patients with broadly cross-neutralizing antibodies. J Virol 2009; 83:188-99. [PMID: 18922865 PMCID: PMC2612342 DOI: 10.1128/jvi.01583-08] [Citation(s) in RCA: 258] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Accepted: 10/08/2008] [Indexed: 12/28/2022] Open
Abstract
Induction of broadly cross-reactive neutralizing antibodies (NAb) is an important goal for a prophylactic human immunodeficiency virus type 1 (HIV-1) vaccine. Some HIV-infected patients make a NAb response that reacts with diverse strains of HIV-1, but most candidate vaccines have induced NAb only against a subset of highly sensitive isolates. To better understand the nature of broad NAb responses that arise during natural infection, we screened patients for sera able to neutralize diverse HIV strains and explored the frequency and phenotype of their peripheral Envelope-specific B cells. We screened 113 HIV-infected patients of various clinical statuses for the prevalence of broad NAb. Sera able to neutralize at least four of five viral isolates were found in over one-third of progressors and slow progressors, but much less frequently in aviremic long-term nonprogressors. Most Env-specific antibody-secreting B cells were CD27(hi) CD38(hi) plasmablasts, and the total plasmablast frequency was higher in HIV-infected patients than in uninfected donors. We found that 0.0031% of B cells and 0.047% of plasmablasts secreted Env-specific immunoglobulin G (IgG) in an enzyme-linked immunospot (ELISPOT) assay. We developed a novel staining protocol to label HIV-specific B cells with Env gp140 protein. A total of 0.09% of B cells were found to be Env-specific by this method, a frequency far higher than that indicated by ELISPOT assay. gp140-labeled B cells were predominantly CD27(+) and surface IgG(+). These data describe the breadth and titer of serum NAb and the frequency and phenotype of HIV-specific B cells in a cohort of patients with broad cross-neutralizing antibody responses that are potential goals for vaccines for HIV.
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Affiliation(s)
- Nicole A Doria-Rose
- LIR, NIAID, National Institutes of Health, Bldg. 10, Rm. 7N246, 10 Center Dr., Bethesda, MD 20892, USA
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54
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McBurney SP, Ross TM. Viral sequence diversity: challenges for AIDS vaccine designs. Expert Rev Vaccines 2008; 7:1405-17. [PMID: 18980542 DOI: 10.1586/14760584.7.9.1405] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Among the greatest challenges facing AIDS vaccine development is the intrinsic diversity among circulating populations of HIV-1 in various geographical locations and the need to develop vaccines that can elicit enduring protective immunity to variant HIV-1 strains. While variation is observed in all of the viral proteins, the greatest diversity is localized to the viral envelope glycoproteins, evidently reflecting the predominant role of these proteins in eliciting host immune recognition and responses that result in progressive evolution of the envelope proteins during persistent infection. Interestingly, while envelope glycoprotein variation is widely assumed to be a major obstacle to AIDS vaccine development, there is very little experimental data in animal or human lentivirus systems addressing this critical issue. In this review, the state of vaccine development to address envelope diversity will be presented, focusing on the use of centralized and polyvalent sequence design as mechanisms to elicit broadly reactive immune responses.
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Affiliation(s)
- Sean P McBurney
- University of Pittsburgh, School of Medicine, Center for Vaccine Research, Program in Molecular Virology and Microbiology, Pittsburgh, PA 15261, USA.
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55
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Human immunodeficiency virus type 1 env trimer immunization of macaques and impact of priming with viral vector or stabilized core protein. J Virol 2008; 83:540-51. [PMID: 19004960 DOI: 10.1128/jvi.01102-08] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Currently there is limited information about the quality of immune responses elicited by candidate human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env)-based immunogens in primates. Here we describe a comprehensive analysis of neutralizing antibody and T-cell responses obtained in cynomolgus macaques by three selected immunization regimens. We used the previously described YU2-based gp140 protein trimers administered in an adjuvant, preceded by two distinct priming strategies: either alphavirus replicon particles expressing matched gp140 trimers or gp120 core proteins stabilized in the CD4-bound conformation. The rationale for priming with replicon particles was to evaluate the impact of the expression platform on trimer immunogenicity. The stable core proteins were chosen in an attempt to expand selectively lymphocytes recognizing common determinants between the core and trimers to broaden the immune response. The results presented here demonstrate that the platform by which Env trimers were delivered in the priming (either protein or replicon vector) had little impact on the overall immune response. In contrast, priming with stable core proteins followed by a trimer boost strikingly focused the T-cell response on the core sequences of HIV-1 Env. The specificity of the T-cell response was distinctly different from that of the responses obtained in animals immunized with trimers alone and was shown to be mediated by CD4(+) T cells. However, this regimen showed limited or no improvement in the neutralizing antibody responses, suggesting that further immunogen design efforts are required to successfully focus the B-cell response on conserved neutralizing determinants of HIV-1 Env.
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56
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Silbermann B, Tod M, Desaint C, Pialoux G, Petitprez K, Slama L, Poncelet H, Moreau C, Mazarin V, Heshmati F, Salmon-Ceron D, Guillet JG, Launay O. Short communication: Long-term persistence of vaccine-induced HIV seropositivity among healthy volunteers. AIDS Res Hum Retroviruses 2008; 24:1445-8. [PMID: 19000023 DOI: 10.1089/aid.2008.0107] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Long-term persistence of HIV vaccine-induced seropositivity in uninfected HIV vaccine recipients remains unknown. The duration of HIV humoral-induced responses was assessed in 72 volunteers who had received rgp160 and/or HIV recombinant canarypox virus constructs able to induce immune responses detectable using standard serological tests. Among the 43 rgp160 recipients, 94% and 83% remained HIV seropositive after 5 and 8 years of follow-up, respectively, while all the 29 volunteers who had received canarypox constructs alone were seronegative after 5 years. Because rgp160 induces long-term persistence (>8 years) of vaccine-induced HIV seropositivity, volunteers should be offered long-term follow-up to monitor their serological evolution.
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Affiliation(s)
- Benjamin Silbermann
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
| | - Michel Tod
- AP–HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, Pharmacie–Toxicologie, Paris, France and ISPB Lyon I, France
| | - Corinne Desaint
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
| | - Gilles Pialoux
- AP–HP, Hôpital Tenon, Service des Maladies Infectieuses et Tropicales, Paris, France
| | - Karine Petitprez
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
| | - Laurence Slama
- AP–HP, Hôpital Tenon, Service des Maladies Infectieuses et Tropicales, Paris, France
| | - Hubert Poncelet
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
| | | | | | - Farad Heshmati
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
| | - Dominique Salmon-Ceron
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
- Université Paris Descartes, Faculté de Médecine, CIC de Vaccinologie Cochin-Pasteur, Paris, France
| | | | - Odile Launay
- AP-HP, Groupe Hospitalier Cochin–Saint-Vincent de Paul, CIC de Vaccinologie Cochin–Pasteur, Pôle de Médecine, Paris, France
- Université Paris Descartes, Faculté de Médecine, CIC de Vaccinologie Cochin-Pasteur, Paris, France
- INSERM, CIC de Vaccinologie Cochin-Pasteur, Paris, France
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57
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Jeyanathan M, Mu J, Kugathasan K, Zhang X, Damjanovic D, Small C, Divangahi M, Petrof BJ, Hogaboam CM, Xing Z. Airway Delivery of Soluble Mycobacterial Antigens Restores Protective Mucosal Immunity by Single Intramuscular Plasmid DNA Tuberculosis Vaccination: Role of Proinflammatory Signals in the Lung. THE JOURNAL OF IMMUNOLOGY 2008; 181:5618-26. [DOI: 10.4049/jimmunol.181.8.5618] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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58
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Vaine M, Wang S, Crooks ET, Jiang P, Montefiori DC, Binley J, Lu S. Improved induction of antibodies against key neutralizing epitopes by human immunodeficiency virus type 1 gp120 DNA prime-protein boost vaccination compared to gp120 protein-only vaccination. J Virol 2008; 82:7369-78. [PMID: 18495775 PMCID: PMC2493346 DOI: 10.1128/jvi.00562-08] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Accepted: 05/12/2008] [Indexed: 11/20/2022] Open
Abstract
A major challenge in human immunodeficiency virus type 1 (HIV-1) vaccine development is to elicit potent and broadly neutralizing antibodies that are effective against primary viral isolates. Previously, we showed that DNA prime-protein boost vaccination using HIV-1 gp120 antigens was more effective in eliciting neutralizing antibodies against primary HIV-1 isolates than was a recombinant gp120 protein-only vaccination approach. In the current study, we analyzed the difference in antibody specificities in rabbit sera elicited by these two immunization regimens using peptide enzyme-linked immunosorbent assay and a competitive virus capture assay. Our results indicate that a DNA prime-protein boost regimen is more effective than a protein-alone vaccination approach in inducing antibodies that target two key neutralizing domains: the V3 loop and the CD4 binding site. In particular, positive antibodies targeting several peptides that overlap with the known CD4 binding area were detected only in DNA-primed sera. Different profiles of antibody specificities provide insight into the mechanisms behind the elicitation of better neutralizing antibodies with the DNA prime-protein boost approach, and our results support the use of this approach to further optimize Env formulations for HIV vaccine development.
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Affiliation(s)
- Michael Vaine
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA
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59
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Aidoo M, Sawadogo S, Bile EC, Yang C, Nkengasong JN, McNicholl JM. Viral, HLA and T cell elements in cross-reactive immune responses to HIV-1 subtype A, CRF01_AE and CRF02_AG vaccine sequence in Ivorian blood donors. Vaccine 2008; 26:4830-9. [PMID: 18640166 DOI: 10.1016/j.vaccine.2008.06.097] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 06/21/2008] [Accepted: 06/30/2008] [Indexed: 10/21/2022]
Abstract
Comprehensive understanding of the determinants of cross-subtype immune responses in HIV infection is critical to developing efficacious HIV vaccines against multiple viral subtypes. Because HIV-1 subtype A or recombinants comprising subtype A are prevalent in Africa and parts of Asia where HIV is spreading, we assessed the determinants of cross-subtype immune responses in HIV-infected blood donors from Cote d'Ivoire to peptides from a candidate CRF02_AG vaccine sequence, a subtype A sequence from western Kenya and a CRF01_AE sequence from Thailand. We present evidence that immune recognition of multiple viral subtypes is maintained by recognition of multiple epitopes. Our data suggest that complete escape of HIV from immune recognition is uncommon. Evaluation of these frequently generated cross-reactive responses should be included in immunogenicity trials of HIV vaccines.
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Affiliation(s)
- M Aidoo
- Laboratory Branch, Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA.
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60
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Kennedy JS, Co M, Green S, Longtine K, Longtine J, O'Neill MA, Adams JP, Rothman AL, Yu Q, Johnson-Leva R, Pal R, Wang S, Lu S, Markham P. The safety and tolerability of an HIV-1 DNA prime-protein boost vaccine (DP6-001) in healthy adult volunteers. Vaccine 2008; 26:4420-4. [PMID: 18588934 DOI: 10.1016/j.vaccine.2008.05.090] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 05/20/2008] [Accepted: 05/23/2008] [Indexed: 11/26/2022]
Abstract
This report describes the safety observations following administration of a polyvalent DNA prime-protein boost HIV-1 vaccine formulated with adjuvant QS21. Local injection site reactions were the most common (65% of subjects), and included type IV delayed-type hypersensitivity (DTH) reactions at prior DNA inoculation sites in 12 of 28 (43%) subjects following protein vaccination. Systemic reactions revealed two cases of vasculitis temporally related to inoculation with recombinant Env protein+QS21 adjuvant. Questions remain regarding the cause of the vasculitis, but the unique DTH observation may have contributed to the high level of immune responses previously reported for this vaccine.
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Affiliation(s)
- Jeffrey S Kennedy
- Center for Infectious Disease and Vaccine Research, University of Massachusetts Medical School, Worcester, MA, USA.
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61
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A chimeric multi-epitope DNA vaccine elicited specific antibody response against severe acute respiratory syndrome-associated coronavirus which attenuated the virulence of SARS-CoV in vitro. Immunol Lett 2008; 119:71-7. [PMID: 18533276 PMCID: PMC7112888 DOI: 10.1016/j.imlet.2008.04.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 04/11/2008] [Accepted: 04/22/2008] [Indexed: 12/11/2022]
Abstract
Epitope-based vaccines designed to induce antibody responses specific for severe acute respiratory syndrome-associated coronavirus (SARS-CoV) are being developed as a means for increasing vaccine potency. In this study, we identified four B cell epitopes from the spike (S) and membrane (M) protein through bioinformatics analysis and constructed a multi-epitope DNA vaccine. Intramuscular immunization of mice with this vaccine was sufficient to induce specific prime as well as a long-term memory humoral immune response to at least two candidate epitopes, S437–459 and M1–20. A DNA prime–protein boost strategy greatly enhanced the antibody generation and the immune sera not only reacted with the lysates of SARS-CoV-infected Vero cells but also neutralized the cytopathic effect of SARS by 75% at 1:160 dilution. The novel immunogenic S protein peptide revealed in this study provides new target for SARS vaccine design; and our work indicated multi-epitope DNA vaccine as an effective means for eliciting polyvalent humoral immune response against SARS-CoV.
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62
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Multifunctional T-cell characteristics induced by a polyvalent DNA prime/protein boost human immunodeficiency virus type 1 vaccine regimen given to healthy adults are dependent on the route and dose of administration. J Virol 2008; 82:6458-69. [PMID: 18448544 DOI: 10.1128/jvi.00068-08] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A phase I clinical vaccine study of a human immunodeficiency virus type 1 (HIV-1) vaccine regimen comprising a DNA prime formulation (5-valent env and monovalent gag) followed by a 5-valent Env protein boost for seronegative adults was previously shown to induce HIV-1-specific T cells and anti-Env antibodies capable of neutralizing cross-clade viral isolates. In light of these initial findings, we sought to more fully characterize the HIV-1-specific T cells by using polychromatic flow cytometry. Three groups of participants were vaccinated three times with 1.2 mg of DNA administered intradermally (i.d.; group A), 1.2 mg of DNA administered intramuscularly (i.m.; group B), or 7.2 mg of DNA administered i.m. (high-dose group C) each time. Each group subsequently received one or two doses of 0.375 mg each of the gp120 protein boost vaccine (i.m.). Env-specific CD4 T-cell responses were seen in the majority of participants; however, the kinetics of responses differed depending on the route of DNA administration. The high i.m. dose induced the responses of the greatest magnitude after the DNA vaccinations, while the i.d. group exhibited the responses of the least magnitude. Nevertheless, after the second protein boost, the magnitude of CD4 T-cell responses in the i.d. group was indistinguishable from those in the other two groups. After the DNA vaccinations and the first protein boost, a greater number of polyfunctional Env-specific CD4 T cells (those with > or = 2 functions) were seen in the high-dose group than in the other groups. Gag-specific CD4 T cells and Env-specific CD8 T cells were seen only in the high-dose group. These findings demonstrate that the route and dose of DNA vaccines significantly impact the quality of immune responses, yielding important information for future vaccine design.
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63
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Cristillo AD, Galmin L, Restrepo S, Hudacik L, Suschak J, Lewis B, Draghia-Akli R, Aziz N, Weiss D, Markham P, Pal R. HIV-1 Env vaccine comprised of electroporated DNA and protein co-administered with Talabostat. Biochem Biophys Res Commun 2008; 370:22-6. [PMID: 18329382 DOI: 10.1016/j.bbrc.2008.02.145] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 02/29/2008] [Indexed: 11/26/2022]
Abstract
Selection of potent yet low reactogenic adjuvants for protein immunization is important for HIV-1 vaccine development. Immunogenicity of electroporated DNA (HIV env) and recombinant gp120, administered with either QS-21 or the orally administered immunomodulator, Talabostat, was evaluated in BALB/c mice. Electroporation of low dose DNA elicited Th1 cytokines and anti-envelope antibodies. Immunization with gp120 protein alone with or without Talabostat elicited lower Th1 and Th2 cytokine levels but comparable anti-gp120 antibodies to QS-21-formulated protein. Boosting of DNA-primed mice with gp120/Talabostat induced similar anti-gp120 antibody titers and slightly higher levels of Th1 and Th2 cytokines relative to QS-21-formulated protein. Induction of CD8(+) and CD4(+) T cells and functional CTL activity was noted. These results highlight the potential use of orally administered Talabostat for efficient protein boosting of antibody and T-cell responses primed by DNA.
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Affiliation(s)
- Anthony D Cristillo
- Advanced BioScience Laboratories, Inc., 5510 Nicholson Lane, Kensington, MD 20895, USA
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64
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The relative immunogenicity of DNA vaccines delivered by the intramuscular needle injection, electroporation and gene gun methods. Vaccine 2008; 26:2100-10. [PMID: 18378365 DOI: 10.1016/j.vaccine.2008.02.033] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Revised: 02/08/2008] [Accepted: 02/11/2008] [Indexed: 11/21/2022]
Abstract
Immunogenicity of DNA vaccines varies significantly due to many factors including the inherent immunogenicity of the protein antigen encoded in the DNA vaccine, the optimal immune responses that can be achieved in different animal models and in humans with different genetic backgrounds and, to a great degree, the delivery methods used to administer the DNA vaccines. Based on published results, only the gene gun-mediated delivery approach has been able to elicit protective levels of immune responses in healthy, adult volunteers by DNA immunization alone without the use of another vaccine modality as a boost. Recent results from animal studies suggest that electroporation is also effective in eliciting high level immune responses. However, there have been no reports to identify the similarities and differences between these two leading physical delivery methods for DNA vaccines against infectious disease targets. In the current study, we compared the relative immunogenicity of a DNA vaccine expressing a hemagglutinin (HA) antigen from an H5N1 influenza virus in two animal models (rabbit and mouse) when delivered by either intramuscular needle immunization (IM), gene gun (GG) or electroporation (EP). HA-specific antibody, T cell and B cell responses were analyzed. Our results indicate that, overall, both the GG and EP methods are more immunogenic than the IM method. However, EP and IM stimulated a Th-1 type antibody response and the antibody response to GG was Th-2 dominated. These findings provide important information for the further selection and optimization of DNA vaccine delivery methods for human applications.
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